Diameters of commonly used drum sanders?

[Bob Hammond]

Hi, finally, I think I'll have some time to build a new drum sander, about 20" wide so that it's possible to sand cross-grain as well as with the grain. I would like to use pre-cut belts, and so I'd like to know (as exactly as possible) the diameter of the drums from different manufacturers. Hmm, I wonder if it would be cost-effective to buy a replacement drum and bearings from a manufacturer. Can anybody provide information?

I have scavenged a 2HP DC motor with variable speed up to 5000 rpm from a treadmill. I'm thinking about putting on a strobe tachometer something like this:

http://www.homemadetools.net/forum/stro ... 9#post6323

https://www.youtube.com/watch?v=-SefCxuU9-Q

[Murray MacLeod]

By "pre-cut belts" do you mean belts that are already glued up like the belts you get for 4" and 6" belt sanders ?

I am not aware that any manufacturer makes these in a size suitable for a drum sander ...and even if they did, and even if you could actually get the belt to fit snugly, how would you hold the belt in position without a really complicated collar system at each end?

Spiral loading is the answer IMO ...

[Bob Hammond]

Murray, thanks - Yes, I mean the spirally wound belts.

I guess that it's just a matter of trigonometry & geometry to figure out the length and leading angle for given drum length and diameter if I wanted to cut them to fit. But I was wondering if the backing cloth of the belts for commercial units is somehow special, e.g., less or more stretch.

[Clay Schaeffer]

It seems like most people eventually buy the 50 yd rolls and cut their belts to length using an old belt as a template. It's cheaper that way.

[Charlie Schultz]

The Jet 16-32 has a 5" diameter drum. The Grizzly dual drum sander has 6" diameter drums.

[Chuck Tweedy]

You mean people actually buy the pre-cut belts? I thought Jet only provided them as templates!!
Seriously, it is super-easy to cut your own from 3" wide belt material. Takes like a minute.

[Arnt Rian]

I built my drum sander with a 700mm/150mm drum (28" x 6" diameter). I don't know how big you could make it before it gets problematic for other reasons, but I figure bigger is better, as it will help to keep the paper cool, to avoid clogging etc. I use 4" wide Klingspor hook and loop paper, even though I don't have the "loop" part on my drum, the thick backing on the paper provides some 'cushioning', which also seems to help against clogging. I cut my own from large rolls, its much more economical.

[Clay Schaeffer]

To find the angle to cut the ends and approximate length of the belt required I would spirally wrap a string around the drum spacing it the same distance apart as the belt is wide. Then I would cut the belt about a foot longer and trim to fit.

[Mario Proulx]

It's dead-simple to roll your own. Way more economical, and you likely will find better quality abrasives, too.

A 2" or 3" wide belt will work fine. For the first one, tape one end of the strip to the drum, and begin wrapping it to about halfway along the drum. Work it until it lays flat and tight on the drum. Grab a Sharpie and a sheet of printer paper; wrap the paper around the end of the drum, making sure the sheet wraps around perfectly(IE: the edges line up), then mark the abrasive strip with the Sharpie. Now release the tape and cut the abrasive(I use a pair of dedicated tin snips for this) along the marked line. There's your angle! Now, scoot the abrasive strip to the end of the drum, and tape it in place, wrap the strip around the full length of the drum, and repeat the paper/Sharpie deal at the other end, cut the strip, and double-check to be sure the fit is right. Once you like the fit, remove the strip, and keep it as your "master" template, or if you have a wooden floor as I do, lay it down on the floor, tack one end down, and with a large permanent marker, or even with paint, mark the floor with the angle of the strip, slightly longer than the strip actually is, then go to the other end, pull the strip tight, and repeat the marks. That's it; you now have a permanent template, right there on the floor.

[Bob Hammond]

I guess that I asked the last, and maybe easiest, question first

But it's not a bad thing to think a project through and ask questions first, as far as possible before getting out the tools.

[Chuck Tweedy]

The angel to cut on the sandpaper will be:

angle = atan(w/(pi*D))

where:
w - the width of the sanding belt
D - The diameter of the drum

E.g. Jet:
D = 5in
w = 3in
angle = 10.8 degrees

And sure enough that is what my belt is cut to.

[Bob Hammond]

Thanks Chuck. I copied the math and made a corresponding sketch. I've decided to keep a journal of sorts- nothing fancy- in case I need to lay the project aside for a week or a month, so that I'll be reminded of what will have been done and what will need to be done.

I was just reading about another guy's troubles with the complicated elevation mechanism of a commercially manufactured sander, and I've looked at other machines too. It seems that I might be ambitious to build a 20" machine from stuff that I can buy locally. Maybe it won't produce material at a rate for day in/day out production work with high precision. But I don't expect to do that. What I have in mind, is to make a machine that produces material that I can refine by handwork in a reasonable amount of time. The operative word here is 'reasonable' -- i.e. what's reasonable for me.

[Warren May]

Many of us have built very reliable drum sanders from locally available parts so it isn't clear what concerns you would have about going forward. I've built 3 iterations, improving each time, and used the same 22"x5" drum with 3/4" pillow blocks, 3/4" steel shaft and a 1 HP 1750 rpm motor. If you get the table and drum well built and stable, it is surprisingly precise. Covering it with formica is cheap enough and makes a decent surface for hand feeding. I think part of that precision is based on sanding the drum to match the table by spinning the drum while passing sandpaper on the table. Also, you can choose your paper mounting system which you can't on commercial models. On the last one (which I had to disassemble due to smaller space when we moved), I used a simpler elevation system that was roughly based on a scissors jack but with supports on both sides of the table. Worked a lot better than the first which was a simple single screw mechanism. I bought a small 10"/20" Grizzly and like it okay but it doesn't give results any more precise than the homemade ones did and isn't great for anything over 10". It is nice, however, to have a powered feed table which I didn't have for the other 2 shop built ones. Changing paper, however, is like wrestling with a Grizzly bear

[David King]

I'd add that the fewer wraps you use (i.e. wider paper) the less it will be affected by stretching. All the papers and cloths stretch especially as heat builds up. It's only a problem when the edges start to overlap at the far end of the drum. That can be a big problem if you are sanding thin maple sides and the DOC doubles or triples at the overlapped edge.

[Bob Hammond]

I've decided to stay with the design for the elevation mechanism that I posted a long time ago (~2004?, it's in the library). It was set up on my lathe and it worked reliably. But I do plan to change the materials for the drum, due to issues of heat build-up and maintaining a cylindrical profile.

A guy down the street gave me a 24" length of 4"D aluminum pipe that might be a good start for the drum.

[Bob Francis]

Will you place disks inside the tube as well as at the ends?

[Bob Hammond]

Yes, I'll turn discs and bore the holes on the lathe to make a tight fit.

[David King]

Have you checked the pipe for roundness? It'd be handy if you could skim it on the lathe once you get it mounted and centered.

[Bob Hammond]

David, that's a good question that I've been pondering.

My lathe is a Delta MIdi woodworking lathe, and I think the slowest speed is 500 rpm. I haven't looked it up yet, but I believe that for a 4" diameter, that would be too fast for truing it up. Perhaps I can find a friend with a metalworking lathe. Another remedy that might see weird at first, is something that I did with an MDF cylinder when it warped a bit. I slathered it with autobody filler, let it cure, and then resurfaced it. I wonder if that would work for the aluminum pipe too.

[Bob Gramann]

When I was still using my home built sander, I used to true the drum by gluing sandpaper to a flat piece of MDF and pushing it through the running sander against the bare drum. You can hear when it gets round. Pencil marks on the drum tell you when you've got it all.