Ruby Loftus Screwing a Breech-ring

I was struck by a reproduction of this painting which was new to me but which is readily available with background information via Google, etc. The technical detail in the painting is impressive but can anyone identify the lathe and, in particular, the device that her right hand rests upon?

This was a very demanding operation and I saw a comment to the effect that a group of incredulous (male) toolmakers had visited the factory to verify the truth of the picture.

BTW, I thought about posting a scan of the painting but it is copyright the Imperial War Museum and I don't want their tanks on my lawn!

I'd hazard a guess that the item under the right hand is some sort of power drive to the cross slide to control cutting of the interrupted thread in the breech ring.

Andrew

Edited By Andrew Johnston on 14/02/2014 16:40:24

An interesting character she was. One of those girls who had an innate ability for practical engineering that would have lain totally undiscovered had it not been for the war.

After the war she was offered a place on an Engineering Course at a college. She declined, preferring to move to Canada with her fiance who had survived the war and had been demobbed.

I'd hazard a guess that the item under the right hand is some sort of power drive to the cross slide to control cutting of the interrupted thread in the breech ring.

The painting appears to show a continuous thread in the component, with a continuous spiral of swarf from the tool.

It would be easier to machine the thread first in the forging, then use a slotter to remove the "spaces" afterwards than try to thread an interrupted surface ?

Nigel B.

edit for grammer

Edited By Nigel Barraclough on 14/02/2014 17:38:35

> BTW, I thought about posting a scan of the painting but it is copyright the Imperial War Museum and I don't want their tanks on my lawn!

You didn't read the small print: "This item is available to share and reuse under the terms of the IWM Non Commercial Licence"

Good painting, but I don't believe that is a screw cutting operation, at least for a breech with multiple thread diameters. For a start the swarf is far too long, second they used devices to automatically retract the tool for cutting the interrupted threads and I can't see where this would be, and finally they lathe is running too fast.. I think she cutting the thread for a simpler breech like the one HERE.

Neil

Edited By Neil Wyatt on 14/02/2014 18:00:14

I've loved this picture for years but never really thought about the points being brought up here. As you say Neil, the blurred faceplate or chuck and the way the coolant is flying off makes the lathe seem to be going very fast for a screwcutting job. Especially since it had to be so precise. That said, she was probably considerably better than I am.

Looking at the bottom portion of the cylinder she is turning, and at the top left edge too, it seems the diameter is larger than it is deeper inside the part. Perhaps she is boring the part to size before starting the screwcutting operation? This could have been one of the operations in "Screwing a Breech Ring"

With regard to the interrupted thread on a breech, would a Bofors gun have had this? I thought it was a quick firing type of anti aircraft weapon in which the shells were dropped into a slot in a stack, rather than loaded one by one into the breech. I know that there is an interrupted thread type breech in the background of the picture. I'm sure someone can shed light on this.

Edited By Carl Wilson 4 on 14/02/2014 18:20:23

Neil Wyatt

Thank you for referring me to the IWM licence. You are right that I had not read it. A quick look raises the question of whether reproducing the painting on this website would be a non-commercial use. I am all in favour, however, of a robust attitude to copyright rules. Was it here that the Clarkson Autolock instructions were not reproduced for fear of repercussions? (I think commonsense ultimately prevailed).

I believe the breech-ring in question is for a Bofors gun.

Look at this:-

**LINK**

It is fascinating, Ruby Loftus and Laura Knight (with fag in mouth!) at the unveiling of the painting of the former by the latter. It also shows filmed footage Ruby working at her lathe. Her faceplate does not seem to be going quite as fast in the actual footage of her working.

The bofors clue is what we needed!

This is from **LINK** the manual for a 40mm Antiaircraft gun that declares it's mechanism to be essentially that of the bofors.

It's an interrupted screw, but only a single thread, not a welin breech.

Neil

Neil, the pic. you have shown is the locking thread of the barrel into the breech. basically the barrel is a quick change barrel as the EFC,s fired decides the life of the barrel.

