# Plans For Heretics (Metric Engineering)



## SignalFailure (Apr 17, 2009)

There are oodles of free plans for small engines floating about the net but few are 'natively' metric. Most of the simple engines I've built to date have been imperial 'conversions' - not a great problem for simple machines but it extends the build/preparation time and increases the chance of mistakes creeping in.

I though it was worth starting a thread where members can list sites that carry (free) metric plans. Here are some of my bookmarks for engines and locos (you might need to use some lateral thinking if you don't speak French, German or Dutch!)...

http://membres.lycos.fr/vapeurlanguedoc/plans.htm
http://www.geocities.com/minidampf/brazil_uk/contents.html
http://jpduval.free.fr/
http://home.iae.nl/users/summer/16mmngm/Articles_htms/Cracker.htm
http://www.davewatkins.pwp.blueyonder.co.uk/idrispln.htm
http://dampfmodell.eu/de/werkstatt/plaene/modelldampfmaschine-v1012.html
http://heetgasmodelbouw.ridders.nu/tekening_overzicht/tekeningen_overzicht.htm


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## arnoldb (Apr 18, 2009)

WHAT "Heretics" ?!!  Thanks for the links - Being a raised-up metric person, these are nice .

Your links are gold to me; I understand a fair amount of German, Dutch is very close to my native language of Afrikaans, English in most of it's various "flavours"/"flavors"  is no problem, and with some very imaginative thinking, even the French makes sense.

Imagine my initial confusion: Up to a few years ago, I didn't know about "thou" in non-metric sense. The first time I read something along the lines of "take a couple of thou off that", I thought: How the heck can you take a couple of thousands of a millimeter off something? (Well, I know it's VERY possible, but not with normal machines at home).

Now imagine my initial confusion... I was raised metric, was taught in metric - you measure in multiples or fractions of meters etc. School mentioned something about "inches" & "imperial". To have any value from forums such as this, I had to "learn" imperial measurements. This became "worse" with my first lathe - an imperial Myford. I quoted the "worse" because it's not that bad; actually it's nice - just a different way of thinking 

Now I find using both metric and imperial fairly easy. I was shocked to multiple responses in the February 2009 "Model Engineer's Workshop" magazine's "Scribe a Line" section about using & converting between measurement systems... Shucks, just learn kids to use different systems & how they relate. _Actually_, just teach kids to "think"! - :-\ Sorry for the rant.

Regards, Arnold


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## SignalFailure (Apr 18, 2009)

Glad you liked those Arnold. I was raised on imperial but as a newcomer decided to buy metric equipment thinking it would be 'future-proof'...life would have been so much easier if I'd gone imperial at the outset!


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## arnoldb (Apr 18, 2009)

Thanks Paul.

I don't think there is such a thing a "Future Proof" though - we are all still connected to the past in some form or another.

I think it's all about state-of-mind. One needs to "keep up" i.e go metric , but never forget the past. What we are doing nowadays with machines was unheard of 2,540  years ago in Egypt when they used the (what I know of as) "el" as a unit of measurement.

Units Measurements will change, weights will change, etc. etc.

Unless Mr. Klotz wants otherwise, I'd happily point you to "somewhere on this site" http://www.schsm.com/index.html - Sorry, no direct reference,as I can't remember where I got it & my Internet connection is slow - where Mr. Klotz has a good "go" at metric/imperial conversions.

Personally, it's easier for me to understand and visualise (visualize  ) "metric" than "imperial" , but at the end of the day, it comes down to the same thing. We are all (in my case at least) trying to build miniature engines. Sometimes a bit of calculation is needed to convert between systems-of-measurement, but hey, that's part of the fun!

Regards, Arnold


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## tel (Apr 18, 2009)

It is quite possible to 'mix n match' between the sysems (as long as you make a note of what you are doing). I have threading tackle for at least 6 different systems.

The little special purpose drawbar in the attached pic is a case in point - 3/8W on the fat end, M6 on t'other


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## Cheshire Steve (Apr 18, 2009)

I am making a model and the plans are in metric of a scale model of an 1865 English beam engine. It is all a fudge, what should be 1/4" exactly, is now 6mm, what should 1/8" is 3mm, etc. The problem I have is all my tools are imperial, and no decent metric taps and dies. So I am trying to convert the drawings back to equivalent imperial (and BA) so I don't have to re-quip to build the model. It is tricky, but it was supposed to be a 1/12th scale model so everything should be in imperial and not metric.

