Bit Choices for Miter-Folding Cuts

      Advice on tooling for miter-fold joint fabrication. April 29, 2011

What type of bit do most use to run a 90 degree miter fold on a machining center?

Forum Responses
(CNC Forum)
From contributor S:
A miter-fold or v-groove bit or blade.

From contributor M:
We use insert bodies for different angles with replaceable knives, and a 9" diameter V grooving saw body with replaceable knives. We got the router bit tools from Courmatt and the saw from H3d Tool. Both tooling types work very well.

From contributor L:
We use V bits made for miterfolding, but the aggregate and saw body system is better. Miter folding solid surface is a real time saver!

From contributor R:
You mean a nested base machining center, right? This is all possible on pods and rails, but your Z registration on a spoilboard is way better and your results will be better using nested as well.

I use a single flute Amana 90 degree replaceable tip bit. There is a lot of back and forth about using a 91 degree bit, and a lot of guys say they do this so there is room for glue. For wood veneers I just don't get it. Corian, eh... maybe. I understand that you want the tips to touch and not get held up by the heel, but two degrees is a lot of space on a 3/4 thick veneered panel. Yellow glue fills a small gap, but I strongly prefer to use a 90 degree bit and have the surfaces much closer together. I have done a fair amount of folding this way with very good results.

Cut out your parts, flip them over and bring the tips to just touch. Use clear 2" packing tape, because it doesn't stretch much and you can see through it to help align and check your miters. Flip the whole arrangement over, apply the glue to the joint with a bottle and small brush, and fold it up.

From contributor R:
Apologies - I have a Vortex bit, though I have used Amana in the past. Both work well.

From contributor A:
We have been miter folding on pod based machines for over 14 years, first with a V bit that was flat on the end (a point pushes the spoilage into the joint), with a second pass with a custom saw blade (at the time it was custom). Now we do it with a horizontal planing aggregate and a 100mm x 100mm cutter. You do have to be careful for z registration, but it works fine.

From contributor Z:
Yes, a nested based machine center. When running the miter fold, is it best to stop just shy of the face veneer? I've tried this with a v-groove bit, but the point had about a 1/8" flat spot. I have now ordered the Amana - just waiting on arrival to give it another try. Thanks for the great info.

From contributor M:
You will want to get as deep as possible with your cut without separating the pieces or shortening the net width of the part. If you pre-tape the parts (we do when practical), then cut to the depth of the tape. The tape acts as a hinge and can be removed when the glue is set.

From contributor W:
Amana part #RC1028 - v-Groove miter fold insert router bit.

From contributor O:
Try Royce Ayr lock mitre cutting tool - works beautiful!

From contributor E:
1/2" compression bit and a saw blade ground at 45 degrees to create a self squaring Z pattern with more glue surface area.

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