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Honored Advisor
krumy205747
Posts: 2,457
Registered: ‎10-28-2009

Simple, self-centering mortise jig

[ Edited ]

Had to unload some tools recently and one of the things I sold was my dedicated mortiser. I didn't use it a lot but enough that I missed it. I decided to make a router jig and this is what I came up with. It's designed around a 12"X12" acrylic router table insert as I already had one.

 

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This is just a couple pieces of particle board 8"X12" with a 3/4" spacer in the middle at the bottom. It's just held together with drywall screws.  I routed a slot on either end in both pieces. The slots are for a simple clamp.

 

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Here is a picture with a piece of stock clamped in the jig base. I know the base is not really necessary but it gives the router a little more stability when cutting the mortise.

 

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I had a router table insert laying around so I routed a couple of 1/4" grooves in it to accept a shoulder bolt. I then bought a nylon bushing, a shoulder bolt, and a lock nut at the local hardware and installed them in the insert.

 

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To set the location I just eyeball the router bit in the center of the stock. Slide the bushings against the jig and tighten them up. It's easy to adjust to get it "just right" It's also easy to adjust for an offset mortise.

 

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The whole assembly is just mounted in vice for machining.

 

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Using a jig base isn't absolutely necessary but it adds stability and lets me cut a mortise right at the end of the stock. You can see in the picture the stock is slightly recessed below the jig body. That way the router is riding on the jig and not wanting to rock back and forth.

 

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The "clamp" is just a piece althread and a couple of handles to squeeze the jig base against the stock.

 

 

It's very simple but works well. The best part is though, aside from the insert which I already had I've got well less than ten bucks in it.

 

Steve K

Where do I get my wood? I'm oppor"turn"istic!!
Community Manager
MSWOODcraft
Posts: 5,364
Registered: ‎10-23-2009
0

Re: Simple, self-centering mortise jig

Much coolness here!

Best,

Matt Seiler
Wood Online Moderator

Honored Advisor
ynoT
Posts: 10,803
Registered: ‎10-23-2009
0

Re: Simple, self-centering mortise jig

That is neat and simple. Thanks for showing us your creation.

 

Tony

"Why worry about things you can't control when you can keep yourself busy controlling the things that depend on you."
Senior Contributor
Larry Doug
Posts: 922
Registered: ‎01-25-2010
0

Re: Simple, self-centering mortise jig

I like it. If I didn't have a dedicated machine, I would build one of these. :smileyhappy:

Honored Advisor
amateur60
Posts: 1,654
Registered: ‎10-24-2009
0

Re: Simple, self-centering mortise jig

Pretty nifty, but self centering isn't the best way to go.  That makes the board thickness critical.  Better to reference off of the show or face surface, and then do the same when cutting tenons.  That way you get faces aligned right even if thicknesses are slightly right. 

Honored Advisor
krumy205747
Posts: 2,457
Registered: ‎10-28-2009
0

Re: Simple, self-centering mortise jig

[ Edited ]

Thank you. I have to admit I haven't used the jig in any meaningful way as yet, and this version is more a "proof of concept" than anything. If/when I do a project I can see the jig being quite a lot longer so I can fashion some sort of stops to control the length of the mortise.  I just knew I had to do something to replace the dedicated mortiser I sold. I don't see it being a really big issue though. I have always cut my tenons referencing off the center with good results. Typically I prepare my own stock and bring everything to thickness at the same time. With care setting up I should be able to get within a few thousanths pretty easily. Nothing a quick hit with an ros can't make purdy.

BTW, I tweaked this version of the jig just a little.

 

IMG_5914.JPG

 

This is the inside face of one half. Routed a relief in the surface and pulled the teeth from a tee nut. What this does is allow the clamp to also act as simple height adjustment when clamping the workpiece.

 

Steve K

Where do I get my wood? I'm oppor"turn"istic!!

 

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