There are a range of small hobby metal-working mini-lathes, made by various factories in China, including Sieg and Real Bull, apparently to a very similar pattern. They’re cast iron machines with approximately 300mm (a foot or so) between centres, though they come, stateside at least, in a slightly shorter and slightly longer version, too. They’re mostly driven by electronically controlled DC electric motors, usually via a two-speed gearbox and toothed-belt drive. They have a gear driven lead screw which can be used for power feed or for thread cutting and they weigh around 40 kilos (88lb). The have a throw of approx 180mm (7″) above the bed.
As lathes go, then, the mini-lathe is small enough to pick up and move around (if you don’t mind lifting 40Kg), but solid enough to take reasonably seriously. The headstock casting sits on the bedway and is bolted down (rather than being cast in a unit with it), most versions these days have hardened bedways, but it’s not really clear to me if this is now standard ex-factory, or a vendor specific option. It has various shortcomings because of being small and built down to a price, but also some very nice features – for example, the spindle speed is continuously variable via an electronic speed control, in both forward and reverse, and the leadscrew drive can be set to disengaged or reversed via a lever on the back. The chuck is bolted to a flange rather than threaded onto the spindle, so the lathe can be worked backwards if desired. Pretty much everything can be replaced or upgraded as required, all bolts are standard sizes and the headstock and tailstock have regular Morse tapers (MT3 and MT2 resp.)
In the USA, they’re known by their nominal size: 7×10, 7×12 or 7×14. That is, (nominally) 10, 12 or 14 inches between centres, although the 7×10 version is, as has been widely observed, more like 8″.
Versions available in UK
As best I can tell, the 7×12 size is the most widely available in the UK, sold by (at least) Machine Mart, Tool Hut, Toolbox, Warco, Chester Machine Tools, Rapid, Sealey and Axminster. Also, Amadeal Ltd. and SPG Tools offer a 7×14 (350mm) version. The lathes come with different names and in assorted colours. As I write (Nov 2011) the prices are £538.80 from Machine Mart, £527.94 from Tool Hut, £499.00 (or £461.50 for the C2A version) from Axminster, £444.26 from Warco, £427 from Chester, £390.00 from Amadeal, £365.00 from SPG Tools and a whopping £691.50 from Toolbox, £614.96 from Rapid and (ulp) £1019.94 from Sealey (all prices include 20% VAT but generally don’t include delivery.) Don’t take any of these prices as gospel, they’re likely to vary wildly, as all of these resellers have substantial offers and discounts from time to time – basically, you can expect to pick one of these things up new for around £500 or less, as of late 2011.
The more expensive versions from Sealey, Rapid and Toolbox are painted red and badged “Sealey”. The specs say this has a 300W motor. It looks very similar to the Clarke one, with 300mm (12″) between centres and a 80mm (3″) 3-jaw chuck.
Tool Hut and Machine Mart sell a yellow Clarke branded version, which appears to be a Sieg, and claims a 300W motor. It has 300mm (12″) between centres and is supplied with an 80mm (3″) 3-jaw chuck. Clarke supply the lathe with an imperial leadscrew, a metric leadscrew is a modestly priced optional extra (around £25).
Axminster offer two versions in pale grey, described as the Sieg SC2 and Sieg C2A. The SC2 is a newer version, with a digital RPM readout as standard and a 500W brushless motor (but no 2-speed gearbox), along with a few other updates. It has 300mm (12″) between centres and an 80mm (3″) 3-jaw chuck. The C2A is slightly cheaper, looks very much like the Clarke one, has the same dimensions and claims a 250W motor.
Warco‘s is green and has an an adjuster in the righthand pillow block for leadscrew end-float. Warco’s claims a 400W motor, and is again 300mm (12″) between centres and supplied with an 80mm (3″) 3-jaw chuck. Warco offer a choice of imperial or metric leadscrew.
Chester‘s, called “Conquest”, is grey/white/silver, and also appears to have the end-float adjustment. It has 300mm (12″) between centres, an 80mm (3″) 3-jaw chuck, a 400W motor and comes with your choice of metric or imperial leadscrew.
SPG Tools show a couple of 350mm (14″) versions with the larger 100mm (4″) chuck, one of which looks very much like the Clarke one (except it’s blue, and longer) and the other has basically the same spec but looks slightly different. Both SPG’s claim a 550W motor.
