Myford ML7 3.5" x 20" gap bed, backgeared and screwcutting
as it appeared in the late 1940s and early 1950s
ML7 - General Specification (full dimensions sheet at the bottom of this page):
Of ribbed box-section, the bed was constructed with a flat top of typically English style, with narrow vertical shears, the nearer one in the gap between the front and back ways being shared by the saddle and tailstock. This was not an ideal situation but, in practice, caused no problems until the bed became badly worn when, as the tailstock was brought close to the headstock, it's central locating tennon became loose. With all the main surfaces at either the same level or at a right-angle to each other, one advantage of the bed design was the relative ease of regrinding with set-up times greatly reduced. The back face of the bed was machined flat and equipped with tapped holes ready to accept a taper-turning attachment. The design of the saddle was interesting: shimmed plates were fitted at front and rear by which means a very close vertical fit could be obtained; at the front, instead of a full-length inner lip, just a short one was employed, no wider than the cross slide, and it was on this surface that tool thrust was taken. A consequence of this quirk is that the four gib-strip adjustment screws along the front edge of the saddle take some skill to set correctly with only two bearing against a firm surface; to get the setting correct the maker's instructions have to be followed to the letter. Towards the end of ML7 production, a New Zealand engineer pointed out that it would be better if the tool thrust was to be taken along the full length of the saddle's inner rear face by using the bed's fourth vertical shear counted from the front. By this means an otherwise unused already-machined surface could be used and (combined with an adjustable gib strip) a much longer and more stable contact obtained. Unfortunately, the New Zealander's proposed method, while possible in an experimental situation, was not suited for production and so Myford - probably following the appearance of an article in Model Engineer Magazine proposing a similar but rather more straightforward modification - came up with a system (from K107657) that involved machining away the original short contact lip at the front and using a modified casting to keep the relative position of apron and leadscrew the same. By this means the saddle to bed contact was arranged against the rear shear, yet the gib strip adjustment kept at the front.
Pressure die-cast in a form of ZAMAK (it looks like aluminium), the apron was fastened to the saddle with three cap-head screws and with the leadscrew clasp nuts guided in adjustable, gibbed ways. On early machines, the reduction gearing between carriage traverse handwheel and rack was exposed (and quickly collect swarf and dirt) - but this fault was soon corrected and a close-fitting cover provided.
Cross and Top Slides
While the Super 7 was fitted from the start of production with a long slide as standard that on the ML7 was always shorter (with 5-inches of travel and four 3/8" T-slots) but with the option, at extra cost, of a longer 10.75-inch slide (and matching longer feed screw) with five T-slots. Even so, the standard slide had a generous 30 square inches of clamping surface and, with the top slide removed, was ready to be used as a miniature boring table or to mount a milling slide or rear toolpost. Until Machine K108718, slotted BA screws and locknuts were used for the gib-strip adjustment but were then replaced by easier-to-set self-locking 5-mm pitch hexagon-socket screws .
Able to be swivelled 63-degrees either side of zero, the 2.5-inch travel top slide was fitted with the same 10 t.p.i. Acme-form feed screws as the cross slide and both carried identical micrometer dials die-cast in ZAMAK; while a "character" part of the machine the early dials are not as easy to read as the properly-engraved units fitted to very late models. The toolpost clamp post was surrounded by three tapped holes, these being intended to accept the mounting screws for the indexing plate used on the 4-way toolpost; as supplied from the factory each hole was sealed with a small grub screw to prevent swarf working its way through to the feed screw and wearing it out.
