@dogknobber It wouldn't be as good as a glass one. Plexiglass is a lot softer than actual glass so is more prone to deformation, meaning the image wouldn't be anywhere near as good.
Nice job, Dan. I did something similar with a hand jig saw and a flat shim stock bar, but it did not turn out half as nice as yours. Can you get away with using a standard blade, or do we need one of those fine tooth finishing blades? And for the poster asking about stainless steel, google is your friend. Dan would just be googling your question anyway. SS has too high a heat range for conventional oven to mold it with heat. However, if it is that thin, just mold it like aluminum foil
hey can you plz tell me can i do this with very thin mirror like stainless steel! if i can what temp would be needed please reply soon its urgent please! or tell me the thickness of the steel that will do same
Dan, first of all I really like your video. Lots of wood information. I would like to offer some input on this video. I would have used a sacrificial piece of plywood clamped to the table saw over drilling a hole into the table. To cut plexi, it is better to use a hollow ground saw blade than a standard rip or cross-cut blade. My last comment is more crucial. NEVER handle the free end (i.e. the portion not against the fence) when doing rip cuts (even with plexi). Very dangerous cut.
Is there something like minimal RPM for cutting acrylic? i heard you need at least 4000 rpm for clean cut on table saw, not sure what kind of saw i need to buy now :<
Anyone remember the old episode of myth busters where there was a theory that they used mirrors back in the day to reflect the sun and burn ships? Well the idiots didnt actually use parabolic mirrors in there testing and experiments they used flat mirrors... So stupid that show is cause as we can see here.. If it was 30 of those parabolic mirrors together it would of easily caught a ship on fire.. WE JUST SAW IT MELT CONCRETE FOR GOD SAKES!!!!
I'm impressed. What I'm curious about is if you ever went back to your high school shop teacher and show him that it is possible!! ?? I just got a table saw...not yet opened, and I'm curious why it bothers people that you drilled holed on the plate. Do they feel it has potential to affect projects? I'm being serious when I ask this...not trying to be rude. I'm a self-taught power tool operator and I'm still learning these things.
I am wondering why solar cells are not manufactured using the parabolic shaping method you spoke of? It would increase each cell voltage output on a quantative scale...
This method would end up with a 1/4" HOLE in the middle of your "art." Try using something like hot glue or double sided tape/masking/painters tape with the same cutting technique.
Also, if you clamped a piece of plywood/mdf to the saw, you wouldn't have to put a hole in your metal table, and you could put as many holes as you wanted in your wood. Treat it like a pseudo deck for your saw.
Love the video. Had no idea a circle was even possible on a table saw. You could possibly save drilling hole in your table by clamping a 3/4" piece of plywood to the table first. Then use a wood screw to hold the piece that you are cutting. Thanks for sharing. I want to try this just for the fun of it.
If you clamped a piece of plywood to the saw table, you could drill your hole in it instead of the saw itself. When you plunge the blade up thru the sacrificial plywood table, it would create a zero clearance insert which would reduce chipping, too.
A router and trammel seems like it would be a more efficient way of cutting circles.
You could do it without drilling holes in your saw table. Make a clamp with two equal length parallel square steel tubes, a fulcrum say 8" tall located approx. 10% down the tube length, a threaded rod running through holes in the short ends from one tube to the other (to lever the long ends together), and a pin extending from one of the long ends - which goes through the centerpoint of the work with the other long end underneath the table. As you turn the rod the pin is clamped to the table.
I think this channel is one of the best in all youtube, for guys that really wants to be energy self sufficient , Dan Rojas is a great teacher and is a really cool dude. is the typical guy you see on tv and makes you feel that you can do anything with the proper tools and the proper knowledge!! nice job GREENPOWER SCIENCE.!!!
loll i was looking to do cheap miror for a telescope .. but i would change sometting on your idea
no hole in the plexy using a technic i learn in fiber glass manequin to save time we use to put the manequin chape on a axel harm and trim off the fiber execess
so i would bring the head of the bolt in the wood and use some aderant surface so the plexy would not slip easy hot glue on the hedge maybe .. anyways ill try it tomorow hehe
Man you broke almost every safety rule in the book. Great ideas though.
Also, you can make a jig that will allow you to make any size circle without drilling holes in your saw table. But please, use your blade guard and dust collection.
I am researching information for a project in my university and I just want to ask you how can i mold a bigger parabolic mirror. I am using right now a parabolic Direct TV dish. can it be used for this process as the mold? Do you have more specific info for bigger mirrors? Thank you!
I am researching information for a project in my university and I just want to ask you how can i mold a bigger parabolic mirror. I am using right now a parabolic Direct TV dish. can it be used for this process as the mold? Do you have more specific info for bigger mirrors? Thank you!
Hi Dan, I tried your system for making the mirror. My problem is; when I pulled it out of the oven, the outside is foggy and only the center is mirrored. is there a certain type of plexi mirror I should use? the backing on my sheet looks like grey fabric adhered to the plexiglass is this normal? It is 1/8th thick and the temp was set at 250, this was tried twice with the same result. Any help?
Hi Dan, I tried your system for making the mirror. My problem is; when I pulled it out of the oven, the outside is foggy and only the center is mirrored. is there a certain type of plexi mirror I should use? the backing on my sheet looks like grey fabric adhered to the plexiglass is this normal? It is 1/8th thick and the temp was set at 250, this was tried twice with the same result. Any help?
Its a tool doing work that he intends it to do, so long as its a beater saw whats the problem? that being said, i would have made a jig it only takes a couple seconds to set up a dead top. actually could help your functionality if the circle you want to spin is bigger in radius than the size of your saw top. if you could come across a bandsaw to make this cut on it really is a lot safer! love the vids, keep it up!
Hi Dan, I tried your system for making the mirror. My problem is; when I pulled it out of the oven, the outside is foggy and only the center is mirrored. is there a certain type of plexi mirror I should use? the backing on my sheet looks like grey fabric adhered to the plexiglass is this normal? It is 1/8th thick and the temp was set at 250, this was tried twice with the same result. Any help?
• DON'T READ THIS CUZ IT ACTUALLY WORKS. YOU WILL GET KISSED ON THE NEAREST POSSIBLE FRIDAY FROM THE LOVE OF YOUR LIFE, TOMORROW WILL BE THE BEST DAY OF YOUR LIFE; HOWEVER, IF YOU DON'T POST THIS TO OVER THREE VIDEOS YOU WILL DIE WITHIN TWO DAYS. NOW THAT YOU STARTED READING THIS DON'T STOP. THIS IS SO SCARY! POST THIS TO OVER FIVE VIDEOS IN 143 MINUTES. WHEN YOU'RE DONE PRESS F6 AND YOUR CRUSH'S NAME WILL APPEAR ON SCREEN IN BIG LETTERS. THIS IS SO SCARY BUT IT REALLY WORKS
nice, what type of plexi do you use? most are not as reflective ...
