Ask the Staff
Question:
I am planning to build some frame and panel doors and wondered how much space to leave between
the panel edges and the inside of the frames for
space balls
to
work best?
Thanks,
Jim Merideth
Ames, IA
Answer:
Jim,
The diameter of a space ball is 1/4" (uncompressed). There is no absolute measurement, but there
are things to keep in mind as you calculate the depth of your grooves and the size of the
panels.
With the space balls slightly compressed (to do their job), consider them at a diameter of 3/16".
Also consider the amount of penetration you want of your panel into the frame.
For example: The viewable part of your panel is 12" x 12" . If you want the panel to penetrate
the frames 1/4" on all sides, you would make the panel 12-1/2" x 12-1/2". A groove depth of 7/16"
gives room for the 1/4" panel penetration and 3/16" for the space ball.
To accommodate a panel 12-1/2" in length, plus room for compressed space balls on all sides, the
dimension from the bottom of groove on one side, to the bottom of groove on the opposite site would
be 12-7/8" or in the case of this example 12-7/8" square.
Let's check the math:
12 + 1/4 +1/4 + 3/16 + 3/16 = 12-14/16" or 12-7/8"
If your panel is plywood, it will not really move seasonally. You just need to be sure it
doesn't have excessive play. For a solid wood panel, it will move across the grain, seasonally.
You may wish to adjust your panel penetration into the frame to handle excessive movement. How you
adjust depends on what time of year you are construction the project.
You could also calculate the compressed diameter of a space ball at 7/32", just to give you
tighter tolerances. The assembly would go easier, but if a solid wood panel shrunk excessively, the
panel could rattle slightly using the tolerances closer to the uncompressed diameter of the space
balls.
Hope this helps.
Regards,
Ed Scent
Highland Woodworking
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