Miterfolds for clean corner joints

A sweet technique for classy corners. November 21, 2003

At the last IWF in Atlanta, I noticed the "V" grooving of materials (i.e. Corian) in order to make mitered joints. The effect was tremendous. Has anyone tried this technique with plywood and with what results? I'd really like to use this technique with some plywood columns, but don't know if it will work or not.

Forum Responses
(Architectural Woodworking Forum)
From contributor A:
We miterfold almost all outside corners in wood, veneer, metal, laminate or solid surface. It works especially well in veneer - we leave the most infinitesimal bit of veneer and then fold it - unbelievable edge. All our laminate tops and most of our solid surface tops have miterfolded drop edge and back splash. We do 3" solid surface radius edges with a special cutter head. Metal is also great - we can leave a significant amount of material and make a very clean soft edge.

From contributor B:
Are you using CNC to cut the miterfold, or some other method? Any ideas on methods without a CNC?

From contributor C:
How do you handle variation in thickness of plywood? The quality in your area must be something. When you miterfold solid surface, do you cut through completely or leave a hairline?

From contributor D:
It's not that hard. I use simple CNC router and work from bottom of plywood up, that way variations in thickness don't matter.

From contributor E:
The only way you should V groove is with an insert tool for a router. A specially designed toolhead also can be used on other machines with a variety of cutting edges.
On a TCT (carbide) has a radius on the bottom of the cutting tool, resulting to machine all the way through the material.

An insert tool (single flute) will have a true point, meaning taping the material and bending it without separating prior to gluing. Also, with an insert tool you have no diameter or angle changes. This happens too frequently on other types of tools.

From contributor F:
We do mitre folds by 45ing the material face up with a table saw. Place the two edges close together, tape with heavy packaging tape on the face, flip, glue, fold. We have done two, three and four sided shapes. Be careful the tape adhesive is not so aggressive as to pull pieces of the face veneer off. Let the piece dry completely, peel of the tape, lightly sand and ease the edge and then finish. Practice on some scrap material first. The method works great.

From contributor A:
I do a fairly large volume, so I ended up buying a used Auto V groover - a superb machine with a Mickey Mouse fence which I replaced with a custom machined one. This is a big investment, but it has paid off at the volume level that we produce. I have a friend in Phoenix who has been miterfolding for years also at fairly high volume and he was using a handheld Art Betterley unit until he upgraded to an Auto V. He still uses the Betterley for some purposes. We did a lot with our Altendorf with the method described by contributor F above - it's slower, of course, but it works fine. We did a bunch of 30 foot long 2' square section box beams a few years back. You are only limited by your imagination.
As far as thickness, we groove from the top down, so it's always right - the only problem is when you are doing a double fold - folding the material back on itself, in which case you have to go to the thickest dimension and then shim for variations.

We cut all the way through anything brittle, including solid surface and just slightly into the tape. Metal and veneer and some plastic will bend if treated right and the edge is even better.

In addition to speed and quality, we have been able to eliminate contact cement almost entirely from our operation. Everything laminate runs through our layup line with PVA glue and the results are much better - so is the environment.

From the original questioner:
Has anyone tried a 90 degree V groove router bit and plunge router? What were the results or what do you think they would be?

From contributor A:
The tip of the bit gets very hot and will dull fast. The Betterly system uses a 7/8 or 1" diameter flat cutter and tilts the router 45 degrees so that the chips are clearing and there are two cutters doing the work. There are also some 90 degree bits with only one insert cutting edge that work very well, but the problem will be getting a consistent depth running it by hand. I dreamed up a number of shop-built machines before investing in the Auto V, though I never built any of them. I think the most likely to succeed would be a shaper with a power feed for grooving close to the edge of a panel, or a very good radial saw like the Omga with extra horsepower that could turn a heavy insert cutter head. Omga actually makes a unit with two saw blades to do miter folding but I've never seen it work.

We've had the Auto V groover about 2 years. It's completely trouble-free and maintenance-free so far, except the dinky fence I mentioned. Also, dust collection is somewhat of a problem.