Mortise Pal Plunge Router Mortising Jig

Mortise and tenon joinery is a fundamental technique that is indispensible in carcass construction. A lot of us were initiated into M&T joinery by chisel, mallet and saw. Even today, when I only have a few M&T joints to make I'll do it entirely by hand - particularly if I'm in one of those mellow moods.

Just about every professional woodworker I know has, at one time or another, made their own M&T jig. And while some continue to use these jigs, by far, the majority have purchased commercial jigs, primarily because they offer a higher degree of precision and versatility. Often, they are just more durable and convenient to use than shop made jigs.

Recently, I had the opportunity to try out a Mortise Pal Plunge Router Mortising Jig. It's been on the market for several years now, and has gone through a couple of iterations - enabling the designers to use their own experience and user feedback to fine-tune the operation of the jig.

The Mortise Pal only cuts mortises, not tenons, which means you'll use this jig for loose tenon joinery. If you haven't used loose tenon joinery before, you'll find it much faster and easier than cutting tenons on a table saw. There really is no difference in joint strength between conventional tenon joinery and loose tenon joinery - provided the tenon stock you use is a precise match for the mortises. You can make your own tenon stock, or you can also purchase it from Mortise Pal, Lee Valley, or several other retail sources.

With the Mortise Pal you can rout mortises from 1/4" to 1/2" wide and 3/4" to 3-1/2" long - which easily covers the range of mortises most commonly used by woodworkers. Mortise depth is determined by the length of router bit that you use.

The Mortise Pal comes with the jig, six polycarbonate guides, stainless steel stop, brass guide bushing with lock nut, centering pin, Allen key and user manual. You'll also need a spiral upcut router bit, some tenon stock, and of course, a plunge router.

You'll likely find, like I did, that the Mortise Pal is an ideal shop jig - it's straightforward in design, superbly machined, easy to use, and the results are consistently perfect. You can almost use this jig straight out of the box. However, I would recommend that you first look though the 12 page user manual, which shouldn't take more than five minutes - particularly if you are new to mortise and tenon joinery.

The plunge router you use should have a 5-3/4" diameter base that can accept a 1-3/16" guide bushing, and accept a 1/2" collet. If the router base is too narrow, it won't safely ride on the top of the jig. The spiral router bit you use should also have an overall length of at least 2-3/8". This is because you loose up to 1-3/8" of the bit to the collet, guide bushing, and height of the jig. If you don't have a long upcut spiral bit, it's a good idea to purchase one along with the jig. Mortise Pal sells reasonably priced 1/4", 5/16", 3/8", 7/16" and 1/2" bits (both HSS and carbide). I also like the bits from Dimar Canada. Likewise, purchase some matching loose tenon stock. Once you're comfortable using the jig you can try making your own stock - initially though, you want tenon stock that is precisely milled to match the thickness of the bit you'll use.

When cutting mortises and tenons by hand there is the often repeated 1/3 rule - cut the mortise and tenons so they are each 1/3 the thickness of the stock. Because of the tight tolerances you can obtain when routing, I've found it quicker and easier to simply use a 1/4" bit to rout mortises on stock 1" or narrower, and a 1/2" bit to rout mortises on thicker stock.

Once you install the brass guide bushing Mortise Pal suggests that you check the concentricity of the collet and the bushing with the centering pin included with the kit. All you need to do is install the guide bushing loosely on your router base, and then mount the centering pin in the router chuck. Lower the pin through the guide bushing, and then tighten up the bushing.

The Mortise Pal is inherently simple to use. Basically, you mark the layout lines on your stock that locate the center of the mortise; select and install the template that defines the width of the mortise; chuck a spiral bit into your router that defines the thickness of the mortise; center and clamp the jig on your stock; and then rout the mortise. Once you've gone through this process a couple of times it will seem very intuitive.

Template carriage lock

Template carriage travels smoothly along stainless steel rods

The 1/8" thick polycarbonate templates are stiff and durable, and two alignment pins make it easy to install them on the jig. The templates are attached to a carriage that glides smoothly without any binding along two 3/8" stainless steel rods, and they can be locked at any location on the rods.

There is one centerline indicator on each end of the template carriage

There is another centerline indicator on the clamping body

Positioning the template carriage precisely over the layout lines on your stock is virtually fool proof. There are three centerline indicators on the jig - simply position them over the layout lines, and then tighten the clamp screw to secure the jig to the stock. Use a marking knife or a fine tip mechanical pencil to mark the layout lines - this makes it easier to more accurately position the template carriage.

The rails on top of the jig are 5/8" thick, and provide ample support for the router. For best results use a series of plunge cuts to remove the waste then make one or two full depth passes to produce a clean mortise.

Jig positioned over the layout lines

Routing the mortise

Perfectly placed mortise

Perfectly mating loose tenon

You can rout single or double mortises in tandem or in a row, on flat or angled stock. Using the stainless steel stop, which you can attach to either end of the jig, you can rout repeat mortises with complete accuracy. Mortise Pal even makes a set of templates that enable you to rout perfect dowel holes.

While not mentioned in the User Guide, you could also rout mortises in 1/2" or 5/8" stock. All you need to do is place a spacer in back of the stock, next to the jig fence (use double sided tape to hold the spacer in place). The issue here is that if you use a 1/4" bit, the walls of the mortise won't be very thick. You'd want to use a 3/16" bit (though finding one with an overall length of 2-3/8" might be a bit of a challenge). You would also have to mill your own loose tenon stock.

The Mortise Pal is an excellent jig that is superbly machined, and should give years of reliable service. Woodworkers of any skill level can quickly rout perfectly fitting mortises every time.

Reviewed November 2011