In my various projects, I have come across a need to cut metal things. Crazy, I know. However the issue is that I lack the funds to purchase a big expensive chop saw that can cut hardened steel, as well as the amount of noise they create.
A few years back, I saw a post in Hackaday of a 3d printed power hacksaw. Now I'm not the type of person who just prints out someone else's designs. When I have a particular set of requirements in mind it then becomes an obsession.
It wasn't until a couple of months ago that I had finally purchased a working 3d printer. My first project would be to design and build this powered hacksaw. The goals are simple: use off the shelf components with near zero modifications required, and must be strong enough to cut hardened steel.
First up, the motor. In this case, I was looking for about 30 rpm. The result of my search is a 12v 30rpm planetary gear motor from eBay. It's small but quite powerful. The price has unfortunately gone up quite a bit.
Next was the linear motion. I decided on Hiwin MGN12 linear rails with two MGN12H carriages. overkill, I know, but I had some on hand.
For the hacksaw, I wanted one that I can bolt right to it. I ended up with a Stanley high tension hacksaw.
And finally a vise. I settled on an ebay 4inch Precision Milling Vise. It's a bit extreme, but so much nicer than those cheap $15 ones.
WARNING: This project can be dangerous, I am not liable for any injury or damage, and am posting this for informational purposes only. Keep away from moving parts! The motor can easily break your fingers.
1x of each:
Required tools:
The build
We need to drill some holes in the frame of the saw for mounting it to the carriages. I designed a jig to do this. The trick is to not drill through the entire rectangular tube, but just one side at a time. A 1/8 or 3.4mm works great. I only drilled two holes per carriage diagonally to maintain the integrity. When you're done, take a small circular file and try to get the holes to line up.
The KP08 hinge bearings have 4mm holes but we're using 5mm screws. Drill these out with the 7/32 or 5.5mm drill bit.
On the printed parts I decided on tapping the holes instead of inserts. You need to take it slow, and back out every few turns or else the tap and PLA will heat up and fuse. Do not use a drill!
Tap the 4 holes on the top of the frame with the M5 tap, and the 4 holes for the fan with the M3 tap.
Tap the 8x saw mount holes with the M3 tap.
Tap one the end of the 2040 extrusion with the M5 tap.
Tap the M5 hole of the auto-off screw mount
Mount the motor to the frame using 4x M3 12mm countersunk screws.
Mount the fan to the frame with it blowing air towards the motor, using 4x M3 20mm screws.
press the rocker switch into the hole on the top, with the off direction facing forward.
screw the toggle switch into the hole on the rear.
Mount the KP08 pillow block bearings to the frame, don't tighten it yet.
Use a M8 80mm screw through the KP08 -> M8 washer -> Hinge Mount -> M8 washer -> KP08 -> M8 washer -> M8 nut
Mount the hinge to the extrusion. Use M5 20mm on the ends, and M5 10mm on the slots.
Mount the auto-off screw mount using 2x M3 12mm countersunk screws.
Mount the saw mount to the saw using 8x M3 25mm screws
Mount the square nuts to the linear rail using 11x M3 8mm socket head cap screws. Carefully slide the rail onto the extrusion, aligning the nuts. Leave the rail about 5mm from the end of the extrusion and tighten down the screws.
Place the MGN12H carriages on the rail, using the provided guide blocks. Use some scotch tape and wrap it around the ends of the rail to keep the carriages from falling off.
Attach the Saw frame to the carriages using 4x 20mm screws and 7x washers per screw. The order is Screw -> washer -> frame -> 6x washer -> carriage.
Mount the crankshaft to the polulu hub using 6x M3 16mm countersunk screws.
Press fit the 608 bearings in the connecting rod using the vise. 2x bearings per end.
