Saturday, June 25, 2016

2x72 belt grinder

UPDATE: I've since upgraded the tool rest system, and was really happy about the upgrade.

I have at least 4 grinder/sander on my bench: disk sander, belt sander, strip sander, bench grinder and spindle sander. While each of them do a specific task, they do over lap a lot. With more and more toy in the shop, I need to find a machine that can replace the many sanders/grinders.

I've been eye on the 2x72 belt grinder for a while now. The design is pretty simple but brilliant, easy to build, sturdy, easy to change the belt and very flexible. With the proper belt, you can sand/grind almost anything.

Most commercially available belt grinders are very expensive, with a VFD, you are looking at an about 3K machine. But really it's easy and cheap to build. I also considered John Heisz's design, I think the build should be solid with wood. But since I bought a TIG welder not long ago, I want to make it out of metal for practice.

I don't have a solid plan before I start, but I know what I want:
  • the chassis should be make from metal tubing
  • the tool rest and wheel/platen arm should also made from metal tubing
  • tool rest and wheel/platen arm should be independent.
  • the tool can be setup in vertical and horizontal positions.
  • VFD is a must, but I don't need very powerful motor

So I started by making MDF wheels, it's an weird order, but I figure once I have the wheel to the right size, I can visualize the machine and figure out the dimension that way. The wheels are made from 3 layers of MDF, I bandsaw-ed then sand to line, then once the machine is done, trued them in place with lathe tool and sanding block. I HATE the dust when sanding MDF. I'm not too worried about the longevity of the wheels, they are not contacting the abrasive side of the belt and I'll apply couple coats of poly on them. And the wheel of my bandsaw held pretty well over the time, I don't see why this won't work for belt grinder. The worst case, I wasted couple hours and need to buy some comercial wheels, no big deal. The wheels all have 1*1/2 bearings. when I later mount the wheels, I didn't use nuts to pinch the two bearings, bearing doesn't like side pressure. I used nylon lock nuts to keep the wheel in place instead, it worked well.

Once I have the rough cut wheel, I lay them out on the table and figure out the dimension of each tubing.

To cut the tubing, I used the table stand for the hand held metal bandsaw, it is one of the best investments I've ever made. Once you have the hand held bandsaw setup as a vertical bandsaw, you have much more control.

Once the tubings are cut, I welded them. To mount the motor, I use a 4x3 angle iron, before weld it on, I drilled and tapped the hole for mounting the motor. The motor is a 3/4 HP 3 PH with 110V VFD, plenty of power for me.

To make it able to tile it to horizontal position, I also made some hole for a pivot point and locking pin. I used some plywood to make the base, figure it can absorb some of the vibration, and save on some construction cost, if they do break down, I can then make a metal base.

With the chassis done, it's time to make wheel attachment. I first made the most common one, a platen. The wheel arm is made from a 3/8 steel plate, I draw with sharpie and cut it on the bandsaw. The tight corners are drilled out with a 1/2 bit first. To clean up the surface, I use ROS, it gives it a lovely mat finish.

With the platen done, I was able to run the machine for the first time, although the wheels are not trued up yet. Oh I forgot to mention that I drilled and tapped 1/4 hole on the corner of the chassis tubing to clamp on the wheel arm tubing. With the pressure at 45 degree, any play between the tubing will not matter anymore, since they will always be pushing to one corner.

Setting the belt grinder to a horizontal position is easy, just unlock two pin, and tilt the machine and push the pins in.

Next is the tool rest (see my new tool rest system), I want the tool rest be able to tile, like the table on disc sander. I used a piece of angle iron as the support piece, drilled series of holes and filed the slot, then welde the piece to a flat 1/4 steel plate. I think I used too much heat and filler when doing the welding, the steel plate was bowled after the weld, I then need to grind it flat again, the good news is that now I have a working belt grinder that makes the job much easier.

The belt grinder is finished! I'm very happy with it. All in all, it cost me about $450 dollars ($350 motor + VFD, $100 metal parts, bearing and hardware)

Tape holder

Emma loves doing crafts, and tape if a tool she use a lot. I always want to make a cute tape holder for her. I prototyped with some ...