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Volman Lathes
Model N, L & T
Lathes of the Late 1930s & 1940s

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Another range of Volman lathes, probably introduced in the late 1930s, was a set comprising the models N, L and T; these were manufactured in a wide variety of capacities (with some 22 different versions available) and each, in comparison with earlier machines of a similar size (with the exception of the very largest examples) had very much higher spindle speeds to take advantage of the latest developments in cutting-tool technology.  The lathes are easily recognised by their use of (plastic-knob tipped) bar levers to select the headstock spindle speeds rather than the "quadrant" type used previously.
Nine different bed widths were made and, as with the smaller lathes, each bed was used as the basis of several different models that were identical  apart from their centre height; thus, the narrowest bed, at 10 5/8" wide, supported two models the 6
1/2" centre height N-16 and 71/8" centre height L-18; the next bed, at 113/4" wide the  71/8" centre height Model N-18 and 77/8" Model L-20; a 13" wide bed was used on the 77/8" Models N-20 and 87/8" L-22. The next three larger beds, at 143/8", 153/4" and 187/8" wide, each provided the basis for 3 models respectively the T-20, N-22, L-25;  T-22, N-25, L-27 and the T-27, N-30 and L-35.  The next bed in the series was 215/8" wide and the basis for two lathes the 211/4" N-35 and 231/4" L-40.  Three lathes, the 221/16" T-35, 24" N-40 and the 26" L-45 were built on the next 247/8" wide bed whilst the most massive bed, at 28" wide, was used for the 261/2" N-45 and 281/2" L-50.
In every case the smallest lathe in each series had a centre height identical to the largest in the range immediately below.
Made from a "semi-steel" cast iron, with a Brinell hardness figure that averaged 200 to 220, the beds were well braced with diagonal ribs; after machining they were ground on planer-type grinding machines. The standard specification included a detachable gap section but, to special order, beds could be supplied without. Depending upon length either two or three supports were fitted with that under the headstock having both a tool cupboard and a sump for the coolant liquid; the coolant pump, when supplied, was bolted to the rear of the leg and arranged with either an independent, flange-mounted electric motor or a belt belt from an extension of the main motor shaft. Unlike the earlier machines a steel chip tray  was supplied part of the standard equipment.
All machines in the series followed a common design pattern with headstocks that were very deep front to back and with the input shaft carrying the well-established combined reversing multi-plate clutch and brake unit. This useful device, controlled by a one lever pivoting from the right-hand face of the apron and another by the screwcutting gearbox, enabled the spindle to be started, instantly reversed and (once in neutral) automatically stopped - so saving a good deal of wasted idle-running time. 6 spindle speeds were provided on the two smallest lathes, the N-16 and L-18; 12 speeds on the slightly larger N-18 and L20 models and 18 speeds on all eighteen lathes in the rest of the range. With the standard 1500 rpm motor fitted the speed range of all lathes, up to and including the 10
7/8" centre height L-27, was 1000 rpm but with the optional 1500 rpm motor this rose to 1000 rpm; unfortunately this led to a less-than-desirable corresponding increase in the slowest speed. The best option was provided by a two speed motor; this enabled the same high top speed to be retained but lowered the bottom speed to 19 rpm - an effective range that spanned a ratio of 100 : 1. When the 2-speed motor was fitted, and the lathe used to the limits of its strength and capacity, the makers recommended the fitting of an improved headstock where, instead of just the most highly stressed ones, all the gears were hardened and ground..
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Volman 18-speed Model JZKN labelled on this works photograph as a "Special"