But re-tooling for metric - that is a different matter - its not just doubling up on the taps and dies - it is every leadscrew, cross-slide, top-slide, milling head, stand drill, power saw, collets, cutters, arbors - in fact almost everything I have is imperial (unless you class BA as metric). 

The strange thing is that when I look for metric taps and dies for scale modelling - I can't find any. What are the metric equivalents of the ME threads ? 

Steve


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## mklotz (Apr 18, 2009)

Arnold,

Almost a year ago to the day, we beat the Imperial/metric subject to death with a vengeance.

http://www.homemodelenginemachinist.com/index.php?topic=1729.0

I got a lot of static for my outspoken defense of metric there so I won't restart the subject here.


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## baldrocker (Apr 18, 2009)

> what should be 1/4" exactly, is now 6mm


Curioser and curioser.
Hunting for a 7mm allen screw the other day the closest I 
could find was 1/4". Now I have a 7mm tap so presumably 7mm screws must be made?
BR


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## RICHARDDV (Apr 18, 2009)

Evidently my fingers are too big and I entered a post before I was thru with it . If you are looking for metric taps and die plate for miniature metric screws try an EBay seller called  Findingking . They are a jewelry and watchmaker supply and I found and bought a nine piece tap and dieplate set (.06 - 2.0 mm) for less than $ 25.00 usd w/ shipping. Thjey have a large supply of usefull small tools and supplies--richard


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## Jasonb (Apr 19, 2009)

Steve you can get close to our (UK) ME threads by using non prefered metric pitches for example 

upto M6 can be had with 0.5mm pitch which is approx 51tpi a bit finer than 40tpi and sizes between M6 & M16 in 0.75mm pitch which is 34tpi close to our 32tpi ME thread. Someone like tracy tools will have these.

If you think you have problems I'm making a Hoglet which is dimensioned in decimal inches, has american threads such as 8-32 for which I am using M4x0.7 and cutting that onto 5/32" rod as its easier to obtain from the ME suppliers than 4.0mm :

Jason


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## Bluechip (Apr 19, 2009)

Jason

In case you are not aware, Live Steam Models at Little Eaton, Derbyshire have a fair selection of small sized metric round in FCMS, silver steel & ( I think) EN8. A download of their catalogue will show ..

I use 'em , they are about 10 mins drive from me. 

Dave

Edit ... and metric Stainless, how I missed that I don't know, it's what I usually get from them ???


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## Jasonb (Apr 19, 2009)

Thanks Dave, I have used LSM in the past its just the fact they tend to supply 1.0m lengths not 12"/300 so if I'd placed the order for all the bits I wanted I would have far more than needed.

And i'm to lazy to print the order form and fax it, also not keen to put 3 digit security no on a fax.

Folkstone Enginering services do metric in 300mm lengths and interestingly sell this as 5/32 as well, presumably as BDMS is usually a though or two undersize this makes 5/32 = 4mm

Jason


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## SignalFailure (Apr 19, 2009)

: I just knew this thread would get hijacked 

Now if someone would start supplying materials in metric sizes that would be good....


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## David Morrow (Apr 19, 2009)

Paul, I have a couple sets of Jan Ridder's plans that I would like to build. I also do all of my work in Imperial even though Canada went officially metric 30 years ago. A few months back someone mentioned using a simple conversion factor for metric to imperial of something like 2.5 : 1 (instead of 2.54xxx). When I finally get to the point where I look at the drawings more closely, I plan to make a simple conversion table in Excel and just hang it on the wall for quick reference.

When you think about it, metric is a simple Base 10 counting system. For us model engine types, most of the heavy math is below 1 inch and is also in Base 10, ie, ten's, hundredth's, and thousandths of an inch.

What really drives me nuts is getting imperial drawings that show dimensions in both fractions and decimals.

Let's un-hijack the thread you guys...


