What to get: Imperial or metric

I'm aiming to purchase a lathe this year. It will be used for hobbies and projects etc. Which is best, Imperial or metric. A DRO will be fitted. Thanks for advice.

If you don't already have other Imperial tools/machines and you don't work mostly on vintage vehicles or the likes with Imperial threads and measurements, metric is a much simpler system.

Working in imperial on my old lathe, making stuff for old imperial motorbikes, I have to keep a calculator and a decimal equivalent chart and pen and paper by the lathe at all times. Old drawings in imperial fractions are a particular pain. What's 3/4" minus 17/64"? Much easier to work out mentally 20mm minus 6.5mm, for instance.

If I were starting out in the hobby, making models from scratch or kits etc using modern metric drawings, though, I'd buy all metric.

Not only is it easier to use, but also easier and cheaper to buy tools and tooling such as reamers, taps and dies, drill bits and so forth in metric. Ditto nuts, bolts and other fasteners. (Unless you live in the USA in which case stick with Imperial perhaps.)

I've been using Imperial for 60+ years and additionally Metric for 40 of those years. Most every tool I have is Imperial.

But if I was starting out, or not very far into it yet, I'd go with metric. Base 10 is so easy to work with. I don't work with fractions unless forced to by circumstances and then I'm mentally swapping the fraction for a decimal value!

Go metric young man!!

Pete

Another vote for metric, as said, much easier to get tools and fasteners in metric.

Thor

If a DRO will be fitted then the dial graduations will not matter as you can switch between metric / inch with the press of a button.

More importantly i would be looking at what threads it can cut , some can do both metric and inch some only do metric or inch .

For most of what i do my tap and die sets keep me out of trouble - up to about 3/4 inch or 20mm anyhow .

Ian

+1 for metric, most tools & fasteners are now metric, much easier working in 10 units, my lathe & mill are both metric.

George.

Having trained in the 1950s my personal preference is to work in imperial,though in my later 25 years I was a desk engineer and we worked in metric,after redundancy I earned a living in my shed and machines were imperial apart from an all metric colchester triumph and an metric A & S mill,as some work was all metric, I found I worked quicker on imperial machines and nowadays I work imperial on vintage engines. Nowadays I would advise a younger person investing hard earned cash in machines and equipment to go metric,there is a cost advantage ,also metric tooling and fasteners are readily available,plus if one decides to upgrade your machines in the future it will probably be easier to sell a metric machine and get a better price.Though I wonder for how long will 5 inch gauge locos and 4 inch to the foot traction engines be built !!!

I have both metric and imperial machines (not my lathe). Metric is favourite by far (although I am completely competent in both), but it is virtually immaterial with a dro, excepting threading as stated above.

I have used most of the different systems over the last half century, or more, and metric is very much universal (SI uits, actually).The only difference for threading is needing a conversion gear, or gears, and the cutter must be driven in reverse ready for the next cut.

Only the US uses feet and inches system as a major nation. All imperial units can be changed to metric units, but for modellers making scale models in 1:2, 1:4, and a few other scales, it might appear to be easier to scale original full sized imperial drawings.

The imperial system will be used less and less as time progresses. That is for sure! Think globally, and realise that most cars made have metric speedometers, not mph ones! Only the US distorts the otherwise almost universal metric system.

Imperial fixings and tooling will become more expensive as time progresses. Metric is already the manufacturer's choice and will be almost universal if (or when) the US were to join the rest of the world in this century.

Most, who advocate imperial, will be older or american. Many british children still only know their height and weght in imperial units - but lots don't know how many inches there are in a foot, or pounds in a stone!

Yes, be brave, go metric. I only bought imperial machines because, for me, old british iron is preferable to lesser quality chinese items.

The mad thing is I grew up entirely metric and only moved into model engineering 15 years ago. Over time I have grown to prefer imperial to the point that I now convert all metric to imperial. Strange but true!

Fizzy

I would describe that as, 'True but strange'

Each to his own really, I grew up with imperial and whilst I might describe something as being a couple of inches long I totally prefer metric.

Ian P

If you like modelling old machinery in scales like 1:12 or you prefer to build older designs, then there's a case for imperial, but for anyone starting out now I'd suggest metric.

The biggest downside of metric are the fasteners aren't good for scale modelling, but being metric doesn't stop you using BA (they are a metric system anyway, just the sizes are converted to inches for the standard).

Whichever you choose though, imperial sizes will be a round for a good time, despite the articles in 1970s and 80's Model Engineers saying that imperial sizes would be gone in ten years.

