Looking for info on the L42 L1A1 scope turrets

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Originally Posted by Roger Payne

IIRC Warren, PL told me that some of the last replacement drums were not fitted with the tiny locking screw. When I fit replacements I do not fit the screw either, & they work fine. There seems to be enough 'friction' between the two parts for them not to slip.

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That is just slipshod, poor workmanship and cutting corners on the part of the military rebuild program.
Some are tight and others are quite loose. There are not many I have to use the wrench on to get the range drum off. The odd one you have to drill out the BA10 screw but not many.
I am not criticizing your work Roger, as you are one of the grandfathers of the 32 scope refurbish program, but why use 4 or 5 wheel nuts on a car rim when one will do. If it is there originally why not put it back. I for one sure would not want to be in the field and have the turret unscrew on me.
It just irks me when the people who designed the thing are not adhered to.
Sort of like the better mouse trap.
Hope I do not or have not insulted anyone but just my 2 cents on the issue.
I am finding the majority of the L1A1 scopes to be in only fair to mediocre condition mechanically, with lots of galled and worn parts. This opinion based is of the ones I have seen and even my own L1A1 scope.
Like the astronauts thoughts when going up: " everything here is by the lowest bidder!!!"

Thanks for your input Warren. You've done a lot more than I have. I should have clarified, that where I rebuild scopes with the original parts (ie. with the provision for the locking screw) I always refit it. However, where I have used a few of the later manufacture drums, I have not drilled them. It might be beginners luck, but so far they seem fine & are giving good service.

I just did not want to think I was sniping as to the grub screw.
I really find it amazing that the rebuilds did or did not have it and some looked like the result of a drunken woodpecker.
I think the record was 7 holes in the turret.
I wonder if they were converted by the Military or by a private contractor.......
I just do not feel comfortable leaving one without the grub screw and I think I would even think twice about a wee drop of blue Loctite.
Just my 2 cents for what it is worth.

Another of those cases like ocular lens retaining ring screws, sunshades and pads, where repeated loosening and tightening causes wear to the threads, and in some cases a bit of stretching perhaps, necessitating a bit more rotation to maintain a similar degree of tightness...

Impressive degree of concretion in there Lance: https://www.milsurps.com/attachment....9&d=1642935393

Dig it out and send off to a pollen specialist maybe? You might have a bit of the Omani desert in there? ;)

What a bugger. Jost posted a long answer and it's disappeared. Here we go again but shorter........

Interesting question with several easy/simple answers. But first.....

What I'm going to say about them is only based on my limited experience of seeing thousands and working on say, a thousand or so. So it's pretty limited......

Just to answer an ambiguity that I think I detected. THE CLICKER PLATE in the No32 Mk2/1, the Mk3 and the L1A1 is the same. It is the RANGE SCALE on the drum slipping scale that is calibrated differently - as someone has already pointed out. The toothed clicker edge extends through 360 degrees for ease of manufacture on late Mk2's, 3's and L1A1's

As for the range drums, what RP says is correct. Later production drums from X&X had the thumbscrew part staked in place to the central axis/spindle (the brass ring between the thumbscrew and the lead screw locking screw). You can clearly (?) see the remains of the 3 equidistant stake marks on the photo of Desperate Dans (DD hereafter) photo. But, this relaxation was only ever successful until it was undone the first time. Then, due to the mechanics of it all, as the thumbscrew is undone on the cleanroom bench, by default, the staked lock is broken. Thereafter, as in DD's scope, on reassembly you MUST revert to the 10BA grub screw. No screw = crap job - I say!!!!

Something else now. No lock screw means that when you rotate the drum around to 0-zero, it's usual position a bit heavy handedly it could start to unscrew. And guess what......... As they tell all first day mechanical engineering apprentices. If something can, then eventually, it WILL. So take that advice on board.

And while we're here, another thing. When the thumbscrew is removed from the spindle, always mark the underside of the spindle with the letter R (or A, azimuth or D deflection) so that the thumbscrew goes back on the same spindle. That way, the 10BA locking screw holes will(?) coincide again and all is well. If they don't or overturn slightly DO NOT turn the thumbscrew back a bit until they do align again. That is ****-poor engineering practice and the hallmark of the devil!. Tighten thumbscrew up and if necessary, re-drill and tap, new grub screw, job done perfectly.

If you reverse the thumbscrew to re-align then all you are doing is to make BIGGER problems the next time because each time the not-properly-tightened drum turns back and forth, the little STEEL screw is chaffing away at both sides of the thumbscrew and spindle. First you notice a tiny bit of backlash between the thumbscrew and spindle until it gets worse and there the problem really starts. The grub screw is sat in a stripped hole and you can't get it out. Yes....., you an screw it in further (maybe) but the problem is still there - and getting worse. This time you will have to drill it out. That is fine - until the threadless grubscrew rotates under the loading of the drill and simply won't come out because the drill cannot grip it to cut it out!.

