Personally, I would order the doors or, if I were making them myself, would try to fnvince the client to go with cope and stick or anything other than miters. Miters are too finicky. Especially with time and MC, they can move
Pipe clamps can be more trouble that they are worth. When we have to do accurate miters, we use a Melamine table to work on to keep it all flat, and a very accurate and firm "L" to push two sides of the assembly up against. Then the other two sides have blocks fastened in place at 4 points - each of the remaining sides of the miters, and we tap wedges into the gaps between the door rails and the blocks to tighten the joints. This allows selective tightening without shifting everything around, and helps put the pressure where you need it. This is slow, but very effective. Be sure to coat both miter faces with glue, wait 3-5 minutes, then assemble.
You might also look at the jigs for picture frames and make your own, but a bit heavier.
David's method is very good, but can take up a fair amount of real estate depending on your batch size and schedule. My approach to gluing miters is to direct the pressure at right angles to the joints. For painted work that can accept filling some pin holes, there are spring clamps like Collins clamps and heavier options available. For clear finished work I use simple fixtures that clamp to the workpieces with ears that can be clamped across the joints, or clamping ears that are hotmelt glued or paper joint glued to the workpieces and sawn off after glueup.
When you use water base glue, a miter that fits perfectly dry, especially a wide one, will open at the tip slightly. You can cut the joint slightly tighter at the tip or use epoxy or a lower water content glue like Unibond.
Or sub it out to a specialist as recommended and relocate the responsibilty to your supplier.
We use a Hoffman joint. The keys do a good job of aligning corners and mostly pull the joints up tight. But we get best results by putting the assembled door into the JLT door clamp reel for 10-15 minutes.
Thanks for all the responses it helps a lot. I looked at Vlad and Jr Rutter websites and I must say you guys do beautiful work I hope some day my cabinets look as good as yours. I am self taught so it may take a little longer but I am inspired. Thanks
We use the Hoffmann keys, two to a joint + glue for smaller doors and larger doors get Dominos in addition to the keys. We've got an Omgas miter saw that does a beautiful miter. The keys are tapered so pull the joint tight. No fighting clamps. Quick assembly.
I have wanted a Hoffman MU2P machine for a while now for molding frame inserts where the back will not be seen, but i wonder about using them on the back of exposed finished product. I just think it would look tacky. You guys have not had any complaints about the visibility of the plastic keys??
No complains BUT we are commercial only, no snobby house wives. To tell the truth most people wouldn't even notice the brown keys and what would they think they were? What is the objection to structural details? Before we started using them in production we stress tested them by building some doors. The official "Frisbee" test. Build some doors with & w/o put them in your display as merely different methods. The speed of production is pretty great. That or there are dedicated machines for making excellent joints. They are expensive and slower. Does your customer really care?
Much of this revolves around similar arguments put forward by the anti Eurobox group. It is again, do you spend the $ to setup for efficient methods or do it the old fashion way with high labor inputs.
To Adam and everyone, the video have no info about cracking of mitered joints, but you simply have to believe or visit, - over 8 years with solid paint and glaze, - no cracks! O please, no reason to play games!
Below the link for over 120 mitered doors and panels kitchen job without single crack over 480 mitered joints!
The increased chance of a cracked line showing on a mitered door would seem to be the nature of wood movement. On an end grain to side gran connection there is only one part with significant possibility of movement, the rail. That movement won't cause any form of gap due to geometry.
On a miter you have two parts moving in relationship to each other. When they change moisture content (inevitable) either the outside points will move away from each other due to the change in width of both parts (increased moisture) or the inside corner will be pushed open when the parts shrink. (Decreased moisture) The only way to avoid either is to have no changes in moisture either from internal moisture at the beginning of the process or due to the environment.
Finish slows the process but typically frame & panel doors are not finished in the panel groove. So even really moisture resistant finishes have a gap in protection.
Anyone claiming to have absolutely no cracked glue lines has achieved perfection in moisture control. Both in their lumber and in their clients control of the environment. Neat trick!
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