Metric!

[paul]

I daresay this has been raised dozens of times before but here goes anyway...

I'm 47 so I was brought up using imperial and metric though we used metric mostly through school and it's my unit of choice for anything these days (apart from miles or mph!).

I bought a simple small steam kit and needed to buy various tools (drill press, decent drill bits, taps etc) to enable me to complete the model. Sincre the kit was of european origin it was all metric which I was quite happy with.

Now I've started on my own model from scratch I find it almost impossible to source materials (rods, tubes, bolts etc etc) in metric! Needless to say I don't want to have to buy a new load of tools - can anyone point me at a supplier in the UK (internet maybe) that can supply metric stuff?

I thought I could 'adapt' imperial stuff but the final straw came yesterday when having almost completed my new boiler I find that the nuts and bolts I was supplied with (that I'm using for water level plugs) are rather loose and not steam tight - I think they maybe a mix of metric and imperial (6mm and whatever the near imp. size is). Desoldering may be in order - not a pretty thought for a novice to silver soldering. Grrrrrrrrrr!!

[havoc]

6mm is close to 1/4"= 6.35mm. Can't you go to MF6.5 for the thread? That way you would avoid having to de-solder and re-solder the bushings.

I'm 47 so I was brought up using imperial and metric though we used metric mostly through school

I would have tought the inverse would have been the case.

[paul]

Thanks Havoc

Not having access to a lathe I decided to make a circular bush and fitting by filing down standard hex nuts and bolts so I've put a lot of effort into these things already - rethreading the nut (bush) would mean remaking the fittings

You can maybe see what I mean here...

www.artefact-rescue.co.uk/asmbly2.jpg

The brass fittings on the front are the ones in question - they are to check water/steam levels so they need to be watertight. I think maybe I've been supplied with 6mm bolt and 1/4" nut - would they fit together loosely?

[Tel]

paul said:

they are to check water/steam levels so they need to be watertight. I think maybe I've been supplied with 6mm bolt and 1/4" nut - would they fit together loosely?

No, a 1/4" will be either 20tpi (W) 40 or 32 tpi (me) whatever BSF is. Unc is the same as Whit - except for the angle of the thread - none of 'em would match the 1mm (25.4tpi) of an M6

As far as steam tight goes the joint does not need to be mechanically tight - bung a bit of telfon tape on 'em
I have fittings on my boiler that can easily be moved by finger pressure but they do NOT leak steam at 100 psi

[paul]

Thanks Tel I think I understand that! I've never encountered teflon tape before - I'm off to look for some.

EDIT:
Oh you mean PTFE tape! I've got loads of that around already

[waggy]

Metric revs are the worst, a pig to convert!

Waggy.

[paul]

I soon realised the the PTFE tape idea was a non-starter - I'd forgotten that the bolts are drilled longitudinally and then at 90 deg (i.e. out through the thread) - tape would block this hole. I'll try it with some fibre type washers maybe that'll do it.

Seems that no-one has a good thing to say about metric and that supplies are hard to come by. Looks like a whole new load of tools are needed.

[gwrfan]

Paul,

Re metrication. Although small hand tools, drills, taps, etc are available in both Metric and Imperial, the basic metal materials that model engineers use are not. You will find that some suppliers are slowly stocking steels and angle section for instance, in metric sizes, but as almost all of our models were/are designed using Imperial measurements, I guess there's still not the demand for the materials we use in metric sizes. As for drills, I find that the metric ones are cheaper, and are usually more than adequate to use in place of fractional or number/letter drills. Unfortunately taps and dies are not, but you can usually purchase metric sets quite cheaply.

Hope this helps.

Geoff

[paul]

Thanks for that Geoff - I'd be happy working with either system (I think! I'd probably have to treble-check everything if going back to working in fractions of an inch though) it's just that my first model required all metric stuff which I had to purchase. I can't seem to find any supplier of materials in metric sizes so it looks like new tools will be needed. I suppose inches and steam go together much better anyway!

