"Ignoramus3537" wrote in message
...
Making of encoder mounting plates requires several accurately drilled
holes. I already made one plate and it seems to work, but I had some
problems/issues with placing holes precisely.

The material is brass (it was a great idea to use brass).

I calulated all hole positions using a spreadsheet. See "Encoder
Mounts" sheet he

http://spreadsheets.google.com/pub?k...en&output=html

To fit it over a 17mm motor shaft, I had to drill a 43/64
hole. (17.065mm).

I do not know of any way how I could drill that hole precisely, with a
huge (comparatively) MT3 drill bit, as any drill bit would wander away
at least somewhat, I think.

As John said, the way that accurately-located and -sized holes are made is
to drill, then bore. You won't get accurate location or size with a drill
bit -- depending on what you mean by "accurate."

You can drill and then ream for good size and roundness, but that won't give
you location. Or drill close to location and then bore for size, roundness,
*and* location.

This is what toolmaker's buttons were all about, and the basic idea has been
the way to produce accurate holes for over 100 years.

--
Ed Huntress