Dimensioning Door Tenons and Space Balls

For raised panel doors, tenon size, mortise depth and space ball size are a small but tricky detail. September 21, 2005

How much smaller is everyone making panels when using 1/4" Space Balls? Our doors have 3/8" tenons. We have been making the panels 1/4" smaller overall, which compresses the balls to 1/8", but sometimes the back lip of the stile or rail cracks out where a spaceball is. Does anyone have any suggestions?

Forum Responses
(Cabinetmaking Forum)
From contributor A:
Most of the door manufacturers use 5/8" tenons. Most small shops use 1/2" tenons. Freeborn charges the same for their cope/pattern sets with any size tenon (3/8, 1/2, 5/8, or 5mm). Freeborn will also sell you the extra cutters separately or buy two profile sets with different tenon lengths and switch back and forth depending on the application. As you've realized its not a good plan to cut down the panels.

From contributor F:
I run a .5" long tenon and I size my panels to compress the .25" diameter space balls .0625" per panel edge.

From contributor B:
To contributor F: So you make your doors 3/8" small, since two balls are 1/2", you compress the balls 1/8", or 1/16" each - did I get that right? Are 3/8 tenons good with these things or should I get the extra cutters to shift to 1/2" tenons?

From contributor F:
To contributor B: Yes, you need a .5" long tenon which equals a .5" deep panel groove. .375" tenons dont leave enough room for the space ball and the panel edge in my opinion. With my 1/2" deep panel groove, I insert a 1/4" diameter space ball which then leaves 1/4" of space for the panel in its uncompressed state.

However, I size my door panels so that they compress the spaceballs 1/16" on all four edges. This means I have 5/16" of panel edge inside the panel groove on all edges. With a 3/8" tenon and panel groove depth, and 1/16" compression of a 1/4" diameter space ball you only have 3/16" of panel edge in the groove.

I suppose it will work that way but if your panel shrinks then you have even less in the groove. As a side benefit to running a deeper groove, you are making a stronger door because you have a longer tenon and more gluing surface.

From contributor T:
My shop is in Montana - low humidity and we ship all over the lower 48. Our raised panels are 5/16" smaller than the opening they go in (5/32") on each side and we have never have problems. Also, I would strongly suggest going to insert tooling. They last 3-4 times longer, the fit is always the same, and in the long run they are less expensive. Also the set up is the same every time. I would recommend checking out Ballew Saw & Tool

From contributor J:
To contributor T: Who's insert tooling are you using from Ballew? I have been a fan of the Freeborn tantung line for a few years now. I would like to switch my cope and stick cutters to insert tooling, but I really haven't been convinced that inserts are that much better than brazed tooling, in price, performance, and sharpening costs.

We run about 5,000 doors a year, mostly in ash, maple and red oak. I do use a Byrd tooling insert panel raiser and back cutter that came with the last big shaper I bought. It really does a good job, but it is expensive to replace all six inserts.

From contributor T:
To contributor J: I use LRH just because that was the one on sale at Ballew when I first started using insert tooling. I would suggest trying it - it is less expensive than sharpening. You can only sharpen so many times before you have to replace or at least re-tip, and the fit is always perfect.