# Best bit size for box joints



## whitelaw66 (Oct 3, 2010)

I've been playing around with a box joint jig that I made that is for 1/4" joints. It works fine on 1/2" stock or less. Also, it gets more difficult to join two pieces when the stock is more than about four inches. So, any thoughts as to a rule of thumb for the best bit size to use in comparison to stock thickness and width?


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## jschaben (Jun 21, 2009)

white66 said:


> I've been playing around with a box joint jig that I made that is for 1/4" joints. It works fine on 1/2" stock or less. Also, it gets more difficult to join two pieces when the stock is more than about four inches. So, any thoughts as to a rule of thumb for the best bit size to use in comparison to stock thickness and width?


Hi - Welcome to the forum
It sounds more like an error in your jig indexing than a bit size issue. It doesn't take much of an error as it is compounded in each subsequent joint. Let's see, you're making 1/4" joints and it is OK until you get to about 4" or 8 fingers. To me, that's pretty close, a little sanding might fix the jig.


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## whitelaw66 (Oct 3, 2010)

Thanks, John. I should add that I'm having more of a problem when using stock that is 3/4". Then I seem to get wavy fingers with the 1/4" bit.


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## bobj3 (Jan 17, 2006)

HI white66

Here's a little rule I use

1/4" wide box joints,, 1/8" to 3/8" thick stock
3/8" wide box joints,,,3/8" to 3/4" thick stock
1/2" wide box joints...1/2" to 1" thick stock
3/4" wide box loints,,,3/4" to 1 1/2" thick stock
1" wide box joints,,,,1" to 2" thick stock

But on your jig it sounds like the indexing pin is not right the button..if you sand one it will change the fit on the others as well.. 

The one below will not flex (good for 1/8" to 1/2" thick stock)
1 PC 1/2" SH 5 Slots Adjustable Box Joint Router Bit - eBay (item 140497751832 end time Jan-12-11 17:09:17 PST)

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white66 said:


> I've been playing around with a box joint jig that I made that is for 1/4" joints. It works fine on 1/2" stock or less. Also, it gets more difficult to join two pieces when the stock is more than about four inches. So, any thoughts as to a rule of thumb for the best bit size to use in comparison to stock thickness and width?


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## Ralph Barker (Dec 15, 2008)

white66 said:


> Thanks, John. I should add that I'm having more of a problem when using stock that is 3/4". Then I seem to get wavy fingers with the 1/4" bit.


Hmmm. That sounds like the 1/4" bit may be working too hard, or something else is flexing. Is this a 1/4" or 1/2" shank bit?


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## whitelaw66 (Oct 3, 2010)

1/4" shank. Thought there might be some flex as well so changed to a stronger base plate on the router. Haven't tried it yet, though.


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## ScottR (Jan 8, 2011)

Adjusting The Fit

If the fit is too tight, tap the fence towards the bit. If the fit is too loose, tap the fence away from the bit.


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## LexB (Apr 12, 2010)

I've use a 1/4-inch bit for box joints in material as thick as 3/4-inches. I don't cut it full depth in one pass though. I take several passes, each about 1/4-inch deep to reach the full depth. I use an Incra LS fence, so repositioning it is no problem. You could probably do the same thing with a home-built jig too, if it's a snug fit in the miter track.


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## Mike Wingate (Apr 26, 2009)

Select the bit to match the thickness of the stock. Or 1/4", 3/8" and 1/2" if using the Incra setup.


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## whitelaw66 (Oct 3, 2010)

Thanks for all the responses. I made a 1/2" jig and that works much better with 3/4" oak. Still needed to give it a couple whacks with a mallet to get it together, unlike the pine I was used to.


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## KUMZUM (Jun 19, 2010)

This may be a sacriledge to mention. But....

box joints can be made quickly and easily on a table saw, with a simple sled and jig. You can get pretty fancy like this:

YouTube - Box joint jig with screw advance


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## whitelaw66 (Oct 3, 2010)

Quickly....true. I don't know how easily considering that guy makes his own wooden gears for the mechanism. His website is pretty amazing.

I haven't tried them on the table saw yet but will probably get around to it. Most of the reason I do more with the router table is because I have a Craftsman table saw with a bizarre miter gauge slot of 5/8".


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## whitelaw66 (Oct 3, 2010)

Turns out my problem was not using a sharp bit. Amazing.


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## Micah (Oct 11, 2010)

*box joints*

Hi,
I'm a very beginner at woodworking, but learning and enjoying the router (+table). Photo is a box under construction that I cut today. (You can also see the crude workbench that I'm building at the same time.) Anyway, I just read something today that I plan to try for these small boxes. That is, if the pieces start with pin and end with slot (evenly, by picking the right height), then all the pieces are routed the same. So, you set it up, clamp all four pieces together, and route them at one time! Credit goes to Bill Hylton's book "Ultimate Guide to the Router Table" page 91.

-Micah



white66 said:


> Thanks for all the responses. I made a 1/2" jig and that works much better with 3/4" oak. Still needed to give it a couple whacks with a mallet to get it together, unlike the pine I was used to.


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## Ralph Barker (Dec 15, 2008)

Micah said:


> Hi,
> I'm a very beginner at woodworking, but learning and enjoying the router (+table). Photo is a box under construction that I cut today. (You can also see the crude workbench that I'm building at the same time.) Anyway, I just read something today that I plan to try for these small boxes. That is, if the pieces start with pin and end with slot (evenly, by picking the right height), then all the pieces are routed the same. So, you set it up, clamp all four pieces together, and route them at one time! Credit goes to Bill Hylton's book "Ultimate Guide to the Router Table" page 91.
> 
> -Micah


That is a useful approach. Just be careful when applying and tightening the clamp. It's easy to get the clamp off-center, or un-square, which can introduce a twist to one or more pieces of stock in the stack.


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