How can you be sure when you buy le plexi that it would effectivly homogeneously melt in the parabolic model, without any apparent stress in the material?
I've been cutting circles on a table saw over 30 yrs now, don't drill any holes in your table top, use a piece of plywood clamped to your table top, raise your blade to protrude through the plywood, that way you can have as many holes as you need without dis-configuring your table saw top. I love watching you videos, keep up the great work. It's a great idea but please people remember there is a blade under there and be safe.
Great "how to" vid, but why can't the attractive brunette with the nice voice and GREAT HAIR get a wee bit more on-screen time?... maybe even a polite intro... lol... ;') There's always a shortage of techno-nerd-babes w/ long hair, so might as well elevate this lady to minor celeb status. Who will second the motion?
Here's an easy way to get around drilling a hole into the saw table, as some tables saws are granite, or very thick cast iron. Buy a quarter sheet of 3/4" of MDF, and build a jig that sits on top of the table and uses the miter grooves to hold it in place, drill countersunk holes in the bottom of the MDF and place the bolt up through the MDF. raise the blade until it cuts through the MDF and into your material. Most table saw jigs use the miter slots to guide or hold them in place.
@josephhaga1 Over the years I have seen this backward blade thing recommended for cutting plastic, sheet metal, scoring plywood and about anything else that one has no idea how to do. Running a blade backwards DOES NOT WORK ON ANY MATERIAL FOR ANYTHING other than messing up the blade and workpiece. In the case of plastic, it wood melt rather than cut.
@ardvarkkkkk I like the idea of a router but I think a rotozip would be a better choice its made for cutting... and as for the backwards blade ask anyone that sides with vinal (glorified plastic) the blade is backwards when the cut it otherwise it shatters the product...
Do you know what sort of temperatures you get to (I know it will depend on the parabolic shape, but what's the ball-park figure for the one you made)? Can it get a 1 in round bar red hot?
I like you guys, thanks for putting it out there on the interwebs. You are creative and ingenious, thanks for sharing.
Dan seems like a bit of a brute sometimes(solar hot water anyone), he slams the materials around a bit and gets more blood stains on them than might be needed, I expect he does not do the finish carpentry on his projects
Denise is a saint for so many reasons but one is letting Dan melt plexi in the kitchen oven.
It's really easy to cut a circle with a router and an attachment. You can also cut plastic with a band saw without any trouble. I do it all the time.
I am a carpenter by trade and I would not drill into the top of my table saw either. An easy solution is to instead make a jig you can attach to your table with clamps, drill a hole in it and glue in a dowel, or just using a screw should work fine. Also drilling or cutting your plexi glass will go much faster with little to no chipping if you use a piece of plywood on top of your working film or under for drilling this will prevent localized high pressure/uneven cutting.
Ugh, please don't use capital letters like you do in the description! My eyes are bleeding, and i couldn't make my whole way through without looking away...
thanks for the tip on cutting the circle. Tried it today. Cut a perfect 36" circle using your method. The best part is after the circle is cut I also have the exact center.
@rkreml :-) go slow and you can cut perfect. Only danger is too fast, the kick is usually only a problem on small circles. Larger ones have too much weight unless you let the run.
PUSH STICK ALWAYS and you actually have a cool PT business:-) I cut about 10-20 a week for a few bucks a cut. Circles are popular. Routers work too but on thicker material unless you have a powerhouse, no point.
good process! you do not have to drill into your table saw though. you can make a jig that rests in the guide rail of your saw with a piece of ply attached to the top of your rail guides. just raise the blade up through that play and then you can drill all holes you want for different diameters without leaving any marks in your saw.
Yeah, I was going to say this too. Use a piece of plywood and clamp it to the table saw, drive a flathead bolt through bottom of wood first. No holes in table saw. Also, you can buy a table saw circle jig. This can also be done with a router and a and saw, btw.
yo dan and denise, i love all of your vids. but maybe you guys should mention some basic safety issue like table saw kickback in this case.. i'd hate to see ppl get hurt from trying this cuz they had never used a table saw before. anyways, keep up the good work :)
21 holes now:-) Still works perfect. I cut a 6ft dia base out of 2x4 glued and screwed together. Cut the circle with a steak in the ground 36" from blade and a pin pivot. 5 minutes to cut through 2x4s
love ur vid and thanks for posting, i wanted to say right away- and yes i am a laymen here- you dont have to drill into your table saw u only need some C clamps and wood and put the screw in the underside of the wood , thread side up, and there u go.
i would imagine one should be able to cut one time all the way around if you work VERY slowly-. hah?
I agree - in a throw away society my point sounds highly moronical
In engineering a jig means no machine modification
Maybe I can wriggle out by pretending I was thinking about countries where these machines might cost several months wage - and drilling holes in a loan machine is not an option
You didn't show yourself removing the finished mirror from the glass parabola form. Does it remove easily or does it stick? I'm sure you'd have to allow it to cool but you skipped through these details. And that mirrored plexiglass is expensive. But this is a very cool method overall.
Duh, mount a sheet of plywood to the tabletop! Of course, make sure that you have a dowel, or a nail located where you want the radius of your cut to be. Then drop your material which you are cutting onto the nail (or have a hole drilled in the material, and mount the hole where the dowel is). Then raise, and spin!
I tried melting plexiglas in an oven once. made the food taste of burned plastic. don't use a food oven.
also there is no guarantee that a curved product is parabolic. a parabola is a very particular curve, not just any curve.
why not use a small satellite dish as the mold, vacuum form onto it and mirror coat the backside, either the chrome paint you can get or silver coating. that should get you an actual parabolic mirror and good size
The Curve does not have to be a true Parabola for solar as the target heated is usually larger than the spot produced. These actually cast an image reflection that it pretty good. True parabolas are great but for solar, not worth the time.
In regards to chrome paint, it does not work well. Chrome plating does but the dish requires stripping. If you go that far you should just do this:
I've always wanted to try gluing some aluminum foil to an old satellite dish just to see how well it concentrates sunlight. Al foil is very shiny on one side and should work, I think.
I agree. might need thin strips to keep from wrinkling too much. it might also be possible to just heat remove the paint on a dish and polish it like Dan R here suggests in another of his videos. but if you want many done right I still believe in vacuum molding clear thermoplastic on a parabolic dish as a mold and then coat it with a chemical mirror like silvernitrate like this: watch?v=hUX_cpFWNso
I second psychomikeo500 - it's totally bad form to bastardize your tools - make a jig like a pro
It's not the waste of the tool that is important - it's the lack of creative thinking that is the problem - making jigs will stand you in good stead for other projects
I cut about 15 circles a day this way, have one saw "bastardized?":-) just for that purpose. Works on wood and acrylic. The only jig I have is for hole free cuts. Keep in mind, this is a $129 dollar saw.
