Lathe Terminology

[Swarf, Mostly!Participant @swarfmostly]

[Swarf, Mostly!Participant @swarfmostly]

I know what a 'plain' lathe is and what BGSC means and I think I understand 'sliding & surfacing'. I also know what an 'ornamental' lathe is/does.

But which particular feature/characteristic (or group of) determine that a lathe is a 'tool-room' lathe?

And what is an 'engine' lathe?

Have I left any out?

Best regards,

Swarf, Mostly!

[Wout MoermanParticipant @woutmoerman25063]

I am wondering about what a capstan lathe is. I know of the capstan in cassette players which drive the tape at constant speed. But I can't see the use of a capstan in a lathe.

There is also a turret lathe but that is one I know.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Swarf, Mostly! on 24/08/2016 21:15:21:

… which particular feature/characteristic (or group of) determine that a lathe is a 'tool-room' lathe?

.

In my limited experience: A 'tool-room' lathe is usually a plain lathe [sometimes even to the extent of not having a compound slide] … But it is built, and maintained, to the highest standards. … Think in terms of Schaublin; Lorch; Hardinge; etc.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Wout Moerman on 24/08/2016 21:24:51:

I am wondering about what a capstan lathe is. I know of the capstan in cassette players which drive the tape at constant speed. But I can't see the use of a capstan in a lathe.

.

The Capstan on a lathe looks more like that on a Ship than in a cassette player.

It 'indexes' a set of tools into place [often automatically, as the slide is retracted]

MichaelG.

[HOWARDTParticipant @howardt]

A capstan lathe was used for repetition, producing the same part over and over again. They could have front and rear tool posts with multiple tools for turning and grooving etc. The tailstock end would be a capstan, a large diameter multiple tool holder which would index when it was wound back after each operation. I used to work on one in my early days, late 60's. The only problem was speed changes causing the drive motor to overheat, as you went from drilling to tapping. But in there day they produced many parts and were widely used in production shops.

I am sure there are a few here who spent many years on them.

Howard

[MWParticipant @mw27036]

Hi,

An engine lathe is I suspect an outdated term to refer to a lathe that is driven under power. Meaning a person doesn't power it basically. Alot of metal lathes used to be treadle powered.

An ornamental lathe is referring to the lost art of ornamental turning, in normally ivory, wood, sometimes jade, jet and other soft stones. Was probably akin to a wood lathe with hand tools but often featured some highly complex mechanical indexing and angle devices, usually to create complex swirls, spirals and patterns in a piece of material, normally for columns. Sometimes ornamental turning lathes were converted metal turning ones, and featured a cross slide and compound slide. 

Michael W

 

Edited By Michael Walters on 24/08/2016 22:21:48

[Anonymous]

I think that 'engine lathe' is simply US terminology for what we call a lathe, ie, general purpose, but screwcutting.

Andrew

[Roderick JenkinsParticipant @roderickjenkins93242]

I've always assumed that a toolroom lathe is a general purpose lathe like we home engineers use, albeit of high quality and used by toolmakers to make the jigs and fixtures for production lathes (such as capstan lathes).

Cheers,

Rod

[Clive FosterParticipant @clivefoster55965]

As I understand matters :-

Sliding and surfacing means the machine can make accurate cuts both parallel to the bed axis and perpendicular to it.

BCSC is Back-Gear Screw Cutting meaning that the machine can cut threads by driving a leadscrew synchronised to the spindle via a train of gears. Its usually understood that the gear train ratios can be varied to cut different threads. Applies to machines with a screw cutting gearbox too although that was a later developement and originally all machines had open gears. The backgear referenceis confusing in that it also applies to the compact system used to get a low range of speeds from a cone pulley driven machine.

The once common precision bench lathe used chase style screwcutting based on short master threads for all common sizes. It was normally used with its saddle locked down to the bed so the slidng cut range was limited to the slide travel and was not necessarily parallel to the bed. Hence S&S and BGSC are important in differetiating what we consider the more common form of late from both the precision bench type and the many other more limited types used in production work.

Many capstan lathes, eg Ward, combine a limited selection of pick-off gears with several pitches of leadscrew for threading duties.

Generally Capstan lathe is British, Turret lathe is American but both refer to machines of similar capabilities and operating principle. Both have a rotating head containg several tools which are successively bought up to the workpiece as the head is indexed round after each stroke of the opreating lever or capstan. Technically the specific difference is that capstan lathes have a separate slide carrying the turret whilst turret lathes run the slide direct on the bed. In practice its geography rather than design which defines which is the generic term.

