Models T and TUD Training Lathes
Both the T and TUD plain-turning training lathes were dimensionally identical to the more highly-specified models and used the same basic castings; however, they lacked any form of screwcutting, power feed and, more often than not, backgear. The rear-drive system usually gave 4 speeds from around 200 to 1200 r.p.m. - although the writer has seen examples with 2-step pulleys on motor and countershaft to give 8. The under-drive models had 5 direct-drive speeds of 210, 340, 540, 850 and 1400 r.p.m. or, with backgear fitted, an additional 5 slower speeds. The development of the training lathes mirrored that of the more highly specified versions changing from rear to under-drive and then incorporating the other small improvements already described. The last versions were of 5-inch centre height and mounted on a version of the more modern-looking stand - and even complete with the splash-back, chuck guard and halogen light unit. Although an attractive proposition, because of their low price, the plain-turning versions are of limited use other than in a training role, for the very simplest of work - or as a back-up lathe for roughing out. Can they be converted to full-specification machines? I do know one person who managed it, but he enjoyed the unfair advantage of working night shifts at the Rolls-Royce aero-engine factory in Derby and had access to, shall we say, a rather comprehensive range of workshop facilities. In other words, the conversion is possible, but not even worth considering - unless you can find all the missing bits and enjoy the skills necessary to make the most of comprehensive turning, milling, grinding, boring and fitting facilities.
Drive Systems, Countershafts and Belts:
Because the 9-inch lathes had been flat-belt driven the maker, following usual practice to optimise grip, had set the pulleys as far apart as reasonably possible. However, even after a change to V-belts (and through two changes of countershaft) Boxford made no effort to take advantage of the shorter centres on which these can run to make the machines more compact. Early lathes, until machine No. 4600 in 1954, used an "integral" countershaft unit of unusual and ingenious design where the pulley system and motor were both mounted on a platform that could be adjusted forwards and backwards on two bars fastened to the back of headstock-end bed foot. The movement was activated a quick-action, two-start thread controlled by a handle on the end of a shaft that protruded through the front face of the bed foot immediately below the headstock. When moving these lathes, take care to support the rear of the countershaft otherwise the bars on which it sits may be bent. On later rear-drive models a very heavily built, separate 16-speed countershaft of different design was fitted with the motor mounted on a rather over-engineered (even unnecessary) horizontal platform. This allowed a separate adjustment to be easily made to the motor-countershaft belt tension. At some point the new countershaft was modified and its right-hand bearing made detachable to ease belt replacement - though it was still necessary to completely dismantle the headstock if a standard V-belt was to be used.
One problem sometimes encountered with both underdrive and rear-drive versions is vibration at high speeds and/or a knocking at lower; this can nearly always be traced to either the large countershaft pulley being out of balance or either (or both) the drive belts being unevenly worn. Well-used belts (or belts with stiff sections, caused by being left under tension for some considerable time) fall into and then ride up the pulleys, effectively varying the drive ratio, causing the speed to rise and fall rapidly and so induce vibration. Should you suffer this problem it's worth replacing both belts (the "T-link" belt on the headstock drive saves dismantling and can also, with advantage, replace the standard V-belts on the other parts of the drive). New, high-quality machine-tool specification belts (which we can supply, just email for details) can make a significant improvement to the smooth running of any machine tool. and then, if that does not affect a cure, removing the countershaft pulleys and shaft and statically balancing them between a pair of lathe centres.
An important point when dismantling Boxford drive systems: the makers were inclined to use two grub screws to lock pulleys to their shafts--the upper screw acting as a lock. So, before getting out the 14 lb hammer, do check first why it won't come apart...
A serious problem with the rear-drive machines, when used in educational establishments, was the difficulty of securing the belt guards against curious fingers. Most schools resorted to bolt-on straps and similar Heath-Robinson approaches and, as a consequence, in 1959, Boxford introduced the "Under-drive" models, a design very similar to the competing Viceroy and as already offered for many years on the American market by South Bend, Clausing, Sheldon and other mankers. With the drive now held securely in the stand behind an electrically interlocked door another advantage emerged: the depth of the machine was reduced to as little as 17-inches (400 mm).