Connect the connecting rod to the crankshaft using a M8 35mm Countersunk screw. Screw -> crankshaft -> M8 washer -> Bearing x2 -> M8 washer -> M8 nut
Fit the crankshaft assembly on the motor shaft. Align the connecting rod with the saw mount. Connect the connecting rod to the saw mount using M8 80mm screw. Screw -> Bearing x2 -> Washer x2 -> Saw Mount -> M8 nut
The wiring is rather simple. Wire the fan in parallel with the motor, connect the positive of the fan to the positive of the motor, and the negative of the fan with the negative of the motor.
Connect the positive to one side of the rocker switch, and the negative to one side of the toggle switch. Connect the other side of the toggle switch to the power supply negative, and the other side of the rocker switch to the power supply positive.
Now make sure everything is tightened. Later you will need to shim some screws to make the saw square. I used M5 shim washers on the KP08 bearing blocks to adjust the angle.
For the wood, I just got whatever was available. I wouldn't go smaller than 10in x 30in x 1in.
Test fit everything on the board. You want some extra spacing so the saw can clear the vise. Measure everything in the test fit, and mark where the screws will go.
Drill pilot holes for the wood screws.
Mount the vise however is necessary. I drilled 1/2in holes and used 1/2in bolts all the way through the board.
A few years back, I saw a post in Hackaday of a 3d printed power hacksaw. Now I'm not the type of person who just prints out someone else's designs. When I have a particular set of requirements in mind it then becomes an obsession.
It wasn't until a couple of months ago that I had finally purchased a working 3d printer. My first project would be to design and build this powered hacksaw. The goals are simple: use off the shelf components with near zero modifications required, and must be strong enough to cut hardened steel.
First up, the motor. In this case, I was looking for about 30 rpm. The result of my search is a 12v 30rpm planetary gear motor from eBay. It's small but quite powerful. The price has unfortunately gone up quite a bit.
Next was the linear motion. I decided on Hiwin MGN12 linear rails with two MGN12H carriages. overkill, I know, but I had some on hand.
For the hacksaw, I wanted one that I can bolt right to it. I ended up with a Stanley high tension hacksaw.
And finally a vise. I settled on an ebay 4inch Precision Milling Vise. It's a bit extreme, but so much nicer than those cheap $15 ones.
WARNING: This project can be dangerous, I am not liable for any injury or damage, and am posting this for informational purposes only. Keep away from moving parts! The motor can easily break your fingers.
Printed Parts:
https://cad.onshape.com/documents/05d66d5106a6ff95c2615771/w/e74a73fe99c3dbe2ec590999/e/d73c038aa2918ee5e956f4c51x of each:
- Connecting Rod
- Motor Frame
- Hinge
- Crank Shaft
- Auto off screw mount
- Saw Clamp Top
- Saw Clamp Bottom
Non printed parts:
- 12v 30RPM motor - XC38PG38S (from ebay)
- Stanley 15-113 High Tension Hacksaw (possible alternative: Stanley 20-036 hacksaw)
- Vise - 4 inch Precision Milling Vise or any decent vise
- 1x 500mm Openbuilds or Misumi 2040 extrusion (need to be able to tap the end with 5mm)
- 12v 4A power supply
- 12v 40mm fan
- Panel mount toggle switch for 11-12mm diameter cutout https://www.digikey.com/short/zzvrj3
- Rocker switch for 20x13mm cutout https://www.digikey.com/short/zzvrqz
- 2x KP08 Pillow Block Bearings
- 4x 608 bearings
- Polulu 8mm hub https://www.pololu.com/product/2693
- 270mm MGN12 Linear Rail
- 2x MGN12H Carriages
- 11x M3 8mm socket cap screws
- 6x M3 12mm Countersunk screws
- 6x M3 16mm Countersunk screws
- 8x M3 20mm screws
- 8x M3 25mm socket cap screws
- 28x M3 washers
- 2x M5 10mm Button head cap screws
- 8x M5 20mm Button head cap screws
- 1x M5 30mm Button head cap screw
- 1x M5 Nut
- 2x M5 extrusion square nut
- 13x M3 extrusion square nut
- 2x M8 80mm screws
- 1x M8 35mm Countersunk (flat head) screw
- 7x M8 washers
- 3x M8 nuts
- 6x 5mm or #10 wood screws
- Bolts for mounting the vise
- various M5 shim washers or sheet metal shim material
Required tools:
- Drill
- 1/8 inch or 3.4mm drill bit
- 7/32 inch or 5.5mm drill bit
- M3x0.5 thread tap
- M5x0.8 thread tap
- Hex drives and wrenches
The build
We need to drill some holes in the frame of the saw for mounting it to the carriages. I designed a jig to do this. The trick is to not drill through the entire rectangular tube, but just one side at a time. A 1/8 or 3.4mm works great. I only drilled two holes per carriage diagonally to maintain the integrity. When you're done, take a small circular file and try to get the holes to line up.
