# Box joint jig for router



## durdyolman (Mar 22, 2013)

Years ago I found a piece of 1/4 plexiglas. Drilled appropriate size holes (slightly larger than the router bit) in the appropriate places. Mounted 4 keys (1/4, 3/8, 1/2, 3/4). (Don't let them interfere with each other). A known size spacer to set the distance from key to bit. I made a few sacrificial push boxes, square all around. (You can see why I call them sacrificial). I can either use the DC in the fence or turn the jig to use the external DC. IMHO better than a TS and dado blades.
Jimmy
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Typical results


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## RogerInColorado (Jan 16, 2013)

Neat Idea. How did you mount the keys to the plastic?


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## durdyolman (Mar 22, 2013)

RogerInColorado said:


> Neat Idea. How did you mount the keys to the plastic?


I used #4 flathead screws on underside to mount the keys. Epoxy might work but I may need to change the keys someday.


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## Wood4Brains (Jul 25, 2012)

I'm not sure exactly how this jig works.

In the second photo, what is that little black piece of plastic (or is it metal) that appears between the router bit and the 3/4 inch wood key? Is that just so that you could position the wood key the right distance before screwing it to the plexi?

Could you explain a little bit more about how it actually works (meaning, what one has to do to the workpiece with your jig) to make the joints?

Thanks. Sorry if I am being thick.


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## 4DThinker (Mar 13, 2013)

I'll guess the black piece is a precise key for setting the bit distance from the rail. Making 3/8" fiingers with a 3/8" bit and 3/8" rail, the bit needs to be 3/8" from the rail. If the fingers end up too tight, then reduce this rail-bit distance just a little to leave smaller fingers. The slots will always end up the diameter of the bit used.


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## durdyolman (Mar 22, 2013)

*I need some new push boxes so*

I decided to make a couple new sacrificial push boxes and at the same time maybe make a pictorial to show more clearly what I am doing. The boxes will be of 17/64 material with 3/8 box joints. (Tip..the key must be less in height than the thickness of the material). I eyeballed the center of the bit to the hole in the jig, and applied clamp #1, never to move again. I placed a known 3/8 spacer between the bit and the key, and applied clamp #2. (This will be where any adjustments are made). I adjusted the bit to 17/64 above the jig surface.







Then I must rout a slot in a piece of scrap. IMPORTANT! Measure the cutout. Some bits vary, some have a little runout. In this case it worked out correctly.














After checking the fit on the scrap pieces, it's time to get to work.







This box fit together so tightly I had to hammer it together. It's glued up now and after a little belt sander action, I'll cut it in half on the TS and have 2 push boxes. (Oak)








I am open to suggestions and comments on how to improve this. tyvm Jimmy


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