All my sizes are fixed and it works fast. Amazing made three round 1/4" acrylic counter tops 30x30 for a local store in 15 minutes.
You sound like YOU'RE the one not thinking. He bastardized the saw by just drilling one 1/4" hole? And if the plywood circle isn't a JIG, what the hell is it? You think he cuts another wood circle every time he wants to cut another piece of plexiglass? You must be a moron.
@OghamTheBold How ridiculous to criticize someone for simply drilling a hole in a saw table. "Bad form to bastardize you tools", did you actually read what you wrote? It's a simple hole in the saw that will have no negative effect what so ever and actually improves the function of the tool. While not new, it's an excellent idea that works well. It is in no way a "waste of the tool" & shows creative thinking. You sound like someone who just likes to criticize people for the sake of doing it.
@Soulrider2012 My comment was not pure criticism - it was - what is known in the trade as - a creative criticism - helpful advice - or merely a suggestion, if you wish
Because nearing 1/4 of a million people have viewed this now - it is better that the alternative method of creating a jig is mentioned
I was not the first person to offer this helpful advice - but I would be happy to be the first
If you attend a - college, university, DIY class - they will teach you these beneficial approaches
To make a perfect Circle you should use a Router on a string=perfect every time even for a beginner.set a nail in the center and adjust the length of the string to get the size radius U want.
Cool video I think it would have been a cool shot if you had time-lapsed the mirror forming into shape. The only reason I thought of it is because I thought that was what you were going to do!
With that perfect circle cut the blade just lies tangent to the circle its pre-calculus math. Nothing is "perfect" but the tolerance is within reason for small projects. A CNC program would work much faster than that if you have access to one and can hold a small tolerance with out drilling a hole in the piece.
there are many more techniques without CNC equipment. You can do so much with a router and little jigs that will give you really complex shapes that you can do with a two/three axis router table.
NEVER remove the guard? Post a video of yourself using your tablesaw with a guard. I'd like to see that. I threw the guard away that came with my saw the day I got it. There was no way I could use it except for ripping or crosscutting strips more than 2" wide. Forget dadoes or rabbits. I make and use plywood push blocks (not push sticks) that keep my hands clear of the blade. I feel safe doing it my way. I've never had a problem, but hey, you may teach me something, I'm interested.
Agreed, Many DIY woodworking shows do not use the useless guard either. We had one from a Craftsman saw, same model run but much older and heavier. The cheap plastic guard came unscrewed and hit the blade, plastic hand grenade.
You do know there is a difference between parabolic mirrors and concave mirrors don't you? What you are making is not parabolic. Parabolic mirrors are made with absolute precision so that all light is concentrated on the very small focal point.
bwilleb, as long as all / most of the light is focused on the end of the stirling motor (which is what he was making the mirror for) it doesn't matter if it hit's a focal point or not.
Regardless, this thing is pretty powerful. I've seen much crappier versions made with mylar that could still burn 2x4's within a few seconds.
how do u know the glass lid that you are using is a perfect circle to the eye it looks perfect, but maybe not mathematically perfect what equation do use to prove that your template is true perfect circle
the glass has nothing to do with cutting the circle, it is only used to get the approximate size needed for the wood/plexi. The circle is as perfect as the the 1/4" drilled hole has play (few hundred microns perhaps?), and as much as the saw vibrates perpendicular to the cut direction, i.e. || to the radius.
If you used a piece of plywood as a sled, similar to a panel cutting sled that you can easily make with the saw, and a countersunk hex bolt, you could do the same thing, and it could be made so that it's infinitely adjustable, and you wouldn't have to modify your tools. A little more effort and you could have a motor turn it while it cuts!
Also, after watching you cut that acrylic on the table saw, I understand why your shop teacher didn't want you trying anything more experimental - no insult.
Hm... I am doing a History Day Project and want to do my board as a large rotating cylinder. Using this I could cut a circle through wood, but anyone got ideas on what to do for the sides? The cylinder is going to be 6 feet high so I am a little puzzled....
You can search a local Plexiglass shop in your area. They come in 4 feet x 8 feet sheets. The charge 180 for 1/8" and 270 for 1/4". See if they have scraps for smaller dishes.
There are two ways to cut a perfect circle with a table saw without drilling into your table top. One is to clamp a 3/4" piece of plywood to the table top and drive a finishing nail into it about half way. With wire snips clip off the nail head and punch down your board onto the nail and follow your method or just chip away with whole cuts.. The other is the same but you would make a table saw sled and nail into it. Neither method damages your table top. CS
You can do this technique using 1/2" plywood with the bolt mounted and sticking up. This way is 10x faster than the nail trick a the chip away method. I just cut 2 45" circles out of 23/32 plywood (almost 1" thick) 7 minutes per circle. There is a video with the other technique but it looks a bit dangerous.
watch?v=OUMV0ku_emw
This is 10x easier and faster. My $100 table saw dose not mind the holes, I have them every 1/4" spaced and it still works perfect for everything else.
I do more carpentry work these days, but in a few months I plan to move back to Tx. and go back into metal fab. My next personal pet project is going to a pulse jet engine (100lbs thrust or so).
Take the plexi and place it gray or protected side up heat and for the parabolic curve. After cooling take paint remover and a cotton ball and remove the gray coating. Next take acetone and clean the mirror. Now you have a FIRST SURFACE mirror. It may take a few trys till you get the parabolic shape just right.
Try a jig, drilled to replace the base on a standard router, with a pin at center point, and a straight cutting bit chucked in router. makes nice clean circles, with no holes in table saw
Can I suggest a much safer and faster way to cut through plexi and most sheet plastic. Just reverse a regular carbide blade. running the blade installed backward will prevent chiping and almost eleminate kick back.
I have a home built furnace, could the fresnel lens (38") that you have on ebay, be used to premelt aluminium cans? It did a number on a steel washer. Just tring to save money and, cut down CO2 from charcoal that heats my furnace.
Yes, the temperature is enough to melt very small amounts of aluminum but not a can as it acts as a giant heat sink and is shiny. You can get 1 pound of aluminum up to 475 with the 38" spot lens. This will save you some heat. Do it in a crucible and you can get 3 pounds to 300 F or 1 pound to 700f.
Use your furnace to finish the job. Make sure it is tightly compacted or the lens will just burn the can vs heating it.
What are the different results you can get from a Parabolic Mirror than you can get from using a magnifying glass? Are Fresnel lenses the same as a magnifying glass in general?
i want coke!
savemyplaylist 7 hours ago
Hi Dan, I love the idea of using your saw to make circle cuts! I have the same saw you do. Robert Veach
jeffgrave 4 weeks ago
What is the difference between these round type shapes versus the rectangular shaped one's?
frontdesk123 1 month ago
i wonder i9f this plexi glass is good enough to make a reflector telescope with?////
dogknobber 1 month ago
@dogknobber It wouldn't be as good as a glass one. Plexiglass is a lot softer than actual glass so is more prone to deformation, meaning the image wouldn't be anywhere near as good.
