Looking to buy that No32 'scope.........

[Peter Laidler]

If you have spotted a likely looking No32 telescope on Ebay, there’s a chance that the only view you’ll get of it is the outside – all newly painted and looking spick and span. Oh, yes….., you’ll also have a carefully worded or guarded description about how good it is and all of the usual crxx. But as many of you (and me, as I see some of ‘em them afterwards…….) soon realize, these careful words really mean zilch once you’ve got it.

So, what do you REALLY need to look for? Well, I’ll tell you what you DON’T need to look for first…….. You do of course, but these things are pretty academic in the great scheme of things. This little essay isn’t the final word and some of the other experts with more or even less experience than me please feel free to add or pass valuable comment.

First is the general condition of the outside. Look, they’re all about 70 years old and some have led a pretty hard life so if the one you are looking at or happen to buy is a bit tatty and pitted, what the hell….., they’re made of drawn steel tube and that’s the nature of the beast. What is a bad sign is one that is thin and pitted right through the ocular end. On the face of it, this might look like a ‘scope to be avoided. The material is very thin at the ocular end simply because the ocular bell-end has been either hydraulically pressed into shape or spun into shape and the thinning of the material is what happens. But I’ll let you into a secret. This thin/pitted/crushed or otherwise heavily damaged ocular end can be machined away from under the rearmost cradle bracket area then internally threaded. A new GOOD ocular end from a donor No42 or 53 can be accurately cut, machined to size and externally threaded to suit. Once both threaded parts have been sweated and screwed together under heat at the melting point of solder, all that will be visible will be a thin hairline. But even then, this hairline will be under the cradle so the strength is intact. I show this in photograph form in an earlier article so maybe one of the more computer literate forumers could cross reference this part of the article with that. BUT, be warned……. The skill in doing this is with the person doing it because the optical axis of the new ocular end MUST be on the same optical axis as the main tube otherwise…. I won’t go into why but suffice to say, that both optical axis must be linear.

Having told you this, then it stands to reason that if the tube forward of the turret housing is damaged, then a similar repair will be similarly ‘easy’ too doesn’t it? This event occurs when previous owners have grafted on a large diameter OG lens assembly in order to gain greater FoV

Next, let’s look at the lenses. I know that we go on and on about these but in truth, even if you had to have a complete new set of lenses made at, say £75 – 80 each, it’d probably cost you £375 - 400. You’ll understand now why a good No42 or 53 for under £100 is good value to a needy No32 owner…… So what’s the worry? The GOOD news is that it is very rare for the erector cell lenses to be damaged because they are protected deep within the bowels of the tube and then, inside a sealed cell. Where they CAN be destroyed is within a Mk3 or L1A1 where the lens cell has to be heated up to break the rock hard cement like mastic to such an extent that it destroys the glass. Not common, but it has happened. The alternative is to destroy the lenses by brutally driving out the erector cell from the OG end. Unlike the Mk1 and 2, the Mk3 and L1A1 erector can only be removed through the rear. So here is the first question you need to ask if you’re looking at a Mk3 or L1A1 telescope
‘Is the main tube dented anywhere from the two rings of the sector cover for 3” rearwards’?
If it is, then the only way that a damaged or dirty or defective erector cell is coming out is by brute force – at YOUR expense!

Taking a basic No42 or 53 telescope, here are the parts that are fully interchangeable with parts for your No32 telescope
Ocular lens set and spacer, No42 Mk1 and early Mk2’s
Ocular lens retaining ring, No42 As above
Ocular lens assy. with housing, No53 Late Mk2 and all 3’s*
Erector cell assembly All
Locking segment All
Segment cover All except some ‘2screw’ Mk3’s
OG lens Mk1’s and 2’s but **
Front shade Mk1’s and 2’s only^

* Can be used in Mk1 and early Mk2 if brazed inner collar removed
**While the OG lens will fit into a Mk3 tube, it is .038” or so undersize and therefore a sloppy fit. As such, it will always act as an eccentric lens and any zeroing will be at best, unreliable. At worst, crap! BUT…, there is even a way around this too!
^ some versions can be threaded deeper to fit Mk3’s but not all

That’s the good news but there’s also some bad news too, so here goes. What you won’t find are the spare parts that I haven’t mentioned so we’ll start there with THE CLICKER PLUNGERS. These are the spring loaded plungers that give the range and deflection scales their distinct ‘click’ and are notorious for snapping at the shoulder of the shaft and head, tilting and jambing up the mechanism. The Mk1 and 2 plungers are a real pig to manufacture, believe me. Too hard and they will simply grind away the case hardened (or occasionally sintered) teeth on the clicker plates. Too soft and the hard clicker plate serrations will wear the plungers away, virtually while you’re looking at them. If you are a Mk1 owner, it’s simple. Just replace the plungers with 5mm steel ball bearings. Alas, not on the Mk2 and 3 because the pitch of the clicker plate teeth renders the use of 5mm balls useless. New Mk2 and 3 plungers have been manufactured but as you can imagine, not cheap so don’t grizzle!

