Cutting mortises - spiral upcut router bit vs drill press forstner bit

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Forum topic by Daveoffinland posted 11-13-2020 03:12 PM 1213 views 1 time favorited 7 replies Add to Favorites Watch
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17 posts in 445 days

11-13-2020 03:12 PM

Topic tags/keywords: mortise

I need to make some mortises in walnut that measure 1/2-in. wide by 2-in. by 1-in. long for a furniture project. Since I don’t have a dedicated mortiser, I’m trying to decide whether to use the forstner bit and chisel method vs. using a spiral upcut bit in my router. It seems like the router method would leave less chisel clean up. Am I missing something?

7 replies so far

View Andre's profile


4737 posts in 3048 days

#1 posted 11-13-2020 03:27 PM

Check out Paul Sellers method with a bench chisel, the chisel clean up, finish is the most fun :)

-- Lifting one end of the plank.

View gwilki's profile


367 posts in 2716 days

#2 posted 11-13-2020 04:09 PM

If you have a router table, I would go with it. Take shallow passes. If you are using a hand held router, as long as you have a template and clamp another piece to the face of the project piece to support the router, you should be fine. For me, drill press/forstner bit would come 3rd.

-- Grant Wilkinson, Ottawa ON

View BlueRidgeDog's profile


884 posts in 1021 days

#3 posted 11-13-2020 04:21 PM

I have a benchtop mortiser. It really is a pain to setup for a few cuts. I have a great router table. It too is a pain to setup for a few cuts. i have drilled them with a forstner bit, but find that actually makes it take longer as you are then trying to take a badly shaped series of holes and make a mortise out of it. If not making a large volume, just cut them with a standard chisel or buy a mortise chisel.

Also, the fanaticism about “don’t bruise the edge” when rocking the chisel is lost on me. It is covered by the shoulder of the tenoned piece. I don’t abuse it, but I certainly don’t panic if I ding it. It is a lot like the inside face of the pin board in a half blind dovetail….it will never bee seen and is structure only.

View Loren's profile


11270 posts in 4890 days

#4 posted 11-13-2020 05:02 PM

If you have a fence for your router various jigs make mortising fairly easy. In some cases parts can be gang clamped and mortised with just the fence. You can end mortise too and use loose tenons too.

Cutting tenons with a chisel is not too slow once you get the hang of it, but keeping the chisel plumb can be a challenge. Sellers has little jigs he made to help with this but they look like kind of a hassle to make the way he makes them using an aluminum plate.

View controlfreak's profile


2889 posts in 843 days

#5 posted 11-13-2020 05:18 PM

I watched a video of Paul Sellers making a door frame and man can he get a tight fitting mortice.

View WoodenDreams's profile


1432 posts in 1153 days

#6 posted 11-13-2020 07:25 PM

If you plan on doing the mortising by hand, There are hand mortising chisels designed to do mortises. I have two Narex brand mortise chisels (1/4” and 3/8”). They were about $20-$25 each

It’s a matter of the way you feel comfortable with. I like doing mortises with a horizontal router jig set-up. Gives me more control vs. on a regular router table set-up. I do have the General mortising jig. It’s still setting in the box unused for the last three years.

View Rich's profile


7455 posts in 1831 days

#7 posted 11-13-2020 10:02 PM

It’s easy to build a simple jig to cut 1/2” mortises. I’m using one right now to cut mortises in the rails and stiles for a new front entry door for the house. In the photo below, I cut the guide slot 5/8” wide to accept a 5/8” OD guide bushing. From there it’s a simple matter of using a plunge router to plunge holes across the width of the mortise, then just slide it back with the bit lowered. The result is a perfectly smooth mortise. If you need it square, some chiseling is required. In my case, I’m doing loose tenon joints, and I milled my tenons with rounded corners, so they’ll fit right in, no chiseling required.

This one is fixed for the 1 3/4” thick pieces for the door. You could also make one that’s adjustable to fit any thickness board. Since I need three different lengths of mortise, I just added spacers, which you can see in the photo. They drop in place.

If you want a more versatile mortiser, take a look at the Morley mortiser, designed by Philip Morley. I built one from his plans that you can see here. You can order his plans for just a few dollars from his web site and then download them.

The next level up is the Leigh FMT. It cuts mortises and tenons, but is quite pricey. I have one of those too. The reason I chose to do my simple jig for this job is the size and weight of the stiles, and the number of mortises I have to cut (there are six rails). I’ve used my hollow chisel mortiser for door stiles in the past, but it’s clumsy. The Leigh FMT is scaled for furniture and the mortises I’m cutting are too long for it. The Morley mortiser could handle the length, but again, I’d be wrestling the board through it, when I felt it was much easier to move the jig along it. So, with this jig I can just fix the stile in the vise and cut away.

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

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