Introduction: One Hour Bench Grinder to Belt Sander Build
My name is Tuomas, and this is my "One hour bench grinder to belt sander build".
I bought a small bench grinder from a yard sale with 20$.
I decided to turn it to a small finishing station with fine grade belt and some sanding and polishing options.
Nice thing was, that it was actually very easy task, and didn't take much time at all.
Here is a video from the very simple building process.
Later on this instructable i will show some simple things how-to improve it.
Its obvious that its possible that your grinder is little different, but this should still give some ideas / solutions for your own build too.
10mm x 30mm flat bar. 3mm steel plate or piece of angle iron or square tubing.
I used two 32mm x 12mm x 12mm (internal hole ) bearings for the front wheel.
35mm x 1.5mm pipe ( wall thickness 1.5mm, gives internal diameter 32mm, then it fits to grinders 32mm shaft)
Screws and nuts.
Step 1: Making the Pulley and Front Wheel.
This couldn't be more simplier than this.
I used 30mm wide belt.
So, i just cut 31mm long piece from the 35m x 1.5mm ( wall thickness ) pipe.
Pipe is placed on top of the grinders 32mm shaft, and secured on its place using original support plate and nut from the grinder itself.
Cutting is done with angle grinder using 1mm thick 3M cubitron cut off wheel.
Thin cut off wheel cuts fast and more accurately and also heats workpiece less than thicker ones.
That's why i rather use them with little thicker materials too. Al cuts on this instructable is made using that same cut off wheel.
To mark right lenght to the pipe, i stacked 31mm high pile of flat bars to my worktable.
Then, keeping scribe on top of the pile, i turned pipe around pushing its side against the scribe.
Make cut next to the line, its much easier to get straight and accurate result. ( remember to cut on the right side of the line )
When trying to cut on top of the line, it easily happens that cut goes little bit side to side, because you can't actually see clearly where center of the cut off wheel is.
That's why it is very difficult to try to keep center of the cut of wheel on the middle of the marked line. (make sense?)
Easier solution for the front wheel is just to use bearings, without making the casing.
In my case. Bearings that i had, we'rent very good sized for that.
Two would have been too narrow, three too wide.
I made casing for the bearings from that same pipe that i used to make pulley.
( 35mm outer x 1.5mm wall )
My 32mm x 12mm x 12mm bearings fitted perfectly inside it.
I marked and cut two 31mm long pieces from the 35mm x 1.5mm pipe.
One for the pulley and one for the front wheel.
After cutting i filed cut ends clean with file.
To lock bearings inside the pipe i hammered "dimples" around the bearing.
My bearings we're 12mm wide.
That's why, i measured two lines around the pipe. To 15mm distance from one to another, i left about 3mm interval to the edge of the pipe.
Then, placed bearing inside the pipe, leaving 4mm distance from the pipe edge.
Clamped pipe firmly between the jaws of the vise.
Then i started to hammer dimples to both sides of the bearing using center punch.
Following the marked lines, i made dimples around the pipe, leaving 10mm interval to previous dimple.
( When you hit dimple on the surface, it makes dimple to the backside too. These dimples keeps bearing on its position )
I made first shallow dimples, then i re-punched them deeper, until bearing was firmly on its place.
In this case, only outer bearing needed to be fastened. Internal one leans against the washer that leans against the "arm"
Front wheel is fastened to arm with M12 bolt, washers are placed both sides of the bearings.
If you have any experience about metal working, this stage shouldn't take more than 15 minutes.
If you are interested to take a look, i used that same way when i made my " Big power file".
In that case i "locked" bearings from the both sides of the wheel.
Step 2: Making the Arm
I made the "arm" from 30mm x 10mm flat bar.
Arm replaces work piece rest on the grinder. Its mounted to same slot where rest originally was.
Because slot was 25mm wide, i had to cut 5mm away from the arm.
Marked the placement and cut piece out with angle grinder.
After cutting i rounded the edges that goes against the slot, to get firm fit. Finally cut it to right lenght.
This stage takes about 5 - 10 minutes. Depending from the experience of the maker.
After cutting i marked the mounting holes. Remember make sure that arm can move on the slot before drilling holes.
On my grinder, work piece rest was mounted with M6 bolts. I made 5.2mm holes to the arm, and threaded them with M6 tap.
For the front wheel i made 10.2 mm hole, and threaded it with M12 tap.
With drill press, this stage shouldn't take more than 5 - 10 minutes.
Step 3: Making the Backing Plate
Backing plate is easier to make from the angle iron, it can be made cut from square tube too.
I made mine from 3mm plate.
Cut it to size with angle grinder, and made 90 degree bend to it with my diy bench top press.
Then i drilled 5mm holes to it. ( i used M5 screws for mounting ) Placed holes symmetrically to the back plate.
Marked its location to the arm, using belt as a guide. And then drilled 4.2mm holes to the arm, finally threaded with M5 tap.
This simple stage takes about 10 - 15 minutes, depending the tools and materials used.
Step 4: Finished One Hour Build
Now your one hour build is ready.
Lets start the assembly.
