Sawdust Drag Chain Derailing Problem

Wear and tear can ruin the fit of a chain and sprocket, causing the chain to jump the track. May 10, 2007

I have a Frick 0 sawmill, and use a drag chain to manage the sawdust. The chain keeps coming derailed off the drive sprocket. Any input on how to keep the chain on track?

Forum Responses
(Sawing and Drying Forum)
From contributor G:
Sounds like it is hanging at some point, then when it comes loose, the chain jumps and comes off the sprocket. Or the sawdust is building up around the sprocket. When I ran a dust chain, my drive was on top, then an idler was set in the floor about 6' before the saw and I used a wheel at the sawdust pile. I ran it as slow as I could. This seemed to work best.

From contributor S:
How is the condition of the drive sprocket? A badly worn one will throw a chain.

From the original questioner:
Thanks. The sprocket looks good, but the chain doesn't seem to lie in or mesh to the sprocket teeth too well. Could the chain be worn out as well as the sprocket? The drag does seem to jerk or catch periodically and I have tried to smooth this out as much as possible. I will try to slow it dawn a bit too, and experiment with an idler on the floor. Is there an optimum amount of sag in the chain from the sprocket to the return pulley out above the sawdust pile?

From contributor G:
"The chain does not mesh or lie in the sprocket teeth well." That sounds like a make fit and hope it will work setup. I would check and see if you have the right sprocket for the chain you are using. As for sag, the longer the chain is, the more sag you can have. I had more trouble with a dust chain being too tight than too loose.

From contributor E:
Ok, this is going to sound a bit off the mark, but I have experience with mountain bike chains and chain rings (sprockets). After about a year of hard grinding on a new set of chain rings, and a new chain, the chain will begin to stretch. When it does that, it starts to wear the chain rings. Visual inspection of the rings will show a hook in each of the teeth where the chain meets it. The wear from the chain will gradually remove material from one side of the tooth. That tends to cause the chain to bind up with the sprocket, causing a phenomenon known as "chain suck". The chain will not come off the teeth smoothly, but will, rather, sometimes stick to the sprocket, and try to go around again. Chain tension will definitely affect how often this happens.

Now, when someone first explained this to me, I said, "yeah, right." Steel doesn't stretch like that. Well, after my bike started doing exactly what people said it would, I removed the chain and replaced it with a brand new one. I took the old and new chains together and hung them from a nail. Darned if the old chain wasn't 1/2" longer than the new one. Now I'm a believer.

The biker's wisdom is to replace the chain and the sprockets at the same time. Otherwise, the old part will wear out the new part faster. I didn't believe that until I went against the common wisdom, replaced just my chain, and then had to replace it again 3 months later. If you've never replaced the sprockets or chain, and it's been a long time, I think you might want to give that a try.