BackstrokeOfTheWest 1 month ago
could it be better to use gasoline or other solvent to "melt to shape" the plexiglass?
truvak 1 month ago
Nice job, Dan. I did something similar with a hand jig saw and a flat shim stock bar, but it did not turn out half as nice as yours. Can you get away with using a standard blade, or do we need one of those fine tooth finishing blades? And for the poster asking about stainless steel, google is your friend. Dan would just be googling your question anyway. SS has too high a heat range for conventional oven to mold it with heat. However, if it is that thin, just mold it like aluminum foil
sheeshalready 1 month ago
you sound gay but yet i love your concept
shortyjk95 2 months ago
You're a fuckin' genius Dan. I wish I would have learned this in school.
blankman091487 2 months ago
hi was wondering if the material used in vehicles headlight is ACRYLIC PLEXI and if they are not are they as effective as ACRYLIC PLEXI
transgenic2000 3 months ago
@CADtekk
The shape is parabolic, meaning the reflection forms a parabola.
caronthegerman 4 months ago
hey can you plz tell me can i do this with very thin mirror like stainless steel! if i can what temp would be needed please reply soon its urgent please! or tell me the thickness of the steel that will do same
mailtorevolution 4 months ago
@mailtorevolution
You want to melt steel in a kitchen oven??
caronthegerman 4 months ago
WOW!!! You good!!!
Th3mast3r69 4 months ago
Hi. Thanks for the video. I have some questions:
- is it matter what kind of a wood?
- is it matter what kind of a glass?
- Is it matter what kind of a pleksi? -- What kind is recomended to use?
Kind regards
airwish 5 months ago
the technique is so wrong cutting anything
troykokura8418 6 months ago
Dan, first of all I really like your video. Lots of wood information. I would like to offer some input on this video. I would have used a sacrificial piece of plywood clamped to the table saw over drilling a hole into the table. To cut plexi, it is better to use a hollow ground saw blade than a standard rip or cross-cut blade. My last comment is more crucial. NEVER handle the free end (i.e. the portion not against the fence) when doing rip cuts (even with plexi). Very dangerous cut.
NavyBlueSTL 6 months ago
Is there something like minimal RPM for cutting acrylic? i heard you need at least 4000 rpm for clean cut on table saw, not sure what kind of saw i need to buy now :<
scuffle 7 months ago
This video has me wondering if you could heat up rocks or tanks of water to use as a storage for the heat needed in the stirling engine you showed.
Chuck
sc6chuck9 7 months ago
Anyone remember the old episode of myth busters where there was a theory that they used mirrors back in the day to reflect the sun and burn ships? Well the idiots didnt actually use parabolic mirrors in there testing and experiments they used flat mirrors... So stupid that show is cause as we can see here.. If it was 30 of those parabolic mirrors together it would of easily caught a ship on fire.. WE JUST SAW IT MELT CONCRETE FOR GOD SAKES!!!!
troubledseed 7 months ago
I'm impressed. What I'm curious about is if you ever went back to your high school shop teacher and show him that it is possible!! ?? I just got a table saw...not yet opened, and I'm curious why it bothers people that you drilled holed on the plate. Do they feel it has potential to affect projects? I'm being serious when I ask this...not trying to be rude. I'm a self-taught power tool operator and I'm still learning these things.
alohachristine 7 months ago
@gcampton666 they just want to be heard and try to make dan look stupid just leave the trolls be ok
protectoroffaith 7 months ago
I am wondering why solar cells are not manufactured using the parabolic shaping method you spoke of? It would increase each cell voltage output on a quantative scale...
lwblack64 8 months ago
This method would end up with a 1/4" HOLE in the middle of your "art." Try using something like hot glue or double sided tape/masking/painters tape with the same cutting technique.
Also, if you clamped a piece of plywood/mdf to the saw, you wouldn't have to put a hole in your metal table, and you could put as many holes as you wanted in your wood. Treat it like a pseudo deck for your saw.
bmw02freak 9 months ago
Love the video. Had no idea a circle was even possible on a table saw. You could possibly save drilling hole in your table by clamping a 3/4" piece of plywood to the table first. Then use a wood screw to hold the piece that you are cutting. Thanks for sharing. I want to try this just for the fun of it.
nathanbrock 9 months ago
very smart, thank you!
MiamiSimon 9 months ago
If you clamped a piece of plywood to the saw table, you could drill your hole in it instead of the saw itself. When you plunge the blade up thru the sacrificial plywood table, it would create a zero clearance insert which would reduce chipping, too.
A router and trammel seems like it would be a more efficient way of cutting circles.
woofworldpa 9 months ago
You could do it without drilling holes in your saw table. Make a clamp with two equal length parallel square steel tubes, a fulcrum say 8" tall located approx. 10% down the tube length, a threaded rod running through holes in the short ends from one tube to the other (to lever the long ends together), and a pin extending from one of the long ends - which goes through the centerpoint of the work with the other long end underneath the table. As you turn the rod the pin is clamped to the table.
agFinder2 9 months ago
she looks a little like micheal jackson at first glance.
kia438 9 months ago 2
dan, what do u mean to v=f8kYbOb2TwA
marioelectrico 10 months ago
@marioelectrico
Change the end of a web address of the same upper video.
airwish 5 months ago
I think this channel is one of the best in all youtube, for guys that really wants to be energy self sufficient , Dan Rojas is a great teacher and is a really cool dude. is the typical guy you see on tv and makes you feel that you can do anything with the proper tools and the proper knowledge!! nice job GREENPOWER SCIENCE.!!!
anarquismoespiritual 10 months ago
loll i was looking to do cheap miror for a telescope .. but i would change sometting on your idea
no hole in the plexy using a technic i learn in fiber glass manequin to save time we use to put the manequin chape on a axel harm and trim off the fiber execess
so i would bring the head of the bolt in the wood and use some aderant surface so the plexy would not slip easy hot glue on the hedge maybe .. anyways ill try it tomorow hehe
GHOSTTOYS 10 months ago
your teacher probably didnt want holes in his saw
paintballgundown8 11 months ago
That is a really cool technique. So smart and cheap to do.
Kudos !
faunflynn 11 months ago
Awesome technique to make the discs for a Wimshurst machine too! I've got one from my old Junior High which needs rebuilding, I may have to try it!
joesmoe71 11 months ago
Awesome technique to make the discs for a Wimshurst machine too!
joesmoe71 11 months ago
Man you broke almost every safety rule in the book. Great ideas though.
Also, you can make a jig that will allow you to make any size circle without drilling holes in your saw table. But please, use your blade guard and dust collection.
tabhorian 11 months ago
would this work on a pocket sized scale???
illKillYouRAWR 1 year ago
This has been flagged as spam show
Hello Dan! This video is very interesting.