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Even on the largest versions the headstock had only a simple a simple oil-bath lubrication system - but with the added benefit of a filtered supply to the front bearing with an oil-flow window fitted on the front of the headstock to let the operator keep an eye on things. The spindle was of "special steel", heat treated (but not hardened) and ground all over; it ran in an adjustable bronze sleeve bearing at the front and ball and roller races at the rear. On lathes up to the L-35 model a hardened and ground double main driving gear was mounted on the spindle close behind the bearing whilst on larger lathes this configuration was changed to a large, lapped, single helical gear. All the gears were manufactured from "
special gear steel" and the layshaft gears (on 5 shafts in the 18-speed headstocks) that were  in engagement with the main gears were hardened and ground and their multi-splined shafts constructed from high-tensile steel hobbed from the solid. Surprisingly, in view of the potential oil leaks (and hopeful infrequency of the need to look inside) many of the models in the range were fitted with hinge-open headstock covers.
Showing the greatest variety in capability and specification between models was the oil-bath screwcutting gearbox. The four smallest models, the N-16, L-18, N-18 and L-20 had a box that could generate 45 pitches from 4 to 120 tpi and the same number of feeds. The next 5 larger models had an improved box capable of producing an additional 27 pitches that, whilst no finer than before did extend the threading range  down to 1/4" pitch. The most limited range was offered on the next 6 lathes in the range where pitches from 1/8" to 30 tpi were available. The seven largest machines had a choice of 63 pitches from either 1/8" or 1/2" to 60 tpi. and these lathes were also fitted, as standard, with dual metric and English boxes - the smaller machines using conversion gears to produce the same effect. Although all but the largest lathes had inch-dimensioned leadscrews as standard (the largest were metric) Volman was able to provide either all-English machines, with inch leadscrews and gearboxes, or lathes with inch leadscrews but metric gearboxes or, where metric work was more likely to be in the majority, machines with metric-dimensioned leadscrews and all-metric gearboxes.
With a "semi double-wall" apron the smaller models had the cross-feed screw drive gear overhung on its outer side - only the largest lathes were fitted with a design where every gear ran on a shaft supported by bearings at both ends. The feed to the apron was by a separate power shaft; this was round with a keyway on some models and hexagonal on others; a worm surrounded the shaft and took the feed, via a worm wheel, into gearing that was held on shafts running through both walls of the apron. The power feeds were selected, or put in neutral,  by a 3-position lever working through a quadrant and on the smaller lathes (N-16 to L-25) engaged by a simple conical friction clutch with a screw-in control knob concentric with the selection lever. Larger models were fitted with a more robust multi-plate clutch and these lathes could also be fitted, at extra cost, with that ever-useful feature - an automatic disengage for the sliding feed. All but the four smallest models had a quick-action feeds-reverse mechanism built into the apron (using gears with face dogs) and operated by a lever pivoting around the powershaft where it entered the left-hand apron wall.
An oil supply was held in the base and pumped, through pipes, to the wearing parts; on larger models the lubricant could also be arranged to oil the bed and cross slide ways..
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117/8" centre height Volman Model N-30

Continued:
The leadscrew was supported in hardened steel bearings where it passed through each end wall of the apron, thus allowing the clasp nut to be a simple, one-sided affair that engaged with the outside half of the thread only. Not all machines were fitted with screwcutting for Volman offered the chance, across the range, of a considerable cost saving by specifying just the powershaft drive to the carriage to give a range of sliding and surfacing feeds.
The saddle was fitted with felt wipers and had large pans extending sideways from its sides - the right-hand one part of the casting, the left-hand one longer and detachable -  that both afforded a cover for the front bedways and leadscrew and provided a handy receptacle into which the operator could put his calipers, micrometers and other tools. 
The compound slide rest was fitted with proper tapered gib strips and the cross slide - already a full-length type - could be ordered with T slots across the back section to mount a rear toolpost or other fittings. The standard toolpost was an all-steel, indexing 4-way type (that could only be set at 45 degree angles) but money could be saved if an ordinary, single-tool holder was specified instead.
The tailstock was of the usual kind that could be offset to turn slight tapers; the centres were self-ejecting and the barrel clamped with a pad-mechanism that minimized any misalignment as it was closed down.
Volman's works and foundry in Celákovice is still in operation today and used by the privatised TOS MEH group for the manufacture of conventional,
CNC/Manual and full CNC machine tools..

77/8" centre height Volman Model N-20

Rear view of the 77/8" centre height Volman Model N-20 clearly showing the compact mounting of the motor on the back of the bed and its 3-step V-belt drive, the pivoted flat bar that operated the headstock clutches and the coolant pump driven from an extension of the motor shaft.

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Volman Lathes
Model N, L & T
Lathes of the Late 1930s & 1940s
email: tony@lathes.co.uk
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