How do I make mullion/muttons

[Peter Quinn]

Not to muddy the waters, but here's what I do. I think that the lap joint that Peter described is best quality, but I personally would rather not have to do any more measuring and precision cutting than absolutely necessary. The method below only requires a grid to fit the door opening, then put away the measuring tools.

Glue up door without a panel so that you have a cope/stick corner joint.
Rabbet out the back side of the door with a router.
Make the grid with dadoed lap joints to fit the opening in the face of the door exactly.
Glue it in with typical end grain treatment (two glue applications a minute or so apart).
Set up the drill press with a 3/8" forstner bit set for about 1/8 - 3/16" depth with a fence that positions the bit right over the intersection of the muntin/mullion and the door frame.
Bore shallow hole at each intersection.
Use thick super glue, accelerator, 3/8 dowels, and a flush cut saw to create inset disks that span the joint and reinforce it.

JR, as usual, your method is brilliant and efficient. Its like a shop made Hoffman key!

We rarely make other than TDL sash frames, but when we do we make them as I described. There is not much measuring involved with installing the grills. You make a door sans panel as you described, you rabbit out for glass, you make the vertical and horizontal bars fit the height and width from rabbit to rabbit, you half lap the center, and use these grills to locate the jig. I dry fit the grills with a small clamp at the center. Make the half laps in the ends of the bars last. You sort of put the grill in the glass rabbit, place the jig, then pull the grill, route the lap, and so on. No measuring at all. It can be done by a blind man without a ruler, which nearly describes me! I use the actual muntin stock to form the quick MDF jig, so there is no measuring there either.