Loose Tenon Mortising Jig (Huh?)
The mortise and tenon joint seems a relatively simple joint to make - until you try to make one, let alone a pair or pair of pairs. The length of the tenoned part(s) is not the "visible length" but the visible length PLUS the tenon lengths. Lots of careful measuring, layout lines, critical machine set ups, critical cuts and attention to parts orientation during cuts. And often, when all the cutting's done, there's shaving and paring to do. And if you blow any of the tenon cuts you often have to make a whole new part. For a newbie, the first experience making mortise and tenon joints can be confusing, frustrating, disappointing, and sometimes - the last experience with mortise and tenons.
But there is another, lower risk, less obvious, and perhaps the easiest method - the "Loose Tenon" - a mortise in both parts and a separate "loose tenon" to fit in the mortises of the two parts to be joined. The parts are all their visible length - no adding tenon lengths. No shoulders to cut. You only need to layout one face on each part. No need to make a new part if you blow a tenon, you just cut another loose tenon.
You can build a simple jig to make mortises in both end grain and side grain. I got this idea from the article "Tight Joints on the Loose" by Bill Hylton in the April 2004 issue of Popular Woodworking and added a pair of modules for mortising mitered corners. You can make this jig on a Saturday and start doing loose tenon mortise and tenon joints the next day. The one I built took a little longer - I didn't have anything to go on other than what was in the article. My hope is that what follows will make things far easier for you.
- a 2 foot' x 4 foot piece of 3/4" ply
- a 2 foot x 2 foot piece of 1/2" ply
- a 2 foot piece of 2x2
- a yard of 3/4" x 3/4" hardwood
- about a dozen 5/16 - 18 carriage bolts with washers and nuts
- a dozen wood screws
- a half dozen hold downs of your choise
- a pair of threaded inserts & bolts to go in them
It's fairly easy to make this jig and the only thing you need to make sure of is that the back edge of the "table" on top of the Base Unit is parallel to the front edge of the Base Unit since it's what.the router guide will ride against
that the "table top" is square to the face of the Base Unit.
Here's the idea. There'll be a parts diagram and parts list, along with a parts layout at the end of this article.
There are two other add ons for dealing with parts with mitered corners. They'll be shown later.
Doesn't look that hard to make does it. Let's see some pictures of this thing ---->