I am researching information for a project in my university and I just want to ask you how can i mold a bigger parabolic mirror. I am using right now a parabolic Direct TV dish. can it be used for this process as the mold? Do you have more specific info for bigger mirrors? Thank you!
ricardoucr 1 year ago
Hello Dan! This video is very interesting.
I am researching information for a project in my university and I just want to ask you how can i mold a bigger parabolic mirror. I am using right now a parabolic Direct TV dish. can it be used for this process as the mold? Do you have more specific info for bigger mirrors? Thank you!
ricardoucr 1 year ago
Brilliant idea!
dawes777 1 year ago
Best thing to have a great edge on the plexiglas it to cut BOTH sides, flipping the plastic at least once.
I have been cutting perfect circles in wood from my table saw for years, glad you put this on here!
I built a jig that mounts in the guide slot and adjusts with the center pin attaching from the top.
It is big but it works very nicely
buzzbbird 1 year ago
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Hi Dan, I tried your system for making the mirror. My problem is; when I pulled it out of the oven, the outside is foggy and only the center is mirrored. is there a certain type of plexi mirror I should use? the backing on my sheet looks like grey fabric adhered to the plexiglass is this normal? It is 1/8th thick and the temp was set at 250, this was tried twice with the same result. Any help?
chancedad0 1 year ago
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Hi Dan, I tried your system for making the mirror. My problem is; when I pulled it out of the oven, the outside is foggy and only the center is mirrored. is there a certain type of plexi mirror I should use? the backing on my sheet looks like grey fabric adhered to the plexiglass is this normal? It is 1/8th thick and the temp was set at 250, this was tried twice with the same result. Any help?
chancedad0 1 year ago
Its a tool doing work that he intends it to do, so long as its a beater saw whats the problem? that being said, i would have made a jig it only takes a couple seconds to set up a dead top. actually could help your functionality if the circle you want to spin is bigger in radius than the size of your saw top. if you could come across a bandsaw to make this cut on it really is a lot safer! love the vids, keep it up!
DovetailFox 1 year ago
Hi Dan, I tried your system for making the mirror. My problem is; when I pulled it out of the oven, the outside is foggy and only the center is mirrored. is there a certain type of plexi mirror I should use? the backing on my sheet looks like grey fabric adhered to the plexiglass is this normal? It is 1/8th thick and the temp was set at 250, this was tried twice with the same result. Any help?
chancedad0 1 year ago
Incredible tutorial i enjoyed watching it and will definitely use a lot of these techniques in the future thanks :)
aragon2235 1 year ago
That chick would make a KILLER Michael Jackson look-alike ! ! !
For a second, I thought it was MJ, like back from the dead!
bRadicalmagic1 1 year ago
• DON'T READ THIS CUZ IT ACTUALLY WORKS. YOU WILL GET KISSED ON THE NEAREST POSSIBLE FRIDAY FROM THE LOVE OF YOUR LIFE, TOMORROW WILL BE THE BEST DAY OF YOUR LIFE; HOWEVER, IF YOU DON'T POST THIS TO OVER THREE VIDEOS YOU WILL DIE WITHIN TWO DAYS. NOW THAT YOU STARTED READING THIS DON'T STOP. THIS IS SO SCARY! POST THIS TO OVER FIVE VIDEOS IN 143 MINUTES. WHEN YOU'RE DONE PRESS F6 AND YOUR CRUSH'S NAME WILL APPEAR ON SCREEN IN BIG LETTERS. THIS IS SO SCARY BUT IT REALLY WORKS
popo2637 1 year ago
it is very nice to hear Denisse´s voice comenting over, it is fresh and feels more proessional on the video. Great video by the way.
truvak 1 year ago
nice, what type of plexi do you use? most are not as reflective ...
How can you be sure when you buy le plexi that it would effectivly homogeneously melt in the parabolic model, without any apparent stress in the material?
Lionel
lionelwushu 1 year ago
that was rather ingenious to drill a hole in your table saw and cut perfect circles
truthisouttheir 1 year ago
I've been cutting circles on a table saw over 30 yrs now, don't drill any holes in your table top, use a piece of plywood clamped to your table top, raise your blade to protrude through the plywood, that way you can have as many holes as you need without dis-configuring your table saw top. I love watching you videos, keep up the great work. It's a great idea but please people remember there is a blade under there and be safe.
dagwood64 1 year ago
Great "how to" vid, but why can't the attractive brunette with the nice voice and GREAT HAIR get a wee bit more on-screen time?... maybe even a polite intro... lol... ;') There's always a shortage of techno-nerd-babes w/ long hair, so might as well elevate this lady to minor celeb status. Who will second the motion?
MajorCaliber 1 year ago
Thank you guys! I love all your ideas!!!
DjGisME 1 year ago
cool video.
JosephStetson 1 year ago
wow great vid! you both rock! thanks for sharing and keep up the great vids!
RamoneTalarico 1 year ago
Thanks for the circle tip. I like the way Denise explains as Dan works.
kokopelli314 1 year ago
This is ingenious. Thanks again -- everyone of your video I want to accomplish.
DreamPharaoh 1 year ago
Here's an easy way to get around drilling a hole into the saw table, as some tables saws are granite, or very thick cast iron. Buy a quarter sheet of 3/4" of MDF, and build a jig that sits on top of the table and uses the miter grooves to hold it in place, drill countersunk holes in the bottom of the MDF and place the bolt up through the MDF. raise the blade until it cuts through the MDF and into your material. Most table saw jigs use the miter slots to guide or hold them in place.
Fentanyl3 1 year ago
Cutting plexiglas with a tablesaw is not an issue, I think your problem is a dull blade.
I work with plexiglas all day and use a tablesaw to cut different shapes with NO chipping. So that part is not true.
flattabang 1 year ago
take that shop teacher!!!!!
johnwilkesbooth1865 1 year ago
Are those ghost chilis in the backgound fo the last scene?
BobD1001 1 year ago
Use a router with a plastic cutting bit. No need to make a plywood piece you won't use and no drill holes in your tools.
ardvarkkkkk 1 year ago
for cutting plexiglass try cutting with the blade backwards.
josephhaga1 1 year ago
@josephhaga1 Over the years I have seen this backward blade thing recommended for cutting plastic, sheet metal, scoring plywood and about anything else that one has no idea how to do. Running a blade backwards DOES NOT WORK ON ANY MATERIAL FOR ANYTHING other than messing up the blade and workpiece. In the case of plastic, it wood melt rather than cut.
ardvarkkkkk 1 year ago
@ardvarkkkkk I like the idea of a router but I think a rotozip would be a better choice its made for cutting... and as for the backwards blade ask anyone that sides with vinal (glorified plastic) the blade is backwards when the cut it otherwise it shatters the product...
josephhaga1 1 year ago
When you drill the plexiglass, run the drill bit backwards. The heat from the friction melts through the glass; no risk of cracking and stuff
TrevorMFTW 1 year ago
Great ideas mate...
niettevragen 1 year ago
kewl ;)
PiezPiedPy 1 year ago
That's cool - or is it "that's hot"
Do you know what sort of temperatures you get to (I know it will depend on the parabolic shape, but what's the ball-park figure for the one you made)? Can it get a 1 in round bar red hot?
ashnaylor 1 year ago
Yes! Great tip. Never thought you COULD use a circular saw to cut a CIRCLE..
