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Weiler Praktikant Lathe Mk. 1

Page 2 - The Prakitant Mk.2 Lathe

Weiler Home Page  Condor   Weiler Primus   Praktikant   Praktikus
 
Weiler LZ330   Commodor   Ergodor   Matador   220, 250, and 280 Series

Weiler LZ280 & LZ300   Weiler LD-220, MD-220, LD-250, LDS-250, LDT-250, MF-220

RDT-260, LZT-280N, LDT-250/6 & Variants

The writer would be interested to hear from owners of the Praktikant lathe

Handbooks and Parts Manuals are available for Weiler lathes

Long enjoying a fine reputation as a maker of high-quality lathes - together with a small range of milling machines, from the 1950s onwards the Weiler Company concentrated on a relatively limited range of conventional lathes including simple plain-turning bench types, production capstan and toolroom-class screwcutting models. Models produced included the Praktikus, LZ330, Primus, Condor, Commodor, Ergodor, Matador, Turnomat and a series known as the HP, LZ, LD, MD, MF and RD. Today, in addition to some CNC machines, the Company still manufactures high-class manual lathes - one of the few surviving makers of such items for which there is a steady if limited demand.
A less expensive lathe than the contemporary Matador and Condor, the Praktikant was built in Early (Mk. 1) and later (Mk. 2) versions - the latter easily recognised by the angular styling and use of dials instead of levers on the headstock and screwcutting gearbox. This article deals only with the older version as current until the early 1980s.
With a 140 mm (5.5-inch) centre height Praktikant was built to DIN 8605 toolroom standard - though it was, as its name might suggest, a lathe intended for ordinary work and employment as an advanced training lathe in schools and colleges. Two between-centres capacities were offered: 500 and 800 mm; the shorter of the two was mounted on a one-piece, enclosed cabinet stand made from welded and braced sheet-steel. The left-hand compartment housed the drive system, the right-hand the coolant tank and electrical switchgear with the centre section forming a locking tool and accessory storage compartment. The long-bed 800 had its stand formed as two welded sheet metal plinths, one under the headstock the other beneath the tailstock with, between them, a slide-out chip tray mounted on four rollers and inclined slightly to the rear. The left-hand plinth held the drive system and the right-hand side the coolant unit and electrical equipment - including the hard-to-reach and dangerously remote switchgear.
Unlike the more expensive LZ330, Condor and Matador models with their choice of variable-speed drive or a 9-speed pre-selector gearbox, the Praktikant used, in conjunction with headstock backgears,  a simple 4-speed gearbox, remotely mounted in the base of the cabinet stand. Lubricated by an oil bath, the box held hardened and ground gears, in an alloy steel, running on splined shafts supported in ball races. Control of speeds was by a large-diameter, wavy-edge handwheel, mounted to the left-hand side of the headstock-end, with a direct reading speed-indicator scale. Drive from gearbox to headstock spindle was by twin V-belts, as was that from the motor, this being mounted below the gearbox, on a hinged plate to allow adjustment of belt tension. As genuine, matched sets of V-belt pairs now appear to be unavailable, (and a pair of unmatched, ordinary belts can cause noise and vibration), today the solution is to use a belt of the accurately made T-Link type.
Early models appear to have been fitted as standard with a 2 h.p. single speed motor, though with the option of, at first, a 2-speed 1.4/2.4 h.p. unit and later a more powerful 1.5/3.0 h.p. - this latter fitting eventually becoming part of the ordinary specification. With the late-type 2-speed motor fitted, the base-mounted gearbox and backgeared headstock combined to give sixteen speeds: 42, 67, 84, 110, 134, 175, 220 and 350 r.p.m. in backgear and 241, 383, 482, 630, 765, 1000, 1260 and 2000 r.p.m in open belt drive. With the single-speed motor the eight speeds available began at a low of 84 r.p.m. (a tad too high when a beginner was attempting to screwcut) and rose to the same high of  2000 r.p.m. Electrical control of the motor's stop, start and reverse was by a handy lever pivoting from the apron's right-hand face - the rod it operated being connected to a switch held within the right-hand cabinet leg; unfortunately, rather low down on the front face of this leg was also the location for the electrical switchgear, non of which were duplicated near the headstock. Should the operator's have been involved in an industrial-quality accident, not having immediate access to an emergency stop button would have seriously impaired his or her chances of avoiding serious injury. If you own a Weiler, arranging a kill switch on or near the headstock - or, as a minimum, one between the stand legs - would be a wise precaution.
Continued below:

