David K

When I set up my Porter-Cable router for a long run of work, I sometimes get 'creep' in the bit. The depth setting I worked hard to get changes, and can get so bad as to ruin the project. It doesn't happen every time, so it's been hard to figure out.

I've been careful to clear out any sawdust from the collet and the socket it fits into, but nothing guarantees this won't happen. It's especially likely to happen with a raised panel bit (the kind in which the axis of the bit is parallel to the plane of the panel).

Is it caused by letting the bit get hot or some other problem I should fix, or is it a problem of an old collet?

rrich

David,

My thoughts are a bad collet or you're clamping on the wrong part of the shaft of the bit.

You should tighten the bit in the collet snugly but not over tighten.

Check the slots in the side of the collet. If they are plugged you won't be able to tighten the bit completely.

If you remove the collet, check the shaft of the router. The inside should be smooth and free of any burrs. It helps to put a bit of paraffin on the inside of this part of the shaft. The lubrication will help tightening and loosening of the collet.

When you put the bit into the collet, do not allow the bit to bottom out. Usually between the shaft and the cutting part of the bit is a fillet. If you try to clamp onto this part of the bit, the bit will slip in the collet.

__________________
Use the right tool for the job.

Rich (Tilting right)
Huntington Beach, California
Remember that when we have the "BIG ONE" everything east of the Rockies falls into the ocean.

TomC

I take it that you are talking about a router installed in a router table because you said it happened with a raised panel door bit. Do you have a router lift or do you have to adjust the router itself?
Tom

firehawkmph

David,
Along with Rrich said about the collet, when setting your height of the router in the table, lower the router lower than where you want to end up at, then slowly raise it to your final height. This will eliminate any slop in the router's height adjustment. Also, only loosen router adjustment clamp on the router enough to let it move up or down. Again, trying to not have a bunch of slop in the movement while trying to set the height. I usually blow out the collet with an air nozzle each time I use it and do like Rich says, bottom the bit out and raise it back up about an 1/8", then tighten.
One other thing when using a raised panel bit. Try cutting in steps and not trying to hog out the whole thing in one pass. It sounds like you are using one of the vertical cutting bits by the way you described it. If you are, make sure your fence is tall enough to support what your are cutting and use some kind of featherboards to keep the panel from wiggling. I use the other type RP bits that are the traditional large diameter cutters with the board flat on the table top while routing. Let us know what you find.
Mike Hawkins

David K

I've been using a router table, but I don't have a router lift. Because I cut panels in stages (about 1/16" per pass) I've been fooled - the bit can wander up, yet the mid-run cuts look fine. Then at the end of the run, I realize I've removed more than was intended.

mickit

Another thing to look at is the collet itself. If it has been tightened without a bit, it can crack at the bottom. The cracks can be so small as to not be visible but still affect the grip.
Cutting and grinding collets was among the first jobs I had when I started at PC years ago. They are hardened, and very brittle. Over tightening. can distort them, I've even seen them split when dropped from work bench height. Also check the shank of your bit...if it's a European or Asian build, it may be13 mm, not a big difference, but enough to let the bit "creep out of the collet.
rrich covered it pretty well, just thought I'd through in that little extra bit