CMT flush trimming bit not flush -- need recommendations for replacement bit

http://www.sommerfeldtools.com/products.asp?ID 
I need a recommendation for a flush trimming bit that is truly FLUSH. Every time I use this bit in my router table to follow a pattern, I end up having to sand the edges down a few more thous for the item to fit (example--shop made inserts). Anyone know if MLCS has one that cuts totally flush with the bearing (bottom bearing, 3/4" diameter)?
BTW, the bit isn't worn--it cut this way when new.
Dave
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Some offset and flush trimmers at the http://patwarner.com/patternbits.html link.
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 bearing is 1.5mils smaller than the cutter. In 10 or 20 passes or uses of that templet, you'll have a pattern 1/64" smaller; not cool. ********************************************* David wrote:

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snipped-for-privacy@patwarner.com wrote:

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
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snipped-for-privacy@patwarner.com wrote:

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
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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.
http://www.patwarner.com (ROUTERS) *********************************************** Chris Friesen wrote:

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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

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tom wrote:

it's a pita when the object is round, rather than straight.
Dave
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Then make yer template a thou or two smaller, eh? You'll have to sand somewhere, so it may as well be a few thousandths off of the template. We're still not sure of all the variables undisclosed in Chris' design. All we know is that his pattern bit cuts a little large. Tom David wrote:

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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.
--
Rick Nagy
Johnstown, PA
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David wrote:

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 www.use-enco.com or the like are ~$6.
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