Apparently there is free on-line access to British Standards On Line via some libraries, but the page on BSOL describing which ones has been taken down.
You used to be able to access via a Northern Ireland library card, but I think that was withdrawn last November.
Unfortunately my Derbyshire card doesn’t provide access as they haven’t bought an account for cost saving reasons.
Lancashire still claims to, but I don’t have a card there; do we have any Lancastrian members?
I think one or two libraries do have access, but only from their own buildings, and some universities allow access, but  via their own intranets.
https://www.lancashire.gov.uk/libraries-and-archives/libraries/access-to-british-standards-online/

Bill

Interesting Michael and particularly that Mitutoyo use 55 deg thread form, i wonder what the others use ?

I suppose on the Mitutoyo thread it is in TPI rather than a metric pitch even though the OD is metric.  The fact that its 55 Deg and maybe the others are 60 deg also adds to the compatibility issue — as for those quoted that do fit and maybe should not I guess the standards are “P” fit  !!

John

Interesting stuff Michael. It seems strange (to me) to mix metric and TPI on a thread. I also thought nearly all modern threads were 60°.

On 21 October 2024 at 13:38 Michael Gilligan Said:

I am a little surprised, and rather pleased, that this topic has captured some interest.

It is probably therefore worth including this illustration of the ‘baseline’ from which all the more recent objective threads have evolved.

.

[ the best scan of it that I have ever found ^^^ so if you have a better one, do please share it ]

.

As is so often the case, we owe it all to Joseph Whitworth !

I have seen an example of the gauges which the Whitworth company made, and the Royal Microscopical Society distributed to the major microscope makers … They are exquisite: and thereby standardisation was immediately triggered.

MichaelG.

Makes good sense to me to dimension in metric, don’t change the thread so as to ensure backwards compatibility, but dimension in metric so it’s understandable by more than old men in UK and Americans.

My Guide to World Screw Threads, lists the following miscellaneous Whitworth form threads-

Condenser tube glands -14 tpi

Drum plugs for mild steel heavy duty drums

Endoscope lamp housings

Microscope objectives and nose pieces

Oil switchgear

Optical instruments (fine motion and adjustment) with tooth depth 10% deeper than standard

Optical instruments (metal tubing, cells and other fittings)

Camera lens flange fittings (R.P.s. standard)

Water well casing

There are so many odd ball threads out there, I seam to remember tyre valve threads being some strange mix..

JmB

Not my experience Vic!

I have just fallen foul of a non standard thread on a Carl Zeiss Jena marking objective, mentioned in the adjacent thread. After getting it working fully, I tried to attach it to the turret of my Olympus BH (standard RMS) and it prooved to be smaller. I cannot judge the thread pitch, but the thread measures 18.97mm, 0.747″. Googling this type of thread, I have been unable to identify it. I will make a short adaptor out of a scrap objective body.