In comparison with almost every other contemporary small (British) lathe, the headstock of the ML7 was a rugged affair. Bolted to the bed by four high-tensile cap-head Allen screws it was aligned by a ground rectangular locating tongue fitted into the gap between the bed ways with two pusher screws, entering from the rear, pressing against the tongue and so holding the headstock hard against the inner vertical bed way. The spindle was in 40-50 tons high-tensile steel and ran in plain, parallel Glacier TI Alloy "half-step" bearings with laminated (0.002") shims between the upper and lower halves to allow a reasonable fine clearance adjustment. Strong bearing caps were used, each bolted down by two socked-headed cap screws and with a ball-thrust bearing fitted in a shielded position at the left-hand end. The spindle was offset from the bed centre line towards the rear - a feature the makers ingeniously claimed in their first publicity sheet: "The distinct advantage of the offset is paramount when turning large diameters, the degree of rigidity being equal to that of a bed 5-inches wide with the headstock centrally disposed." The spindle on early machines was fitted with a pair of simple little No. 2 size wick oilers (easily neglected) while later models had proper drip-feed lubricators where the supply of oil could be adjusted (according to the spindle speed) and the quantity remaining easily inspected. The dimensions of the original spindle - 1.125" diameter, bored through 19/32", No. 2 Morse taper, front bearing section 1.25" diameter, rear bearing section 1", bull gear section 1.125", 12-threads-per-inch nose (the threaded section being about 0.62" long) backed by a plain register 1.25" in diameter and 0.4375" long - were carried over to the Super 7 and only changed with the advent of the new-for-2001 Super 7 Plus. The drive from countershaft to spindle was by a 3-step aluminium pulleys with a proper, full-sized A-section V belt that allowed full use to be made of the motor's power (generally 0.33 h.p. on early lathes and 0.5 h.p. on later). The robust backgear assembly (clustered at the front, beneath the spindle line) meant that speeds down to around 25 rpm could be achieved with greatly increased torque - and no risk of belt slippage - ideal for both screwcutting and turning large blocks of metal held in a four jaw chuck, or on a faceplate. On both ML7 and Super 7 that part of the (bronze) backgear carried on the headstock spindle was in the form of a "sleeve pinion" - that is, the small gear was extended to form a long bush on which the pulley was pressed, the whole assembly rotating on the spindle when backgear is engaged - a design that did much to enhance the lathe's ability to run reliably at slow speeds for long periods. Unfortunately, the assembly did contain a weak point: the three-step aluminium pulley was only pressed onto the sleeve - and it is not unknown for it to become loose and rotate. However, if the assembly is stripped, cleaned and the pulley secured onto the sleeve with a smear of low-strength Loctite, all will be well.
Changewheels and Screwcutting
Myford Series 7 10 changewheels of all years are 20 D.P. with a 14.5-degree pressure angle, 3/8" thick (0.375") with a 5/8" bore (0.625") and 1/8" keyway (0.125"). Supplied as standard with an ML7 or Super 7, the changewheel set comprised: 2 x 20, 25, 30, 35, 38, 40, 45, 50, 55, 60, 65, 70 and 75t. To cut a wide range of metric threads required, in addition, just two 21t wheels.
In place of the crude assembly used in pre-war years, with plain-bore changewheels running directly on studs and retained by split-pins and washers, the changewheel drive on the ML7 was properly engineered. Hardened steel pins were employed, carrying bushes keyed into the gears and with neat, quick-release washers retained by slot-head screws allowing the gears to be changed quickly. Unfortunately, the nuts holding the studs were still behind the banjo, making any alteration in position a fiddly, time-consuming business (on the Super 7 the nuts were moved to the front, and the design of pin assembly improved with the use of a bronze bush). The changewheels, like the belts, were enclosed inside a neat, thin-walled cast-aluminium cover. Tumble reverse was fitted as standard, allowing quick reversal of the saddle drive - and so speeding up the boring of deep holes, etc. Setting the tumble-reverse lever to "neutral" meant that high speeds could be used without having to drive the changewheel set - and this made an already very-quiet lathe even more acceptable in a domestic situation - many being used in attics and even spare bedrooms. The 8 t.p.i. left-hand thread leadscrew was of Acme form, 5/8-inch diameter and ran in Oilite bushes. On the original ML7 both the tumble-reverse and backgear levers were tipped with lovely little acorn-shaped plastic knobs - in what must have been a subtle reference to Nottinghamshire's woodland heritage. For details of the screwcutting gearbox fitted to the Series 7 Myford lathes, see the section below about the Super 7
Able to be off-set on its sole-plate for taper turning, the tailstock was fitted with a 1-inch diameter barrel, threaded 8 t.p.i. and with a No. 2 Morse taper - so allowing heavy-duty drilling. The barrel was bored clear and passed through the handwheel - an arrangement that did have some advantages, notably if used for long-hole boring when woodturning. Arranged so that it sat underneath the barrel - and so passed through the greatest mass of material - the tailstock spindle lock was of the proper (and powerful) split-barrel type. A further advantage of this location was that it removed the need to incorporate a boss on the back of the tailstock body to hold the locking mechanism, though there was a slight inconvenience in having to reach over to grip the lever.
Although the ML7 changed very little during its production life some improvements were made: the early machines had no oil nipple on the headstock pulley (essential to lubricate the long bronze bush that was formed as part of the backgear) but this is easily retro-fitted; by 1950 the countershaft had been given more substantial uprights and the back made solid instead of having three open panels: the original ball-spring "Bennet" oilers were replaced by proper nipples to which a pressure oil gun could be applied to blast out dirt and drive oil to where it would do some good (note: all nipples, on all models of the Myford 7 Series, took oil, never grease): by 1960 the tailstock casting was filled in and its "off-set" guide moved to a thicker part of the casting: in 1969, from machine K90494, a cast lug was added to the headstock to provide a location point for the lever-action collet closer - this had previously been supported by a loose bronze bracket, clamped by two Allen screws to one of the cast-in strengthening ribs behind and immediately below the front headstock bearing.
