Metric or Imperial

[MattMoore]

Hi all,
I'm in the process of setting up a workshop at home for engineering.
These engines I keep seeing posted are really getting me excited about working metal.
I'm a joiner by trade and work in metric, albeit to 0.5mm tolerances most of the time,
Not quite engineering standards. Although my Dad was a trained pattern maker, but thats another story.
I'm assuming that the majority of people here stick to one unit of measure.
But I see a lot more imperial than metric.
I'd like to try and stick to metric for making the engines and some tooling I need at work.
Will I encounter any problems sourcing material and hardware in metric?
Or should I try and get my head round imperial?
I only really want to buy one set of measuring tools, and tooling so your comments will be greatly received.

Thanks

Matt

 

[bentprop]

Hi Matt.I would say it depends on your location.In the UK,Europe or Australasia,metric is the standard,whereas in the USA,imperial or US standards are used.
Suppliers stock both,but in the US standard is probably cheaper,everywhere else,metric is cheaper,and easier to get.
If your confident with metric,stick with that.Personally ,I find metric the easiest,because that is what I was brought up on.
Welcome to this great hobby,and whatever form it takes,enjoy it!
Hans(New Zealand)

 

[mklotz]

You'll get more meaningful answers if you put at least some hint of your location in your profile.

I'm an American living in America and my recommendation is that you use metric unless you happen to be modeling in the USA. Here Imperial tools and parts are cheaper and more easily available so going Imperial is an option to consider. Otherwise, the Imperial system is a complete nightmare - both directly for its idiot units and indirectly for its absence of any sensible standards. If metric is a tenable option economically in your location, use it and revel in the fact that you can.

 

[rake60]

Hello Matt

Your introduction post did say you were from the UK.
That being the case, I would stay metric.

Where I work we get prints in both Imperial and Metric dimensions.
Our measuring devises are all Imperial, but dividing a metric size
by 25.5 doesn't seem to be too overwhelming for anyone there.

In my home shop all my model work is in Imperial sizes except for
the small threads. The local hobby shop only had a Metric Mini
Tap and Die set in stock the day I decided I need one. That too
is no problem since the area hardware stores stock all the small
metric size screws, bolts and nuts.

Rick

 

[MattMoore]

Thanks for the replies so far,
I am based in the UK (i've updated my profile now)
It's only from my reading material that I have assumed the majority of things to be done in imperial,
But I think thats mainly down to alot of the writer being trained before decimalization.
I'm going to be purchasing asian machines when I get round to that, am I right in understanding that
on the imperial machines they sell, the lead screw is still a metric one?

Thanks

 

[Tin Falcon]

kinda like the others said
Location Location Location!!
What is the prevailing standard in your area.
Most US catalogs have a limited supply of metric sized materials drill rod etc. Maryland metrics is an industrial supply house that specializes in metric tools hardware and materials. mdmetric.comlocated on the edge of Baltimore MD
The other challenge in the US may be finding a lathe and mill with metric dials and threads. Although I did come across a NOS small metric lathe on e-bay that I set up for a friend(No motor or tooling) Edestal brand IIRC.
Harbor freight and others have electronic digital calipers that switch from inches to mm with the push of a button . But finding metric micrometers in the US may be harder.
I remember the big push in High school that the US was going metric within ten years , that was almost 30 years ago.
so browse the industrial supply catalogs to see what is available.
hope this helps
Tin

 

[Lew Hartswick]

Where I work we get prints in both Imperial and Metric dimensions.
Our measuring devises are all Imperial, but dividing a metric size
by 25.5 doesn't seem to be too overwhelming for anyone there.
Rick

I hope you don't use 25.5 at work Rick.
...lew...

 

[zeusrekning]

Yeah Rick I'd like to talk to your quality control guys. :big:

 

[rake60]

Alright, would you believe 25.4??? LOL

I'm a machinst, what more can I say?
Actually I multiply the metric size by .03937
To convert an Imperial size to Metric I multiply by 25.4

I HAVE done that wrong in the past.
Looked at the part and thought, "That ain't right!"

Rick

 

[bob ward]

If you are of average intelligence stick with metric.

Imperial is only for clever people who can do fractions and can divide stuff by 16 32 and 64

 

[tattoomike68]

One unit or the other means nothing to me unless you are talking threads. metric bolts cost more here, same with taps. other than the cost factor it means nothing to me, a number is a number.

I have made all kinds of stuff over the years and the units was never an issue, I just made the parts.

 

[DickDastardly40]

Matt,

I think it depends on what you want to make and how you prefer to make it.

For instance, I'm making a triple engine from scratch, the plans are imperial, therefore that's what I'm working in for this project. If you don't mind making it up as you progress a la Bogstandard or to suit what tooling you already have then whatever you are most comfortable in may suit. If you are intending to build from a kit then what the native code of that will be your default.

