Homemade Electric Power Hacksaw

What to do when you need to cut up rather big solid blocks of steel, brass or aluminium? You can mutilate them with angle grinders or try to cut it up in a milling machine, but the most convenient way is an electric / automatic hacksaw or band saw. Unfortunately most of those are large space eating cast iron monsters. There are no (at least non that I know of) good industrial smaller types, so there is only one way to go: the DIY-way...

Inspired by the very nice electric hack-saw made by myforboy (watch it here: http://www.youtube.com/watch?v=P5Tu_zoO828 ) I start building one myself. It's a very straight forward machine, but there are a few very unforgiving and important parts that will need al your efforts to get it right (at least: I had to...)

For al the DIY-mechanics and machinists out there who are also thinking about building one there self, here's what I used, had to buy and could use out of the old scrap & junk-box, and some problems I encountered.

the biggest problem I encountered was to get the whole thing rigid. Without rigidity you will get a 'walking' saw that will find it's own way through your workshop, house, street etc....
The most important part that will make or break it is (obvious) the saw and it's sliding mechanism. I had to make a few different kind of 'wagons', but finally came up with the one you can see in the movie: a solid steel 'wagon' (I call it a wagon, can't remember a better English word) that has a snug fit around a solid steel square bar. The top part of this wagon doesn't have any hard work to do, so I made that part out of POM-plastic. Two grease nipples are for very easy oiling the wagon and sliding bar. Only thing I had to buy was the square steel bar, not very expensive.

The saw itself is a ordinary steel hacksaw for the common standard blades. The only thing I did is weld a piece of flat steel at the top, for rigidity and for easy connecting it to the wagon. At the top, just before the wagon I welded a metal ring with a spring loaded ball in it. This pushes the saw away from the square steel bar and works like a guide and shock absorber, I found out this little thing makes the whole machine a whole lot smoother then without it, so it's something to consider also using when building our own.

Next important part (well, let's face it: almost every part in such a straight forward and simple machine is important) is the power transmission: the motor and pulleys are from an old and broken down drill press (180 Watt), that's connected to an axle which is placed in a gear reduction box, that on it's part powers a eccentric placed drive-bar connected to the saw.
One thing I found out is: let the eccentric move counter clockwise, this will push the wagon a bit upwards on a saw stroke, you'll get a steadier and smoother saw stroke then when the eccentric moves clockwise.
Had to buy the reduction gearbox, had to pay € 15 / $ 10 for it second-hand, so that's not much I guess. You see in the movie the speed is moderate, I found out that faster strokes does not always equals faster cutting. Faster strokes can make the saw getting hot, make aluminium 'pasty', or just clogging up the whole thing with saw dust.

The rest is rather obvious I think: the vice is made out of an old spindle + it's lead screw, saved from an discarded paper cutting machine. The The table is made out of a flat plate of steel that I found somewhere. The whole construction is build upon some very thick and strong synthetic building material, looks a bit like POM, but is more compact. Anyway: easy to handle and very strong.

Last thing to mention are the weights: I first had a 1,5 Kg block of steel placed upon the end of the square bar. But it was to heavy when cutting plastics, tubing or other softer materials it pushed the saw to fast through these materials. For steel it was just fine.

I cut three pieces of round stock (each around 0,5Kg and yes: I did it on this hacksaw ;-) Machined them on the lathe, made a parallel bar above the square sliding bar and voila: adjustable weights for rather precise vertical control. The pulleys give me the possibility to control the horizontal speed of the saw. Very convenient 'cause when cutting -- let's say -- some kinds of aluminium I found out that a lower speed and a little heavier vertical load sometimes gives better and faster results.

Hope you enjoy the movie, comments are welcome!

Category:

Science & Technology

Tags:

• metal work
• diy
• metalworking
• lathes
• milling machines
• cutting metal

[dpsilver1]

Nice build man I never considered making something like this but I'm gonna now lol but u should probably develope a way to increase and decrease the blade travel to ensure even tool wear and also reduced cutting time

[novoltny]

@dpsilver1

thanks for the compliment! and indeed: a system to change the blades position with respect to the workpiece is a very nice thought, but you can also change the position of the workpiece with respect to the blade, that's a lot easier ;-)

good luck with building, and when finished: put it on youtube, I would like to see it!

best regards,

Novoltny

[valveman12]

Congratulations on a nice build. I'm sure you'll get a lot of work out of it and the satisfaction you built it yourself.

[novoltny]

@valveman12

thank you! and indeed it does do a great job

regards,

Novoltny

[algae1000]

Nice clean job! How many RPM for the motor, and what is the reduction ratio? Do you know what the reduction gear was originally used on? You got a very good deal on it.

[novoltny]

@algae1000

thanks, motor is about 1400 RPM (I guess, no info on the motor),

Don't know where the gear originaly is used for, it's a VF30 from a Italian firm called Bonfiglioni, reduction ratio is 14x.

[MrAbazat]

@novoltny

OK

[tld5500]

@novoltny OK, I understand. You make perfect sense. I agree, it is a good size. Thank you for responding.

[novoltny]

@tld5500 main reason I've built this saw is the size, not the price: most factory made machines are big and heavy cast iron blocks, and I don't have room for those things, this one is doing the job for me, so big enough.

prize: if you gonna buy a new factory made power hack-saw and size & weight doesn't matter, then building one will be definitely cheaper. But I reckon you can buy an old semi antique one second hand for around € 200 / US$180.

best regards,

Novoltny

[tld5500]

Is it cheaper than a store bought machine? You had broken down machines and parts from other things to use. I would probably have to buy all of it, and machie the things I could not purchase. In the end, the time and money might have gotten me a factory bandsaw? Just wondering