Drum sander burning wood

I have a new Jet 18/36 belt sander. Removing .3 mm using 80 grit paper works well, but as expected, the finish is a bit rough.

Today I tried using 180 grit for the first time. The job is a biggie. About 500 mm by a meter so it uses the whole width of the drum. I changed the paper from 80 to 180 and lowered the drum by .2 mm. By the second pass, it was leaving substantial burn marks on the wood. The result after three passes can in the picture below.
Attachment 434826

According to the destruction manual burning is likely caused by a couple of factors. The first is the job is traveling to slowly past the drum. That was a likely cause. When using the sander with 80 grit and removing .3 mm, I had to reduce the speed from a max of 10 down to 4. So, I put a new length of abrasive onto the drum, lowered the drum by .2 mm and cranked the speed up to 10. After two passes it was starting to burn again. See the next picture.
Attachment 434827

The abrasive is Vitex from The Sandpaperman. What gives? Any ideas please?

What wood are you using?

I have had the same experience at the local Wood Workers Club, with Red Gum, and had to increase the feed speed and pass the timber through several times at the same height setting to get rid of the burn marks.

This is a common problem with drum sanders. Particularly when sanding using the full width of the sander. The probable causes you have mentioned are valid, but there is a need to add one other - dust extraction. A wide board requires better extraction than a narrow one. If you are only using a 1hp extractor with a small hose fitting you are going to have trouble. This is not to say it can not
be done, it just means a much shallower cut each pass.
By the way, an old thong (foot wear) makes a good paper cleaner.

Oh, I forgot to add - Make sure you clean the burn off the paper before you continue. If the burn mark is left, it will burn even worse next pass.

Reducing your removal per pass may help.
I remove 0.05 to 0.1 per pass on my drum sander, and i clean paper regularly.
Any burns are removed from paper before continuing.

Even with good dust extraction (and this is probably the limiting factor), when sanding wider boards on a JET 16-32 with papers finer than 120 grit I'd flip up the cover and clean the paper on the drum with the rubber block thingy just about every pass. It's rare to get more than a couple of passes (even at fast feed) without the paper clogging and burning the timber.

If you don't have the rubber block, a length of scrap white PVC pipe works well too.

Thanks for all the comments. They make a load of sense. :2tsup: I will do as suggested.

I had the same problem and found that best results are achieved when removing between .05 and .15mm per pass (dependant in board with).

Of all the WW machines I own the drum sander took me the longest to learn!

Just a thought.....if JET's 'SandSmart' technology works as advertised, surely you should be able to just set the belt speed at maximum and leave it at that? If the resulting load on the motor is too high (when taking off more material), SandSmart should drop the belt speed to stop the motor tripping the breaker? Given the rotating speed of the drum, I've not found belt speed to have much impact on the resulting surface finish for coarse/medium grit papers.

Or doesn't it work that well? My 16-32 doesn't have it, but I've seen some online videos of people buying the required parts from JET and upgrading their older 16-32 machines to add SandSmart.

Agreed that it’s largely a matter of impatience, trying to take too much off with one pass.

I use up to 350 grit on my drum sander, but at that grit the contact has to be the merest touch. At 240 grit it works fine, so you can go a lot finer then 180 without an issue.

Dust extraction is also an issue and some timbers are a problem. Blackwood is the timber I use that can be problematic and some pieces I just give up on. Wide boards are a problem because they are seldom truly flat and the higher bits create more contact the you expect.

0.2mm is a lot to take off at one time with 180. I would be trying for one half of that or less. Putting the board through making no contact, then moving the head down while passing through and keeping going till just making contact. Then winding down a tiny bit on each pass.

Clean the tracks on the belt off with oven cleaner and/or a water blaster - otherwise they keep reappearing on the same spot.

I found it was love/hate with my first drum sander, several times giving up on it before coming back to it and finally getting good results out of it but only with a much greater appreciation of its limitations.

Additionally, I have noticed that the timber tends to warm up appreciably, and by alternating the side sanded has a beneficial effect on the burning.

Quote:

---

Originally Posted by cava

Additionally, I have noticed that the timber tends to warm up appreciably, and by alternating the side sanded has a beneficial effect on the burning.

---

Good point, especially with very dense timbers

Generic 16/32 drum sanders (as sold by a number of outlets) seem to have the worst problems with burning but they all can do it. I have a Swiss-Tec 19-38 and it is significantly better than my previous generic 16/32 but it still burns sometimes.

As others have already said, the Jet should be able to do the job for you depending on how much material that you try to remove AND the timber that you are sanding. Going faster should make the problem worse because it causes faster heat build, I would have thought.

Some timbers contain chemical compounds that react very badly to the heat generated by a drum sander. As Aaron has said, I find Blackwood (Acacia melanoxylon) one of the most difficult. Other oily, resinous or greasy timbers can also quickly clog the belt and cause burns. Slash pine and radiata pine are very bad because of the resins and quickly ruin the belt - so it is best to never put them through a drum sander.

I have found that, in the worst cases, I have to use a sharpened screwdriver to remove the burn lines.

I've always been reminded that the drum sander is not a thicknesser and as such only the lightest passes are required, and I have yet to encounter your problem. The sander I use squeals before it burns. There's some good advice above and I will also take note of these also.