Which machinery you buy or have access to may have a bearing on what it easiest to produce. It is awkward (not difficult) to cut a imperial thread on a metric lathe (or vice versa). Try not to mix metric and imperial on the same job (not always possible). As regards measuring tools an inexpensive digital caliper is an easy method to switch between the two. I have a 6" steel rule I always double check larger sizes with as it does both without having to press a button.

I don't find that one code is more expensive than another in the UK, though getting esoteric premade fastenings may be more difficult.

Hope this has helped.

 

[compound driver 2]

Hi
All my working life I have used imperial, Some £40,000 in tools are all imperial. I think il stick with imperial its easier to use and makes a lot more sense given that I work on 100 year old designs.

If your even half comfortable with a system stick with it but be prepared to convert a lot of the decent drawings from imperial to metric.

Cheers Kevin

 

[gilessim]

Hi Matt, I'm also a woodworker by trade (and English but 15 years in Italy) at school we still used imperial but soon had to change to metric. For staircases and stuff I use both with the metric and inches tape measure, maybe only found in the UK!, using which was nearest! (laziness!) now, for engine work, I printed up some tables ,decimal and fractional imperial to metric and stuck them on the wall to help me with the over the pond plans.

I wouldn't worry to much about stock sizes being metric if you're making something with imperial dimensions as it will only help you to be more precise with your machining!, the only problem I've found really is with drill sizes and reamers but you can get easily drill bits in 10ths of a mm (also in 100ths if you're lucky and rich!), reamers and laps, you can make yourself to take of a few 100ths if you need to and I'm sure I don't need to tell you to adapt, using the kit that you have if you can, rather than spending 20 quid on a reamer ,or something, that you may never use again!

Thread sizes, as DD says, can be a pain but BA or metric you can easily get there and they're close enough to the american sizes to not create too many problems!

One thing I find very useful is the number drills, I got mine in the UK, together with yet another conversion table stuck on the wall, for small stuff, there is nearly always one very close to the size you need, metric or imperial.

Hope you get my drift and that this helps you! ,lots of cleverer guys than me on this site BTW!

Giles

 

[SignalFailure]

Hi Matt

As another relative newcomer from the UK I decided to go metric although being almost 50 by nature I think of most stuff in imperial. My vernier/lathe/rules have both units only my drills and taps and dies are uniquely metric.

For me their are two downsides to metric:

1 Many materials are still only sold in imperial sizes (at least at my prefered supplier) so you almost always have to at least skim some metal before starting any real work. For example if the plans call for an accurate 3mm dia rod you might have to use a 1/8 and lose 0.175mm. This situation is set to improve I'm told but we have been officially metric for ages so don't hold your breath!

2 The vast majority or plans (free or otherwise) are in imperial and therefore require conversion which for a newbie considerably increases the likelihood of mistakes. That said, the conversion process does make you think about the model in great detail at the outset! For the uber-simple engines I've made there haven't been any major issues but I wouldn't fancy tackling a locomotive or traction engine with only imperial drawings!

If I had to start over I think I'd probably go for imperial - I'm just as comfortable with the units and both the above issues would disappear. Thinking about it I haven't got that much invested in taps/dies/drill so I might just go 'old money' anyway!

 

[compound driver 2]

HI
One other point in passing. metric threads just never look scale nor do the bolt head or nuts.
At least with BA (ok BA is a metric derivation) theres a fighting chance of getting a scale looking fitting. Same with the model engineer thread sizes both 40tpi and 32 tpi. These if your really seriouse can represent a lot of old English threads at scales like 1 inch to the foot and 2 inch to the foot.

Cheers Kevin

 

[Bogstandard]

Bob said.

If you are of average intelligence stick with metric.

Imperial is only for clever people who can do fractions and can divide stuff by 16 32 and 64

That is why we gave it to you colonials in the first place. We knew in the future you would stick with it because you couldn't come up with your own standards. Look at you now, US still in the dark ages, and making for your own market, the rest of the world in a shining standard light. UK can understand both.

But joking aside, if you are happy with metric, stick with it, and understand imperial when it hits you. You will find after a time, working in both comes naturally.

A digital micrometer and vernier, plus a thread and size conversion chart, will basically be all you will need to get started.

John

 

[gilessim]

Well I think this says it all

One unit or the other means nothing to me unless you are talking threads. metric bolts cost more here, same with taps. other than the cost factor it means nothing to me, a number is a number

 

[13AL]

John said- "UK can understand both"

Can anyone understand this metric system??
am I missing something?? it's a six inch ss that i have had for years.

 

[SignalFailure]

Guess: is it something to do with typesetting (points)?