Router method for mortising?

[Alan Tolchinsky]

Hi All, What's your method/jig used to do mortises using a router? I am going to try loose tenon joinery and wanted to use my plunge router to do the mortise. What's your method and what type bit do you recommend? Thanks Alan

[Dave Richards]

Alan, now I would use my WoodRat to do it but BR (Before Rat) I would make a quick jig of MDF with a slot cut on the piece that lays on the surface to recieve the mortise. I would use a guide bushing on the router base and size the slot accordingly. I would generally use an upcut spiral bit since this will tend to eject the chips. I would not try to cut the entire depth in one pass.

Good luck.

[Herb Blair]

Alan,
I use either a jig that I construct from scrap if doing a lot (i.e. a table, etc) or use a edge guide attached to my plunge router. I use a upcut sprial bit, typically a 3/8" or 1/2" bit, depending on what it is.
I bought a Jet mortising machine, but it pretty much just takes up space, or I use it to make the corners square it the project requires that they be square.

Herb
Carrollton, TX

[Jim Becker]

The good news is that just about every book on routing includes a jig or three for mortise routing. It's easy to quickly construct "temporary" jigs for this, too, out of scraps. And then there are the commercial jigs, such as the WoodRat, JDS and Leigh M&T. I think that if I were going to be doing a lot of M&T, I'd look seriously at the Leigh or JDS or a shop-built version with "it slices, it dices" capablity. But so far, quick and dirty temporary jigs have sufficed for those times I choose to use loose tenon joinery.

[Alan Tolchinsky]

Thanks guys. I'm going to make a simple jig first to see how I like it using a spiral upcut bit. Then I can see if I need to build a full blow horizontal mortising machine. Alan

[Dan Cameron]

I've seen mortisers built with various exotic x-y slide mechanisms, but I put together this very simple unit. It is basically a horizontal router table with two additions. One is a square board with an adjustable stop (or fence) and provisions for clamping down the workpiece. I refer to this board as the "sled". The other addition is a pair of adjustable side fences which are set using a square to be at exactly right angles to the router mounting plate. The length of the mortise is the distance between the side fences plus the bit diameter minus the size of the sled. The width of the mortise is strictly the bit diameter, and the router is positioned to center the mortise in the workpiece.

In use, the sled is held down on the table just as one holds a workpiece down on a table saw,jointer, or whatever. To start, the sled is held against the left side fence and pushed slowly towards the router mounting plate. This plunges the bit into the workpiece. Next, the sled is held against the router plate (and down) and is pushed left to right until this motion is stopped by the right side fence. The sled is then moved away from the router plate while holding it against the right side fence (and, of course, down).

I cut my mortises with multiple passes using the above procedure, each pass going about 1/4 inch deeper. To avoid the inconvenience of having to change the bit depth between passes, I have a set of sticks of widths 1 inch, 3/4 inch, 1/2 inch, and 1/4 inch which I place between the sled and the router plate to limit the depth of each pass.

[Alan Tolchinsky]

Dan that's a great jig. I just made a simple one that I use with an edge guide but it has two problems. First if I don't hold the router fence tight against the jig the bit wanders and the mortise gets wider. And it has no stops so the mortise length can increase if you're not careful. It looks like your jig takes care of those problems. Thanks Alan

[Jamie Buxton]

...
First if I don't hold the router fence tight against the jig the bit wanders and the mortise gets wider.
...
Thanks Alan

Alan, think carefully about which direction you're moving the router. If you move it one way through the work, the bit will try to move the router toward the face where your fence is registered. If you move the router the other direction, the bit will try to pull the router and its fence in tight to the workpiece face. Moving the router the right way assures that the mortise stays the width you intend. Moving the other direction is just begging for trouble.

Jamie

[Alan Tolchinsky]

Thanks Jamie, Good point about the direction. I was having some trouble holding the router steady as I plunged it. I have to find a way to release the lock lever more smoothly when I plunge. Thanks for your help. Alan

[Mark Singer]

Alan,
I make a jig from MDF or baltic birch ply. Leave the mortise with rounded ends. Use an upcut spiral bit....1/4" is fine. First pass plunge to 1/3 depth and then move router around. Increase depth on second pass ...plunging all areas first and moving the router, Use a compressor to blow out the chips. Third pass completes the mortise. Make the tenon stock from hardwood like maple using the tablesaw to rip to mortise dimensioon. Use the router table and a roundover bit to match the mortise radius . Rip a couple of shallow glue troughs in the stock. Make sure each tenon is 1/8" shorter than the combined mortises. Try a dry fit and sand on a disc/belt sander if necessary. It makes a strong joint.

[Jamie Buxton]

Thanks Jamie, Good point about the direction. I was having some trouble holding the router steady as I plunged it. I have to find a way to release the lock lever more smoothly when I plunge. Thanks for your help. Alan

If you're mortising on the edge of a board so thin that the router threatens to rock, you can clamp another board to the first to give a wider area for the router to sit on. I put the workpiece down on the bench with the mortise edge down, put the second board down beside it, and clamp them together. Because the two boards are resting on the bench, those faces are the same height when you turn them over to do the mortising.

[Bill Patterson]

Taunton Press sells a book called Router Joinery by Gary Rogowski. Rogowski shows three methods for creating mortises. He also discusses loose mortieses as well.

Check it out:

http://www.williamppatterson.com/1.%20Web%20Pages/Router%20jig.htm