Box joint gadget.

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TReischl
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Re: Box joint gadget.

Post by TReischl »

I have this rule when I am working with stuff that needs close tolerances:

Do NOT adjust the geometry of the workpiece to suit the tool.

The geometry should always be the ideal size. If I am making .25 box joints those joints are drawn to .25 on both pieces no "tolerance" is built into them.

The reason is simple, modifying geometry leads to mistakes, offset the wrong way, etc. Plus if you go back to the job sometime in the future it is easy to forget that you changed the geometry to suit the tool. And, it is much easier to just click on the Edit Tool button, tweak the cutter and recalc the path. The original spec for the tool remains unchanged if the Edit button is used.
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cusoak
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Re: Box joint gadget.

Post by cusoak »

Well today I had some time to play around putting the finger joint box together.
Just a little sanding and it went together fine nice tight joints.
The only thing is that the fingers hang past the sides about 1/8" is that right.
Now some of that is the thickness of the material. It is baltic birch which is not .25 but .232 in thickness.
So what would be a normal size to stick out past the sides to sand off.
The gadget is ok But what I really want to learn how to do is cut the joint off the front of my Shapeoko.
Jeff

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TReischl
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Re: Box joint gadget.

Post by TReischl »

An 1/8 is a lot to sand off if you ask me. Most folks I know shoot for about a 1/64th when doing normal woodworking. When I do them on the cnc I add about .005. One caveat: I run my stock through a drum sander and I measure it very carefully. So it is consistent and a precise size. BTW, I usually program things like that AFTER I have prepared the stock. If you program first then you have to either leave a lot of excess to account for errors or drive yourself insane trying to thickness things to a predetermined thickness, for no good reason. Plywood is always a problem because it varies so much.
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cusoak
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Re: Box joint gadget.

Post by cusoak »

Ok I want to make a box that is 3.5" deep 7" high and 7" wide.
I want the top and bottom of the sides to have the ends with the finger joints.
I want the top and bottom to have the finger joints on ends only. So that the 4 corners are where the finger joints are.
Can that be done using the box gadget.
Is there some way to cut the vectors at the corners of one edge and then reconnect it with a straight line.

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Adrian
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Re: Box joint gadget.

Post by Adrian »

cusoak wrote: Is there some way to cut the vectors at the corners of one edge and then reconnect it with a straight line.
Node edit mode, cut on the two nodes (or delete the span) and then use the Join with a straight line tool.

You can also do it with the Interactive Trim (scissors tool) and the Join with a straight line tool.

Mark Jones
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Re: Box joint gadget.

Post by Mark Jones »

cusoak wrote:
Mon Aug 05, 2019 12:51 pm
Well I ran the box joint gadget yesterday and cut out a box. And of course it did not fit together. joints to tight.
So I was using .25 material and an .125 end mil in plywood.
I did not put anything in the allowance box.
So my question is this.
IS the allowance bases on anything other than just a guess
If that is correct what might be a good starting point for an allowance.
Jeff
I found that .006 was a good number for quarter inch plywood. It's still tight. I don't dry fit them any more. They fit and I glue them and come out cleaner if your not pulling them apart dry fitting as it damages the plywood. I have made over 10 boxes of various sizes using quarter inch plywood. They are strong with 1/4" box joints.

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