Troubleshooting Wide-Belt Sander Tracking Issues

Some wide-belt sander sanding belts don't reflect light properly to the automatic tracking sensor. Here's a fix. May 15, 2014

I bought some new 3m belts for my Jet wide belt and they won't track. Has anyone had this problem? It acts like the eye is seeing right through them, although I can put something as thin as a piece of paper in front of the eye and it will activate. I take the new belt off, replace it with the old one and it works fine. I tried a different (both 80 and 120g) new belt with the same results. These belts are the good ones, not cheap. Do these sanders take a specific kind of belt? I really don't see how it would make a difference since the thin paper will make the electronic eye work.

Forum Responses
(Cabinetmaking Forum)
From contributor S:
I thought I was nuts when this happened to me about two years ago. I ended up putting a piece of paper towel over the eye and that made it less sensitive and allowed it to respond. I can only assume the particular belts 120 grit 3M (I think the label said made in Brazil.) I believe these belts are optically transparent to the specific light frequency used on the tracking eye system. Other belts tracked fine. And yes, a piece of paper would make the tracking respond in my machine (Lobo 37 inch) I am using a different brand now and no problem with everything back to normal. Sometimes my electronics background is helpful. Your presumption is correct it is "seeing right through” the belt. This worked for me.

From contributor R:
Paint the edge of the belt on the inside.

From contributor M:
Contributor R’s got it. The back side of the belt is reflecting the sensor light, just like the reflector does to keep the circuit open.

From contributor T:
I had to switch from 3M to another brand because this happened to me several times. It was puzzling though because it didn't happen on every 3M belt, just the 150 grit. Glad to know I wasn't the only one.

From the original questioner:
It seems like a pain on every belt, but it worked.