Lets look into the turret housing now. The range and deflection mechanism works along a multi-start screw threaded system of what are basically nuts and bolts pulling a cursor slide for deflection and diaphragm nut for range. If any of these parts are missing, then you are in BIG schtuck! Don’t assume that because you can SEE a grat and/or a crosswire that these parts are present because it doesn’t necessarily follow. So on that basis, one question you MUST always ask is this.
‘Does rotating the range and deflection drum move the grat left/right and up/down’.
If it does, then those important parts are present. If the answer is evasive or they don’t move, then think again. It could spell BIG trouble. One I was presented with recently, bought unseen from ‘that’ auction site was missing the complete range diaphragm and nut. This simple question could have saved the day. (although to be fair, the ‘scope in question had been waterlogged and was too fogged/misted to see through although a quick look through from the OG/front end would have identified the problem) And yes, before you ask, the drums turned and the clickers clicked too.

What else do we need to know…….? Ah, yes. It goes without saying that if you’re offered a telescope missing the range or deflection drum(s) then avoid it like the plague unless a) you have a friend who is a VERY competent model engineer and b) a set from which he can back engineer new. And if they’re missing, then so will the lead screws plungers and springs, diaphragm and on a Mk3, the diaphragm shoes and springs too! That leads us on to the next question that you need to ask because a bit of judicious photography might have disguised the fact…
‘Are any parts missing’? followed up with ‘Are any screws missing either’? Not that screws can’t be easily replaced BUT it’s another indication that a parts is missing – even if it’s just the screw! The days when every Instrument Shop had a drawer full of old Mk2 drum assemblies left over from converting them to Mk2/1’s are long over

That’s just about it. So how do I summarise this? I’d say ignore a tatty old tube and even broken and dirty lenses. These things can be easily fixed. But take a good, long hard look and reconsider when it’s a case of missing internal parts.

Hey……, and while you’re there…… If you like this article or have learned anything, then tick the thanks box. It won’t cost you a penny but it’s a means of feedback for me! And feel free to add your comments

Worth adding here - Sept '16 - that a small figure 6 on or close to the locking segment cover plate indicates that the cover plate screws have been opened up to 6BA as a minor repair

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Peter Laidler]

Good question just been asked. Jeees, don't be shy, every Q is a good one! What if the grat and crosswire appears to be is missing? How will the seller KNOW whether it's just the grat and crosswire or the complete diaphragm is missing?

The answer is this. Generally speaking, you'll always see the remains of the old post or crosswire. But, if they are totally missing, then look into the OG end of the telescope and wind the range or deflection drums full travel. If you look carefully, you'll SEE the front face of the diaphragm sliding across the round opening in the face of of the cursor. It should be pretty obvious because the focal point of the OG lens is on the graticle. But if you're not happy, then just unscrew the range drum lead screw locking nut two or three turns and manually pull and push the lead screw. If the diaphragm is there, you will actually SEE the bottom part of it starting to obstruct the round opening of the cursor slide.

No diaphragm, no sale!

[Roger Payne]

Hey DPL,
Hadn't seen this little gem as I was away in France when you posted. It's most informative. Now, speaking hypothetically you understand; just supposing one had a (small) bag full of rather sad, rusty, dented, but genuine ex-Indian issue No32's in one's garage, all in need of major life-saving resuscitation; what effect would bead/sand blasting have on the pitted or damaged tube, financially & aesthetically? And of course, is the ostensibly life-saving blasting off of rust going to cause any other further damage, perhaps that might not immediately declare itself?

Your thoughts please!

ATVB.