Early under-drive lathes had their countershaft-spindle bushes pressed directly into the material of the motor platform itself, with the belt-tensioning handle mounted externally on the left-hand side of the cabinet. With the handle so temptingly placed many owners were inclined to use it as an unofficial (and dangerous) substitute for a clutch. In 1960 the countershaft was modified: the shaft diameter was increased to 0.75" and, in 1966, further improved when the shaft was increased to 1-inch diameter, the bearings fitted to removable brackets, the belt-tensioning lever repositioned within the cabinet base and the access door (like the educational versions) provided with a micro-switch that stopped the motor should it be opened by even a fraction of an inch.
While rear-drive lathes had 6, 8 or 16 spindle speeds all the under-drive machines, with the exception of the variable-speed VSL, were limited to 10. With some variations, because of special orders or educational and training use, the usual range on the back-drive type was 30 to 1250 rpm while the Mk. 1 and Mk. 2 Underdrive types of all models (CUD, BUD and AUD) generally ran at 40, 66, 105, 165 and 270 r.p.m. in backgear and 210, 340, 540, 850 and 1400 r.p.m in open belt drive. However, on the latter machines (at extra cost) the factory could provide a more powerful motor and a "high-speed" pulley set that increased the maximum to just over 2000 r.p.m. - but at the sacrifice of increasing the bottom speed to such an extent that it was difficult for beginners to cut threads.
It's well known that a lathe fitted with a spindle clutch is a good deal easier to handle than one without - and it remains a mystery why the only Boxford ever so fitted (as an option) was the ME10. Its design was similar to that used on the Myford ML7 with a brake-drum housing formed inside the countershaft drive pulley and an operating lever working through a push rod and toggle-arm that opened and closed a pair of brake shoes. Owners of clutch-equipped lathes report that the unit is not only reliable but has a pleasingly light yet positive action.
Metric & English Screwcutting
All models of belt-drive Boxford - from first to last - had 18DP changewheels, 0.375" wide. with a 14.5° pressure angle, a 0.125" tooth depth, a 9/16" bore and a 1/8" keyway. Standard changewheels can be purchased online here, the 100/127 metric transposing gears here and the 127/135 metric-to-inch transposing gears here. Because the company had strong connections with the educational and training world, many lathes sold during the 1950s were specified as "all-metric" machines. Interestingly, although large numbers were sold set up in this way, some were fitted (but probably unknown to their first owners) with an imperial leadscrew driven by a metric-conversion changewheel set. The factory was obviously keen to use up stocks of leadscrews that would otherwise have languished unused in their stores - and must have guessed that the likelihood of schoolchildren ever being allowed to use a lathe to cut threads was little better than zero. This, needless to say, resulted in a great deal of confusion when the machines eventually passed into private hands. Boxford's careful control of production costs has, however, done every subsequent owner a considerable favour for, providing that the lathe has its original set of changewheels the addition of a few more produces, at little cost, a dual metric/English screwcutting machine. Later metric machines, and all the metric-gearbox equipped variants no matter what their year of manufacture, were fitted with a proper metric-specification 3 mm-pitch lead screw.
Identical to that used on the original 9-inch South Bend, the screwcutting and feeds' gearbox contained components that were neither hardened or ground and lacked oil-bath lubrication. Instead, a lever-action oil can had to be used on a series of ball-oilers to lubricate the spindle bearings with the gears attended to by squirting inside on a hit-and-miss basis. Even so, the box is remarkably reliable and, if oiled generously, will not give trouble.
English and metric screwcutting versions are different, but can be easily distinguished one from the other: the English box has the diagonal line of indent holes on the right-hand half of the box's front face while for the metric version they are on the left.
