Mike's Instrument Book...Question about bezel radius

[Crescent]

For those of you familiar with Mike's book on building instruments, just curious as to why for a "3 inch" instrument, the radius shown for the front bezel is 1.40' (this would make it 2.80'). I'm sure there is an explanation for it, but it beats me.

[Tripacer]

Crescent,
A standard 3 1/8" instrument fits in a 3 1/8" hole. There is a bezel that is about a 0.10" thick reducing the opening to about 2.8 or 2.9". I am out of town today; but I will measure that for you tomorrow. I made a mold of a 3 1/8" instrument bezel and cast them out of resin plastic. They make the instrument front very realistic. I have had my instrument panel cnc cut at a local avionics shop according to standard hole sizes for 3 1/8 and 2 1/4 instruments and Mikes designs bolt right in.
By the way I used 6-32 rivnuts on the face deck and then 6-32 screws fasten the instrument to the panel. Exactly like the real instruments.
Tripacer

[Crescent]

Thanks Tripacer.

[Tripacer]

Cresent,
I have posted a couple of pic in the General Aviation section of the photo gallery. I included a pic of a real instrument. The outside of the bezel measures 3.115" which is 10 thousands less than the 3.125" standard. The thichness of the rim seems to vary but most give about a 2.8" opening.
My mold and cast resin bezel measures 3.115" outside and 2.88" inside opening.
Hope this helps.

Tripacer