Stuart S50 metric conversion

[Mark WebsterParticipant @markwebster13123]

Sorry if this has been done before but I've just taken up model engineering. I'm about to start the S50 model and was wondering if anyone out there had converted the plans to metric. If so would they be kind enough to send me a cocopy any thanks

[Mark WebsterParticipant @markwebster13123]

[Ian S CParticipant @iansc]

Mark,There is no great dificulty in doing it yourself, either with a calculator, or if you have digital calipers, you have conversion at the push of a button, its all part of engineering. I,v solved the problem for me, I use both, although most of what I build is my own design.

Welcome to Model Engineering,  it's proberbly a good idea to try and learn a bit about imperial measurements, just as I'v had to teach myself metric.  If you get into some old stuff,  you may find inches, and parts there of match the origional better than the metric,  also you are quite likely to find old stocks of metal, maybe salvaged bits, it might be 1/4 inch when you want 6 mm, 1/4" is just a fraction bigger than 6 mm and so on.    Ian S C

Edited By Ian S C on 04/02/2013 09:52:30

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

I learned out it is not difficult to read fraction at the caliber when i am using imperial measurements.

To example: 1/4" is also 4 parts of 1", 3/16 is 3 parts of 16 parts = 16 parts of 16 parts is same as 1"

[GaryMParticipant @garym]

Hi Mark,

It might not be as simple as that. I only started model engineering a year ago and for my first project built the simple oscillating engine here

**LINK**

This is dimensioned in metric but uses BA threads. When I came to buy some of the materials I found it was easier to source imperial sizes for some parts. So I made it with a mix of metric and imperial. The silver steel for the shafts was imperial. The frame was specified as 20mm but I used 3/4" etc. I think I learned more by adapting some of the dimensions to imperial and figuring out which ones were critical to its operation.

As someone who went to school in the sixties and seventies I think I find this easier than some people and quite often work interchangeably in both units.

It still amuses me that B&Q sell 8' x 4' sheets of wood as 2440mm x 1220mm.

Gary

PS I'm hoping to start the S50 soon. Delayed by purchase of milling machine.

[Joseph RamonParticipant @josephramon28170]

Thanks Jens,

For half a century I've been confident I understand imperial measurements.

With your help, now I don't any more

Seriously if you have an imperial design you have three choices:

1. Learn to use imperial measurements – not as hard as it may sound.
2. Convert to round metric measurements – takes a lot of care as the differences add up. For example 1/4" is closest to 6mm but 2/4" or 1/2" is closest to 13mm not 6+6=12mm.
3. Convert to exact metric measurements – things will go together without adjustment, but awfully fiddly as most of the sizes will be awkward numbers

Ironically, if you aren't confident with both systems, option 2 could prove the most difficult.

In practice, you may end up using imperial stock (and accepting that 1/4"=6.35mm for example) for some parts, rounding some dimenisons to the nearest mm and making other parts to match, and doing the conversions where you need to machine parts to match with parts from imperial stock.

Don't forget the easy way to convert a fraction, such as 5/16" is:

5/16" = 5 / 16 *25.4

Joey

[KWILParticipant @kwil]

As someone who went to school in the fifties, I work in either system. If in Metric, measure in metric, if in Imperial, measure in inches. It only becomes a nuisance when you try to work in both at the same time

[DismalduncParticipant @dismaldunc]

Hi mark s end me a personal message with your e mail address and they shall be yours .

i converted the plans when I built mine.

Dunc

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

For all newbies and other who need refresh the gray brain cells: How to read fractional inches in the caliber as here.. 

http://www.stefanelli.eng.br/en/en-vernier-caliper-pachymeter-calliper-simulator-fractional-inch.html

Edited By Jens Eirik Skogstad on 04/02/2013 19:56:12

[Sub MandrelParticipant @submandrel]

> A 1/4" or 0.250" or 6.35mm is nearer 6.5mm than 6mm, but why not work to 6.35mm? it is after all just a dimension.

As, despite the naysayers of the last forty years, imperial materials are still readily available why not just use the imperial stock and only convert those sizes you have to machine?

Neil

[Mark WebsterParticipant @markwebster13123]

Thanks for all the messages. I am used to imperial measurements, I grew up in the 60/70ties . My lathe is metric as is most of my other gear. I converted my last project but it didn't quite turn out right. That's why I was wanting the conversion that had already been done and works well

Once again thanks for all the helpfully messages

Regards

Mark

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

I never thought about the lathe had metric or inches, yet I used metric or inches when I made things from drawing either in metric or inches. I have not used the calculator after I learned to read inches in caliper.

Practice makes master!

[AndyfParticipant @andyf]

Some folk make heavy weather of converting from metric to imperial. For example, the diameter of this Ebay item from Hong Kong.

Andy

[LambtonParticipant @lambton]

Mark,

I assume that you have purchased a kit of parts from Stuart Models for the S50 engine. In this case you will have received some imperial stock for the piston rod, valve rod, crank shaft, etc. that will need to “run” in accurate holes i.e. reamed holes in the covers and gland nuts, con rod ends etc. . So you will need to purchase the necessary imperial reamers for 3/32”, 1/8” and ¼”. These reamers will always come in handy for future projects especially if you make any more complex Stuart models.

Everything else involves making parts that fit properly together regardless of which measuring system you use. For example bore the cylinder to 5/8” or 16mm and after lapping make the piston to fit the bore. This also applies to cylinder covers (ream the holes though as described above).

I am sure you get the general idea. My advice is not to get hung-up on exact conversions from imperial to metric or especially from fractions to decimal inches as this can lead to unrealistic dimensions e.g. for item 27 valve chest cover 35/64” = 0.546875” 14mm would be fine (= 0.5512&rdquo.

Eric

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