Changewheels and English/metric and metric/English conversions
"English" threading Lathes with an 8 t.p.i. leadscrew and changewheels for screwcutting (i.e. without a screwcutting Gearbox) were supplied with the following changewheels when they left the factory: *16, 24, 36, 40, 44, 46, 48, 52, 54, 56, 60, *80, *72/18 compound, *80 idler (with boss). (* gears on machine as dispatched from factory for standard feeds)
To convert a non-gearbox English-specification lathe to cut metric threads the following gears are needed: 20, 100, 127/100 combination
In addition, to cut the following five pitches extra gears are required as follows: 0.45 mm = 18t gear, 0.55 mm = 22 t gear, 0.65 mm = 26 t gear, 0.7 mm and 3.5 mm = 28t gear
Metric Threading Lathes with a 3 mm pitch leadscrew and changewheels for screwcutting (i.e. without a screwcutting gearbox): were supplied with the following gears as standard. *16, 24, 28, 30, 36, 40, 44, 48, 52, 56, 60, *80, *72/18 compound, *54/18 compound, *80 idler (with boss)
(* gears on machine as dispatched from factory for standard feeds)
To convert a non-gearbox Metric-leadscrew lathe to cut English threads the following gears are needed: 18, 22, 26, 38, 54, 64, 88, 135/127 compound, 48/24 compound.
"English" threading Lathes with a screwcutting gearbox had a standard ex-factory drive train consisting of: 20t, 40t, 56t and an 80t idler. To convert this gearbox to cut Metric threads the following gears are needed: 24, 26, 28, 32, 36, 44, 48, 127/100 compound
Metric threading lathe with a screwcutting gearbox had a standard ex-factory drive train consisting of: 20t, 45t, 50t and an 80t idler. To convert this gearbox to cut English threads the following gears are needed: 38, 40, 44, 52, 56 and a 135/127 compound.
An interesting point concerns VSL models fitted with the L00 headstock spindle: on these lathes a screwcutting gearbox was standard - but some had different internal ratios and the English/metric and metric/English conversions gears arranged to be more compact with pairs of 64/54t and 76/65t respectively instead of the usual 127/110t (inch to metric) and 135/127t (metric to inch) gears. At one time it was believed that all gearboxes on the L00 VSL lathes had the altered internal ratios but several examples have been found in the USA (one being a VSL500 manufactured in 1977 with serial number V.S.L. 71861-L00) where this is not the case, the gearboxes being of the earlier, ordinary type. It is suspected that, while Boxford fitted a different gearbox to the earlier VSL models with the L00 spindle nose, this practice was discontinued and later editions of the manual not updated to reflect the change. If you buy a gearbox-equipped lathe that appears not to generate the pitches shown on the screwcutting plate check the special manual produced by lathes.co.uk, it shows all the ex-factory arrangement of the changewheels.
All the gears necessary to generate metric and other pitches are now available at a good saving on the factory price
Early headstocks, certainly those up to the introduction of the Under-drive models, were fitted with Timken bearings having 14 rollers and marked "Precision 5" (the front bearing coded 2720 for the cup and 2788 for the cone). Today, when available, these "selectively-assembled" units are very expensive - several hundred pounds each - but, as Boxford fitted later machines with cheaper standard-specification bearings (17 rollers and a shallower cone angle) there seems to be no good reason why a substantial saving cannot be made by using the latter in all versions of the lathe. For most lathes - apart from the VSL with its larger spindle - the front bearing should be a Timken single-row taper roller with a 30207 cone and 3027 cup. The rear is a Timken with a 2720 cup and a 2788 cone. However, to be absolutely sure, it's best to strip the headstock and check the numbers on your bearing before buying new one From December 1975, around Serial No. 35000, the headstock bearings were listed as being "greased for life"; however, these were not sealed bearings, but just packed with what the makers hoped would be sufficient lubricant to last for many years. If a lathe without grease caps has been standing unused for several years it would be wise to strip the headstock and check to see if the lubricant has solidified.
If any Boxford is run very hard, at high speed while taking deep cuts, it is not unknown for the spindle bearings to overheat; although a modest rise in temperature is quite normal, should the headstock casting temperature exceeds around 40°C it's best to stop and let it cool down. One solution, seen by the writer on an Underdrive model, was the fitting of a computer case fan in the sheet-metal belt cover on the back of the headstock. This was controlled by a temperature probe, switching on at 40°C and off at 35°C and the lathe was able to run all day on its highest speed taking deep cuts on resilient materials.
