Thread: Balancing and truing Drum for Drum Sander

Originally Posted by Stetwood

Question # 1 is the shaft heavy enough to prevent flexing on a 900+mm length?

Yes, don't forget that when the individual circles of ply, etc. are glued together it becomes one solid drum and the bits of the shaft that matter are the end bits which should only be 100mm at the most before being clamped in the bearing blocks.

Originally Posted by Stetwood

Question # 2 using these materials and methodology with how much certainty can I be that the drum will be balanced?

You can be certain that the drum is perfectly round and fitted to your sanding table. That is all that is required.

The drum may not necessarily be balanced, but unlike car wheels they don't need to be balanced. However, if you wish to balance the drum, after final sanding, spin the drum by hand a number of times and note where it stops.

If it stops at the same spot all the time add weight on the opposite side of the drum, and repeat untill finally balanced. Usually screwing on some washers on the ends of the drum is all that is needed.

Originally Posted by Stetwood

Question # 3 what RPM of the drum are most shopbuilt drums being used at?

Not sure, because it is decided by the motor and the size pulleys used. I tried working it out but forgotton what I worked out.


I posted a detailed thread on how I built mine, a search may be helpful.


Peter.

I balanced mine by injecting space invader foam into it and letting it run for a while, it took the wobble out of it.

Al

Al, he is building a solid drum, yours was a hollow one if I remember correctly.


Peter.

Originally Posted by Sturdee

Al, he is building a solid drum, yours was a hollow one if I remember correctly.


Peter.

Arhhh, yes you are correct Peter.
I made mine from Crapiator staves.

Al

To Sturdee & Ozwinner:

I read both of your methods of making a drum sander, and both are classics. I am also following goldenearing. ( but he hasn't posted in a while)

I posted a similar question on another site and one response was that I would need a 32 mm shaft.(http://www.cnczone.com/forums/showthread.php?p=295223#post295223). But he made his from thick wall PVC. I had thought that if the epoxy and glue up job was first rate the smaller shaft would be good. I changed my plans by adding another brace, bringing the pillow blocks in from 100 mm to 15 or so.

I know everyone is interested in seeing the finished product, but I could post the plans I drew up.

I am sure that yr homemade ones are a lot better than my $800+ orange one. As for balance... it started having an odd vibrate and rattle a couple of weeks ago and on investigation I found a bit of old chinese lead type-set (would have been used to print newspapers before computers) loose on the inside of the drum. So I found where it had been glued in and set it back in place with five minute epoxy and its going fine, sortof.

Well mine isn't built yet, but if it doesn't work there will be nobody to blame and certainly very little warranty on it.

Forget putting sandpaper on the table and using that to true up the drum, doesn't work very well. Instead make a sled, I just used a piece of melamine coated mdf with some 80 grit stuck to it. Bung a handle on it so you can move it back and forth under the drum. Works like a charm as long as both faces of your sled are parallel. I use mine to thickness guitar tops, backs and sides, I run the digital calipers around the edge of the workpiece and I'd be lucky to find a difference of half a thou, so the sled is a pretty accurate and fast way of truing up the drum.

As to rpm, don't worry about it. It'll depend on the diameter of your drum. Instead, think of feet per minute (or meters per minute). Most of the commercial thickness sanders are rated in feet of sandpaper per minute. The specs for these are usually quoted on maker's websites. From memory (it's been years since I made mine) about 2800 - 3300 feet per minute seems to be pretty standard. So find out how many feet per minute you need, see what rpm your motor runs at, and get pullies to match. It might be cheaper to get the motor and pullies first, then you can adjust the diameter of your drum to get the feet/minute you're after. Otherwise you'll find yourself searching for the right sized pullies to match your drum size, and may have to get them made, which will cost a motza. CBC Bearings sold me off the shelf pullies pretty cheap, even machined one out for me to match the shaft diameter.

Then it'll be time to seriously think about dust collection

Originally Posted by Paul B

I just used a piece of melamine coated mdf with some 80 grit stuck to it. Bung a handle on it so you can move it back and forth under the drum. Works like a charm as long as both faces of your sled are parallel. I use mine to thickness guitar tops, backs and sides, I run the digital calipers around the edge of the workpiece and I'd be lucky to find a difference of half a thou, so the sled is a pretty accurate and fast way of truing up the drum.

have you got a pic of ur body sanding setup
pretty keen to see how you do it
tnx

Sorry mate, my digital camera has had the richard. Gotta go buy another one at some point.

An update on the Drum sander I built using a newsprint roll core as the drum. It is now almost seven months since I started using this drum. I run it at least seven hours per week and find that it is still in as good condition as when I started. On speaking with staff from the local rag they advise that the core is perfectly straight and round as it carries a couple of tons of paper when new and would shake the place apart if it wasn't. I can highly reccomend this as a very simple drum to get and use.