Myford ML7 Gearbox Identification: Factory, Third-Party and Homebuild Units Explained
What Is That Gearbox on My Myford ML7?
If a Myford ML7 arrives with a gearbox you don’t recognise, there’s a good chance it isn’t a Myford factory unit at all. Third-party and home-constructed screwcutting gearboxes were fitted to ML7s throughout the lathe’s long production life, and quite a few circulate today. Don’t panic. It doesn’t devalue the machine.
The Factory Myford Gearbox
Myford made their own screwcutting gearbox for the ML7. It mounts to the left end of the headstock and drives the leadscrew through a set of selectable ratios. The later quick-change version has a top-mounted lever for three positions and a sliding quadrant for finer selection. The unit is clearly branded, and if yours looks like this, identification is straightforward.
That said, the ML7 wasn’t always sold with a gearbox. Many machines left the factory equipped only with a change-wheel set. Any gearbox is therefore an add-on that someone fitted after purchase — which is why unbranded or unusual-looking units are so common on the used market.
Third-Party and Homebuilt Gearboxes
Several gearbox designs were published in the model engineering press specifically for Myford lathes. Three families appear most often on used machines.
The Sparey Design
One of the earliest published designs. It appeared in article form and was widely replicated by home machinists over the years. Build quality varies considerably from one unit to the next.
The Machin / Algoa / Hemingway Family
David Machin published a gearbox design in Model Engineer magazine — issues 3919 to 3935, odd numbers only — based on an earlier Algoa design. Hemingway Kits later commercialised this as kit HK155X, which remains available today. A gearbox from this lineage is probably the most common unidentified unit you’ll find on a used ML7. If you can match your box to the Hemingway drawings, you’ll know exactly what you have and where to get spares or missing parts.
Fully Homemade Units
Some owners built gearboxes entirely to their own design. These vary wildly. If the unit looks like nothing in the published literature, this may be what you have. Check the casting quality and machining before relying on it for precision work.
How to Identify Your Gearbox
Start with Tony Griffiths’ lathes.co.uk, specifically the page on early and third-party ML7 screwcutting gearboxes. It carries photographs of several known variants alongside brief descriptions of their origins. That page alone resolves most identification questions.
Look at the casting carefully. A factory Myford unit will typically carry a product reference or foundry mark. Third-party commercial kits often have a maker’s mark too. Homebrew examples usually don’t, and the finish will tell you something. Poor casting, inconsistent machining, and improvised mounting arrangements are signs you’re looking at a one-off.
The pitch range also helps. The available ratios on a Sparey, a Machin-pattern unit, and the factory gearbox overlap but aren’t identical. If you know what threads it cuts, you can cross-reference against the known specifications for each design.
The Backlash Question
Backlash on a used ML7 is routine. It appears in three main places: the cross slide feedscrew, the top slide feedscrew, and the leadscrew and carriage drive. Some of each is expected and acceptable. Too much means adjustment or eventual replacement of worn components.
Cross slide backlash is often just a loose grub screw. The collar between the feedscrew and its bearing surface has a grub screw that sets the end float. Slacken it, push the screw in to seat the collar, then back off just enough for smooth rotation and re-tighten. The official ML7 manual on ManualsLib covers this clearly. Five minutes of work, often a significant improvement.
Leadscrew and half-nut wear is a different job. If the slop is in the carriage movement rather than in the slides, that points to the apron or leadscrew nut. Fine for a winter strip — not worth tackling piecemeal while the machine is still in use.
Before You Dismantle Anything
Photograph everything before the winter strip. The gearbox drive arrangement — how it connects to the spindle and how it feeds the leadscrew — is easy to reassemble wrong without a reference. The same goes for any change-wheel quadrant in the drive path.
Myford ML7 spares still exist. The Myford name has continued through various ownership changes, and there’s a healthy secondhand market for parts. If the gearbox turns out to be a Hemingway-pattern unit, the original kit drawings will tell you exactly what’s needed to make or source anything that’s worn or missing.