Aprons and Power Feeds
Putting aside condition and accessories, what, one might ask, is the most important consideration about its specification that most be born in mind when choosing a Boxford lathe? The answer is - the apron. It is sometimes not appreciated that lathes with power-feed aprons - the Models A, AUD, B, BUD and VSL and B - not only benefited from power cross feed but also a range of slower longitudinal feeds than the Models C and CUD, the reduction through the apron's worm-and-wheel gearings meaning that the feed rate was reduced by a factor of 0.3. In addition, because the power-feed drive was taken from a key running in the slotted leadscrew, the thread in the latter was needed only for screwcutting, so preserving its accuracy and saving wear on the expensive clasp nuts. As the Model C lathes, with their plain apron, need to have the leadscrew clasp nuts engaged for a sliding feed, this causes them to be worn well before any other part of the lathe. As the nuts are only occasionally available - and expensive - any version of the Models C is, unless in really sound condition, best avoided. The power-feed apron on the Boxford was identical to that used on the South Bend "9-inch", with the drive taken through what was, in effect a cone clutch wound into engagement by a star-shaped knob on apron's front face. If this clutch is allowed to slip (by regularly running the carriage up against a bed stop for example) the mating surfaces of the cone will eventually become polished and, no matter how tightly the knob is screwed in, will slip badly. The solution is to strip the clutch and roughen all the friction surfaces - the spilt cones and their seating - with fine emery cloth; once done this will allow the drive to deep cuts with only the lightest of pressure on the control wheel. A useful thing to know when dismantling the apron is that the screw in the centre of the clutch wheel has a left-hand thread - it appears to be 3/16" BSF (British Standard Fine). On late machines, for both safety and ease of use, the clutch wheel was prevented from rotating by the use of needle-roller thrust bearings fitted to both front and back of the engagement shaft with a peg added to its end that located into a hole in the cover plate. These late-model aprons can be instantly recognised by their black plastic clutch-control wheel, the earlier type being in cast-iron. Unfortunately, the clasp nuts, though of a straightforward design, do tend to fill up with swarf and dirt and so, to protect the leadscrew, it's worth removing the apron from time to time and cleaning them out carefully. In the case of the Model C, where the clasp nuts are in constant use (taking the place of the power-feed mechanism) it may be necessary to pick embedded material from the thread roots with a sharp-pointed tool. An adjustable friction device - a spring, ball bearing and socket-headed Allen screw - located underneath the apron towards its tailstock end helped to hold the clasp nuts in both their open and closed positions.. An interesting article on rebuilding a Boxford/South Bend/Hercus power-feed apron can be found here and detailed photographs of the power-feed apron here
Apart from the method of retaining the barrel-feed screw, and a centre-height change from 4.5 to 5 inches, the design of the tailstock remained unchanged throughout the life of the machine (though there was a cosmetic improvement when the Mk. 2 Under-drive machines were introduced). The 11/16-inch diameter barrel had a travel of 21/8 inches, carried either inch or metric ruler engravings, and occasionally both, with a self-eject mechanism for the No. 2 Morse taper centre. Although the barrel clamp was a proper compression affair the operating lever was too short and, consequently, it can be difficult to get enough force to lock things down solidly. The top could be set over on the sole-plate for a maximum distance of 5/16-inch for taper turning and, while the bed clamp was entirely adequate, it did need careful flat-by-flat adjustment of the base nut within its retaining slot if the lever was to lock in the ideal place some 30 degrees forward of vertical.
Virtually every accessory is interchangeable across the model range and, in addition, many of those made for the 9-inch South Bend, and Smart and Brown Sabel (and other clones) also fit. Even the fixed steady from the later 5" lathe is useable on the smaller machine (and visa-versa) if you are prepared to give up a little of its maximum capacity. Sadly, Boxford accessories do tend to be far less common than those for Myford lathes and hence are more digfficult and expensive to find on the second-hand market. Amongst the hardest items to find are the standard and compound milling slides; the former used a very robust main column that fitted into the hole in the cross slide normally occupied by the top slide and was supplied with a T-slotted table and a vice, both able to be used independently on the cross slide. Boxford also produced a beautiful dividing unit based on the same fitting - but this was always an astronomic price - and very few can have been sold. The compound milling slide is, likewise, very hard to find and, being so versatile, greatly sought after.
One very unusual accessory - so far only one example has come to light - was a headstock spindle dividing attachment. Probably made as a one-off to satisfy an order from the Post Office Research Station at Dollis Hill in London, the assembly consisted a block, fastened to a machined surface on the face of the headstock, that contained an indexing plunger - this engaging in a ring of holes drilled into a large disc mounted on the end of the headstock spindle.