[Peter Laidler]

Good point raised by DRP there concerning the delicate subject of what do you do with a grotty tube in the first place. The only answer I know is the UK MoD answer which is a rusty/pitted tube is really academic in the great scheme of things. It’s just like a rusty pitted rifle....... It is nothing more or less than corrosion whatever nice kindly words you like to put on it! It’s just one of those things. But given the right treatment, such as the fine bead blasting and removal of all the rust then the phosphate coating (this is the actual rust proofing incidentally) then it’s ready to go. The aesthetics are really of no further concern.

Where it DOES get a bit dicey is if the bead blast operator goes a bit beserk and just turns the pitting into holes! As a general rule, the MAIN parallel tube isn’t a problem so far as blasting holes through the pitting whereas the ocular bell-end IS a cause for concern and can easily be penetrated. In that case, in the Army world, the telescope would be in for the chop of course. It’s not only those ex Indian Army telescopes that are heavily pitted and have seen a hard life either. There were plenty of well used No32’s and L1’s like this believe me! But in the civvy/commercial world, then a relatively simple grafting job is the only answer. I’m not keen on the ‘polish out the pitting’ school of thought either for sound mechanical reasons. It is what it is and like your Land Rover Chassis, if the pitting is there and treated properly, then it ain’t going nowhere else!

One alternative is to chemically de-rust the tube as detailed at some length in the restorers forum a year or so ago. This is a far more gentle process but alas, not a good key for the phosphate treatment.

In short, if the corrosion is bad, try chemical de-rusting first. Then shine a torch inside and any pin pricks of light will indicate a hole. A sound looking tube just go to the bead blaster.

But a further word of advice as raised by another forumer....... NEVER, ever, ever leave blind threaded screw holes open in the item within 100 yards of the bead blasting cabinet. Always put screws BACK INTO the holes. At all of our workshops we had some square plates that could be screwed down onto the open turrets thereby keeping the screw threaded holes AND inside the turret area free of grit.

Hope that’s answered the Q DRP.

[Roger Payne]

DPL,
Cheers for that. I am glad that, subject to your mentioned provisos, the bead blasting is generally ok as I think there is not much alternative with the majority of the scopes that have been to India. I don't know if there is an explanation for this but the pitting always seems to be deepest where the tube is thinnest (ie the ocular end).......!! Maybe this is because scopes were left for years in humid conditions with the lens caps left on....??? Here, if it is bad, I would agree that replacement of that part of the tube with a donor part from a No42 or 53 is a good idea. I think you know that my late machinist salvaged a few scopes for me by this method, some years ago. He silver-soldered them for me though, rather than threading & soft soldering. It seemed to work.

ATVB

[jmoore]

Here, if it is bad, I would agree that replacement of that part of the tube with a donor part from a No42 or 53 is a good idea. I think you know that my late machinist salvaged a few scopes for me by this method, some years ago.

I'm wondering if a new section could be turned as well. Might require some secondary operation on a mandrel if the wall thickness becomes too thin to be managable. Would save the donor 42/53 scope for more dire repairs.

I don't know if there is an explanation for this but the pitting always seems to be deepest where the tube is thinnest (ie the ocular end).......!! Maybe this is because scopes were left for years in humid conditions with the lens caps left on....???

If they're spun to shape might it be the area of highest residual stress?

[Roger Payne]

Thx JM. I'm sure a new section of tube could be manufactured de novo, but I guess up to now at least, using a donor 42 or 53 has probably been a cheaper option. I suppose a lot depends on what skills one has & whether one can do it oneself.

Re the 'residual stress', I'll take your word on that one. I think you have a background in engineering which I do not (I am a largely self-taught tinkerer!). Residual stress to me was how I felt when I got home from work after a bad day!

ATB

[jmoore]

One advantage to doing a new section would be the ability to integrate a stepped section that slips into the old tube in some cases. Stronger and easier than doing a separate join ring.

[Peter Laidler]

Having done plenty of them using the donor No42/53 ocular end and got it off to a fine art, I'd just say that going down the 'making from new' road is over complicating matters. I have had to re-repair two previously repaied by the by the silver soldering method when the butt-joint between the taper and the large ocular diameter had failed. Anyone going down the new ocular end road should consider a threaded or sleeved/undercut joint of say 5mm or so long/deep the join of which is mid way under the rear cradle cap. There's loads of strength in the join which is reinforced by the clamped cradle cap.

And thanks for all the thanks chaps. Nice to assess the feedback

[jmoore]

Just saw a No32 mk 1 on EBAY from Germany $1630 FYI

http://rover.ebay.com/rover/1/711-53...item5653595448

S/N 2517