I needed a small table saw for cutting small things ... like printed circuit boards. I've used angle grinders, hand saws, nibbler tools and they are all too wasteful or take too much time to cut up a small (30 x 50 mm) board.
I used to have a full size table saw, but that's just too big for cutting these little pieces.
Then I thought, if I used a small motor and attached a mini circular saw blade to it ... that'd be just about right!
Next, I looked on the Internet for mini circular saw blades and, lo and behold, found some.
While I was looking around for mini circular saw blades and various other bits and pieces, I realised that a saw wasn't the only thing that I could use in my workshop that could be driven by a small motor ... lathes, drills, band saws ... hmm ... there's some scope here.
I've pulled my multi tool back to just a mini table saw for now.
E-Bay Shopping List ($35.58)
- 1 x PWM DC Motor Speed Controller, $2.81
- Mini Circular Saw Blades, $3.78
- 12-24 V DC motor (with JT0 chuck, mounting bracket, chuck key and connector) $15.99
- 2 x 8 mm bore pillow block, $3.36
- 20 T drive pulley $1.89
- 32 T drive pulley $3.21
- 150 T timing belt $1.32
- G2 idler pulley $3.22
Hardware Store Shopping List ($9.50)
- 1 x 45 mm x 1000 mm x 2.5 mm aluminium flat bar ($4.50)
- 1 x 25 mm x 1000 mm x 25 mm aluminium angle bar ($5.00)
Other stuff that I had or made
- M3 screws (about 30)
- 10 mm Aluminium rod
- 10 mm steel rod
My mate turned the axle on his lathe, otherwise it would have cost a fair bit.
Step 1: Fitting the Motor and Pillow Blocks
I made a box from the aluminium flat bar and aluminium angle bar that's 150 mm x 120 mm.
The motor is fitted by copying the mounting holes in the mounting bracket onto the front face 150 mm piece of aluminium. I had to drill out the motor shaft hole and then I used an auger to widen the hole (plus a round file). Making the holes for the mounting screws slightly larger than the M3 bolts so that I had a little bit of wiggle room.
The pillow blocks were mounted on the front and back faces and then I marked up the screw holes and the axle hole. The screw holes are tapped so that I don't have to use a nut and bolt ... just a bolt. It's pretty important to minimise the hardware that's sticking outside of the tool so that there is nothing there to catch on the belt.
I mounted the pillow blocks as high on the face as possible so that the axle would be at the top of the finished tool ... this gives you more room for the circular saw blade and makes sure that the blade will end up above the table top.
The holes for the axle need to be wide enough for the pulley and the chuck.
Step 2: Fitting the Axle and Pulley Drives
The axle was the biggest hassle while building this tool. I couldn't find any bar stock that I could just reduce one end for the chuck and that would fit the pillow blocks.
I ended up asking a friend to turn the axle on his lathe for me. I've included the dimensions for the axle here so that you can make it yourself (or ask a friend).
I had an engineering company quote for the axle ... because it was a small job and blah blah blah they quoted $200 AUD! I declined their generous offer.
The chuck end of the axle is 5 mm and is an interference connection. That is, you hammer the chuck onto the axle and the very tight fit makes it stick. Or you could use a hydraulic press.
Because the axle is cut from 10 mm stock, the shoulders hold the axle in place and grub screws are not needed to fix the axle to the bearings in the pillow block.
On the other end of the axle, the 32 tooth pulley driver is fixed with grub screws.
The 20 tooth pulley driver connection to the motor shaft is a bit tricky. Again, finding parts that fit is a challenge. I had an 8 mm aluminium bar that I drilled a 1/8" hole in and pressed it into the 8 mm bore of the pulley driver. Then I drilled out the 2 M3 grub screw holes through the aluminium bar and replaced the grub screws with 10 mm M3 bolts so that the bolts clamp through the driver directly onto the shaft.
I also fitted an idler pulley between the axle and motor to put more tension on the belt and prevent the belt from slipping.
Step 3: Belt Drive
The belt drive is fitted as pictured. The idler pulley is fitted by drilling a 5.5 mm hole in the front face of the machine and then tapping the hole out for an M6 bolt.
The idler is loose on the M6 bolt, so I fitted a nut between the idler and the body of the machine. There's about a 3 mm gap between the idler and the nut. This is so that the idler can travel up and down in the space without causing any friction with the belt.
Finally, the idler is positioned so that the belt is tight enough that it doesn't slip and loose enough that you can put the belt on. The easiest way to put the belt on is to loop it around the 20 tooth pulley, then, while turning the axle by hand, slip the belt over the 32 tooth driver and, finally, while turning the belt, slip the belt over the idler. It's a little difficult, but not too bad.
Step 4: Fit the Electronics
Finding somewhere for the electronics was not easy!
I fitted the speed controller and toggle switch on the left side of the machine. The potentiometer knob fits through the hole so I had to drill and then bore the hole a little bit at a time so that it has about 1 mm clearance around the knob.
I've also drilled a hole through the machine where the 12 V power supply will go.
Well ... I've put it together now and tested the power on my electronics bench ... it all works nicely.
My next task is to make the table top for it, which I will make from some ply-wood, and a base.