My 19th edition 'Machinery's Handbook' gives data on the American Standard
Microscope Objective Threads (ASA Br.11.1958),
"The thread is based, on and interchangeable with, the thread introduced and
adopted many years ago by the Royal Microscopical Society of Great Britain,
generally known as the 'RMS' thread, and now almost universally accepted as
the basic standard for microscope objective mountings."
It appears that the basic thread form is based on BSW (British Standard
Whitworth). The data are listed in Imperial (inch) units and only one class
of thread is provided in the Standard.
There is only one nominal size having a basic major diameter of 0.800 inch
and a pitch of 0.027778 inch (36 TPI). The thread is single-start type.
Hope this helps.
Regards,
John.
----- Original Message -----
From: "Mark Dapoz" <md@xxxxxxxxxxxx>
To: "olympus @ Zuiko . sls . bc . ca" <olympus@xxxxxxxxxxxxxxx>
Sent: Monday, April 29, 2002 3:08 PM
Subject: Re: Re: [OM] Need Information
>
> On Mon, 29 Apr 2002, Wayne Harridge wrote:
>
> > Are these sizes converted from metric, seems like the numbers are pretty
> > weird for imperial ? Is RMS a metric standard ?
>
> I believe RMS was a British standard so it's likely the original
measurements
> were in imperial units. Although .794" is extremely close to 2cm, so
perhaps
> they did use metric units.
> -mark
>
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