Amadeal’s is a Real Bull CJ18 7×14 version. It has 350mm (14″) between centres and the larger 100mm (4″) 3-jaw chuck. This one claims a 550W motor, and also has an end-float adjuster for the (metric) leadscrew.
All apart from the Axminster SC2 version have two speed gears as well as a continuously variable electronic speed control, the bigger brushless motor in the SC2 is reckoned to handle lower speeds with higher torque, eliminating the need for a gearbox.
Amadeal also offer a wide range of spares, including a 14″ bed conversion kit for shorter Real Bull lathes, and the spindles with integral 4″ chuck plates. I wouldn’t like to say which, if any, of the Real Bull parts would fit Sieg lathes or vice-versa, but they certainly look very similar. I’m not sure what accessories or how many change gears are supplied with each version – mine (Clarke) came with a total of ten, there are six in the photo on Axminster’s site, though. A replacement set isn’t too expensive. Change gears, at least, seem very likely to be interchangeable between Sieg and Real Bull – I read somewhere that some machines have broader 4mm keys on the spindles, but the keys could be swapped or modified (or keyways in the gears altered, or additional keyways cut) and the spindle sizes and gear pitches are the same as far as I know.
I have no affiliation with any of these companies, nor do I assert that this is an exhaustive list, they’re just the suppliers I could find with a bit of web searching. I’m not sure if there are any subtle differences besides those noted, which might make one or the other worth paying more or less money for – it may perhaps be that the more expensive ones are built and calibrated with more care by their respective resellers, I have no way of knowing. I certainly wouldn’t assume that they’re all the same, or finished to the same standard, just because they look similar. The Clarke one I have seems reasonably tight and well-aligned, but that might be because of its former owner, most people make adjustments to these as soon as they get them home.
The photos are scaled-down screenshots from the respective suppliers’ web sites, used without permission – they may not be representative of their current offerings, and I don’t claim to represent these suppliers in any way. If there’s a problem with using any of the pictures, I’ll willingly and immediately remove them on request.
All are basically metric machines, with metric screws for the slides, and general dimensions and fitments being metric, but they tend to be supplied (the Clarke one at least) with a 16tpi imperial leadscrew for thread cutting (the same leadscrew is used for basic power feed). A metric leadscrew kit to replace the imperial one is a reasonably cheap optional extra (around £25). They’re normally supplied with 80mm (3″) 3-jaw chuck and a plain dead centre for the tailstock. Other spares and options, like steady posts and digital read-outs for the slides, a four-jaw chuck and so on are variously priced, and whichever lathe you have, you’ll probably do well to shop around the different suppliers for these. People are using 4″ and 5″ chucks on these lathes, too, mostly with adapter plates, though a spindle with a 4″ flange is available from the manufacturer. Adapter plates can be bought ready-made for the 4″ chucks, though many prefer to make their own.
Change gears and many of the drive gears in these lathes are nylon or similar plastic. Nylon gears don’t generally need lubricating, to the best of my knowledge, and I’ve read somewhere that you shouldn’t use regular mineral-based grease or oil on plastic gears as it tends to weaken them. I don’t know if this is actually true, it’s just something I read. I believe that nylon absorbs mineral oil and swells, which is why you don’t use mineral oil in nylon-lined bowden cables, and I know stuff tends to stick to grease and that grease mixed with filings and swarf makes excellent grinding paste for soft materials, so my personal prefefrence is to keep the nylon change gears non-greasy. Thelittlemachineshop have a mini-lathe user guide, however, which recommends grease for the change gears. My gut feeling is that grease isn’t actually going to hurt, as long as it’s clean, and it may make the gear-train quieter and smoother, but that light mineral based oils (and especially stuff like WD40) should be kept away from plastic gears.
One U.S. company, thehobbymachinestore, will supply a complete set of change gears, or indeed a complete set of all gears made from steel, at what seem to me very reasonable prices. Ultimately, I’m inclined to swap all but one of the drive gears to steel, I’m ambivalent about the change gears – the plastic ones seem to work well enough and need no grease (at least I don’t think so – thehobbymachinestore recommends greasing them). The reason I would prefer at least one nylon gear in the main drive? Basically, because I’d rather strip a gear than bend something more substantial, in the event of a bad crash or overload. Also, nylon gears run quieter.