I always found myself needing a bench mounted disc of belt sander for rounding edges of wood mainly when building wooden toys for my son. Being a tight ass meant that shelling out NZ$180 for a unit like the one in the photo was not an option especially since i could get a bottom end angle grinder for only NZ$15 + a snading disc attachment for $NZ8
Mount it to a box, add a solid work surface and TADA a 10000rpm wood destroyer..!!
Step 1: Find a Suitable Box
First find or make a wooden box - at least one side and the top must be pretty square to each other. I used an old nail box.
Step 2: Procure Cheap Angle Grinder
Buy the cheapest angle grinder you can find, this one cost me $NZ15 for 10,000rpm and a 12 month warranty. 100mm is the smallest available but you could get bigger.
Also get a disc sanding attachment, either the sticky back type or the velcro type will work.
Discard the angle grinder handle and safety guard, then attach the sanding disc to the spindle.
Step 3: Mount the Grinder to the Box - Cut Slot
Mounting the angle grinder and cutting the top slot was actually a series of steps but they all happened at once to get the arrangement right so i will document them all here.
I first positioned the grinder with the centreline of the spindle about 30mm from the top of the box. This meant having it on an angle.
Next i screwed the 2 square pieces of timber as shown to the side of the box to locate the grinder.
Then i drilled a series of holes on each side of the grinder body and used 6mm cable ties to secure it down. Cable tie ends are inside the box.
I didnt really trust the cable ties at first so i decided to make a steel bracket to fix the existing handle mount hole to the wooden block - as shown in the second photo. This may actually be overkill but hey it is going at 10,000rpm.
Cutting the slot in the top of the box was actually done before the sanding disc was attached - just make sure it is big enough to allow at least 10mm clearance around the disc - you dont want it touching anything.
Step 4: Attach a Solid Work Surface
You need a solid piece of wood for the work surface, make sure one edge is straight and square (not chamfered at the top)
Position the square edge about 1mm away from the angle grinder disc face.
I could have just nailed it down but that would make changing the grinder discs impossible without removing the grinder.
My solution to this was to hinge the work surface and hold it down with a sliding bolt latch - the photos show the installation pretty well. Main thing to note is that the wood doesnt touch the sanding disc but is as close as practical to the disc.
Step 5: Add a Base and Fire It Up!
If you box doesnt have a base like mine didnt, add one since it will help keep all the sanding dust inside.
Also add another cable tie to hold the power cord if required, it will depend on your grinder orientation.
Now plug it it and sand some wood....
I dont know how powerful proper disc sanders are but this one howls..!
Ii is best to use the side of the disc that is travelling downwards to sand with as the dust goes into the box, if you use the other side it goes up into the air....
A safety guard could be added if required also.