Snipe with a Wide-Belt Sander
Troubleshooting a wide-belt sander performance problem: it's making a "dip" in the piece. October 2, 2007
I purchased a used widebelt sander. No bells or whistles, just a plain 36" widebelt sander. When I run a five piece door or face frame through the sander, I get a dip in the stile as soon as the rail passes the drum. I loosened the hold-down bar thinking it was putting too much pressure on the panel and as soon as the rail passed, it did not have as much surface to hold down and it raised up and caused the dip or snipe. But the problem with this is the panel slips on the belt and then causes the snipe for other reasons.
From contributor G:
Replace the belt if it's worn. Make sure the belt to sander distance is correct and back up anything you send through with another piece.
From contributor T:
You may help this by resurfacing the feed belt. If it is hard and glassed, it will let the door slip. Resurfacing will also help make everything parallel.
From contributor D:
If and when possible, run the doors and frames through at an angle. If the sander has a platen, you may also try lowering it to make contact with the material. I had a sander that did the same thing. I cured the problem by running at an angle and taking many light passes. Is the bed supported with 4 jack screws or 2? If 2, there could be a rocking motion in the bed causing this as well. If this be the case, the bed can be tightened up with an adjustment to the guide blocks.
It's on 4 screws. And how do you resurface the belt? That may be a dumb question, but until now all I have had in the past is ROS and a Performax drum sander. Still learning.
Contributor G, what are you talking about, "backing it up" - are you talking about laying another board or sheet of ply under the door or face frame?
From contributor D:
To re-surface the conveyor belt, put on an 80 grit belt and raise up the bed until the conveyor belt starts to make contact with the sanding belt. Do this until the whole conveyor belt surface has been touched.
By backing up, you want to feed another sacrificial board just behind the piece in question, as to push the lead board along.
From contributor L:
To resurface, glue a 6" x 4' long piece of new 80-100 grit belt to a piece of 1" thick MDF at a diagonal angle across the MDF. The MDF should be as wide as your belt is and you should take very light passes. A few passes with no contact at the beginning to get your bearings on height is okay. Better to miss than to take too much. Take off as little as you can to get the job done.
From contributor V:
Your problem is most likely with the hold downs not being adjusted properly. They must be of even pressure and allow the piece to travel through on an even plane - not pressing on one end more than the other, and allow the piece to travel under hold down without a temporary pause, which causes the dip.