Engine lathe is American terminology usually applied to what we in Britain would term a BGSCSS machine i.e. the now common metal workers lathe. It derives from the obsolete meaning of engine as a device for doing something before it became commonly associated with prime movers e.g. steam engine, internal combustion engine. In Victorian and pre-Victorian days most mechanical devices of any complexity outside the horological world tended to be called engines, at least until they became common enough to get their own name. Back when the term engine lathe first became common lathe would be understood to refer to a simple machine which merely rotated the workpiece. Little more sophisticated than a watchmakers turns, bodgers pole lathe or the modern cheap hobby market wood lathe. An engine lathe referred to a machine having extra equipment ("engine" ) driven off the spindle so it could do more than simply rotate the work. For example screw-cutting or power feed equipment. Old style back shaft power feed can easily be seen as a simple "engine" bolted on to give additional capabilities.

Toolroom lathe is basically the high end, deluxe version of the normal manual lathe. Especially for American makers, e.g. SouthBend, who tended to use the term for a machine sold fully equiped with chucks, taper turning unit and collets. In British practice more associated with machines made to be very rigid and very accurate. Often a bed wider than spindle height is taken as the minimum distinction. Usually limited in spindle bore and bed length too. Mostly a shed load of special job accessories in the catalogue and always very expensive. The distinction tended to evaporate as more modern production techniques bought more ordianry machines up to standards approaching that of the true toolroom lathe. Time was an ordinary made down to a price machine might not even have proper graduated dials on all slides. In later years many toolrooms got on just fine with Colchester Triumph 2000 and similar machines which were certainly made down to a price but still had more than adequate accuracy. That said the true toolroom machines from the likes of Holbrook would still do a better job, especially on obdurate materials, but post war the difference in performance steadily evaporated and toolroom tended define a machine of high accuracy and capable of taking heavy cuts. Most DSG machines for example. The brochure for my wartime Pratt & Whitney model B 12 x30 clearly illustrates the start of this evolution.

Clive

PS long posts take time to write!

Edited By Clive Foster on 24/08/2016 22:37:53

Edited By Clive Foster on 24/08/2016 22:38:50

Edited By Clive Foster on 24/08/2016 22:39:28

 

Edited By Clive Foster on 24/08/2016 22:41:11

[JAParticipant @ja]

There is a difference between a capstan and a turret lathe which was very important when I was an apprentice. However I have not got a clue what it is now (50 years later). Possibly the tailstock of one was on a secondary slide. I do remember that capstan lathes were operated by semi-skilled men, an employment classification that I believe no longer exists.

JA

Posted before seeing the above reply.

Edited By JA on 24/08/2016 22:46:38

[John Stevenson 1Participant @johnstevenson1]

Capstan lathe has the sliding bit on the bed.

 

Turret lathe has the sliding bit on a separate self contained turret.

 

Edited By John Stevenson on 25/08/2016 00:01:41

[Clive FosterParticipant @clivefoster55965]

John

Thats interesting. My copy of Lathework published by Newnes, revised edition 1943, says the opposite viz turret slides on the bed, capstan has short slides on a separate mount. Relavent section shows pictures of a Ward no 13 turret lathe clearly showing the turret unit slides directly on the bed and a Herbert 2S capstan lathe showing that the slides are on a separate carrier fixed to the bed. Seems to agree with other books I have but that was the easiest one to look things up in. Skinny at only 140 odd pages.

Personally I'd have called both machines in your pictures capstan lathes but I never had owt to do with production work so all academic to me.

Clive.

[RainbowsParticipant @rainbows]

I thought turret was the american word for capstan.

[HopperParticipant @hopper]

Posted by JA on 24/08/2016 22:45:04:

I do remember that capstan lathes were operated by semi-skilled men, an employment classification that I believe no longer exists.

YOu would probably have to possess a Certificate IV in Machine Tool Operational Technology (Metal) to crank the handle on a capstan lathe these days. ISTR in Oz the blokes cranking the capstans in the '70s were called Second-Class Machinists and qualifications were basically two arms, two legs and a heartbeat.

[Ady1Participant @ady1]

It depended on the operator (doesn't it always)

Some post WW2 capstan dudes could do all their own setting up stuff and brought along their own extra widgets and bits for maximising speed and outputs

They could crank out huge amounts of accurate parts the same day as being given a new job

Some ended up in the post WW2 model aero-engine industry

[Author]

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