I'd go to Edmond Scientific site and you can get parts like all get-out!
They are an Optical leader for science.

Martin


On 2/19/2016 9:08 PM, Bill Baxter wrote:
My son, who is in graduate school, uses a high quality but no longer
made microscope for his home studies. Recently, one of the small brass
pinions broke in the focusing unit and he asked me if I could repair it.
I was able to disassemble to access the pinion which is on a rod.
Unfortunately, since the scope is no longer made, the exact part is no
longer available, but I have determined that a 64p 16T 0.4 modulus would
fit it almost exactly except that the bore is too small (it is 3mm and I
need it to be 4mm... actually a bit wider at #21 drill bit sized).
Unfortunately, web searching cannot locate a pinion of the proper bore
size (all are either 2 or 3mm bore), so I am thinking of getting one of
the 3mm ones and drilling it out to #21 sized. The problem is that this
needs to be very precise and if off by even a little will cause binding
and other problems in the focus mechanism. So I pose the question: How
would I go about drilling this out from 3 mm to #21 accurately using
ONLY hand drill, vice, etc as I have no access to lathes, presses, etc?
Thanks!