MACHINE SHOP TIPS #58 Bridgeport Mill DRO part 2 tubalcain

[psient]

I am thinking about what this means

If each was off by .0005 and you measured across all four would you've accumulated .002 over? Would you conclude that the DRO is subject to this minor variation or is it too small to judge between the verifying instruments (could be one or the other). BTW my experience has been when the tool blinks it's right on the graduation boundry so in this case it's telling me less than .0005 off when it blinks.

[havebenthere]

Enjoyed the video. I also noticed the reamer wobble somewhat. Also I wondered about the drill chuck as most have .0025 to .004 tir with the more expensive the lesser amount. The minor problem the first time makes for a great learning experience. I'm glad you include all that. Makes the wheels turn in my head. That's what a great teacher does. Thanks again!

[aryesegal1988]

As usual, thanks a lot Mr. Pete for all the time and effort it takes you to share with us all that info! :)

[norbsli]

If you need to be accurate a DRO realy pays out. Thanks for the video.

[TedRobotBuilder]

I think this shows that center-punching isn't as good as digital feeding. Maybe the best way would be to make your first mark with a punch and then work from there with the digital feed for the rest of the holes.

[1232sean]

i really wish you had gone to the 10,000th scale on the micrometer.

thanks

[capnthepeafarmer]

I don't know how you did your measurements on your DRO, but if you did the hole location by being zero on the first hole then moving to 0.625" then 1.250" then 1.875" et cetera, I believe you are seeing a GD&T error. The dimension measured from the first hole to all subsequent holes should be the most accurate (ornate), however, measuring hole to hole you'll see more error.

[647762816]

Close enough for government work. Thanks for video.

[outsidescrewball]

Great follow up, thanks.....

[overr8ted2]

that was much closer that time it mush have been the center drill last time

i also see a lil wobble in the ream it might have a a very small inpact but

1.0005-1.0000 man thats close

[token5gtd]

@overr8ted2

definitely a little wobble with the reamer.

[adetheblade100]

how did i know after watching #56 that would be really bugging you somewhat ? glad to see you have satisfied yourself with the dro `error`. keep up the fab vids. compulsive viewing !!!!!!!!!!!! cheers Ade

[cyrex686]

I was looking for ward to the follow up, glad to see you revisited the last series. It had me really curious as to what happened. So, now I know how much not using a center drill can cost in accuracy.

[Swanny383]

Good vid, as always, I am courious though, what the hole 1 to the 4th spacing error was if any, Wouldn't the 1-4 show the largest possible error of the sample?, I am not asking a question, or being a stickler, I am just thinking a loud, given a 1/2 thousanth over 1" is very small, but if you had say 12 or 20 holes over say as many inches, could that all add up to "my bolt or pin, or dovetail won't fit ." Just thinking a loud. All things considerd I wonder how the dial on the table compared.

[grieske]

@Swanny383 I guess that, since the DRO gives an absolute position, 0.0005" is just twice the variable error in the DRO, and it hardly matters how far away from each other they are. I'd assume that the error due to the heating up of the workpiece is small. Carbon steel has a linear expansion coefficient of 12e-6 K^{-1}, so over a length of 1", an increase in temperature of 10K introduces an error of 0.00012". Don't let it get hot, though. Too warm to tough is inaccurate.

[grieske]

@grieske typo: tough -> touch

[TheBakachan]

Great and informative, as always. I can't wait for the next videos!

Thanks!

[smackbabie]

Good stuff as usual.

[danratsnapnames]

keep the videos coming.. youtube is now the new collage.. the more you document your skills, the more you'll teach others.. LIKE ME! thank you so much.