One-Belt Versus Two-Belt Wide-Belt Sanders

      Shop owners discuss wide-belt sander choices. March 13, 2007

Question
We are about to purchase a wide belt sander, and for a similar amount of money have the choice of a second-hand two belt, two roller machine or a new single belt with roller and pad machine.

The machine is for sanding kitchen doors, face frames and other solid wood parts to 150g for painting and 180g for lacquering. Ideally we'd like to put through veneered MDF carcass pieces to prepare for lacquering.

We are leaning towards the single belt machine for the following reasons:
- Most work requires leveling off joints using 80g, probably two passes, then one at 120, then finer. If we use two belts, the back one is only useful half the time.
- It's new.
- The machine is simpler.
- The roller pad combination gives a better finish than just a roller.
- The machine is smaller and fits in my workshop better.

Am I going down the right route?

Forum Responses
(Solid Wood Machining Forum)
From contributor H:
You're going to change and retrack a new belt every time you want to change grit? What about the time involved? The idea behind a two belt/roller system is that the first belt levels the board and the second belt finish sands it.



From contributor J:
If you're planning on sanding MDF panels, you'll want a very good platen. Ideally one with individual fingers to be able to control the pressure and avoid sand through. With just a roller, you're going to have a tough time sanding your veneered MDF without cutting through.

The better platens make for a more costly machine, though. For solid stock like doors, face frames, etc. a simpler machine will do. Best bet would be to run some test pieces through both machines to see what they do on your work. Then you'll be able to make an informed decision.



From the original questioner:
Contributor H, the tracking is fully automatic pneumatic and a belt change takes a couple of minutes max. Does that change your view? Also, we will be light users - these machines are designed to run day in, day out but we will be around one full day every week.


From contributor R:
We bought a single-belt SCM machine about 2 years ago for exactly the same needs you describe. It serves us very well. Takes under a minute to change belts. If we're doing a set of kitchen doors, that is really negligible time loss for the advantages that you mention.


From contributor T:
We have a 42 inch wide two head widebelt. We weren't necessarily in the market for a two head machine but this one looked like a good value at the time. Changing belts is the obvious economy here, but not the real one. The real advantage to a two head machine is that you can feed more doors into it before you have to stop feeding and start retrieving. Two head machines have a longer conveyor system which means that it also takes longer for the door to travel through the system. This extra travel time gives you the opportunity to feed more doors into the sander at one time.

We typically will load three groups before retrieving them. They feed onto a cart at the back of the machine. The second group slips over the first group and the operator is at the back of the machine to collect the third set. Sanding more doors at once means the machine is running for a shorter time span. This means less electricity used and less wear and tear on the machine.



From contributor A:
Another advantage with a two head machine is the oscillation. For rough stock removal you want a faster oscillation; with a two head machine, you set it and forget it. Going back to what contributor H said, there is no such thing as a really automatic tracking system that I am aware of. There are tracking eyes (electric or, in your case, air actuated) to keep the belt on the roller, but you still have to watch the belt when it is first put in to make sure it is tracking properly. I believe this is what contributor H was referring to. However, if the two head machine doesn't have a platen, don't buy it. It is that simple. You need a platen for what you are doing.


From contributor F:
3 years ago we did use a 36 wide single head. After that we got a 53 inch wide 2 head sander. We buy half as many sanding belts for this new sander. We produce d-fir doors and pitch buildup on belts is a problem. On the single head sander, employees often didn't change to a coarser grit for first pass sanding. Now we don't have that anymore.


From the original questioner:
Thanks to everyone who replied to my initial question. We now have a Griggio GC95 950mm single belt roller and pad sander installed. It's cut our sanding time dramatically and the results are great. Changing belts takes seconds and there is no tracking issue. For painted work we can get away with 120g finish, for a current job in oak we have taken it to 150g.


From contributor L:
I have just deposited for a 36" Timesaver wide belt sander. I make 20" wide kitchen cabinet doors with 16" panels. Is it possible to use 2 18" wide belts of different grits, 150 and 180, on the single roller and get the same result as having a 2 belt machine? I am very short on space.


From contributor F:
I don't think it's possible or smart to run two different belts 1/2 as wide as the drum at once. Each sanding grit and material of belt cloth paper has a different thickness. Most sanders have an adjustment on the end of the drum. The thinner or finer the sanding belt, the more you lower the drum in relation to the hold down and pinch rollers. Also, it may be possible the two belts will run into each other and blow up. Most sanders have a photo cell on the far side of the belt. Every time the belt runs into it the top roller changes direction and this constant oscillation will keep the belt from running off to one side. The edge on the photo cell side needs to be free of damage. The photo cell needs to be free of dust in order to work. We used to have a Timesaver. Just about every time we changed a belt, we had to readjust the tracking as well.

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