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South Bend Series 20 Lathe
- probably the rarest South Bend lathe of all -

South Bend Series 20 Photo Essay

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South Bend Manuals & Catalogs

At around the time that the precursor to the most successful South Bend lathe of all was being launched, the Model 5, Type 405, the Company were also working on a new small lathe, the Series 20 Toolmaker. When introduced in early 1934, under Catalog No. 520, this new machine was priced at $158, this being twice the cost of an equivalent capacity if basic 405 that was listed at $75. Although the Toolmaker was shown in the 1934 Year Catalogue, by the middle of 1935 it had disappeared, perhaps setting a record for the shortest production run of any South Bend model. Cataloged as a rather special and expensive little lathe, it was, in fact, of absolutely conventional South Bend design and really little more than a copy of the regular 8-inch Model produced from 1931 until 1933 - though increased in size by around 20%. In addition to an identical design, the two lathes also shared the same changewheels, these being of 18 pitch although, oddly, the stud gear on the output of the tumble reverse had a 1/2" bore instead of the 9/16". As the ordinary changewheels could not be used (as on other models), the Company providing a set of three with each lathe of 16t, 32t and 64t. Like the Model 5, the Series 20 had no option of a power cross feed, nor a screwcutting gearbox, carriage travel for both threading and feed being by engaging and wearing out the leadscrew half-nuts.
One interesting aspect of the ordinary 8-inch was the option of a rather magnificent built countershaft carried above the headstock (seen here on a classic Dennis Turk restoration) listed by South Bend as the
Silent V-Belt Motor Driven Lathe, and this too was made available for the Series 20, though in a modified form as the vertical casting, being fastened to a larger lathe, required some additional clearance for the rear of the headstock and backgear assembly. As with other South Bend models a variety of drive systems, stands and combinations of these was available even to build-it-yourself plans for wooden benches.
Although the original Model 5, Type 405 used a different bed to the Series 20, in 1936, when the former morphed into the Type 415 (and later 9-inch Workshop Model), the Series 20 bed was adopted for this much improved version. A beautifully restored and perfectly original Series 20 can be seen here.
In order to distinguish the various versions of the Model 5, the lathe was given a Model Type designation that reflected its drive system and between-centres capacity, the latter being available in a range of sizes: 6" and 12" - though one would expect few of those to have been sold - and, more usefully, 18", 24" and 30". Although prices started at $108 for the shortest machine, by the time something useful like the 24-inch model, the price had risen by $30 (28%) to $138 - which does seem rather a lot for an extra 18 inches of
gray cast iron with a 50% steel mixture with three V-ways and one flat way accurately planed and hand-scraped.
Continued below:

Continued:
Running in bearings formed direct in the cast iron of the headstock (a system widely used by South Bend and noted by them to give in excess of twenty-years service) the carbon-steel spindle was bored through 3/4" and was lubricated by small oil caps with feed to the bearings by wick. Although the similarly-priced 9-inch Junior was fitted with bronze bearings - lapped and adjustable for wear - the remaining specification for spindle and headstock was identical with the latter hand-scraped to the bed and the former with a 1.5-inch 8 t.p.i. Nose, a No. 2 Morse taper socket and carrying a 3-step cone pulley to run 1-inch wide flat belt that gave, in conjunction with backgear, six speeds from 39 to 596 r.p.m.
Screwcutting was from a 3/4" diameter, 8 t.p.i. Acme-form leadscrew grasped by double nuts and driven by a set of changewheels supplied that allowed pitches from 4 to 40 t.p.i. to be generated, this range including use of the  previously mentioned set of three stud gears. Extra changewheels were also sold, at $5 each to extend the threading range up to 80 t.p.i. 
Standard for the era, the usual type of standard South Bend compound* slide rest assembly was fitted with the cross-feed screw held in a housing that screwed into the front face of the saddle and a top slide that could be swivelled through 180. Rather small zeroing micrometer dials, graduated to read 0.001" were fitted and left in a lightly polished steel.
Fitted with a No. 2 Morse taper spindle with self-eject to the centre, the tailstock could be set over for the turning of slight tapers and had a reservoir to hold a supply of highly poisonous white lead and a dipper rod to apply it to the centre.
As with many other South Bend models through decades of their production, the short-lived Series 20 could be had as a basic unit, or with individual extras priced separately or complete with all the necessary
regular equipment  in a ready-to-run state. In the case of the Type 30 these included: a 1/4 h.p. motor wired to a reversing switch with a V-pulley; the necessary belt; a graduated compound rest (top slide),; faceplate; toolpost; two 60 centres; an adaptor to sleeve down the spindle nose; a set of screwcutting changewheels; wrenches; lag screws; washers; installation plan - and copy of the very useful South Bend Book "How to Run a Lathe".
An very experienced rebuilder of the South Bend lathes comments: " In my working with the lathe I would compare its quality to the 9-inch workshop lathes built after WWII.  Even the spindle is of a better quality than the workshop lathes built up till 1939 - when they went to the capillary oil feed and case hardened and micro polished spindles.  I would also say the material and construction of the spindle on the 20 series is quite comparable to the 1937and later wide bed R and T Series 9 inch lathe."

*meaning the cross and top slide - although South Bend always used compound to mean just the top slide)..

The South Bend Silent V-Belt Motor Driven countershaft as used on the Series 20 Toolmaker and also available for other lathes in the Company's range. The V-belt referred to was only from motor to countershaft, the final drive being by flat belt. This model was listed at $190 complete with Regular Equipment that included: 1/4 h.p. motor wired to a reversing switch with a V-pulley; the necessary belt; a graduated compound rest (top slide),; faceplate; toolpost; two 60 centres; an adaptor to sleeve down the spindle nose; a set of screwcutting changewheels; wrenches; lag screws; washers; installation plan - and copy of the South Bend Book "How to Run a Lathe"

Simplex Motor Driven Bench Lathe with standard equipment - priced at $156 in 1934 with "Regular Equipment". "Simplex" referred to the fact that this was the simplest form possible of a remote countershaft available

Basic bench-mounted version of the Series 20 Toolmaker with overhead "Double Friction" (i.e. clutched) countershaft

Intended to be run at 255 r.p.m. the Double Friction (clutched) countershaft gave forward and reverse motion to the spindle

Bench-mounted version of the Series 20 Toolmaker with a self-contained horizontal drive countershaft at $158 - with Regular Equipment but less the bench

Series 20 Toolmaker with a 36-inch long bed mounted on the maker's plain Floor Leg Stand and supplied
With a clutched-equipped (double friction) countershaft for fastening to a wall or ceiling. $150 with Regular Equipment

Series 20 Toolmaker with a 36-inch long bed mounted on the maker's Floor Leg Stand with Oil Pan
and a clutched-equipped (double friction) countershaft for fastening to a wall or ceiling. $169 with Regular Equipment


South Bend Series 20 Photo Essay

South Bend Home Page   South Bend 9-inch Workshop   South Bend Model 5

South Bend Manuals & Catalogs

South Bend Series 20 Lathe
- probably the rarest South Bend lathe of all -
E-Mail Tony@lathes.co.uk 
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