Question about frame and panel...

[Jim Kappel]

So I'm making a frame and panel (both doors and sides) for an armoire.

Here's the question...
How much space do I allow for expansion? If the distance from groove to groove is 16 1/4", how wide should my panel be cut to?

Thanks!
Jim

[Chris Friesen]

Depends on the wood species, current moisture level in the wood, and expected minimum/maximum moisture content.

[Jim Kappel]

It's walnut and I don't know the moisture content.

[John Keeton]

Jim, just for clarification, the measurement you have given is from "bottom" of the groove to "bottom" of the opposite groove?

Some other questions that I would look at before making a decision would be -
What is the panel constructed from?
Which way does the grain run?
What is the moisture reading on the wood, and what is the ambient temp and rel. hum.?
What will be the conditions where the finished piece will be situated?

I don't want to overly complicate this, but when I build in the summer here in KY, the wood is generally as expanded as it will be all year. So, I rarely allow for expansion, but try to not end up with a panel that will be too narrow in the winter, or in the air conditioning. Lot of different factors at play.

[David Schmaus]

How deep is the groove?

[Jim Kappel]

Wood is Walnut.

Groove is 3/8 deep, so measurement is from depth to depth. I'm planning to leave 1/8 total expansion because here in MN it's pretty warm and somewhat humid (about 55-60 dew point) relative humidity of 65.

I called my area Rockler and they gave me 1/8 inch based on the above.

Agree?

[John Keeton]

Jim, I still think the critical issue is the present condition of the walnut. If it is not really dry, that really becomes a big factor. Can you borrow a moisture meter to find out? If it was kiln dried, and has acclimated to the shop, then it may have reached an equilibrium.

[George Bregar]

If it was kiln dried, and has acclimated to the shop, then it may have reached an equilibrium. +1. Likely only to shrink at this point.

[Jim Kappel]

It is kiln dried and has been in the shop for years.

[David DeCristoforo]

My "rule of thumb" is that the panel width is 1/8" less that the total length of the rail (measured from the ends of the tenons). This leaves plenty of slack for all but the widest panels. I use the same deduction for the height simply to maintain the same "reveal" at the top and bottom.