Screw threads again

[Michael GilliganParticipant @michaelgilligan61133]

I don’t want to intrude upon Bill Phinn’s cycle thread discussion … but I would like to share this with fellow microscopists and anyone else with a serious interest in thread-forms and/or  Imperial/Metric approximations.

https://www.photomacrography.net/forum/viewtopic.php?t=12404

It should be self-explanatory, so there may be no need for replies or discussion

… that’s fine by me.

MichaelG.

.

Edit: __ incidentally, it’s interesting to note that Japanese standards are available at relatively modest prices.

https://www.standardssupply.com/product/JIS-B-7141-2012/

[peak4Participant @peak4]

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You used to be able to access via a Northern Ireland library card, but I think that was withdrawn last November.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

[John HaineParticipant @johnhaine32865]

Weird that BSI charge for old and basic specs when you can download all the latest 3gpp specs for mobile networks, tens of thousands of pages, for free.

[JohnFParticipant @johnf59703]

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

[Michael GilliganParticipant @michaelgilligan61133]

I’m not sure what this forum’s downsizing routine might do … but here [hopefully] is a better grab from the Mitutoyo brochure:

.

.

MichaelG.

 

[VicParticipant @vic]

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°.

[Michael GilliganParticipant @michaelgilligan61133]

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.

[Michael Gilligan]

On 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.

[old martParticipant @oldmart]

I’m glad that most objectives adhere to the same standard which originated in England. Mitutoyo objectives are very specialised and expensive, mostly used in high end measuring machines.

I have noticed that vintage objectives refer to focal length in mm, predating the current magnification figures.

[Michael GilliganParticipant @michaelgilligan61133]

Just to clarify what prompted me to start this topic

Both of the objective threads mentioned are 26mm diameter [which is bigger than the RMS standard]

The Mitutoyo is stated to be 0.706mm pitch [nominally 36tpi]

the example measured appears to be so, and also of Whitworth form.

The Nikons are “commonly believed” to be interchangeable with the Mitutoyo objectives, but the measured example is convincingly shown to be 0.75mm pitch, and appears [to my eye] to have a 60° trapezoidal thread.

Such discrepancies would be of no consequence to Messers Harley and Davidson, but they have been known to cause difficulty on microscopes.

Clearly it must be possible to manufacture something with a class of fit that ‘accepts’ either … but specifying that could in itself be quite a challenge !

Here’s the ebay listing that started me off on this :

https://www.ebay.co.uk/itm/394653241414

MichaelG.

[VicParticipant @vic]

“Such discrepancies would be of no consequence to Messers Harley and Davidson”.

Thats an eloquent way of putting it! 🤣

[jimmy bParticipant @jimmyb]

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

[old martParticipant @oldmart]

Since the number of threads are less than four in the mounts, the small difference in pitch would not be noticed in practice.

[bernard towersParticipant @bernardtowers37738]

Not my experience Vic!

[Neil LickfoldParticipant @neillickfold44316]

The Whitworth form with a full radius on the root and crest, actually makes for a stronger component, especially if it is to be heat treated after being cut.

We have made parts at work that are the 55deg with the Whitworth root radius , but in a metric pitch.

[old martParticipant @oldmart]

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.

[Michael GilliganParticipant @michaelgilligan61133]

I don’t do FaceBook … but it appears that my Google Fu is strong tonight

This might get you to the information you need:

.

.

MichaelG.

.

Ref. __

https://www.quekett.org/wp-content/uploads/2018/05/amadio-catalogue-1858.pdf

[Michael GilliganParticipant @michaelgilligan61133]

[ update on the ebay cone ]

.

Mixed emotions, but ultimately I am delighted to have received a straight answer from the Seller.

MichaelG.

.

[Michael GilliganParticipant @michaelgilligan61133]

My Nikon BD Plan objectives having safely arrived from Israel, I can confirm to my own satisfaction that they are NOT threaded 32tpi

MichaelG.

.

Scale Divisions courtesy of Rabone Chesterman No. 28R

[Michael GilliganParticipant @michaelgilligan61133]

Just putting this to bed

The adapter that I purchased from China arrived today

Beautifully made and black-anodised … it fits the Nikon threads as sweetly as I could ever wish.

[ No, I don’t intend trying to measure it ]

MichaelG.

[bernard towersParticipant @bernardtowers37738]

Michael, I have to say that I am a bit wary now about Chinese filters /adaptors after a recent experience with a Chinese circ pol on my 100mm macro. It became impossible to remove by normal methods so in the end took the glass out and collapsed the rotating part and then did the same with the fixed part. All came out without a single mark on the lens threads (PHEW) but on closer inspection of the filters anodising it looked very coarse, possibly the result of high amps for a quick turnaround?. And because of this, managed to get a good grip on the filter thread IMHO.

[Michael GilliganParticipant @michaelgilligan61133]

Sorry to hear that, Bernard

I may have ‘hit lucky’ [we shall probably never know] but this adapter is as close to perfect as any I have seen.

MichaelG.

[Author]

Posts