Jig saws just aren't as much fun. I'll enjoy this tip for a long time.
Thanks agaun.
jgore27 1 year ago
Can you just melt a square instead?
I like you guys, thanks for putting it out there on the interwebs. You are creative and ingenious, thanks for sharing.
Dan seems like a bit of a brute sometimes(solar hot water anyone), he slams the materials around a bit and gets more blood stains on them than might be needed, I expect he does not do the finish carpentry on his projects
Denise is a saint for so many reasons but one is letting Dan melt plexi in the kitchen oven.
MrFoofoodog 1 year ago
dude I can tell you love burning, its the only thing you do with the parabolic dish, do something else with the mirror
rockmetal999 1 year ago
It's really easy to cut a circle with a router and an attachment. You can also cut plastic with a band saw without any trouble. I do it all the time.
conspiracy777 1 year ago
I am a carpenter by trade and I would not drill into the top of my table saw either. An easy solution is to instead make a jig you can attach to your table with clamps, drill a hole in it and glue in a dowel, or just using a screw should work fine. Also drilling or cutting your plexi glass will go much faster with little to no chipping if you use a piece of plywood on top of your working film or under for drilling this will prevent localized high pressure/uneven cutting.
darat23 1 year ago 2
Ugh, please don't use capital letters like you do in the description! My eyes are bleeding, and i couldn't make my whole way through without looking away...
mattegeniet 1 year ago
Lol If I was your wood shop teacher I would let you try it either!!!
No student of mine is going to a hole in my table!!!! LOL
social3ngin33rin 1 year ago
Couldn't you use such a parabolic mirror for a dobsonian telescope? Or are the tolerances too low?
eulercircles 1 year ago
thanks for the tip on cutting the circle. Tried it today. Cut a perfect 36" circle using your method. The best part is after the circle is cut I also have the exact center.
rkreml 1 year ago 6
@rkreml :-) go slow and you can cut perfect. Only danger is too fast, the kick is usually only a problem on small circles. Larger ones have too much weight unless you let the run.
PUSH STICK ALWAYS and you actually have a cool PT business:-) I cut about 10-20 a week for a few bucks a cut. Circles are popular. Routers work too but on thicker material unless you have a powerhouse, no point.
SAW easy fast safe accurate.
Thank you for the comment stay safe!
GREENPOWERSCIENCE 1 year ago 3
What about the back of mirror you just made? Did you spray something on? Thank you for your brilliant ideas.
joekimtkd 1 year ago
You can also set your guide at an angle and use the blade to cut troughs in timber
StevoJN 2 years ago
Excellent! Its a shame the teacher did not let you try this at school.
ultimatehandyman 2 years ago
that was an awesome trick, thanks for sharing!
katholamew 2 years ago
good process! you do not have to drill into your table saw though. you can make a jig that rests in the guide rail of your saw with a piece of ply attached to the top of your rail guides. just raise the blade up through that play and then you can drill all holes you want for different diameters without leaving any marks in your saw.
Techie04 2 years ago
Yeah, I was going to say this too. Use a piece of plywood and clamp it to the table saw, drive a flathead bolt through bottom of wood first. No holes in table saw. Also, you can buy a table saw circle jig. This can also be done with a router and a and saw, btw.
sincitycyclops 1 year ago
I would just mirror the cooking pot lid "for about a buck." why go through all of that? Laziness is the mother of expedience.
eldrama1 2 years ago
It's called GREENpowerscience for a reason.
KwameNewton 1 year ago
i am a carpenter and i like it so i will traing to make in my shop
jihadcy 2 years ago
Comment removed
jihadcy 2 years ago
You can also put a one to two layers of clear packaging tape along both sides of the cut to help reduce chipping.
barjuszin 2 years ago
yo dan and denise, i love all of your vids. but maybe you guys should mention some basic safety issue like table saw kickback in this case.. i'd hate to see ppl get hurt from trying this cuz they had never used a table saw before. anyways, keep up the good work :)
914SECHS 2 years ago
Next week, how to cut a square out of plywood using a hammer and a 12mm masonry bit.
adysav 2 years ago
Safety Note: Cut this material with more safety equipment!
The MSDS sheet for plexiglass says:
PERSONAL PROTECTIVE EQUIPMENT
Respiratory: Wear dust mask.
Hand: Protective gloves.
Eye: Chemical safety goggles.
MacKenzie 2 years ago
21 holes now:-) Still works perfect. I cut a 6ft dia base out of 2x4 glued and screwed together. Cut the circle with a steak in the ground 36" from blade and a pin pivot. 5 minutes to cut through 2x4s
Rolls like a tire, really cool.
GREENPOWERSCIENCE 2 years ago
love ur vid and thanks for posting, i wanted to say right away- and yes i am a laymen here- you dont have to drill into your table saw u only need some C clamps and wood and put the screw in the underside of the wood , thread side up, and there u go.
i would imagine one should be able to cut one time all the way around if you work VERY slowly-. hah?
poosaypirate 2 years ago
I agree - in a throw away society my point sounds highly moronical
In engineering a jig means no machine modification
Maybe I can wriggle out by pretending I was thinking about countries where these machines might cost several months wage - and drilling holes in a loan machine is not an option
OghamTheBold 2 years ago 2
You didn't show yourself removing the finished mirror from the glass parabola form. Does it remove easily or does it stick? I'm sure you'd have to allow it to cool but you skipped through these details. And that mirrored plexiglass is expensive. But this is a very cool method overall.
7188181 2 years ago
Duh, mount a sheet of plywood to the tabletop! Of course, make sure that you have a dowel, or a nail located where you want the radius of your cut to be. Then drop your material which you are cutting onto the nail (or have a hole drilled in the material, and mount the hole where the dowel is). Then raise, and spin!
AmazGraz 2 years ago
I tried melting plexiglas in an oven once. made the food taste of burned plastic. don't use a food oven.
also there is no guarantee that a curved product is parabolic. a parabola is a very particular curve, not just any curve.
why not use a small satellite dish as the mold, vacuum form onto it and mirror coat the backside, either the chrome paint you can get or silver coating. that should get you an actual parabolic mirror and good size
DanFrederiksen 2 years ago 4
DO NOT EXCEED 190F.
