Machine tools for the Modeller

Though I have been building model railway locomotives for upwards now of 40 years, it is only in the last 10 years or so I think that I have started to get more deeply involved with using machine tools to help me make them. Yes, I did have a Unimat SL tucked away for the odd drilling job and turning up of a brass dome or two, but none of this work really merited the word precision engineering.

And I have to admit, that even now, I am only groping my way forward towards better things. However, you learn by your mistakes, and each of us I have found, makes different ones of our own, as well as repeating those of others.... A key lesson is however, to be able to decide whether a failure in producing a component on a machine is due to 'operator skills deficiency', or a deficiency on the part of the tool.

Put a skilled turner in charge of a worn out lathe, and chances are that he - or she - will still be able to produce quality work. Someone without the knowledge or 'feel' as to what is acceptable backlash, and what is wear, has no reference points, and - as I did in the beginning - is constantly 'fighting the machine' as well as one's own limited skill set.

Boxford lathe
                    picture - small
Yes, I know it is a bit of an overkill for turning 1/76 scale locomotive driving wheels, but it was a bargain....

Before going much further I feel I should stress that the thoughts that follow are those that I have arrived at in attempting to find workshop and machine solutions to my own particular set of needs. Read, note and inwardly digest, certainly. But don't take them as gospel.

So, what advice would I offer to someone starting out to equip a workshop for 4mm and 7mm scale locomotive building - whether scratchbuilding or from kits?

Starting out? Get a Bench Drill not a Lathe

I think I would start by suggesting the purchase not of a small lathe, but a precision bench drill. I've look at the Proxxon TBH, several times as a replacement for my Sieg X1 micro drill, and there are other similar machines out there. This - with a proper machine vice that does not allow the work to 'tilt' as the jaws are tightened up - will allow you to drill truly vertical holes.

I would caution about trying to kill two birds with one stone by buying a combination lathe and mill/drill. A dedicated bench drill will be easier to get large flat plate material onto - such as a locomotive side frame in Gauge 0 - as well as giving you a larger flat surface upon which to slide the machine vice around for those awkwardly shaped jobs that come up ever so often.

Most railway modellers think of lathes in terms of turning up their own locomotive fittings - domes, chimneys and safety valves etc. However, where the lathe really comes into its own is when you need to make odd sizes of screws, studs, bushes and even shafts. It's role is more in improving the mechanical integrity and running qualities of the model locomotive mechanism, even if the model is only electrically powered. In fact, I personally have found that boiler fittings are best turned up freehand using a graver and rest. And even then, if you can buy a nice lost wax cast brass item that is accurate for your prototype - though sadly, many of them are not - use it, don't waste valuable modelling time making it, 'all over again'.

Lathes: Hobby, Watchmakers', Plain Turning

Now, on with the motley, as Pagliacci once said (or sung...). Table-top lathes aimed at hobbyists - and that includes the Toyo, Peatol, Sherline, Taig, Unimat SL, 3, 4 and its clone the Sieg C0 - are fine for working in soft metals such as brass and aluminium. But they don't have the necessary rigidity for taking heavy cuts on steel, and if you think this is what you need to do a lot of, you will be forever running back and forth skimming off a 0.01 mm each time until you get down to the required diameter.

Having plumped at one point for the larger Sieg C1 lathe over the C0 'Unimat clone', I still have a lot of regard for the latter, as it is in many respects a 'big' lathe in miniature. The C1 can take larger diameter work, offers power feed and screwcutting, but in hindsight, I feel that there is not that much in it.
Incidentally, if you are considering a C1, don't forget the Hobbymat which is an interesting alternative, though it does have some design quirks of its own.

Most of these smaller lathes do not come as standard with a compound slide that can be set over for tapers, though usually one is available as an add-on accessory. For 99 per cent of the time, you won't need it - see my comment on boiler fittings above - and it is often the case that these items appear to be designed as an afterthought.  On the Unimats, Sieg C0 and C1, and the Hobbymat, the centre height precludes the use of a separate toolpost - the tool bit is clamped directly into the compound slide end. Which means that each time the tool is changed, you need to set it up at centre height all over again. There usually is no room to use a quick-change toolpost either where each cutting tool is all ready set up at centre height, or as I am now tending to do, just have two or three toolposts that I swap in and out as required.

Before moving on, it may be worth mentioning for completeness here the Cowells lathe. This has been developed to a very high level of precision and quality, from a basic design that dates back to one of the many 'value for money' English model engineering lathes that were available in the 1930s through the early 1960s. It is still made today, in very limited numbers, each machine being individually hand assembled, but because of its reputation, commands very high prices even when one does surface upon the second-hand market.

Do not confuse these small 'hobby' machines with the larger watchmaker and precision plain lathes such as the Pultra, Lorch, Boley or Schaublin 65 and 70 models. The problem here is that though they are 'industrial' quality machine tools, most of them are getting on for 60 years old now, and if they have been used in a production environment, will need re-adjustment and replacement of many of their key wearing components. The good news is that both Pultra - in the form of Barry Starling -  and Schaublin are still in being, though the prices of genuine spares can be eye-watering.

Plain Lathes are no Plain Janes

These 'plain' lathes do not as a rule have screwcutting facilities, because they have no carriage as such. The cross slide is clamped to the bed, and the compound slide - either set to parallel or the required taper - undertakes the sliding cut. By eliminating the sliding ways and carriage of the conventional 'engine' lathe, rigidity of the cutting tool is improved, which together with angular contact ball or precision fitted plain bearing headstocks, allows these machines to take heavier and more accurate repeatable cuts at high speeds, leaving a consistently fine finish on the surface of the component.