Weiler Praktikant Mk. 1

Continued:
Identical in design to that used on other contemporary Weiler models,  the bed of the Praktikant was formed as a heavy box section with the deep walls cross-braced by diagonal ribs. Cast from a normalised Meehanite iron it had a flame-hardened, close-grained finish to Brinell 450 and carried two ground-finished V ways and two flat - the carriage of course running on one pair and the tailstock the other.
A rigid, box-type casting, the headstock held a spindle manufactured from a case hardened and ground manganese chrome alloy steel, bored through 1.4" (36 mm) and running super precision bearings - a double-row, cylindrical roller in a tapered-seat housing at the front and a combination of tapered roller and a ball-thrust at the rear. Fitted with a No. 5 Morse socket (with a hardened sleeve provided to take it down to a No. 3 Morse) the spindle nose was formed with a DIN 55022/5 flange - this simple, sturdy and accurate fitting suffering from the drawback that every time a fitting was changed three bolts had to be removed and replaced. As a point of interest, the short taper used on the DIN 55022 fitting, and the PCD of the its studs, are identical to those used on a D1-5 Camlock fitting - data here).
Totally enclosed and lubricated by an oil bath, the screwcutting and feeds gearbox reflected modern practice in having moved away from the traditional Norton-type with its open tumbler slot that invited the ingress of dirt and swarf.  While a 24 mm diameter, 6 mm or 4 t.p.i. leadscrew provided a screwcutting drive, power feeds were driven by a separate slotted shaft that passed through the apron to drive the usual worm-and-wheel mechanism. As the box incorporated the leadscrew and feeds' reversing mechanism, this obviated the need to some form of tumble-reverse assembly in the leadscrew drive. All gears were mounted on hardened and ground shafts running in ball races and the box could generate (though only when used in conjunction pick-off gears from the standard or extended set) a range of 52 English pitches spanning 2 to 72 t.p.i., 27 metric from 0.25 to 12 mm pitch and 9 Module from 0.125 to 4.0 mod.  Longitudinal feeds were provided in normal and coarse ranges (again, by employing the additional pick-of gears) with 39 of the former ranging from 0.019 mm to 0.912 mm (0.0007" to 0.0336" and the latter giving 39 from 0.040 mm to 1.920 mm (0.0014" to 0.0672" - all per single revolution of the headstock spindle.
Held in ball thrust bearings at both ends the 6 mm pitch (or 4 t.p.i.) 24 mm diameter leadscrew, which was reversible when worn, was protected by a shear pin and used only for screwcutting, being engaged as required through dog clutch.
Double-walled, the oil-bath apron was a model of simplicity and strength. Shafts ran at both ends in bronze bushes or ball races with all gears heat-treated and cross-shaved. Feed direction - sliding or surfacing - was selected by a push-pull knob and, as the feed-shaft passed through a knock-off wormbox, the engagement and disengagement required only the lightest of touches on the lever - no matter how deep the cut. The drive from the feed shaft was fed through a spring-loaded slip clutch that both protected the entire mechanism from harm and allowed both directions of feed to be equipped with adjustable stops that, when contacted, caused the drive to slip. Unfortunately the carriage traverse handle was fitted to the left, so positioning the operator's hand to receive stray, red-hot turnings - though as compensation the wheel was equipped with a large-diameter, friction-setting micrometer dial that read to 0.2 mm or 0.1" for accuracy in turning to a shoulder length or into a bore.
Of Acme form, the cross and top slide feed screws ran through bronze nuts and were supported on ball races; the cross-feed nut was of the anti-backlash type and able to be adjusted to remove play without dismantling. The micrometer dials were of large diameter, dull-chrome plated and fitted with friction adjusters that were light to move yet secure enough to prevent accidental resetting. The full-length cross slide had a travel of 150 mm (5.9"), was machined with two traverse T-slots behind the top slide (so allowing a rear toolpost or other accessory to be mounted) and carried a 100 mm (3.9") travel top slide that could be rotated through 90 each side of central and mount tools up to 16 mm (0.63") deep using the standard clamp-type toolholder.
Fitted with a captive handle and an eccentric bed lock, the set-over tailstock had a close-fit, honed bore that held a hardened and ground No. 3 Morse taper, 40 mm (1.56") diameter spindle, graduated with 1 mm spaced ruler lines for a length of 80 mm (travel was 85 mm/3.35"). A usefully large micrometer collar was fitted and the spindle locked by a proper split-compression bush.
Supplied with each new Praktikant was a complete set of electrical equipment - enabling the lathe to be run immediately upon delivery - a hardened spindle nose sleeve to take the fitting down from a No. 5 to a No. 3 Morse taper, a 170 mm (6.75") diameter catchplate, Morse centres for headstock and tailstock, a carriage stop, a set of eight pick-off changewheels: 20, 24, 25, 30, 32, 35, 80 and 120 teeth, pressure grease and oil guns, spanners, a set of five shear pins for the leadscrew drive and an operation manual..


Changewheel drive to the screwcutting and feeds' gearbox

Double-walled, the oil-bath apron was a model of simplicity and strength. Shafts ran at both ends in bronze bushes or ball races with all gears heat-treated and cross-shaved. Feed direction - sliding or surfacing - was selected by a push-pull knob and, as the feed-shaft passed through a knock-off wormbox, the engagement and disengagement required only the lightest of touches on the lever - no matter how deep the cut.

To provide spindle speeds the Praktikant used, in conjunction with headstock backgearing, a simple 4-speed gearbox remotely mounted in the base of the cabinet stand. Lubricated by an oil bath, the gearbox held hardened and ground gears, in an alloy steel, running on splined shafts turning in ball races.


Totally enclosed and lubricated by an oil bath, the screwcutting and feeds' gearbox reflected modern practice in having moved away from the traditional Norton-type with its open tumbler slot that invited the ingress of dirt and swarf. 

Optional lever-operated collet closer

Page 2 - The Prakitant Mk.2 Lathe

Handbooks and Parts Manuals are available for Weiler lathes


Weiler Home Page  Condor   Weiler Primus   Praktikant   Praktikus
 
Weiler LZ330   Commodor   Ergodor   Matador   220, 250, and 280 Series

Weiler LZ280 & LZ300

Weiler LD-220, MD-220, LD-250, LDS-250, LDT-250, MF-220

RDT-260, LZT-280N, LDT-250/6 & Variants

The writer would be interested to hear from owners of the Praktikant lathe

Weiler Praktikant Lathe Mk. 1