Bit to use for Mortise/router jig

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Forum topic by sreilly24590 posted 05-21-2018 03:06 PM 592 views 0 times favorited 7 replies Add to Favorites Watch
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146 posts in 1207 days

05-21-2018 03:06 PM

Topic tags/keywords: jig question router joining mortise router table

So I built a simple mortise jig and have a few more elaborate jig plans to try before settling on which to use and suspect the simple will work fine on some projects. But I need to start somewhere and am unwilling to buy a mortise machine at this point. Maybe down the road should I find I’m making tons of them. But for now I’m looking at what’s best in the way of router cutters to use to make these. Do you go for a cutter that equals the width of the mortise making a single pass or smaller and make multiple passes? Use a simple upspiral cutter or a compression cutter? I realize the depth of cut is multiple shallow cuts till the final depth. It’s the width of cut I’m referring to.

From looking at some of the posts I see where building a project such as a work bench would require a large mortise and multiple passes are likely needed especially depending on the router you’re using. Currently I have several handheld older routers and a Bosch 1617EVS with plunge base but it’s 2-1/4 HP and likely a larger router would be better for larger mortises or go slower and more shallow with each pass on the lower HP models?

Be gentle as this is my 1st trip down this long sought after process. I actually bought a set of decent mortise chisels back a while ago when on sale knowing that I’ll get there but now looking harder at actually doing some mortises has me looking everywhere on how to do them correctly and safely. This forum has been an inspiration on information and ideas. I haven’t seen anything on using a router table but possible?

Any thoughts/ideas? Where to look and how to proceed?


-- Steve, Virginia

7 replies so far

View Robert's profile


3748 posts in 2256 days

#1 posted 05-21-2018 03:13 PM

Yes always try to match the cutter to the mortise width. I recommend a spiral up cut bit.

You can use a router table except for end grain cuts, but I recommend a jig and plunge router.

-- Everything is a prototype thats why its one of a kind!!

View Rick  Dennington's profile

Rick Dennington

6948 posts in 3970 days

#2 posted 05-21-2018 03:41 PM

^^^^.........This I agree with 100%.......Your 2 1/4 hp router will work just fine for cutting mortisies…..If you have a speed control on the router (between 0-5), I’d run it on between 2 or 3 speed….You’ll need to practice on a piece of scrap or two to get the right setting….You’‘ll know when you hit it….!!!

-- " There's a better way.....find it"...... Thomas Edison.

View Sludgeguy's profile


57 posts in 898 days

#3 posted 05-21-2018 04:50 PM

I use a spiral upcut bit in a single pass and square up the ends with a chisel.

View sreilly24590's profile


146 posts in 1207 days

#4 posted 05-21-2018 05:19 PM

Thanks guys.

I actually just finished watching Paul Sellers’s video on hand cutting mortises here which is really good. But I like the idea of the clean router method. Now has anyone found a really good jig or jig plan?

Is there a calculation for determining the proper mortise width?

Thanks again for the insightful replies.

-- Steve, Virginia

View Rick  Dennington's profile

Rick Dennington

6948 posts in 3970 days

#5 posted 05-21-2018 05:55 PM

I normanly don’t cut mortises with a router, but I have a few times in the past….I have a mortise machine that I’ve had for 20+ years….It’s a Delta, and it cuts mortises from 1/4”-1/2”...To me, once you get the machine set up properly, you can cut mortises pretty fast, and squaring up the ends is a snap…..Personal preference, I guess..!! If you’re using 3/4” material, usually a 1/4” mortise will do…..Just measure over a 1/4” from the edge of the board, lay out a 1/4” wide mortise in the middle of the board by ever long you need it to be, and draw it in….that’s the standard way of doing it….if you want an off-set mortise, then lay it out that way….!! Then determine how deep you need the mortise, and make the tenon a 1/4” by the depth: Example: the tenon should be a 1/4” x 3/4”-1” long… just need to make the tenon fit the mortise…..+ or—a hair…!!!!!

-- " There's a better way.....find it"...... Thomas Edison.

View bondogaposis's profile


5790 posts in 3126 days

#6 posted 05-21-2018 06:05 PM

I think a plunge router is pretty essential for cutting mortises with a router, at least it is for my jig. I match the bit to the mortise width and use a spiral up-cut bit. A 2 1/4 HP router is enough power.

-- Bondo Gaposis

View Rich's profile


5619 posts in 1365 days

#7 posted 05-21-2018 06:19 PM

I did a project for Philip Morley's mortiser design a while back. The beauty of it is that it has a single 5/8” slot for a 5/8” OD bushing to ride in and the bit is centered in it for easy alignment. The bit can be any size from 1/8” to 1/2”.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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