Neil

Both my lathe (AUD Boxford) and big mill (with DRO) are metric and I have a couple of locos on the go which are both drawn imperial. On the whole not a problem I just keep a calculator and paper to hand and convert to metric e.g. 7/16 divide 7 by 16 and multiply by 25.4 and machine to that figure. I started when things were changing from imperial to metric and find metric easier. Metric machines were my choice and although neither are new or modern machines they are accurate and do allow me to cut things like both metric and imperial threads. Horses for courses at the end of the day.

Edited By Bob Brown 1 on 26/08/2016 11:09:20

I don't make models and all my machine / component designs are in metric, so metric machines would be preferred. Depends what you do, then. I can imagine that a metric lathe would be a curse if you are building a scale (imperial) model.

Although my milling machine has metric leadscrews, I tend to use the DRO so it's pretty much irrelevant.

On the other hand, my lathe (Bantam) has metric cross and top slides but annoyingly the main leadscrew is imperial, so when I cut treads I have to use the 100/127t conversion gears and use the alternative gearbox tables. When (if!) I fit the DRO to the lathe, the threads will become less relevant for manual operations. In the meantime, I can use the metric micrometer dials to get pretty accurate results with care.

Edited By Muzzer on 26/08/2016 11:37:24

If you are to purchase a Chinese lathe which I have you will find that metric and imperial are the same. The lathe was purchased as a metric but the only difference from the imperial is the .025 mm riveted sign on the dials. The top slide has 40 per revolution which is either 1mm or 40 thou, the saddle has 50 which is 1.25mm or 50 thou, I know I am out by a few tenths but .025 mm x .0393701 = .00098, or .001 divided by .0393701 =.0254 mm. This is what I have found with my lathe, they are made so they are affordable, on the parts list only one lead screw for the top and saddle are made. I am only stating what is on my lathe but I am sure that other makes must be the same. I was a bit confused when I brought the lathe but its quite handy when working in imperial if needed, and now find it easy to use now I'm use to it.

Robert, thats a bit of a genralisation based on your lathe, mine and my mill have imperial screws as do a lot of others which can be purchased in either metric or imperial, only the quill on mine is metric but thats for rough measurement anyway so of no consequence.

As has been said if you are fitting a dro then it will not make much difference other than threading.

I'm happy to work in either depending on the original design and only have DRO on the mill. Having recently designed two steam engines in metric I found no problems getting suitable sized therads and scale looking fixings plus metric threads work better on a truly metric model as they fit the off the shelf stock sizes

I would agree with previous posts that Imperial is best if making models of items that were originally built in inches, it makes scaling easier.

I joined a company as an apprentice where all the drawings and tooling were imperial for making large diesel and gas engines for ships, generators and pumping oil and water but then they decided to build a metric diesel engine under licence.

They decided, quite rightly in my opinion, to redraw the drawings in Engish but retaining the metric measurements and to re-equip all departments concerned with metric equipment.

All the workers in those departments were instructed to work in metric and not to convert from one to the other. That worked very well.

I was happy to use metric measurements until the government of the day said " you will get used to metric measurements in everyday life".

That did it, I no longer use metric measurements in England as fay as possible and always ask for items in Imperial.

For "fay" read "far"

About ten years ago I bought a new metric Wabeco milling machine. The imperial version would have cost about £250 more. It goes well with my imperial lathe and I don't have any problems. I do use a lot of scrap paper, though. Both are now fitted with DROs.

JA

Edited By JA on 26/08/2016 13:16:24

No indication of size and budget and intended use. Used imperial much more common than metric but new you can take your pick. However many new are a kludge trying to meet both USA and EU market so can have compromises, though not all.

One problem that has been designed onto lathes in the last few years is the gearbox if fitted having some ratios suited to imperial and some to metric so you end up with loose change wheels to change just as if you had an all imperial machine. There must be some versions out there that are properly designed for metric, but maybe not available in the UK.

Area3fitter – if you are young enough to have been weaned on metric then I would go for metric without any doubt.

I have an imperial lathe, a metric milling machine, a British shaper in imperial but with a metric clapper box and a cupboard full of tooling in both metric and imperial plus drawers full of metric and imperial fixtures. Constantly converting from metric to imperial and back again has been a way of life for many years and my tattered old Zeus book shows it. It will fall apart sometime soon but life will go on - there are three more copies of it up on the shelf!

Yet I still feel more comfortable working in imperial. I can instantly envisage what 3/8” looks like - but 9.525mm? - I’ll get m’book then !

Rik