Routing deep Mortises

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Forum topic by Marty5965 posted 05-06-2013 07:14 PM 1344 views 0 times favorited 3 replies Add to Favorites Watch
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161 posts in 2556 days

05-06-2013 07:14 PM

Hi Guys,

Still pretty new to power tool woodworking and am trying my hand at routing mortises. I have a 2 1/2” long 1/2” router bit and need to create 2” deep x 3” long x 7/8” wide mortises. Obviously I need multiple passes but was wondering if there is a difference between depth and width?

By that I mean, if I use an edge guide I can start the first pass. Is there a difference in completing that one to full depth in multiple passes then adjusting the edge guide to nibble away the width at full depth or, do I have to change the edge guide for each lengthways pass and take the mortise down to full depth but at full width (if you see what I mean).

Seems to me changing the edge guide every lengthways pass would introduce lots of margins for error.


-- Marty, Wilmington, OH, learning every day....

3 replies so far

View SCOTSMAN's profile


5849 posts in 4196 days

#1 posted 05-06-2013 07:23 PM

I take it to the desired width a bit at a time so make first cut to desired width then deepen a little to desired width and so on.I find this best way of getting there without slipping along the way. Alistair

-- excuse my typing as I have a form of parkinsons disease

View Loren's profile


10477 posts in 4259 days

#2 posted 05-06-2013 07:24 PM

Usually the ends are plunged to full depth first and the
waste in between removed in passes about 1/4” deep.

For a wider mortise, cut a narrow one to full depth,
then clamp a piece of scrap the width of the offset
you need for the second pass to the piece you
are mortising. This way you can leave the fence
set up the same. Then plunge the ends of the
second half of the mortise and waste out between
as before.

For wider mortises I often make a template and use
a guide bushing, eliminating the fence. The template
approach is almost foolproof.

View brtech's profile


1066 posts in 3533 days

#3 posted 05-06-2013 07:40 PM

Usually you rig up something to guide both edges with one setting and free hand in between. A template is great if you are doing a bunch of the same sized mortises, but you can just clamp two straight boards the right width apart to get your router to route out the edges in one pass.

You can use the scrap on the edge guide trick to get the “far” edge routed and free hand in between if you want.

In your case, you only need two passes to get 7/8” with a 1/2” bit.

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