The KP08 hinge bearings have 4mm holes but we're using 5mm screws. Drill these out with the 7/32 or 5.5mm drill bit.
On the printed parts I decided on tapping the holes instead of inserts. You need to take it slow, and back out every few turns or else the tap and PLA will heat up and fuse. Do not use a drill!
Tap the 4 holes on the top of the frame with the M5 tap, and the 4 holes for the fan with the M3 tap.
Tap the 8x saw mount holes with the M3 tap.
Tap one the end of the 2040 extrusion with the M5 tap.
Tap the M5 hole of the auto-off screw mount
Mount the motor to the frame using 4x M3 12mm countersunk screws.
Mount the fan to the frame with it blowing air towards the motor, using 4x M3 20mm screws.
press the rocker switch into the hole on the top, with the off direction facing forward.
screw the toggle switch into the hole on the rear.
Mount the KP08 pillow block bearings to the frame, don't tighten it yet.
Use a M8 80mm screw through the KP08 -> M8 washer -> Hinge Mount -> M8 washer -> KP08 -> M8 washer -> M8 nut
Mount the hinge to the extrusion. Use M5 20mm on the ends, and M5 10mm on the slots.
Mount the auto-off screw mount using 2x M3 12mm countersunk screws.
Mount the saw mount to the saw using 8x M3 25mm screws
Mount the square nuts to the linear rail using 11x M3 8mm socket head cap screws. Carefully slide the rail onto the extrusion, aligning the nuts. Leave the rail about 5mm from the end of the extrusion and tighten down the screws.
Place the MGN12H carriages on the rail, using the provided guide blocks. Use some scotch tape and wrap it around the ends of the rail to keep the carriages from falling off.
Attach the Saw frame to the carriages using 4x 20mm screws and 7x washers per screw. The order is Screw -> washer -> frame -> 6x washer -> carriage.
Mount the crankshaft to the polulu hub using 6x M3 16mm countersunk screws.
Press fit the 608 bearings in the connecting rod using the vise. 2x bearings per end.
Connect the connecting rod to the crankshaft using a M8 35mm Countersunk screw. Screw -> crankshaft -> M8 washer -> Bearing x2 -> M8 washer -> M8 nut
Fit the crankshaft assembly on the motor shaft. Align the connecting rod with the saw mount. Connect the connecting rod to the saw mount using M8 80mm screw. Screw -> Bearing x2 -> Washer x2 -> Saw Mount -> M8 nut
The wiring is rather simple. Wire the fan in parallel with the motor, connect the positive of the fan to the positive of the motor, and the negative of the fan with the negative of the motor.
Connect the positive to one side of the rocker switch, and the negative to one side of the toggle switch. Connect the other side of the toggle switch to the power supply negative, and the other side of the rocker switch to the power supply positive.
Now make sure everything is tightened. Later you will need to shim some screws to make the saw square. I used M5 shim washers on the KP08 bearing blocks to adjust the angle.
For the wood, I just got whatever was available. I wouldn't go smaller than 10in x 30in x 1in.
Test fit everything on the board. You want some extra spacing so the saw can clear the vise. Measure everything in the test fit, and mark where the screws will go.
Drill pilot holes for the wood screws.
Mount the vise however is necessary. I drilled 1/2in holes and used 1/2in bolts all the way through the board.
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