I've never had one fail on me yet but I have had a few where the owner has attempted to unscrew it with the sunken grub screw still in place. It’s all lessons learned from the really experienced old instrument teccies and my few years since the 60’s

On a well used telescope that’s been around the block a few times it’s only natural that there will be signs of previous grub screw locations. Waste not, want not of course. I recently had one, almost at the end of its life from Brian Dick that had more vacant semi circular holes than a second hand dart-board! Maybe Brian should put a picture of that one up. And that telescope was a picture of what I’ve explained here. I tightened it up, tested the operation and guess what….. Yep, had to drill and tap yet another locking screw hole. But it’s fixed for good.

Maybe I have explained now why some of these old telescopes have lots of holes around the drums and why some of the holes look a bit moth eaten – or look like they’ve been got at by a butcher-bubba king. It’s because instead of getting the tele looked at when you feel the backlash coming on, the users just leave it and leave it and leave it….. Holes get elongated, threads strip and before you know it, it’s xxxxed!

At the workshop instrument bays we always had a drawer full of rebuilt drums using inspected parts built up into serviceable assemblies. Those made up from mix-and-match parts from others, broken for spare parts always had a few extra unused holes. On these – and on telescopes sent out into service – the open holes around between the thumbscrew and the spindle, we pressed a black mastic sealant called LUTING into the hole which covered it up and kept the damp/moisture out. Simple

And something else too. Never, never not ever drill the 10 (or later, 9 or 8BA) holes freehand. Always set up un a drill press and universal table. I had one with the broken drill bit in the hole!, but an easy fix

One other thing I ought to point out is that if you have unscrewed the grub screw and the thumbscrew won’t unscrew, DO NOT blindly turn it regardless. Sometimes there’s a second grub screw below the first as added security – just to xxxx you about.

There, that wasn’t too bad was it. All you need to do is ask and I’ll try my best to answer

For the very bravest repairers, where the grub screw holes DO align but the thread is stripped OR where they are almost in exact alignment, then we could and did drill out to 9 or 8 BA and re-tap. That way we could use the little 3/16 grubscrews from the No2 binocular ocular cell assembly

Thanks Peter. I obviously only remembered half of what you'd said! I'll drill them or carefully centre pop them (where I'm using new parts) in future.

Going back to the range scales - both of those shown are metric, as can be seen by the same spread of range grads from 1 to 10, but only the one is 'M' marked. Presumably a few slipped through the net.

Peter:
Much thanks for chiming in.
I was rather hoping you would.
Nice to see you back.
I was really taken by the poor quality of the L1A1 scopes that I have seen.
They were quite abominable in MY OPINION...
Some L42's were almost mint and others were as you say over the pond "bog standard".
No attempt was made to clean out the dried paint on the adjusting screws, stripped screws and galled heads, etc.
Roger and I had a long chat about this the other evening and he shared with me what he remembered of what you had told him on the subject of the missing grub screw.
I still think it is poor workmanship to send something out the door like that and I must assume the designers had something in mind putting it in on the original No.32, Mk.3.
Was the conversion done in house or done by an outside contractor???
Outside contractor might explain the poor quality of some conversions or as I now see them.

---------- Post added at 11:33 AM ---------- Previous post was at 11:27 AM ----------

I have found the second 10BA grub screw more than once.
Also the mess that results from unscrewing a drum without removing the grub screw(s) using vise grips on the turret and bushing.
I will post some pictures of the resultant mess that can occur as I kept them as examples of what comes in.

"Just a quick clean up and dust the lenses
There is not really that much wrong with it."

The rifles were sent for conversion to Enfield from the various Ordnance Depots around the Country on a rotating basis due to the shortage of serviceable No4T's in the system. The telescopes were shipped out to the various Base or Command workshops around the country, close to the Ordnance depots, to be converted, cleaned, tested and returned. It wasn't a difficult job. Once converted, they were returned to the Ord Depots where they were mated up with the rifle again.

There was always a bit of confusion over the engraving..... Hence the reason for the slight variations you will encounter. Until it was finally codified..

Some owners might see that their scope started out as a No32, then converted to an L1A1, then re-engraved to suit the codified engraving - and then re engraved to revert it back to No32 Mk3 in order to equip the No4T's that were part of mobilization stockpiles. At the end there was a total shortage of telescopes that the equally easy converted 2/1's were converted. Mind you, telescope shortages were but nothing compared to the shortage of wood furniture.

The L1A1/L42 was a good - or bad - example of something being done on the cheap. As was said at the time, new build on the zillions of new ex Fazakerley bodies was a far better option but so said, the skills required were not available then. That ignores the fact that while BSA rifles were selected because of continuity of manufacturing tolerances, so were the new 50's production Fazakerley bodies. And they were new.

Thread 26. I always wondered where my little engraving head tool went DRP!

A few examples of what comes in the door.
I think I tossed a couple in the bin.
The bushing has had the die run on it to clean it up as as originally the threads badly smeared.