Thanks again.

Paul

[greasemonkey]

Hi Geoff
Having just put a caliper across an assortment of my stock material I'd say nearly 50% of what I measured was metric and purchased within the last year!! Guess it depends upon were you buy your supplies. I am starting to use more metric threads now than BA sizes. Tooling is easier to get in metric and cheaper as well ,DRO enable you to work in what ever units you choose. Polly models now stock a range of metric bolts and nuts.
regards

Andy

[gwrfan]

Hi Andy,

I expect that quite a bit of our materials is not actually Imperial anymore, although it's listed in the catalogues as such. I've just turned 3 pairs of wheels and 3 axles for a half inch press fit. I wanted to centre the wheels on a piece of half inch round BMS, but found they wobbled. The BMS was actually about 0.0015 undersize! However, the brass rod I had was half inch!

Geoff

[dscott]

At work with modern students I come across many different ways of artists measuring things.
Sometimes they use metric for cutting timber which is useful as the dimention saw is in cm. One girl in supprise, told me that she used the big numbers on her tape as she thought they looked more modern, and they were on top!
The best was from an all girl group several years ago explaining that they all knew what 6 inches looked like, but had no idea on 150 mm.
I work in both and keep thinking that my designs should be done in metric. 517 class and 4409 etc, the latter is in metric. but as most of the people who are interested are used to the old system have reveretd to imperial for the little auto tank..
The Imperial is a pub in here in Exeter.
David Scott.

[Jo]

What frustrates me is number drills. Unlike good old imperial that you just multiply by 25.4 to get metric, or visa versa. Every now and then there is a weird numerical value for a hole that every time needs to be looked up to match it with my metric drill set.

Or is there a trick that I've missed?
-----------------
P.S I've even started thinking about converting to metric on my Myford....

[havoc]

That's what so nice about standards...having soo many of them.

[gwrfan]

Jo,

I have a chart (A3 size) fixed to my cupboard door, which has all three drill types. It's so easy just to thumb down to find the exact size that you need, without the need to multiply, divide or whatever. It starts at No 80, and ends with 13mm.

Geoff

[Steve M. W]

Geoff

is this A3 chart available or is it one you have made up?

Steve

[spurley]

There is always the good old Zeus book for this sort of gen Sometimes they come up on ebay for a penny!! Full of excellent information and data.

Cheers

Brian

[gwrfan]

Hi Steve (and others),

My drill chart was reproduced from the pages of an old Reeves catalogue, but I don't think the Reeves 2000 catalogue has the same format. I think I copied both pages, stuck them together, then enlarged them using a photocopier.

Geoff

[alanstepney]

You could look here:

www.alanstepney.info/page8.html

[houstonceng]

Hi

I made my own drill chart on an Excel spreadsheet 1/64 to 3/4 imperial, A - Z letter, 80 - 0 number and 1 - 14.75mm. As you say, the Metric or Imperial diameters are easy but the others had to be entered from Machinery Handbook.

Then you sort from smallest to largest and, just for reference, I then made it calcualte the difference in "thous" and "mm" from the previous size. That way, if I pick a metric drill for an imperial tapping size, I can see by how many thou it's bigger or smaller.

I had a number of charts, tables in books, information from Tap manufacturers, etc, etc, (including a "home made mini zeus" that they made all us young lads make dye-line copies of and fold up when I first went to work) giving tapping and clearance sizes for BA, ME, Metric, BSF and BSW.

Of course, the various donor charts don't always agree, so I just added the data to the spreadsheet with suitable key to denote its origin. Now I just pick the tapping size within the range of sizes recommended from all of those sources from the one chart - with a bit of "experience added" (ie towards tight or loose depending on the material).

The whole prints out on a few sheets of A4 and, one day, I might laminate a set. Meanwhile, I just priont off another copy when the one in the WS gets too tatty.

If anyone can offer a suitable web-site to publish it, I'd be happy to donate it to the world - - - - E&OE of course.

Andy