Many of the 'old-skool' model engineering authors 'pooh-poohed' the plain lathe, because they have no carriage, and thus cannot be 'racked' backwards and forwards with the handheel along the bed to rapidly do bar reduction work. And of course because they can't cut threads with changewheels. But consider that even with something like the Pultra, with a compound slide that has a mere 45mm of  movement, this is getting close to the maximum effective sliding cut that can be achieved with some of the smaller hobby lathes - especially if the tailstock remains in place upon the bed.

Remember too that in a production environment, metal removal will be reduced to the minimum by designing the component to come out of the nearest stock size of bar, or else from a casting. It is only the impecunious amateur model engineer who's time is not chargeable, who indulges in laboriously turning down a salvaged bar end into the (relatively) small components required for say, a model steam locomotive.....

On the subject of screwcutting, I am not so sure that this is really necessary in the smaller scales, as for even Gauge 1 live steam work, a tap, or die held in a tailstock dieholder would suffice for most of the thread sizes one would need.

Of course, such a facility is handy to have if you need to make bits on one lathe for ones that are missing from another one, and where the thread you need to cut is too large to comfortably use a die or tap.. Such as would be required for a spindle thread, for a lathe that's no longer in production. But that's moving into completely different territory.

I need now to mention the MiniLathe, just so's I don't get irate emails from people saying I haven't. At 40 or so Kg, It is about the same weight as a Pultra or small Lorch when the motor, chuck, cross and compound slide etc. are all present-and-correct. But - and in my opinion only - I encountered what I would term quality and design issues with the one I briefly owned, though in fairness, this must now be 10 years ago, and perhaps they have got better since then... To cut a short story shorter, after about three months, I just gave up the unequal struggle, sold the Mini Lathe, and went out and bought me a fully-tooled ex-schools Boxford BUD for not much more than that what I got for the C3.....

Weight, The Enemy

Which is where we get to a crossroads. If you want a lathe that you can lift off the bench and put away under the bed or on the shelf, I reckon that 20 Kg is about the maximum for a 'safe' manual one-person lift. If you are happy to accept the limitations I've outlined - or your circumstances are such that that's all your budget or space allows for -
then the choice of one of the hobby class machines is made for you.

But before laying out some hard cash, do remember than some of the smaller larger (sounds like a contradiction here...) and heavier machines can be dismantled to move them. It all depends on how frequently you need to do this. Alternatively, consider mounting the complete machine on a cabinet that is fitted with castors. Most of the users' handbooks that I've seen exhort you to 'level the machine and then bolt it down securely', but needs must when the devil drives, and if its a choice between getting something bigger - and heavier - that will do a great deal more than the average hobby lathe, then go for it.

As an aside, I did toy once with the idea of bringing a 325 Kg Smart & Brown Model L into the house here in pieces, assembling it all, and then sliding the machine into the far corner of the living room on some nice nylon castors (to avoid marking the parquet, you understand...). But sanity returned, once I realised that however pretty it might look to my eyes, it might not be the sort of thing to endear one to visiting lady friends.....

Finally, if you have not got a copy, please beg, borrow, steal (or even buy) a copy of this book:: "The Amateur's Lathe" by L. H. Sparey, published by Model & Allied Publications.

Lathes, Shapers and Other (Model) Engineering Snippets

The features on this page are presented more as a 'How I done it', rather than a 'How to', and as regards some of the electrical work detailed, will probably make any IEE-qualified technicians reading this reach for the whisky bottle.

Pultra 1750 plain turning lathe

Pultra 1750

Bought on the rebound after losing out on bidding for a Smart & Brown Model L, this has replaced the Sieg C1 as the 'house lathe'. (I.e. it gets to live in the warm, and I get to use it all the year round...)

Drummond hand shaper

Drummond hand shaper

I sold my Boxford shaper, but it was only a month before I suffered withdrawal symptoms. So I went and bought myself one of these....and I now know what rocking horse poo looks like!

Converting a Boxford BUD to single phase

link to
                      Boxford lathe page

Also some notes as to how to change the drive belt from intermediate countershaft to headstock on these light engineering lathes.

Sieg C1 'Micro Lathe' Review

Sieg C1

The Sieg C1 is now also gone, but am leaving the page up on the website in case its contents might be of use to other people seeking an unbiassed overview of the machine. 

Mini Lathe C3 lead screw half nut fix

C3 clasp nut fix

Someone has asked about my modification to the C3 Mini Lathe apron to improve the engagement of the lead screw half nuts. So from memory, I have put together some notes which might prove useful to those mini lathe owners facing the same problem. As an aside, a moderator on one of the Mini-Lathe forums actually messaged me to the effect that 'No one else has flagged this up as an issue'. I just being 'picky' (again)?

Boxford Shaper Recommissioning

I I'm not sure now whether I did the right thing by selling it on. as a little job has of course came in soon after I waved it goodbye on the back of a small trailer, where it might have come in handy. However, I'm leaving the feature up in case other people might find it interesting.

                      shaper image - small

Setting up work in the lathe's 4-jaw chuck

I've added these notes on this piece of elementary lathe work, because even though the trick of using two chuck keys at once seems to be common knowledge amongst the professional machinists out there, for those - like me - who don't have ready access to a friendly time-served turner, it may bear repeating....