The Curve does not have to be a true Parabola for solar as the target heated is usually larger than the spot produced. These actually cast an image reflection that it pretty good. True parabolas are great but for solar, not worth the time.
In regards to chrome paint, it does not work well. Chrome plating does but the dish requires stripping. If you go that far you should just do this:
watch?v=f8kYbOb2TwA
Thank you for the comment:-)
GREENPOWERSCIENCE 2 years ago
I've always wanted to try gluing some aluminum foil to an old satellite dish just to see how well it concentrates sunlight. Al foil is very shiny on one side and should work, I think.
inventor2010 2 years ago
I agree. might need thin strips to keep from wrinkling too much. it might also be possible to just heat remove the paint on a dish and polish it like Dan R here suggests in another of his videos. but if you want many done right I still believe in vacuum molding clear thermoplastic on a parabolic dish as a mold and then coat it with a chemical mirror like silvernitrate like this: watch?v=hUX_cpFWNso
DanFrederiksen 2 years ago
Great work! Keep it up!
AmericanREPUBLICNow 2 years ago
I second psychomikeo500 - it's totally bad form to bastardize your tools - make a jig like a pro
It's not the waste of the tool that is important - it's the lack of creative thinking that is the problem - making jigs will stand you in good stead for other projects
OghamTheBold 2 years ago
I cut about 15 circles a day this way, have one saw "bastardized?":-) just for that purpose. Works on wood and acrylic. The only jig I have is for hole free cuts. Keep in mind, this is a $129 dollar saw.
All my sizes are fixed and it works fast. Amazing made three round 1/4" acrylic counter tops 30x30 for a local store in 15 minutes.
GREENPOWERSCIENCE 2 years ago
You sound like YOU'RE the one not thinking. He bastardized the saw by just drilling one 1/4" hole? And if the plywood circle isn't a JIG, what the hell is it? You think he cuts another wood circle every time he wants to cut another piece of plexiglass? You must be a moron.
limeytrash 2 years ago
@OghamTheBold How ridiculous to criticize someone for simply drilling a hole in a saw table. "Bad form to bastardize you tools", did you actually read what you wrote? It's a simple hole in the saw that will have no negative effect what so ever and actually improves the function of the tool. While not new, it's an excellent idea that works well. It is in no way a "waste of the tool" & shows creative thinking. You sound like someone who just likes to criticize people for the sake of doing it.
Soulrider2012 1 year ago
@Soulrider2012 My comment was not pure criticism - it was - what is known in the trade as - a creative criticism - helpful advice - or merely a suggestion, if you wish
Because nearing 1/4 of a million people have viewed this now - it is better that the alternative method of creating a jig is mentioned
I was not the first person to offer this helpful advice - but I would be happy to be the first
If you attend a - college, university, DIY class - they will teach you these beneficial approaches
OghamTheBold 1 year ago
@OghamTheBold guess the pro's got a lot to learn!
porpoisefathom 1 year ago
To make a perfect Circle you should use a Router on a string=perfect every time even for a beginner.set a nail in the center and adjust the length of the string to get the size radius U want.
Perfect every time!!
187cisoULcRUNcHER 2 years ago
and no holes in your table saw...
spiderpig85 2 years ago
wrong again.....:) to make a perfect circle you should use a CNC :)
djpickle68 2 years ago
this is awesome
newmondo 2 years ago 4
Awsome use of the saw! I cut larger arks with a skillsaw but never tried such a tight radius!
I found plexiglass at delviesplastics
fireofenergy 2 years ago
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dsadasdaa25 2 years ago
This is awesome !
b0dhran 2 years ago 2
where do you get a plexi glass mirror?
JudyWonn 2 years ago
i would have made a jig that locates in the miter slot and could have then made a movable pivot in the wood panel laying across the saw top.
psychomikeo500 2 years ago
absoultely freakin awesome, nice work and good use of the table saw!~
bikeforfree 2 years ago
You showed that shop teacher xD
BackFlash2K 2 years ago
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CAPS I LIEK TO TALK IN THEM!!!!!!
paperninjathefirst 2 years ago
I love when someone tells you what you can't do and then you DO IT!
darkvader47 2 years ago 14
Cool video I think it would have been a cool shot if you had time-lapsed the mirror forming into shape. The only reason I thought of it is because I thought that was what you were going to do!
Good work. I subscribed.
manzilla86 2 years ago
Thank you for subscribing and for the time lapse idea.
Best Regards
Dan
GREENPOWERSCIENCE 2 years ago
With that perfect circle cut the blade just lies tangent to the circle its pre-calculus math. Nothing is "perfect" but the tolerance is within reason for small projects. A CNC program would work much faster than that if you have access to one and can hold a small tolerance with out drilling a hole in the piece.
england5050 2 years ago
The presenters method is practically wise for demonstration purposes. He is genius.
JUNVIC2006 2 years ago 2
there are many more techniques without CNC equipment. You can do so much with a router and little jigs that will give you really complex shapes that you can do with a two/three axis router table.
hanseich 2 years ago
No wonder his shop teacher wouldn't let him try it! Removing the guard is NEVER a good idea. Just use a scroll saw dude.
ksprad72 2 years ago
NEVER remove the guard? Post a video of yourself using your tablesaw with a guard. I'd like to see that. I threw the guard away that came with my saw the day I got it. There was no way I could use it except for ripping or crosscutting strips more than 2" wide. Forget dadoes or rabbits. I make and use plywood push blocks (not push sticks) that keep my hands clear of the blade. I feel safe doing it my way. I've never had a problem, but hey, you may teach me something, I'm interested.
deezynar 2 years ago
Agreed, Many DIY woodworking shows do not use the useless guard either. We had one from a Craftsman saw, same model run but much older and heavier. The cheap plastic guard came unscrewed and hit the blade, plastic hand grenade.
GREENPOWERSCIENCE 2 years ago
how much cost the plexiglass?
SpeedMetal4635 2 years ago
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this sucks my dick
meowzers15 2 years ago
thx maaaaaaaan
alsalamiali900 2 years ago
You do know there is a difference between parabolic mirrors and concave mirrors don't you? What you are making is not parabolic. Parabolic mirrors are made with absolute precision so that all light is concentrated on the very small focal point.
bwilleb 2 years ago
You're just making a concave mirror. It is inaccurate and probably only 20% of light makes it to the focal point. The other 80% is lost elsewhere.
bwilleb 2 years ago
You're so smart. I'm glad you can contribute valuable perspective.
Loaki9 2 years ago
bwilleb, as long as all / most of the light is focused on the end of the stirling motor (which is what he was making the mirror for) it doesn't matter if it hit's a focal point or not.
Regardless, this thing is pretty powerful. I've seen much crappier versions made with mylar that could still burn 2x4's within a few seconds.
kaje01 2 years ago
Wow, that's cool. You're really ingenius.
fruitfast777 2 years ago
I know we are. But I was just answering someone's question. Please let me live, oh great shane. I promise I'll be good.