There is a high degree of parts interchange-ability between the various models - and also between South Bend 9-inch lathes and Boxford; three popular improvements to the latter are: fitting a screwcutting gearbox, a power cross feed apron and a T-slotted cross slide. For the gearbox and power-feed conversion you will need, as a minimum, not only the major parts but also the correct changewheels (20t, 45t, 50t and an 80 idler with a boss) the slotted leadscrew and the correct "Y-shaped" changewheel bracket. The bracket used on the B and C is, incidentally, slightly different, and if fitted will tend to foul the gearbox. On early lathes it will be necessary to drill an extra hole through the bed at the headstock end to take the third gearbox mounting screw. The South Bend has a rack-and-pinion carriage drive of a coarser pitch than the Boxford and it may be necessary on some machines to make an adjustment to the height of the leadscrew by inserting shims between hanger brackets and bed. The leadscrew will also need to be swapped over, or the existing one modified to fit the gearbox, and a slot milled along its length to drive the apron worm wheel. When everything is in place check (by hand and with the changewheel bracket removed) that the assembly rotates easily. If it doesn't, slacken the screws holding both the gearbox and the leadscrew hanger bracket and re-tighten them a little at a time, rotating the leadscrew while you do so, in order to locate the fault. Unfortunately, there is a caveat to all this for, while the gearbox is a problem-free fit - and nobody has yet found any difficulty with the apron and cross-slide arrangements - if the parts come from a South Bend there may be a problem. Experienced South Bend mechanics report that the company did not hold the tolerances of saddles fitted to the C to the same tightness as those intended for an A. The result is that the gear on the cross-feed screw may not mesh properly with its apron-mounted drive, being either too slack or too tight. Interestingly, the writer knows of one Boxford that was successfully fitted with the (single-tumbler) screwcutting gearbox and gear drive from a South Bend "Heavy 10": the box bolted straight onto the Boxford bed with the only change necessary being to the tumble-reverse gears that needed changing to match that on the end of the spindle.
The T-slotted cross slide is a direct replacement for the standard unit and makes the lathe significantly more versatile - being able to accommodate a rear toolpost and various non-Boxford milling slides. The T-slotted slides are relatively expensive items but excellent new UK-made units are now available from us--email for details.
It is worth noting that, when supplied by the works with a taper-turning attachment, lathes were fitted with a different design of cross-feed nut held on with two screws instead of the usual boss - these too, along with standard nuts, feed screws and micrometer dials, can all be supplied.
Parts and Accessories Availability
lathes.co.uk usually have a supply of high-quality UK-made accessories and spares suitable for Boxford lathes - including new T-slotted cross slides, faceplates, backplates, changewheels, cross feed screws and nuts, micrometer dials, etc. These parts also fit South Bend and many other South Bend "clones". The design of the T-slotted cross slide has recently been revised to improve its versatility and now features a slot across the front - as well as three to the rear - and fully machined sides. These modifications allow the unit to be adapted as a small boring table - and provide flat vertical locations against which jobs can be registered. The later type of "inset" rotational scale for the top slide is also included, so the unit can be used in place of the normal slide for ordinary turning operations.
If your cabinet stand has broken or non-operating handles and locks replacements (Part Nos. 7/09302 and 7/23057) can be obtained from http://www.faparkes.co.uk/
Floor Space and Weights
Under-drive lathes with shorter beds (up to 24" between centres) take up very little room in relation to their capacity; their stands are often only 450 mm (17.5 inches) deep with short-bed lathes of all types (either stand or bench-mounted) being approximately 1200 mm (47 inches) long (not much more than a Myford ML7) while long-bed versions run to about 1350 mm (53 inches).