The breech of the L40/70 is a sliding block, like most high velocity guns. It fires what is called 'Fixed Amm.' that is it has the projectile fixed in the case. The breech block operates in up and down mode. It is opened by a system of levers under recoil. The loading is automatic from the vertical magazine or clip load.

The designation L40/70 is a way of saying the barrel length. 40mm x 70 = 2.8M. The early ones were 40/60.

The latest models are Laser guided, a control stand has a man pointing a Laser stick at the target and all the guns in the battery will follow that pointer.

Clive

I served my apprenticeship with Royal Ordnance and I can remember that they had some pencil sketches in the board room of women and men on war work:- one was of a woman operating a capstan lathe she was wearing a turban that reminded me very much of my own mother, another was of two men working a rolling mill I can't remember what the third was of, the first time I saw these sketches was at my apprenticeship interview they must have made an impression on me as I was as nervous as hell at the time. About 10 years after Royal Ordnance was taken over by BAE systems the sketches disappeared from the board room, I did ask what happened to them but never got an answer, I just hope they weren't "lifted".

Clive right about the breech action on the bofors:- use to use them for ammo development but that's another story.

Stew

Drove me potty not seeing the image.

Licenced under non-commercial licence

Edited By Oompa Lumpa on 14/02/2014 22:37:44

Hi all

At the end of the you-tube footage (Carl's link above), Ruby operates the control lever referred to by Andrew.

Looks a bit like engaging half-nuts on a lead screw. It's operated while the lathe mandrel is stationary but seems to engage easily enough.

Jim

In my early days in the army I went to Weybourne with a TA LAA unit from Tyneside, the Bofors guns were manually traversed and elevated to follow the targets.

The targets were US drones and flew at a speed of 300mph and our lads could not turn the handles fast enough to keep up or obtain a lead on the target drone and could not bring them down. Being canny Tynesiders they devised a method of waiting till it approached and fired when it was in the zone and did obtain a few hits.

The US contingent had a radar controlled gun that locked on and the barrel swung over and always hit the drone.

The drones came down in the sea and were retrieved for repair and I had a look at one, it had flat 4 cyl engine and was filled with foam to keep it afloat, it came down on a parachute. They also had a drogue that was towed behind a propellor plane which was much slower , much to the delight of our lads.

Clive

Thanks to everyone who responded and apologies to Oompa Lumpa!

Absolutely no need apologising to me, my thanks to you for expanding my horizons.

graham.

The armouries tended to use special machines or modified machines just to produce one job,a fixture appears to be bolted to the faceplace and the breech rings held in the fixture,to continuously screwcut one job the machine may have had a special leadscrew of the same pitch as the breech ring and a thread engaging device fitted to the saddle so that an operator just had a simple lever to engage screwcutting rather than the unskilled operator having to look at thread cutting dials and engaging half nuts at high speed with risk of missing the correct nut position and scrapping the job ,unskilled operators can work very fast on such machines when a bonus system is employed,

One thing to bear in mind is that all the breech threads have the same start positions, its no good making breech rings with thread start positions anywhere around the hole!

This means that any spare replacements are all the right fit and work as fitted.

Clive

Graham you beat me to it, I was going to take a photo of the print on my wall, through a mirror, would that still count as copyright infringement............ or a photograph of one of my bikes in the lounge with a nice picture in the background

Also I'm sure I read in one of Curleys books or articles, and in it he reckoned during the "troubles" women could centre a 4 jaw chuck faster than any bloke he has ever seen, I believe his reference point was during a period he spent training the above to use lathes etc, during said troubles, I may not be exact in my description but I hope not to far off, my Nana worked in one of these places in Coventry, as I understood it from listening to her and her next door neighbour reminiscing, said trouble definitely happened or was it all propaganda........

Anyhow the picture looks cool no matter what you opinion on the reasoning behind it, the print I have came via a book called female war artists, if anyone is interested Ill post the ISBN No..........