Shop Made Pneumatic Drum Sander


 
This shopmade Pneumatic Drum Sander does double duty as a handy extra table surface when not being used as a sander. Made of 1/4" steel, both the 3" angle and the 6"x6" square tube make this a stable, smooth, heavyweight sander. Castors make it easy to move around the shop. The 3/4HP 1725RPM Marathon motor drives the 1" diameter shaft via some PowerTwist link-belt. Much of the materials used in building this were found at the local junk yard for relatively little money.
Two pins are easily removed allowing you to lift off the plywood table top surface (seen in background, reinforced with steel angle). With the top removed you have a heavy duty pneumatic drum sander that's whisper quiet and smoother than any machine in my workshop.

Like so many of my projects at home, this machine is only 95% complete. Not yet finished is the motor cover, pulley cover and dust collection hood. I actually have a dust hood but it looks so bad I removed it for the pictures.

   
 
This type of sander uses a pnuematic drum, either 3" or 6" in diameter and 9" long. Here you can see the 3"x9" drum. The drum is not solid, but is innertube-like, with a air valve at one end that allows you to inflate the drum to the required pressure. It can be adjusted to be very hard or very soft and flexible. This type sander is often used when sanding things like canoe paddles and boomerangs, but I've discovered it's great for all sorts of sanding requirements. After rounding ober the edges of wood with my router, I usually use this sander to sander the newly rounded edge. I've used it on most of my projects and I surprised how much I actually use it. It's the most used sander in my shop.

On the right side of the shaft, I've mounted a few cotton buffing wheels. I haven't used them yet.


 

I decided to make this sander after seeing two similar machines, one made by Ritter and the other by Sand-Rite, that sold for over $800. This cost me less than $200 to build.

Sources for parts
Local Junk Yard 
3/4HP 1725RMP Marathon motor ($15)
Salvaged 1/4" steel angle
Salvaged 1/4" steel tube 6"x6"x32"

McMaster-Carr
One 24" x 1" diameter machined steel shaft ($20) (part#6061K55)
Two flange-mount bearings ($24/pair) (part#5913K54)
Four shaft collars ($1/each) (part#6432K25)
Two pulleys ($12/pair)

Lowes
Saftey-pin power switch ($6) asme as many Delta benchtop machines use
Four 2.5" castors
Three 6" cottom buffing wheels ($5/each)
Grade-8 bolts
14-3 SJOW wire and plug

Highland Hardware
One Delta 3"x9" pneumatic sanding drum ($50)
PowerFlex link-belt ($25)

Klingspor Sanding
Various 3"x9" sanding drum sleeves

 

 
Building hints
Building this was relatively easy, but here are a few points:

Using a 2" hole saw in my Milwaukee drill, I cut two holes in the top end of the square steel tube, about 3" from the top edge.  This hole is to allow the back side of the flange mount bearings to sit into the tube and let the flange sit flush on the steel.  Since these type of bearing are self aligning, the two holes don't have to be alginged perfectly, but I was able to get them within 1/64" of each other.

Using a 1/2" drill bit I drilled two holes in one side about 5" from the bottom edge.  Using a metal cutoff wheel on my 4-1/2" grinder, I cut three lines.  Two vertically from the bottom edge of the tube up to each of the holes and another horizonally between the two holes.  This produced a square cutout in the tube along the bottom which allowed me to easily mount the motor with the shaft and pulley inside the tube.

The rest was pretty much simply drilling a few screws here and there to mount the tube on the bottm pieces of angle, and attached the castors and motor.

The only trick to all this is securing the drum to the shaft.   The price of a machined shaft that had threaded ends, either internal or external to the shaft, was $80 compared to a plain shaft at $20.   So I went with the plain shaft and shaft collars.  The way to get shaft collars to grip the drum tightly so the drum doesn't slip when the shaft turns wasn't hard once I figured it out.  What I did was mark the spot on the shaft where the set screw of the collar would touch the shaft.  Then using a file and my Dremel, I filed out two notches, tapering inwards toward where the drum would be.  So when I slide on the drum, I place the collars are tight as I could to the drum. But then when I tighted down the collar set screw, the screw hit the tapered cutout and shifted the collar towards the drum as I tightened. This held the drum on the shaft as tightly as if the shaft had a thread and I used a large bolt.
 
 

(diagram to come)

© 2008 Mark Goodall