BTW, the bit isn't worn--it cut this way when new.
Dave
Some offset and flush trimmers at the
Understand these (and most trimmers) are purposely undersized. Given the cutter diameter = or > than the bearing diameter and the templet will get wasted away.
Say the bear>
Pat, I was afraid that might be the case. I hope someone makes a bit that exactly matches the bearing diameter. Being a careful sort, I keep the bit ever so slightly below the pattern so that it won't get damaged. I hope some mfgr has a flush trim bit that doesn't try to "save us from ourselves". :)
Dave
In order for that to happen you'd have to be running the bearing against the portion of the template that you cut the previous time, no? The only way I can see that happening is if you're flipping your templet over.
If you run the bearing against the same portion of the templet all the time, how does the templet get trimmed?
Chris
Most straight trimmer bits with bearings are such that some of the cutter has to be against the template. Doesn't take much if you use both sides of the pattern to make a mess of things. (Do no joinery or close work and it matters not.) Moreover, distal bearing guided cutters (bearings on the end of the tool) almost always slice up the template if they are = or > than the OD of the bearing.
And, unfortunately, it is rare that everything is so square and flat that the router doesn't tip from time to time. In that event, a flush-flush trimmer will gouge the hell out of the templet. You have a better chance if the cutter is 4-8-10 mils smaller than the bearing.
FWIW, I'd just put a few sheets of thin cardstock between the template and the piece I'm cutting and allow the cutter to cut on that rather than your template. It's a lot cheaper than buying new bits or templates.
Yabbut, this is a cut on a router table. Chris, what thickness is your template? It would seem that your template would be reasonably safe from trimming if it's 3/16ths or thicker, even when switching from top bearing to bottom bearing, with only a good eyeballing of the cutter height. A few thousandths of sanding doesn't sound too bad, however. Tom snipped-for-privacy@patwarner.com wrote: snip > And, unfortunately, it is rare that everything is so square and flat
after Chris Friesen wrote: > > In order for that to happen you'd have to be running the bearing against
it's a pita when the object is round, rather than straight.
Dave
The bearing on the bit is replaceable, right? So can you find someone who can machine a collar to fit around a slightly-smaller ball bearing, to make that fit just perfectly? I've used a wrap of tape to make a pilot bearing larger, on occasion.
Any good machine shop can turn out a dozen different-size collars in an hour, so you can 'fix' this problem on a variety of bits and even choose your pilot to do rough cut/fine cut passes for best finish. Final cuts of less than .005" don't give good finish, generally (very dependent on edge quality).
Because the bearing race is hardened, changing the diameter by grinding is unwise. New bearings from
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