Sunday, March 21, 2010

Box joint jigs for the router table -part one

I don't know wether I should be praising the merits of the Grr-ripper today or explaining the build of my new box joint jig.
This picture shows how useful the Grr-ripper can be when working with small stock and needing dead on accuracy.
The part cut is oak and will be the guide bar for my 1/4" box joint template.
I cut it in a matter of seconds in complete safety and it measures 1/4" on both ends of the stick. That's first for me as the saw usually creeps up on the loose end of a piece like this. I would not attempt this without a grr-ripper on a table saw.

With the gripper I was able to cut 3 keys for the jig in less than 3 minutes including set up time.
I set the saw gap with metal lathe cutting tools that just happen to come in fractions so I have a range of them from 3/16" to 1/2" and use them instead of measuring. (look for them at any tool shop that sells metal lathes.
The Grr-ripper allows one leg to sit on top of the wood while the other leg can be adjusted to balance the rig when passing over the blade.

I left the keys full length for the glue up so they would rest on the base of the jig and be parallel to the sliding table
I'll cut them off long enough to hold a series of boards for gang cutting the box joints. Incidently, that is why I abandoned my other style of jig. This seems like it will give me more control over the cuts.

The way I positioned the keyway is shown here.
I cut the first a slot in the jig dead center and just slightly higher than 1/4".
I want the ends of the joints to be just proud of the sides for finishing.
The method for getting the keyway position is simple now.
Just put the first keyway in the first slot and and a suitable key spacer next to it. ( in this case the 1/4" measuring bar stock.
Lock the jig at the back and run the lslot.

What I have now is a "carriage" with the keyed jigs mounted on the front.
The carriage follows the outside of my router guide bushing allowing me complete freedom to push and or pull the stock past the cutter.
I don't have to line up the router bit anymore as the brass bushing takes care of it as long as the router dosen't move in the table. ***** a caution for those of you that pull your router out for other tasks.*

Here's a shot of the bushing I used. I used a fairly large one - (3/4") in anticipation of also using this jig to cut my pins for dovetails. ( more on that later)

Today I had time to run some 5/16" stock and test the jig for spacing and accuracy.
It took a bit of getting used to so I ended up cutting about 5 joints before I got the hang of it but here's what you should be able to get with this jig:

I will now make notes in my log book for future reference. This generally shortens my setup time next time I use the jig.
This is the jig I made first , then realized it used a lot of materials up for each size change.

A pic showng the front of this jig:

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