I've always done my mortises with a drill press/forstner bit, but
recently decided to try using a plunge router (with an edge guide) and
a spiral upcut bit.
The results were somewhere between disastrous and hilarious. At least
in my untrained hands, there's too much play to keep the upcut bit from
snagging somewhere along the line and destroying the mortise
completely. (Throw in dangerous in the front of this paragraph while
you're at it...)
I'd like to try using the upcut bit on a router table, but somehow
rasing and lowering a piece of hardwood freehand (against a fence) onto
a spinning bit seems like it could be even more
I've googled with no luck...anyone know of a link that teaches this
decided to try using a plunge router (with an edge guide) and a spiral upcut
bit. ...anyone know of a link that teaches this technique?
One link is from Highland Hardware's website - download "Tage Frid's
Mortising Jig" from this page - available in a pdf or as a separate
html page. A few more pictures would help in my opinion, but it's
Also, I just made a jig that's somewhat similar - simpler but less
adjustable. It might give you ideas depending on your application.
Basically a rectangle of 1/4" hardboard, with a cut-out of about 6 3/8"
x 12 3/8" (depending on the size of your router sub-base and desired
mortise size). Then I took this rectangle and screwed it to a piece of
MDF for the router base to ride on, and since the MDF extends beyond
the hardboard, it is a good clamping surface also. Plunged the router
with 1/4" spiral upcut bit through the MDF, and you get the exact
cut-out shape you'll get on your workpiece. Some centerlines inside
that MDF mortise and on your workpiece help with alignment. Clamp
MDF/hardboard jig to workpiece and plunge away - works well with
shallow mortises of a single size, at least (that's all I've done so
far). This is essentially 4 fixed edge guides on a sub-sub base, if
that makes sense.
I agree that trying to lower a piece onto a spinning bit on the router
table is a bad idea - not sure about hilarious, but it sure has
potential for disasterous or dangerous.
From your free hand experience I am guessing that you tried to take too
much out at a pass AND quite possibly you were routing in the wrong
direction causing the edge guide "not " to be pulled against the edge of
We do the fence thing all the time when we need blind mortises. Cheers, JG
wood firstname.lastname@example.org wrote:
That's exactly what I do, with stop blocks clamped to the fence(s) to
define either end of the mortise. Tilt the board (end-to-end wise) on
to the bit in the center, so the tile doesn't mess up the ends of the
mortise. A firm grip _IS_ required. <G> For items too long for stop
blocks, I'll use a block at one end or the other, and a stop mark for
the remaining end.
Try staying shallow for your first practice attempts, as the bit will be
much less likely to grab. With experience, I can do a 3/8" wide x
3/4"-1" deep mortise in one shot, and have good results and no unwanted
On the flip side, you could always build one of the many jigs out there
and mortise with a plunge router right side up.
Once you get the hang of it, the table method is fast, plenty safe, and
Do you have the workpiece firmly clamped? Are you only taking 1/4 deep cuts
at a time? Are you holding the router with both hands and keeping adequate
pressure against the guide? If you are doing all of this, plunge cutting
mortices is safe and easy.
Mostly dangerous. It's only funny until someone looses a finger.
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