During 1973, from machine K111727, production was rationalised around just one 7-Series bed, that for the newly-introduced, power-cross-feed Super 7, this being easily identified by a much deeper recess along the front face, a feature necessary to allow the much deeper power-feed apron to fit (there is a possibility that these beds were stamped with a serial number having a suffix "C". The change of bed also allowed the use of the Super 7 cast-iron apron and 3/4" diameter leadscrew (the Super 7 leadscrew nut clasp-nut handle is another recognition point). All these improvements that mean late versions ML7s have the very best specification of all. The last ML7 manufactured (K140848) left the assembly line on the 31st of January, 1979.
ML7: Speed Range:
As supplied to the UK market (with a 50 Hz 1425 r.p.m motor) the ML7 had a speed range of: 35, 62 and 110 in the 5.78 : 1 ratio backgear and 200, 357 and 640 rpm in open drive. Although it is perfectly possible to raise the top speed by increasing the size of the motor pulley, it is wise to bear in mind that the maximum recommended speed of the original white-metal bearing spindle is 1000 r.p.m. The writer has known machines to be run at much higher speeds, without apparent ill effect, but these were in good condition, carefully set up and with an increased flow of top-quality lubricant from their oilers; a worn machine treated like this might not take at all kindly to the treatment.
At one time, in order to permit higher speeds to be reached reliably, the option of a kit containing bronze headstock bearings and a hardened spindle was available - though at a cost well above that for the standard items. However, in later years, replacements were always provided as bronze-bearings (because the oil feed to the bearings is "constant loss", it is important to make sure that, every time the machine is run, both oilers are topped up and opened to give a generous rate of feed - one drop per 30 seconds as a minimum). I have seen countless ML7 lathes that, despite having given more than sixty years of service, still had bearings that were "spot on". Of course, the oil has to go somewhere and runs down the front and rear faces of the headstock to end up in the chip tray. If your headstock appears to be leaking oil, don't worry. However, if it's not, do worry…...it's run out.
For quiet and smooth running the makers recommend a resilient-mounted motor (with rubber rings isolating the main housing from the foot) and, so equipped, an ML7 will turn almost silently. While all Super 7s had a clutch fitted as standard, on the ML7 this was an optional extra - but one well worth having. The ML7 unit economised by utilising the brake shoes from the front wheel of a Nottingham-made Raleigh moped, the "Gadabout".
Unfortunately, one-phase motors are not the most reliable of devices. They are best run near their rated capacity all the time (i.e. worked nearly flat out); if such a motor is switched on and off frequently against "no load" the windings will be damaged and, if run through a cycle where it is started, worked briefly, stopped and started again, the capacitor will fail prematurely.
It is very important not to "over-motor" a Myford (or indeed any other lathe); any accident or dig in will have far more serious consequences - and if the machine is worked beyond its capacity, excessive wear will occur. Early ML7s were fitted with 1/3 hp motors, later ones with 1/2 hp - the latter a figure that should not be exceeded. Apart from the very first examples, the Super 7 has always been equipped with a 0.75 hp motor (necessary to pull the top speed of over 2000 rpm) and this too should be respected as an absolute maximum. The original Brook-Crompton motors are very expensive; however, direct replacements, of exactly the same specification but more economically priced, are now available.
Buying a Used 7-Series - and value for money:
When contemplating a used Series 7 Myford its age is irrelevant (unless you require a particular specification); mechanical condition is everything and I have seen many machines over 70-years old that have had either so little use - or been so carefully taken care of - that they appear to be virtually "as-new". While late machines had their serial numbers stamped into the front of the bed, just to the right of the gap, earlier versions in a difficult-to-find location punched into the vertical way on the rear of the bed at its tailstock end. If you can find a good-condition ML7, especially one with the original bed machining marks intact and wearing its maker's paint, it will represent tremendous value for money. In addition, even if the machine shows signs of careless use, most mechanical spares are available direct from the factory (or their successors) to restore it to "as-new" condition. With the removal from the spares-counter of the teenage girl, it was even possible (when the long-serving works manager Malcolm Townsend was in charge) to talk to somebody who knew the lathe intimately. Don't be tempted to make or modify parts yourself - use original components and preserve the authentic look and feel of the machine - this will not only enhance its value, but also make using it a much more secure and enjoyable activity. Many an enthusiast has found that buying a well-worn machine and restoring it to useable condition is a fascinating exercise that demands the application of numerous skills to produce a useful (and valuable) end product.
It is much more difficult to find a good Super 7; competition for them is strong, which raises prices well above those of the ML7 - often twice as much, model for model; the ML7 really is the bargain version.
A selection of used Myford lathes can often be found for sale here and photographs of a superbly restored ML7 here