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## Tin Falcon (Apr 19, 2009)

As far as conversions if you allow 1 MM to equal 1/32 of an inch things will come out even and you will get a slightly large model. or let 1 mm = 1/16 and make a smaller version yes not a exact 1:1 conversion but you do not have to re size stock. 
If you are converting imperial prints to metric you can do the same thing. But Using 1/16 =1mm will make a smaller model(Roughly 2/3 size) and 1/32 =1 mm will make a larger one. (Roughly 1- 1/4 ) 
For those in the states that want to build metric and need metric stock try looking at mdmetric.com/
They also carry British thread form tools and whit worth hand tools. 
Tin


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## Jasonb (Apr 19, 2009)

I just press the button on the caliper/mic/digital scale to get a conversion 

Jason


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## David Morrow (Apr 19, 2009)

Jasonb  said:
			
		

> I just press the button on the caliper/mic/digital scale to get a conversion
> 
> Jason



Unfortunately, when you're working off a set of drawings, moving your mic/caliper exactly to a stated dimension then pressing the imperial / metric button to get a conversion is an awfully impractical process. Do that a couple of times and you're bound to find another way very quickly.


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## John S (Apr 19, 2009)

David Morrow  said:
			
		

> What really drives me nuts is getting imperial drawings that show dimensions in both fractions and decimals.



What sends me ballistic is getting MACHINING drawings in fractions ? WTF ? have you ever seen a lathe or mill with fractions on the dials.
Some people may know in their head what 23/64's is but I don't.
With imperial there are always two dimensions, fractions and decimal, with metric there is only decimal, you NEVER see 6 1/2mm on a drawing, it's always 6.50mm 

JS.


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## HughT (Apr 30, 2009)

Hi Paul,

Coincidentally I am actually working through as many of the old imperial designs as I can, converting them to metric units, re-dimensioning to account for 'rounded-up' dimensions, modeling to an accuracy of 6 decimal places and finishing with a set of working drawings dimensioned to 3 decimal places (dual dimensioned), presented in 2 formats - traditional b/w outline and rendered. Each project also has dual format 3d assembly models in Autodesk DWF and Adobe PDF formats.

Each project consumes about 80 hours as I also check operational parameters to ensure that everything is 'set' right.


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## cobra428 (Apr 30, 2009)

Hi Guys,
I had to jump in here. Fractional dims, 2 place dims, and 3 place dims have a unwritten or written meaning (if the designer put it in the title block of the drawing). Usually you can take the fractional to mean +/-.015, 2 plcs +/-.010 and 3 plcs +/-.005 tol.
Converting fractional to mm and visa versa.....they sell charts for that with tap drill info on it too. The other method is dividing 23 by 64=.359375 which rounded off (5 and above goes to the next highest)= .35938 =.3594=.359. mm to imperial .03937*mm=imperial.
Hope this helps
Tony


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## shred (Apr 30, 2009)

As others have said, it's not so much the conversion factors-- digital calipers and DROs and calculators and all make that pretty painless, its that the materials and tools are much harder to come by in the 'foreign' units. 3mm threaded rod is as annoying to come by here as say #4-40 rod in a metric country. Yeah, it can be done, but it's so much easier to 'go with the flow', especially if you're scrounging materials.


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## HughT (Apr 30, 2009)

cobra428  said:
			
		

> Hi Guys,
> The other method is dividing 23 by 64=.359375 which rounded off (5 and above goes to the next highest)= .35938 =.3594=.359. mm to imperial .03937*mm=imperial.
> Hope this helps
> Tony



Hi Tony,

The problem is not the level of decimal places - it is the dimensional accuracy I was referring to with original plans - from my own experience it seems quite common practice for the original draughtspersons to set an accuracy level when dimensioning in 'inches' to 1/32, 1/64, 1/128 or whatever ...etc etc. The majority of plans that are currently freely available tend to dimension to the nearest 1/32 of an inch which equates to 0.794mm - this can accumulate throughout the design and ends up with things not quite fitting together or in some cases not working at all. If you look at Elmers designs they are dimensioned to the nearest 1/32 of an inch.


Its not the fault of the original designer its just something that needs to be considered when converting units from these old designs.


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## cobra428 (Apr 30, 2009)

Sorry for my misunderstanding. The Imperial plans for the kits I bought have the dim mix all over them some even a combo of imp and mm. I have never seen what the free plans look like, just the stuff here, that people made from them.
Tony


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## HughT (Apr 30, 2009)

cobra428  said:
			
		

> Sorry for my misunderstanding. The Imperial plans for the kits I bought have the dim mix all over them some even a combo of imp and mm. I have never seen what the free plans look like, just the stuff here, that people made from them.
> Tony



Hi Tony,

Thank you, but no apology necessary - I was not very clear in my original post. I have only seen the plans that are freely available, some museum archives and the Elmers collection!


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