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.
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 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.
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". :)
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?
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
Chris Friesen wrote:
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.
snip > And, unfortunately, it is rare that everything is so square and
after Chris Friesen wrote:
> > In order for that to happen you'd have to be running the bearing
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
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.
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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