Re: ATM 2" focuser actual ID Diameter

[Kurt Hillig <khillig@Chem.LSA.UMich.Edu>]

On Thu, 19 Jun 1997, Patrick & Bronwyn Scharf wrote:

> I am about to start making a 2 inch Crayford focuser, but would like to
> know what is the ideal ID diameter to turn out in the focus tube. I
> would like to make it useable for a variety of different brands of
> eyepieces so would appreciate some feed back on exact OD sizes of these.
> Also what is the best exact ID size for 1.25" eyepieces. 

The true ID of a 2" draw tube should be 2.005" give or take a thou; for a
1.25" tube, make it 1.254".

ODs of eyepiece barrels varies a bit, typically from exact to 0.010" under
nominal size; occasioanlly they're a thou or two over, but I haven't heard
of anyone running into anything bigger than that.

When I make adapters, etc., I make OD's 0.002" under nominal, and ID's
0.004" over nominal; but I can afford to be careful with each piece, the
folks who turn out hundreds at a time have looser tolerances to keep
manufacturing costs reasonable....

                            Dr. Kurt Hillig
  UMNet Administration     I always tell the    fax (313)763-2180
 University of Michigan     absolute truth     phone (313)647-8778
Ann Arbor, MI  48109-3297    as I see it.    X.500 khillig@umich.edu

 >> Computers were invented to help people waste more time faster <<