Origins of the Hoffman turret spacing

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People have asked about what the turret lug spacing is on the Hoffman turret boards
It's a weird convoluted story that goes back to 1992 or 1993


Hole spacing on the Hoffman turret boards goes way back to the first template I made in the early 90's
The lug spacing is actually .296875 inches which is 19/64ths inches
I had a piece of aluminum that was the backing plate for a computer tape backup cartridge
I did not have any accurate way to make templates back then as CNC machines did not exist.
The dimples in the metal plate gave me a perfect places to drill template holes
So the computer tape backing plate worked great as a first way to drill holes in G10 board material

I still have the original metal template that I used to create the bigger metal drilling template

Here's a pic of the original one

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Later on, I had a machine shop make me a real template

It was 18 inches long x 3.125 inches tall
It was 1/4 inch thick 6061 aluminum

It had 9 rows of 3/32 inch holes and 59 columns
That's 531 holes

The idea was to make thin drilling mask that sat on top on the drilling template
The mask was held in place using 3/32 inch steel pins
The mask would only expose holes that needed to be drilled

Each board type that I made had it's own mask

Here's a couple shots of that template and a Princeton Reverb mask

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I used the template and mask system for several years.

Later on, I built my own custom CNC machine from scratch
Some where in 2007 or 2008 is when I built it

I still use that CNC machine to this day

It has save me many ours of labor over the years
Once you learn CAD and CAM you are good to go (That's another story and was a big learning curve)

Here's a shot of my drilling CNC and a fixture I use to hold the board material

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I have info on my CNC machine and other projects here on EL34world.com
https://el34world.com/Misc/Cnc/CNC0.htm