CNC cutting finger-joints

[physics]

Hiya!

I have access to a CNC router table at the local makerspace, and realized it can probably cut down on the time for me to fabricate some cabinets. The one thing I'm unsure about is the finger-joints. Assuming I'm only able to work with the bit perpendicular to the sheet stock, I'll have to cut "dogbones" for the internal corners of the finger joints (picture from here https://cutlasercut.com/getting-started/cnc-machining/):

 Now I've seen that there are ways to minimize their visibility (https://fablab.ruc.dk/more-elegant-cnc-dogbones/), but I was wondering if anyone has any strong opinions about dogbones in general for finger joints. Effects on strength, durability, air-tightness of cabinet, extra work to fix these issues, etc.

Thanks!

[nauta]

Hey man

Wouldn't the glue fill the little gaps? I guess Fender and everybody else didn't worry about it since they made openback cabs and covered everything with tolex

If you're gonna go with varnish then maybe that will fill the gaps? You could paint the inside corners sort of sloppy as a poor man bandaid or add caulking but that might just dry out and fall off.

Maybe most of the gap is taken care of when you bang it together.

Peace

[makinrose]

I'm writing to give you little perspective on how box joints are cut by the bigger cabinet makers. I've worked with several cabinet makers over the years and also have my own experience making box joints in my shop. None of those makers use a CNC machine to cut box joints them although they use a CNC router for many of the panel cuts. For smaller widths most makers use a hauncher which is a machine that can cut box joints into several panels at once. However, when the width of the board exceeds the hauncher capabilities the panels are routed with a hand router and a jig. Pretty much all of them use 1/4" box joints or rarely 1/2 inch joints. If you are using solid wood for any of the material being able to compensate for slight cupping can be done on the fly with a jig and router. This is essential if you plan on working with pine. I'm not saying doing it with a CNC isn't possible only that there are probably complications that make doing it as described earlier more practical. I hope that is helpful!

[physics]

Hey man

Wouldn't the glue fill the little gaps? I guess Fender and everybody else didn't worry about it since they made openback cabs and covered everything with tolex

If you're gonna go with varnish then maybe that will fill the gaps? You could paint the inside corners sort of sloppy as a poor man bandaid or add caulking but that might just dry out and fall off.

Maybe most of the gap is taken care of when you bang it together.

Peace

Maybe the glue would fill the gaps? Not certain. I think Fender didn't bother with finger joints at all but I could be mistaken. I think for the smaller tool sizes I've seen people say you can just undersize 'em a little and then bang 'em together for a snug gap-free fit. I think I'll have to use a slightly larger tool for the 3/4" baltic birch I want to use, and I'm not sure how things will pan out there.

Thanks for the ideas!

[physics]

I'm writing to give you little perspective on how box joints are cut by the bigger cabinet makers.  I've worked with several cabinet makers over the years and also have my own experience making box joints in my shop.  None of those makers use a CNC machine to cut box joints them although they use a CNC router for many of the panel cuts.  For smaller widths most makers use a hauncher which is a machine that can cut box joints several panels at once.  However, when the width of the board exceeds the hauncher capabilities the panels are routed with a hand router and a jig.  Pretty much all of them use 1/4" box joints or rarely 1/2 inch joints.  If you are using solid wood for any of the material being able to compensate for slight cupping can be done on the fly with a jig and router.  This is essential if you plan on working with pine.  I'm not saying doing is CNC isn't possible only that there are probably complications that make doing it as described earlier more practical.  I hope that is helpful!

Hmm, now that is an interesting idea. I don't think the shop I have access to has a hauncher, but maybe I can get it on the list of wanted items. The hand-router and jig may be the easiest method for the near future since it avoids having to make a sled jig for the table saw or fiddle with round corners. Thanks for the ideas!

[physics]

Some further thoughts: with a router I may have to fiddle with an additional backer board to sandwich both sides of the workpiece to avoid tear-out, so I might have to do a bunch of fiddling with clamps. Table-saw only requires one piece, which can be part of the sled. I don't want to sink time into a sled, but I see that there exist purpose-made box joint jig sleds with the capacity for tall boards like the Incra i-box, which is comparably priced to the dovetail/finger-joint router jigs I've been looking at. So that's another possibility. I'll probably go with the router jig if I can figure out a way to keep the 2nd backing board clamped in place while just moving the jig and it's backing board, or if I end up being wrong about needing the 2nd backing board.

[makinrose]

Some further thoughts: with a router I may have to fiddle with an additional backer board to sandwich both sides of the workpiece to avoid tear-out, so I might have to do a bunch of fiddling with clamps. Table-saw only requires one piece, which can be part of the sled. I don't want to sink time into a sled, but I see that there exist purpose-made box joint jig sleds with the capacity for tall boards like the Incra i-box, which is comparably priced to the dovetail/finger-joint router jigs I've been looking at. So that's another possibility. I'll probably go with the router jig if I can figure out a way to keep the 2nd backing board clamped in place while just moving the jig and it's backing board, or if I end up being wrong about needing the 2nd backing board.

In case it helps:  I have the Porter-Cable standalone jig and the Incra i-box.  I find the Incra much harder to use with wider boards since any tiny error in spacing compounds with the more joints you cut.  The Incra works great for drawers and other narrow pieces but I had trouble with wide pieces.   The Porter-Cable is a great jig---no complaints.  I've looked into the various Lieh jigs which look awesome but haven't pulled the trigger on one.