Angus Bryant Symons

[Michael GilliganParticipant @michaelgilligan61133]

“Thread Correcting Lathe”

[Michael GilliganParticipant @michaelgilligan61133]

Whilst browsing around lathes.co.uk I came across this little Gem, which ticks the right boxes for one with a compulsive-obsessive interest in precision instruments and machines.

Does anyone have any experience of this lathe, or anything else by Angus Bryant Symons ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

For info. here are some references to patents.

111,693 is particularly interesting.

MichaelG.

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Edited By Michael Gilligan on 08/11/2014 08:35:12

Typo in title corrected by JasonB

Edited By JasonB on 09/11/2014 09:18:16

[Neil WyattModerator @neilwyatt]

Missed that!

Yes, very intriguing. I wonder how they calibrated each machine's 'wavy slot'

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 10/11/2014 21:24:54:

… I wonder how they calibrated each machine's 'wavy slot'

.

Somewhat cryptic description here

[quote] The contour of the slot in the correction bar is determined from accurate measurements of the pitch of screws cut in the lathe. [/quote]

I have a nasty feeling that the process involves repeated [and very accurate] measurements, combined with expert application of a suitably fine file.

MichaelG.

Edited By Michael Gilligan on 10/11/2014 22:27:20

Edited By Michael Gilligan on 10/11/2014 22:27:53

[Brian WoodParticipant @brianwood45127]

Hello Michael,

I recall there was a extremely similar machine sold on ebay a few months ago, I don't remember this specific maker being named but then how many specialist makers of such equipment would there have been on those days?

The example offered was said to be very rare having been bought new (with the original purchase documentation and handbook) by his father but it was missing some vital parts, notably the front slot fittings and the current owner was unloading in a sale of his late father's workshop with the declaration that he was largely unfamiliar with the machine. I must say I was tempted to buy it as a restoration project as it otherwise looked to be in nice condition but sanity prevailed in the end. The old man may well have been working on it and vital bits were stored elsewhere when he died—who knows?

I thought at the time it was an intriguing machine, thank you for providing useful links and references to follow up

Regards

Brian

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

Many thanks for the additional notes [it's probably a good thing that I didn't see that one]

Looking at the Science Museum web page, I note that theirs [a Mk.II.] was made by Glenfield and Kennedy for Bryant Symons.

… Was that perhaps the name on the ebay item ?

MichaelG.

Edited By Michael Gilligan on 11/11/2014 17:27:21

[Brian WoodParticipant @brianwood45127]

Hello again Michael,

I have just read some of Tony Griffiths page on this lathe, the one I was referring to was indeed made by Bryant Symonds, I remember the reference to the cost of a house as the sale price in the war time.and that corresponds with the time the seller's father bought his example.

Brian

[Robert DoddsParticipant @robertdodds43397]

Michael,
The Tony Griffith description suggests that the pitch correcting idea was superceded in the thirties. In the late sixties I was involved with using a trio of Pratt and Whitney Jig /Drill positioning tables as multi spindle drilling machines for pcb's They were driven by NC controls from 8 hole paper tape and the 40" x 20" table traverse was through recirculating ball screws. It was early days for this type of screw and P&W used exactly the same pitch correcting method to acheive a +/- .001" positional toleance over the whole table travel, each machine having its own calibrated cam track to turn the ball nut. Needless to say they didn't have additional proportional pitch variable feature.
Bob D

[Michael GilliganParticipant @michaelgilligan61133]

Bob,

Thanks for that … The transition from Analog to Digital control of such things must count as the 20th Century's "Industrial Revolution", and I think your P&W machines may be a significant milestone in the story [being one of the last uses of an analog corrector on a machine tool?].

• A friend in Sheffield used to work for Rabone Chesterman, and described the corrector cam for their linear dividing/ruling machine, which adopts the same general principle.
• My own collection [of relics for future restoration] includes a magnigicent Gaertner Toolmaker's Microscope which does not have a linearity-corrector, but does have a pitch-adjusting facility for its calibration.

Grateful for any more info. about the P&W machines.

MichaelG.

[Robert DoddsParticipant @robertdodds43397]

Michael,
There is little evidence now of the P&W machines. I have just one photo of the prototype as we were building it but it shows most of the features of the machine. It was designed to drill upto 4 holes simultaneously in each of two multilayer motherboards destined for 1960/70s mainframe computers
Holes on a .100” pitch were drilled for mounting the sockets to take 4 rows of plugin boards plus additional holes for intersect connections that were through hole plated on the buried pcb layers.

Referring to the photo the Tape-o-matic was fed an input off 8 hole teleprinter punched tape to define X and Y position data and also the sequence of the two banks of 4 high speed drills to deploy at each stop position. These were powered by the 8 solenoid valves on top of the arms feeding an air cylinder attached to each drill head. Heads typically run at 20,000 rpm for 0.042” carbide drills but had a max speed of 45,000rpm.
The frame design bore some resemblance to a railway buffers structure and seemed to be quite stable but in the end the machines proved to be distorting with the arms swinging side to side on a random basis, making the overall +/- 0.003” positional tolerance very difficult to achieve.
Eventually this was found to be caused by movement in the building. The machines were sited on the first floor of a steel framed building, one corner of which was on a clay bed that moved with the seasons and the weather. It applied sufficient twist to the floor plane to influence the drilling machine frame and caused the movement of the arms carrying the drill heads.
The solution was to mount the entire machines on pneumatic cushions that isolated them from the twisting floor. Each machine had three reference levelling pads to keep them stable and in normal incremental table movements this was fine, however they had also got a high speed jog mode with a supplementary AC drive and magnetic braking. This movement would cause the machines to rock to and fro in an alarming manner on the very flexible air cushions for a few moments but fortunately without detriment to the machine accuracy as it resumed drilling.
A further machine was taken from P&W that had a smaller table and came with a rear pillar to which we attached a custom designed head to carry the multiple drill spindles.
Bob D

[Michael GilliganParticipant @michaelgilligan61133]

Bob,

Many thanks for taking the trouble … It looks a wonderous beast.

Much appreciated.

MichaelG.

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