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Derbyshire 750 Lathe
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Largest of the Derbyshire Precision Lathes, the Models 750 and A (both still current) shared many accessories and parts - but the two machines, though so similar in appearance and function, did differ significantly enough for the makers to advertise them separately. Almost certainly developed from the Gilman lathe (their story can be found here), the 750 was usually shown in a production set up, and the A (more frequently) as a toolmakers' version with a compound slide rest and with the prices set differently. In 1970, for example, the basic bed and headstock for an A cost $579 but that for a 750 was $495; a ball-bearing Model A headstock was $384, for the 750 it cost $300; a complete cone-bearing headstock for a Model A was listed at $325 whilst for a 750 the price dropped to $208, a huge difference. The result was that a complete bed and headstock assembly, fitted with a lever or hand-action collet closer - and ready to take any of the identical (and commonly priced)  accessories - tailstocks, slides rests, etc. - cost  $695 as a Model 750 and $800 as a Model A.
The overall length of a mid-1950s 750 was 25" with a bed length of 22" and a between centres' capacity of 12". The centre height was 75 mm (2.953") and the maximum collet capacity 0.315" (5/16" or #80 metric). Both plain cone-bearing and ball-bearing headstocks were available, the latter, when fitted with a variable-speed drive unit, offered two speed ranges: with the initial drive pulleys set at a ratio of 1 : 1 speeds went from 600 to 5,000 rpm whilst setting them at 2 : 1 gave 1,200 to 10,000 rpm - with a maximum recommended speed of 18,000 rpm. No figures where given for the cone headstock model, but it must have run very much more slowly. Some of the many accessories developed for the two lathes are shown here.
It is likely that early versions of the Derbyshire 750 may also have been marketed by Stark Company during the 1950 as their No. 2 lathe..

An early 1950s Model 750 with a beautiful (but less expensive than nickel plate) crackle-black paint finish. The centre height was 7.5 cm, (giving a swing of 67/8") and the bed 22" long - with a between-centres' capacity of 12". The spindle on the model illustrated is of the 12,000 rpm ball-bearing type and fitted with a with a Spring-bind brake assembly which simultaneously stropped the spindle and opened the collet.
In the illustration the lathe is driven from underneath by an infinitely variable-speed motor made by the Master Electric Company of Dayton, Ohio". This was an all-metal unit, of an essentially simple "swash-plate" design, where the drive and output shafts, (splined and laying one above the other) were each fitted with two opposed cones, one fixed, one free, which engaged with the tapered sides of a large ring which passed between them. Turning the external control wheel resulted in the upper right-hand and lower left-hand "free"cones being moved simultaneously along their respective shafts - so altering the radius at which they engaged with the ring and hence changing the ratio between them and their relative speeds. The unit selected for the 750 had a speed range of 500 - 5000 rpm.
These devices were beautifully made - but very expensive; by the mid 1950s a 0.25 hp unit was $350, against a list price of around $60 for an ordinary motor. Despite this, many were to be found in applications as diverse as food-packaging machinery and military hardware - and at a stroke they solved the problem of building a speed-reducing countershaft unit for a small lathe or miller. However, when they go wrong, they can be difficult and expensive to repair and by the late 1960s had been replaced by various forms of cheap electronic speed control.

A Model 750 from 1969 fitted with a quick-action collet closer, screw and lever-feed compound slide rest and a 6-station capstan unit.

1969 Model 750 with a screw-feed cross slide and lever-feed tool slide.

A 1970s Model 750 with ball-bearing headstock spindle (#3804) on the maker's steel cabinet stand (#3860) and fitted with a 6-station Turret (#3610), Double Compound all-lever-feed Slide Rest (#)3652 and driven by an electronically-controlled, infinitely variable-speed motor (#10245).

A rather desirable assembly - a wider view of that illustrated on the main 750 page.
This complete unit consists of a Model 750 lathe (#3800) with a compound slide rest (#3654) a six-position Turret (#3610), Master variable-speed electric motor (#3741) together with its reversing switch (#3743), mounting bracket (#3680) and belt guard. Keeping the lathe company on the bench is a Model 750-S Micromill.

Variable-speed motor by the Master Company of Dayton, Ohio, U.S.A.




email: tony@lathes.co.uk
Home   Machine Tool Archive   Machine-tools for Sale & Wanted
Machine Tool Manuals   Machine Tool Catalogues   Belts   
Books   Accessories


Derbyshire 750 Lathe
Derbyshire Home Page  Magnus Lathe    Elect Lathe    Model 750    Model A    Micromill    Derbyshire Precision Drill   Derbyshire Collets   
Pinion Cutter

Very high quality Reproduction Sales Catalogs
are available for Derbyshire lathes.