Ps. We have 4.4%, not 5%.
eddiequest3 2 years ago
how do u know the glass lid that you are using is a perfect circle to the eye it looks perfect, but maybe not mathematically perfect what equation do use to prove that your template is true perfect circle
Awak666 2 years ago
When doing stuff like this it's all, as he said, more of an art than a science. Experiment. and discover things.
eddiequest3 2 years ago
the glass has nothing to do with cutting the circle, it is only used to get the approximate size needed for the wood/plexi. The circle is as perfect as the the 1/4" drilled hole has play (few hundred microns perhaps?), and as much as the saw vibrates perpendicular to the cut direction, i.e. || to the radius.
knoxjeff 2 years ago
dan: oven temperature, 252 degrees are farenheit or celsius?
thanks
cheordinario 2 years ago
oven temperature, 252 degrees are farenheit or celsius?
It's usually Fahrenheit, here in the states.
eddiequest3 2 years ago
According to Google (252 f = ? C), 122.22 Celsius appears to be correct for shaping plexiglass.
VCat2006 2 years ago
Dan since you already had the hole drilled to match your plexiglass you
didn't show how to determine where
to drill that hole. Was the plexiglass
placed at deadcenter of the blade, or
was it placed for the front edge?
LarryMReed 2 years ago
If you used a piece of plywood as a sled, similar to a panel cutting sled that you can easily make with the saw, and a countersunk hex bolt, you could do the same thing, and it could be made so that it's infinitely adjustable, and you wouldn't have to modify your tools. A little more effort and you could have a motor turn it while it cuts!
Also, after watching you cut that acrylic on the table saw, I understand why your shop teacher didn't want you trying anything more experimental - no insult.
nominalvelocity 2 years ago
You two are filled with tremendous info. Thanx, I can't wait for more!
MKUltraGurl 2 years ago
Hm... I am doing a History Day Project and want to do my board as a large rotating cylinder. Using this I could cut a circle through wood, but anyone got ideas on what to do for the sides? The cylinder is going to be 6 feet high so I am a little puzzled....
AcademicAllStar 2 years ago
Go to our channel and view the vertical wind turbine series.
GREENPOWERSCIENCE 2 years ago
That's some very unusual ways of using a table saw! I would get kicked out of the shop for doing that, but anyway, I like what you're doing!
bellaggio1770 2 years ago
I really like the way you used the low heat in the oven to form the dish. Does it release from the glass lid or does the glass lid become part of it?
okiesound 2 years ago
They release very well, it does not stick at all.
GREENPOWERSCIENCE 2 years ago
where do you find the plexiglas morrors and how big do they get aprox.
sabrewolfbilly 2 years ago
You can search a local Plexiglass shop in your area. They come in 4 feet x 8 feet sheets. The charge 180 for 1/8" and 270 for 1/4". See if they have scraps for smaller dishes.
GREENPOWERSCIENCE 2 years ago
There are two ways to cut a perfect circle with a table saw without drilling into your table top. One is to clamp a 3/4" piece of plywood to the table top and drive a finishing nail into it about half way. With wire snips clip off the nail head and punch down your board onto the nail and follow your method or just chip away with whole cuts.. The other is the same but you would make a table saw sled and nail into it. Neither method damages your table top. CS
Seezor 2 years ago
You can do this technique using 1/2" plywood with the bolt mounted and sticking up. This way is 10x faster than the nail trick a the chip away method. I just cut 2 45" circles out of 23/32 plywood (almost 1" thick) 7 minutes per circle. There is a video with the other technique but it looks a bit dangerous.
watch?v=OUMV0ku_emw
This is 10x easier and faster. My $100 table saw dose not mind the holes, I have them every 1/4" spaced and it still works perfect for everything else.
GREENPOWERSCIENCE 2 years ago
I'm often ahead of my teachers in the same way. Being literally raised in a metal fabrication shop can do that to you.
sockpuppetsfromhell 3 years ago
Taking shop for the easy A+ Grade:-)
Do you still work with metal?
Best Regards
Dan
GREENPOWERSCIENCE 3 years ago
I do more carpentry work these days, but in a few months I plan to move back to Tx. and go back into metal fab. My next personal pet project is going to a pulse jet engine (100lbs thrust or so).
sockpuppetsfromhell 3 years ago
invest in a band saw there is Another way to do it with a table saw...
jfxcoll 3 years ago
wow I never would have thot it possible to cut a circle on a table saw.
Congrats on all your good work.
:D
SafeArmsReview 3 years ago
GREAT episode! Very industrious. I'd like to get an even bigger template (glass lid). Great! :)
slinkee2k 3 years ago
What a great idea for cutting a circle on a table saw. Thank you very much for this!
drgeyer1 3 years ago
where did you get the plexi glass mirror?
you should try vacuum forming it. looked like it came out pretty good just with gravity though .
I had this idea a few months ago, i wanted to make a telescope with the mirror. Problem is the mirror is on the back side of the plexi glass, right?
treborly 3 years ago
Take the plexi and place it gray or protected side up heat and for the parabolic curve. After cooling take paint remover and a cotton ball and remove the gray coating. Next take acetone and clean the mirror. Now you have a FIRST SURFACE mirror. It may take a few trys till you get the parabolic shape just right.
1foxtrot70 3 years ago
Try a jig, drilled to replace the base on a standard router, with a pin at center point, and a straight cutting bit chucked in router. makes nice clean circles, with no holes in table saw
Carlstens 3 years ago
Can I suggest a much safer and faster way to cut through plexi and most sheet plastic. Just reverse a regular carbide blade. running the blade installed backward will prevent chiping and almost eleminate kick back.
dustychode 3 years ago
sound like george walsh amw
w33dbluntz 3 years ago
any idea on how to cook down a larger plexiglass mirror on a larger parabolic circle? like 36"
pipersmitty87 3 years ago
I have a home built furnace, could the fresnel lens (38") that you have on ebay, be used to premelt aluminium cans? It did a number on a steel washer. Just tring to save money and, cut down CO2 from charcoal that heats my furnace.
fly2000jtb 3 years ago
Yes, the temperature is enough to melt very small amounts of aluminum but not a can as it acts as a giant heat sink and is shiny. You can get 1 pound of aluminum up to 475 with the 38" spot lens. This will save you some heat. Do it in a crucible and you can get 3 pounds to 300 F or 1 pound to 700f.
Use your furnace to finish the job. Make sure it is tightly compacted or the lens will just burn the can vs heating it.
GREENPOWERSCIENCE 3 years ago
I'll recommend to use security glasses for cutting Plexiglas.
kurwinsky 3 years ago
What are the different results you can get from a Parabolic Mirror than you can get from using a magnifying glass? Are Fresnel lenses the same as a magnifying glass in general?
RetroTheory 3 years ago