Buying a lathe

Posted on July 10th, 2005 in Opinion by Julian Edgar

I bought a metalworking lathe the other day. It’s something that I’ve wanted for years, but now the purchase has occurred, I am filled with trepidation. Why? Because I know nothing about metal turning.

I first decided that I really needed a lathe when a few years ago I was building a small wind generator. The design was based around a stepper motor salvaged – I think – from a printer. The impeller comprised the blades taken from a plastic fan. But when I came to match the two up, the shaft of the stepper motor was much smaller than the hole in the mounting hub of the fan blades. Easy solution? Well, there would have been if I’d had a lathe: just turn-up a bush with the right internal and external diameters. But without the lathe, I was forced to scrounge for tubing that had just the right wall thickness. In the end, all I could find was the plastic barrel from an ink pen – hardly a good choice for long-term strength.

Then, when I was building my electric bike (series starts at Building an Electric Bike, Part 1 ), I needed a lathe like no other tool. I was making an assembly that would couple the electric motor’s shaft to a roller that would bear on the tyre, so transmitting the torque. I kind-of had the shaft, but the roller part had to be a larger diameter. I stuffed around drilling-out old sockets and the like until I had something that could be force-fitted over the shaft. Of course, the thing turned out eccentric, and so ran with a wobble that in fairly short order destroyed the bearings. I ended up paying money to small machine shop that turned-up a beautiful, knurled roller/shaft assembly. The skills to machine that (and to silver-solder on a splined section of the original shaft) were beyond any beginner, but still, if I’d had a lathe, I would have been ahead from the beginning of the project.

And then there was the fitting of a supercharger to my Toyota Prius. For that project a lathe would have been more than handy at least a number of times. Firstly, part of the bracket had to stand proud of the surface to which it was being bolted. Needed was a bush of exactly the right length and internal diameter – length, so the plate sat flat; and ID, so the bolt passing through it was subjected only to shearing forces and not bending. (The bush would be welded to the plate.) But without a lathe, I was reduced to grinding-down an oversize and over-length bush that I found. Secondly, while I was lucky and the original supercharger pulley turned out to give the desired boost, during most of the development it was odds-on that a new 3-rib supercharger pulley would be needed – another use of the lathe.

The lathe which I didn’t have.

Small lathes tend to fall into two classes. Brand-new and cheaply made, or older and very expensive. Yes, like other durable machine tools, it’s quite easy to pay a lot more for a lathe that’s 20 or 30 years (or more) old than it is to buy a brand-newie. But if looking at new lathes, what would be suitable? Very small lathes are available at a number of outlets.

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Even the Australian electronics retailer, Jaycar, sells one for AUD$799, minus stand. However, despite looking at their unit a number of times, I always remained unimpressed – just something about the feel of the knobs, the free-play in the lead screws – things like that. Plus by the time you added a four-jaw chuck, face plate, tailstock chuck and stand, the cost went up substantially.

The Jaycar lathe has a distance between centres (ie the longest object that can be continuously machined) of 250mm and a swing (the radius of the largest cylinder that the lathe can machine) of 140mm. So it’s only a very small lathe – and that didn’t worry me. With every use I had so far considered, quite a small lathe would have been adequate.

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That led me to look for other small lathes, including those from Clisby Miniature Machines. These Australian-made lathes use extruded aluminium beds and are tiny – just about small enough to fit in a shoe box and light to match. They use 12V motors and the power supply and motor speed control need to be provided by the purchaser. That didn’t worry me at all and when I saw the pricing (AUD$504 including 3- and 4-jaw chucks, tailstock chuck and faceplate) the little lathe was very attractive. So how small is it? Try 114mm between centres and a swing of 63mm!

But it wasn’t the small size that in the end put me off – it was the fact that these machines are obviously primarily designed for soft materials. You can machine steel, said users, but you need to take very small cuts indeed. And of course, neither of these lathes can cut screws – that is, have the ability to form threads on a rod.

Then, when I was in Sydney, I visited a major secondhand machinery store. The old guy there had some very good advice.

“Don’t buy any of the cheap and small new Chinese crap,” he said. “We sell it here but it’s just rubbish – it’ll drive you mad.”

Instead, he suggested I needed a certain type of lathe that had been on sale for a few years. Secondhand, it would probably set me back only three or four thousand dollars… he gave me a pamphlet showing what it looked like, but I already knew it was no good – it was well beyond my budget.

I kept looking at eBay, watching medium size lathes selling for typically $1500 – $2000. Hell, even one lathe with no more information than its brand and the fact that the (now divorced) husband had taken the chuck with him when he headed into the distance, sold for more than I could afford to pay! Then I saw it.

Metal Lathe, 24 inches between centres.

Hmmm, 24 inches is nearly 700mm – that’s way bigger than the littlies I’d been looking at, although in absolute terms, still a small lathe.

Metal  Lathe
On Stand – Single phase

“Southbend” made in UK

5″ Centre Height
24″ between Centres
¾” Bore 3 morse taper
2 Chucks
3 Jaw with reverse jaws
4 Jaw
2 Face Plates

Full set of change gears for imperial thread cutting

A lot this I could barely understand, but it appeared that it came with accessories including two chucks and could form screw threads.

All in good working order
Pick up Glasshouse Mountains Approx 1 hr north Brisbane CBD

I live about 1 hour south of Brisbane and so the lathe was within easy pick-up distance with a car and trailer. But the big attraction was the starting price – AUD$450. It was probably a pretty old lathe – but so what? At the time I was staying interstate with my parents, and when I casually mentioned the availability of the lathe, my father sat up straight.

“South Bend!” he exclaimed. “I learned to turn on a South Bend!”

An engineer who graduated in the early Forties, he’d used a lathe as part of his course. It’s a fond memory, although I doubt he’s touched a lathe in the 65-odd years since. But still, it was an endorsement of the brand.

I pondered my bidding strategy, and in the end sniped at $1003. (That is, I got a third party website to bid on my behalf only 20 seconds before the auction ended.) However, the sniping proved to be not needed – the bidding had peaked at a leisurely AUD$510…

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So now installed in my little workshop is a lathe. I can’t yet use it – the seller didn’t include any tool-bits – but I can admire it and grease its exposed metal bits, look at its battle scars – it’s obviously an old machine – and admire the elegance of its design.

In fact, curious as to its age, I did a web search and found that South Bend (who incidentally is a US – not UK – company) still support their lathes, to the extent of being happy to identify the age of the tool from its serial number. I duly emailed off the number and received the build date: 1941. So not only is the lathe significant in that it’s the brand that my father first used, it’s probably also the very same model…

It’s a nice sentimental quirk, but this is going to be a working tool, not an ornament.

So right now I am buying every old book I can find on fitting and turning, and reading and reading. Tomorrow I hope to buy some tool bits – then the adventure can really begin!

One Response to 'Buying a lathe'

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  1. Chris G said,

    on August 3rd, 2008 at 11:25 am

    All to the above same here live at south brisbane, wanting a metal lathe for years worked in many steel factories seen them being used, time to get get one,, mmm what one what for,, Im thinking of maybe making hobby steam engines