Weights vary with bed length and specification but the approximate maximum figures likely to be encountered (as longer-bed examples) are:
Model A 172 kg (380 lbs)
Model B 166 kg (355 lbs)
Model C 163 kg (360 lbs)
Model AUD 263 kg (580 lbs) Model Mk. 2 AUD 276 kg (610 lbs)
Model BUD 256 kg (565 lbs) Model Mk. 2 BUD 269 kg (595 lbs)
Model CUD 254 kg (560 lbs) Model Mk. 2 CUD 267 kg (590 lbs)
Model VSL 300 kg (660 lbs)
Model ME10 141 kg (310 lbs)
Because a Boxford can be broken down very quickly into manageable lumps moving one is relatively easy - a standard Underdrive model can be transported in most hatchbacks with the rear seats removed. With the two screws securing the tailstock-end leadscrew hanger bearing removed the entire carriage can be slid off the bed; the changewheel banjo can be slipped off after pulling the leadscrew or gearbox input gear off its shaft (don't loose the key); the headstock is secured by two bolts, the front one of which poses the greater challenge and requires a very short open-ended spanner and some knuckle-scraping work to undo. If the lathe has a gearbox, leave it in place - and try not to remove a lathe from an under-drive stand; a compound was used to stop coolant getting into the wrong places and effectively sticks the lathe down; once broken the hardened sealer has to be chipped off and the joint remade.
Notes on Lathes Fitted with 3-phase Motors
If your Boxford has a 3-phase motor the best conversion is to run it from a variable-speed inverter; these are wired direct to the motor and replace the lathe's conventional electrical controls. For more in inverters see: http://www.yfdg.cc/page27.html Unfortunately, most Boxford lathes were equipped with either a 0.5 or 0.75 h.p. motor and these, if the lathe is to be run to its maximum capacity, are barely adequate. Although more expensive, the writer would recommend replacing the original; 3-phase motor with a more powerful one; in his experience this transforms the lathe, making it so very much more useful and easy to use.
If a conversion to 1-phase electrics is desired, while the rear-drive machines have a reasonable amount of space behind the lathe to fit a replacement motor (although capacitor boxes may have to be relocated) the under-drive lathes are a little tight on room and, although the conversion is perfectly straightforward, there are one or two simple points worth bearing in mind: the original motor, if 3-phase, will almost certainly be 0.5 h.p. if originally supplied to the education and training market, or 0.75 (and occasionally 1 h.p.) from the industrial sector. Replacing it with a modern 0.5 h.p. 1-phase motor will mean, inevitably, that the lathe will no longer be able to start on top speed and, even if it does, will have insufficient power to be useable. The experience of many users suggests that a minimum of 1 h.p. is necessary for a successful installation, while others consider that an even better solution is to use a 1.5 h.p. motor. In the latter case, problems may be encountered getting it into the limited space available, especially if it's a modern type with a large plastic box shielding the capacitor and terminals. First, install the motor as far back on its mounting platform as possible (you will need to drill new holes in the plate) having first checked that there is still enough room for the belt-tensioning rod to function properly. Second, to enable the motor to clear the floor, lift its mounting platform as high as possible on the over-centre adjuster and use a shorter T-link belt for the drive - it might even be necessary to adjust the length of the tensioning rod to accomplish this. Another trick is to remove the plastic box from the motor and remount the capacitor remotely, preferably in a place where replacement is easy when it fails (as it will). Do not forget to engineer a suitably safe cover for the terminals and clip any new wires securely to the stand. As a last resort, because the base of the motor compartment is open, the stand can be mounted on raiser blocks at each corner and the motor allowed to hang down into the space created.
If the original 3-phase wiring and switches are intact leave them all in place and wire the replacement motor to a new switch with fresh cabling - this makes a future re-conversion to 3-phase (or the 3-phase motor run from a variable-speed inverter) an easy matter, and might even enhance the value of the lathe.
Alternatively, and especially if the lathe has coolant and low-volt lighting fitted, consider running it from a 1-phase to 3-phase phase variable-speed "Inverter"; although a little more expensive than a motor change, once you have one of these units it can be used to power other 3-phase machines, all of which are more readily available, and invariably cheaper, than their single-phase equivalents. As the inverter provides a variable-speed output it will, if coupled to more than one motor - the suds pump for example - vary the speed of both. In practice *many people who have combined several motors running from one unit report that it causes no problems. With prices now at an affordable level, the advantages of inverters are becoming more widely appreciated - and a small lathe fitted with one is certainly a much easier, more versatile and safer tool to use.
If you have the slightest doubt about wiring in a new motor or switch - or otherwise modifying the electrics on your lathe - pay a suitably qualified electrician to do the job for you. It will be money well spent.