The Shop > Wood & Stuff
Drum/ Thickness Sander
Lew_Merrick_PE:
S. Heslop -- I have made several variations on drum-type thickness sanders over the years on support of my original trade training as a luthier (lute and guitar maker). The design that I find most useful is to use a piece of thick-wall tubing as the drum and then to spiral wrap (1-1/2 inch or 40 mm) wide strip abrasive media to the drum. DOM (Drawn Over Mandrel) tubing typically only varies a couple of thousandth's of an inch (call it 0.05 mm) from perfectly cylindrical in lengths up to 20 inches (500 mm) (and your abrasive media will vary more than that), so the only real challenge is getting the tubing mounted on a shaft. Personally, I make a press-fit plug that has a shoulder to fit the tube that I attache with (strong) set-screws.
I do not have access to my current beast (it is in storage due to a lack of space), but I built it back in the 1990's. The thickness adjustment is a pivoted piece of laminated (good cabinet quality) plywood that is faced with UHMW polyethylene. A high-tack conveyor belt drives the piece through the sander. The run surface of the belt is 40 inches (basically 1 m) to support infeed and outfeed of guitar ribs. I can hold a bit better than +/-.010 inches (+/-0.25 mm) using this set-up.
S. Heslop:
--- Quote from: Lew_Merrick_PE on January 14, 2015, 11:19:55 AM ---S. Heslop -- I have made several variations on drum-type thickness sanders over the years on support of my original trade training as a luthier (lute and guitar maker). The design that I find most useful is to use a piece of thick-wall tubing as the drum and then to spiral wrap (1-1/2 inch or 40 mm) wide strip abrasive media to the drum. DOM (Drawn Over Mandrel) tubing typically only varies a couple of thousandth's of an inch (call it 0.05 mm) from perfectly cylindrical in lengths up to 20 inches (500 mm) (and your abrasive media will vary more than that), so the only real challenge is getting the tubing mounted on a shaft. Personally, I make a press-fit plug that has a shoulder to fit the tube that I attache with (strong) set-screws.
I do not have access to my current beast (it is in storage due to a lack of space), but I built it back in the 1990's. The thickness adjustment is a pivoted piece of laminated (good cabinet quality) plywood that is faced with UHMW polyethylene. A high-tack conveyor belt drives the piece through the sander. The run surface of the belt is 40 inches (basically 1 m) to support infeed and outfeed of guitar ribs. I can hold a bit better than +/-.010 inches (+/-0.25 mm) using this set-up.
--- End quote ---
Shame you don't have access to the sander, i'd like to see it!
For the drum I was going to try making a stack of MDF disks and turning them round. Unfortunately I don't have a lathe big enough to try the pipe method, but i'll keep it in mind in case the MDF doesn't work out. I think the biggest risk with MDF is the stuff changing dimensions over time as it absorbs/ loses moisture.
How did you attach the sandpaper to the drum though? I was thinking about going with velcro since i've seen other people use that, but i'm still skeptical about if it'd hold or not (on the edges at least). The other method i've seen is to physically hold it at both ends with a sort of clamp/ screw and making the cutout in the drum for that might be easy with the MDF disks.
S. Heslop:
Ran into a problem already. Got the MDF stacks for the rollers glued up, and started turning them true with this setup.
The problem is that it's producing an undulated surface where the looser MDF in the middle... fluffs out.
Still not sure on the solution. I'm thinking I could turn them down further and slip/ glue on a piece of PVC pipe and then turn that to size, or I could dilute down some varnish and try soak it into the MDF to harden it so it turns better. I've already messed with the cutting tool (chisel) geometry and angle a bit, and it didn't seem to make a difference. Nor did sanding it.
Oh one thing I don't think I mentioned is that i'm trying to build this without using the lathe at all, for the sake of the video. I'm also not going to use the pipe and end caps idea for these rollers since I want to try turning in a slight crown to see if it helps with tracking the conveyor belt.
chipenter:
Sand it with a solid flat block then seal it .
awemawson:
Make up a 50 / 50 pva glue / water solution and saturate it. Leave over night to dry then try turning it again, or possibly block sanding it
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