- Mount arm to the grinder, leave bolts loose.
- Mount the front wheel. Use suitable washers to adjust its distance from the arm.
- Install the belt, and thighten pulley. ( Using grinders original support plate and nut )
- Tension the belt by pushing it with suitable tool from the head of the first mounting bolt.
Then tighten second bolt, and after that, tighten the first.
- Make sure that the arm is on the right line with the grinder and belt runs straight. Straighten it if necessary by
pending the arm / work piece rest to the right direction until belt runs straight.
Now you are ready to sand.
Note: You don't necessarily need to use threaded holes for mounting. You can bolt the arm and front wheel trough too. I just liked that threaded holes are little easier on use, and possibly gives neater result too.
Next steps are about improvements, every build can be improved and modified.
Step 5: Improvement / Modification 1 : Making Wider Pulley.
I made my sander for to be used with 1 1/2" wide belts.
But you can easily turn yours to use wider ones, if you like to.
Simple solution is to use extension nut.
Grinder uses M14 thread. So, solution is to use extension nut, and screw it to the grinder.
Suitable length threaded rod, is fastened to extension nut, side plate, or angle grinder backing plate is fastened to the threaded rod. Very simple.
125mm and 180mm angle grinders also uses M14 thread.
That allows to use different backings from angle grinder to fasten the pulley.
This gives many extra options for the use:
- You can use Rolock sanding and polishing abrasives, scotch brite.. etc.
- Velcro / hookit / "sticky" sanding papers..
There is loads of options. You don't need to settle to, just "disc sander" attachment.
Because "neck" of the angle grinder backings are nearly always cone shaped. It keeps pulley leveled with the shaft and supports pulley from the inside.
Changing the backing is fast, just unscrew it and replace.
You don't necessarily need to use angle grinder backings.
Fasten the pulley using original support plate and screw from the bench grinder.
Note: Grinder runs to the way that tightens backing or nut..
But, when you turn it off, it is possible that those get loose, if not tightened enough.
Step 6: Improvement / Modification 2: Increasing Pulley Diameter and Belt Speed.
First picture shows the simple solution, if you happen to found suitable pipe that fits around the smaller pulley.
I found a piece of 35mm (inner dia ) 50 (outer dia ) pipe. I pressed original pulley inside it with my diy bench top press.
But, luckily there is a solution for the ones that doesn't be able to found suitable pipe.
Solution is to use 35mm and 50mm ( or greater ) hole saw's.
1. Choose the material for the wheel, ( plywood, plastic - i personally like to use old plastic chopping boards )
2. Place a piece of wood under the wheel material.
3. Clamp both pieces firmly to the drill.
4. Make first hole with the smaller hole saw. ( Keep parts clamped all the time)
5. Make hole with the bigger hole saw. Plywood piece under the pulley material, centers bigger hole saw with the smaller hole.
6. Make enough "doughnuts" and glue them with epoxy on top of the pulley pipe.
I think its somewhat important to use that pipe piece inside the bigger pulley, it keeps pulley on the same level with the grinder shaft. And, bonus is that when its hollow, you can use those angle grinder backings!
Step 7: Improvement / Modification 3: Making Belt Tensioner.
Another improvement is to add belt tensioner.
This short video shows how it works in use:
1. Picture shows the materials that i used: 3mm x 20mm flat bar. 80mm and 50mm long pieces.
2. I used my "Simple vise modification" to bend the longer piece.
3. I made a bend to 30mm distance from the end to the first side.
4. And then another bend to 15mm from it to the other side.
Bends are easier to make if you first bend both sides just a little, then increase the angle of the both bends until cap is big enough that "arm" of the grinder fits inside the bends.
Then bolt longer and shorter bars tightly together, You can use same bolt for mounting the tension wheel.
I used three bearings and M5 screw as a tensioning wheel.
Finally: Measure placements for the mounting holes, and optional spring.
About the spring: You might notice that spring is not for tensioning the belt.
Its for keeping tensioning wheel on the same level with the pulley and front wheel.
It pulls tensioner from the other side and same time it lifts the outer end of the tensioning wheel and tracks belt to run on the middle.
Because tensioner is bolted to the arm, bolt is left little loose, so it can move "open and closed". Bolt is locked with locking washer. That leaves little clap to the tensioner, spring removes that clap.
Step 8: Final Toughts and Hints..
First, choose the belt that you want to use.
Then make the pulley and front wheel.
Use belt, and wheels to find right lenght of the arm.
If you want to use backing plate with the tensioner.
Note that you need to place tensioner to the opposite side than backing plate, to be able to loosen the belt.
Tensioner can be placed both ways, to the up or down side of the arm.
I placed mine to "up", and back plate to the down side, because i also wanted to mount bigger wet stone to my bench grinder.
And to be able to do that, i tilted the whole grinder 90 degrees.
This also allows me to use both sides of the belt.
More from the "bigger wet stone"- modification comes later.
Thanks for watching!
Here is a video about making another kind of diy belt sander hack, if you happen to be interested about the subject:
Participated in the
1 Hour Challenge