Mortising Jig - Feedback welcome


bbaude

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Hey Folks,

I had posted earlier that I was struggling with my first attempt at mortising with a router.  The general consensus was to keep practising.  I had suggested a jig and it was generally agreed to be a good idea.  So here is the concept I came up with in the spirit of the mortising block jig I have seen used.  It should be able to handle vertical and horizontal pieces up to a reasonable size.  The idea would be I would clamp the ears of the jig onto my work bench and the plug router sits up top with an edge guide on.  Also note, the T-Track is present but doesnt show any stops (but that is the intent).

Front View of the Jig (I have removed the dimensions but the main piece here is 14"x14")

smaller_mblock_assembled.jpg

Side-angled view of the jig (shows t-track and groove for the router's edge guide, ears for clamping)

smaller_mblock_assembled2.jpg

Front view with the holder and a horizontal sample.

smaller_mblock_assembled3.jpg

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A couple projects ago, I built this simplified version of a similar jig to the one you've designed. It was my first project with loose tenons and I thought it would be a throw-away jig, but I've used it on two other projects since. In the picture, I've marked out my mortises on each piece, but I don't do that anymore. That was the first project I used it on and I was paranoid. Now, I just mark first piece, setup the jig and cut mortises. On my last project, I cut ~30 mortises one evening with it. Not as fast a Domino, but not bad!

I built it off this design:

http://thecraftsmanspath.com/2007/09/25/loose-tenon-joinery-budget-alternative-festool-domino/

 

jig.JPG

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  • 3 weeks later...

OK, you have a jig. Now, to get the most accurate mortises with your router, you should use  up spiral bits and begin cutting each mortise by straight plunging many times, moving over about 3/4 of the bit diameter before each plunge. Then go back and plunge the router to full depth desired and then move the router side to side slowly to clean the mortise out. The two step process of plunge cutting to remove the majority of the wood, followed by the side to side motion to clean the remainder out, will minimize the effects of side pull of the bit and the resulting mortise width error that you can get without this plunging action to remove the bulk of the material. It is the Leigh recommended way to use a Leigh FMT jig.

Charley

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