# Box joint jig accuracy



## Kryten602 (29 Sep 2017)

Guys, I need some advice from an expert on jigs. I made this box joint jig for my table router and it works well, everything lines up but when I test assemble two sides without glue there is always a tiny bit of play. Once glued they're acceptable, but when dry they could be tighter (from the ones I've seen on YT. Where is the tiny bit of inaccuracy coming from would you guess? 1/2" joints by the way.


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## MusicMan (29 Sep 2017)

I am almost certain that it is the distance of the peg (into which you slot the cutouts) from the router cutter. I have a commercial one working on similar principles, and this distance is adjustable for tightness of fit. If you want them tighter you should move the peg a fraction closer to the cutter. If it is all glued up, try paring one side and shimming the other.

Keith


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## Kryten602 (29 Sep 2017)

Thanks very MusicMan. Very helpful. I will try your suggestion. As you mentioned it, what type of commercial adjustable jig do you have? It always annoys me that the mitre slots in different makes of table routers, table saws and band saws all seem to have different size grooves. There must a market for an adjustable slip to fit all makes of machine tools.


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## Steve Maskery (2 Oct 2017)

MusicMan":2zodsaf6 said:


> If you want them tighter you should move the peg a fraction closer to the cutter.



Keith, are you sure about that? I think it is the other way round. Moving the peg towards the cutter will make the fingers even narrower and therefore sloppier, won't they? Moving the peg away will make the peg fatter and therefore tighter. Or am I just suffering from nearly-midnightness?

FWIW, this is my offering, and it is adjustable:
https://www.youtube.com/watch?v=eKEB-BIq9qI&t=1s


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## Kryten602 (3 Oct 2017)

Yes, thanks Steve. I was thinking about this before I posted and that's what I was thinking. The 1/2" bit is correct, so the pegs need to be slight wider so moving it away from the cut makes sense. Thanks for posting.


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## MusicMan (3 Oct 2017)

Sorry, yes Steve, you are right, move the peg further away! Senior moment ....


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## monkeybiter (3 Oct 2017)

I've built both types, fixed indexing peg and adjustable like Steve Maskery's, I'd strongly recommend the adjustable type. Easily tuneable for very nice fitting joints.


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