Question for Peter Laidler - No 32 Scope v No 42 Scope

[paulseamus]

Peter

Having read and re-read your Knowledge Library Post "No42 and No52 Sights .....Have you ever thought?", I have a question.

I have recently obtained a No32 MkII scope, #10930 by H.B.M. Co.

The Occular lens is scratched. This scratchd lens is contained in a brass occular lens assembly housing.This housing is about 1 7/16" (36mm deep)

I have in the cupboard a H.B.M. Co. No42 Sight that has an occular lens in "as new" condition, but this lens is not contained is a brass occular lens assembly housing. It is fitted directly into the steel body as per a No32 MkI.

My question - is it possible to have the larger No42 lens fitted to replace the smaller No32scratched lens? That is to say is it feasible to modify either the lens and or the housing?

Thank you

Paul

Information

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[Roger Payne]

Paul, Peter probably hasn't noticed your posting yet, but no doubt he will correct me if I'm wrong.
Yes, in principle you could swap the lenses over, BUT, as it sounds like you have an ocular lens cell in your Mk2 scope there will be no retaining ring hard-soldered inside the front end of the ocular housing ('bell') of the scope. In all No42's & earlier No32's (which have the individual lenses mounted directly into the tube) there is such a retaining ring inside the scope tube to stop the lenses dropping in too far. Obviously, in the No53 & later No32's with the self-contained lens cell, this is unnecessary as the lenses are located together in the cell. Thus, if you want to fit the earlier lens arrangement you will need to accurately seat a retaining ring before you go any further.

It would be easier to:
1. Put up with the scratch (if it is not central on the lens)
2. Try & swap your No42 for a No53 as this scope has the ocular lens cell, like your No32 Mk2.

Hope this helps.

ATB

[paulseamus]

Roger

Thank you for the reply.

I am trying to determine if an Optical Technican could reduce the diameter of the No42 lens so that it can replace the No32 lens.

In these days of mass produced glasses, churned out in the thousands, for large chains of optometrists, it is proving more difficult than I anticipated to find a optical tech.

I will start my hunt for a good No53 sight.

Thanks again

Paul

[Peter Laidler]

Thanks Paul and Roger. There IS a way round the 'problem' but It'll take a little while for me to formulate the answer. Give me an hour over the weekend to reply

Regards, Peter

[paulseamus]

Peter and Roger

I had another good look at the sight last night, whilst reading Peters Book, "An inside view of the Snipers rifle telescope"

The sight, HBM Mk2 No 10930, has the following issues.

- Occular lense - pitted
- Objective lense - scratched
- Cross wire - broken but still visible
- Graticle post - missing
- Eye lens retaining ring - missing
- Front shade locking screw - missing
- OC assembly locking screw - missing
- Steel sight tube - light internal corrosion visible when OC assembly is removed

Given the above, I will send the sight on to Fultons, so that it can be assessed first hand and hopefully re-furbished.

Thank you for your guidance.

Paul

[Peter Laidler]

Ugggggggggggggg. Deep sinking feeling......... What is the 'OC' that you describe? To save yourself some money, you'd better send the old No42 along too!

But the answer to your original question is this. If the scratch is on the flat plano side of the ocular lens - as they usually are, then any lens polisher, even your average do it while you wait spectacle lens polisher should be able to polish the scratch out flat, across the whole lens - within the bounds of how deep it is of course. You will then have to focus the grat again and........ anyway, it can be done fairly easily.

If the scratch is on a double convex lens, as in the OG or some variations of the oculars this is a bit more problematical because the same lens can be polished, but this time, instead of being polished flat, it has to be polished with the radius and this ain't so simple unless you have the correct kit! But if you do have a tame lens grinder, the way around this for the oculars is to tell him to grind BOTH lenses to a plano convex (that's radiussed on one side and flat on the other.....) form as I have done occasionally

Insofar as grinding the larger diameter Mk1 and 2 ocular lenses to fit into the smaller diameter later Mk2 and 3 ocular cell housing............. Yes you can but you have to be even MORE careful because unless the lens is ground EXACTLY concentrically, you will end up with in effect a prism - just like the OG lenses of your No2 binos (and the prism of your Patt 18 telescopes.....) where the rays of light..... Oh I won't go into it but it could be a buggers muddle!

If I had a set of early Oculars and needed a set of later occulars, I'd just ask anyone if they want to swop because good early large diameter lenses are scarcer than common later, small diameter lenses.

Anyway, a bit of good news now. I've had the Patt 18 OG lenses made as I promised, about 8 pages ago and Mike 1967, DRP, Newcastle, Nigel, Simon and Warren said that they'd be interested in one (?) each. I waited until the test lens had been fitted into the needy telescope and it's perfect. The price to me was £70 each so they are here if you want them. After this offer the price will increase as the small stock reduces

[Peter Laidler]

Someone just asked me with the reverse question to Paul...... Can you use the late Mk2/Mk3 lens cell in a Mk1 telescope. Yes, BUT! You will need to machine out the inner lens seating ring or better still, melt the silver solder holding it in place and hook it out, clean off the residue and screw in the lens cell. That might be easier said than done because the parts are not interchangeable