Four years ago I built The Almost Useless Machine, a tiny machine that tries to cut a wooden dowel. Here comes the second incarnation, a bit stronger and a bit more robust.
There are quite some videos of home made power hacksaws out there. I think I watched all of them. I thought, I could build something similar. So I started designing, ordering parts and materials.
Parts
The motor is a wiper motor, I guess. It runs up to 17 Volts and has quite some torque. Unfortunately I found out later that it gets really hot after a while.
The power supply is a adjustable 65 watts notebook power supply.
All other parts, excepts bearings, nuts and bolts, are machined out of aluminum.
Electronics
To control the motor I designed a simple PCB with a small 8-bit AVR (ATtiny25) as brain. The controller reads a pot and puts out a PWM signal to drive a MOSFET, which in turn, drives the motor. I added a microswitch as endstop to the arm, so that the motor stops when the work is done.
PCB was made at OSHpark. It has only through hole parts, space was not an issue for this project. Very easy to solder.
A controller is not really required by the project but it adds some nice features like a soft start of the motor.
Making of
Here is a bit of how the whole thing was machined and how it’s put together. All in all it took almost 5 months of spare time.
Wrap-up
As usual, I learned a couple of things. And I screwed a couple of things. Several parts have been done two or even three times, before I got them right. One of the ways I fail often, goes like this: I already invested quite some time into a piece and now I have to do an “easy” job, like drilling two aligned holes. Then I think “Hey, that’s easy, I won’t use the drill press, I’ll do that by hand!”. Then the holes aren’t perfectly aligned and you are able to see it, even from the distance.
Dang! Try to remember that!
Still, I think it came out nice and I like the way how it’s slowly chewing through the aluminum.
Links
tinkerlog 
a functional work of art
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What’s with the “almost”? This seems like a perfectly serviceable, if somewhat small power hacksaw.
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