Box Joint finger/socket width issue

I’m designing a box to be carved out of cheap pine 3/4" wood. I’ve included a picture of the assembled box from Sketchup along with a copy of the two svg files I use in Easel. I’ve also included a link to my project. I have an X-carve that is a little over a year old with only a laser modification. My question is about the box joint widths. In my SVG file each finger and socket is 0.777" wide. The carved pine comes out with each finger at about 0.747" wide and each socket at roughly 0.805" wide. I’m telling Easel that the wood is soft maple (because the pine is so soft) and I’m using straight cut 1/8" bit. I was hoping someone might have a suggestion for me as to how to get the fingers and joints much closer to the goal of 0.777" wide.

Thanks
Jared

shelf-longside



Have you measured the actual width of a straight line in order to establish effective bit diameter?
All bits are not 100% true in size and most routers have some degree of runout. Hence the need to do a line measurement in order to compensate.

I am unfamiliar with the Sketchup->SVG work flow so can not say if errors can be introduced during that stage.

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This is my guess as well, at first blush.

Would you mind clarifying what measuring the line means? I’m carving the pins with outline setting in easel so I assume it takes the bit width in to account.

Thank you
Jared

Easel take the width you entered into account, not any deviation from slight diameter variation (bit) , run-out (router/collett) or deflection (the CNC itself)

Makes perfect sense, thank you for explaining! I think that did help a bit but I’m not getting the end result I’d like to see. Maybe I’m just being too picky and the joints I’m getting are as good as it can get.

I went in to inkscape and reduced the line size on the shape to the smallest unit possible in case that was what you were meaning by measure the line. I understand now that wasn’t what you meant, I’m not sure if that helped.

I’ve carved a test square and took a hand full of readings. (0.129, 0.130, 0.132, 0.131) They average to 0.1305. I assume what you were saying was take that average and put it in to the easel as the bit size.

20 mins later… I carved a test… A bit closer to the .777 results I was looking for on both pin and socket (0.763 and 0.783)

With the increased bit size from 1/8 to 0.131 the deviation in pin to socket went from 0.055" down to 0.020".

Unfortunately after that one good test I’m seeing roughly the same results with my work products and I’ve run other tests and seeing different results as well.

I’ve also noticed that if I measure the line as its being created it grows in width. With my 1/8 straight edge flute bit the first pass measures 0.120, then the second pass measures 0.121 and so on until the last pass ends at .131… I also notice that the straight cuts parallel to the X axis (going against the grain of the pine board) are not as wide as the straight cuts that parallel the Y axis (going with the grain of the pine board).

My Dewalt is set at speed 2 and my IPM is 40 with a cut depth of 0.06.

This last picture is of the gap in the width of the pin/sockets when two pieces have been completed.

Thank you very much to everyone who responded and would appreciate any other advice.

Sounds like your machine might not be fully calibrated if you’re cuts keep getting larger on each cut.

You won’t have it fully flush because you are putting a square peg into a rounded ended hole. You might want to add dogbones.

Have you played with the box generator in easel? It will automatically add them to the inside corners so you can get it more flush (but you will have a small circle in the cut, but your corners will fit flush. Depending yon your finish you could fill them)it’s pretty easy to use for these kinds of boxes.

If the width increase the deeper you go this suggest that your router isn’t truly perpendicular to the work piece. As in slightly tilted or raked Z-axis.

Difference in width when going along vs across the grain indicate backlash/tool deflection due to the difference in “resistance” when carving. The harder the wood press against the toll the more it will deflect. It may also be contributed by difference in rigidity in the X vs Y axis.