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AlexW91

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am i being to fusy to expect to buy plans in metric?

i,m looking at my 1st build, and i know its relatively easy to convert, but to start changing a fraction to a decimal then x 25.4 is becoming a pain i can do without. ok doing 1 or 2, but they just dont convert ? or am i being stupid.. ie 1/2" = 0.5 x 25.4 = 12.7mm !!! now come on... 12.5 or 13mm i can cope with...

i have been trying to find metric plans for a simple (ish) static beam engine for ages now, without success.

any help guys for a simpleton ?
 
Just get a digital vernia gauge. That will convert for you at the touch of a button.
 
Buy the pocket calculator Machinists Calc Pro! Does that really good.

Seriously, you should better start from scratch than try to convert imperial drawings to metric. I tried that once and then sold the plans.


Nick
 
cheers guys, but the conversion itself, ok. 1/2" = 0.5 x 25.4 = 12.7mm !!! now i have 12.5mm tools and 13mm.. so which is it..


never mind bloody 3/16th and all that nonsence...
 
It's neither, it's 1/2".

Depends what your lathe and/or mill are calibrated in.
But either way you still have to measure to 0.05 mm or 1 thou or so. You can't rely on tool accuracy.
Even a good reamer in gunmetal will give you an undersized bore.
So it really doesn't matter a lot.
 
It's nearest to 12.7 mm

But if you are having problems with tools to decimals of mm, then just buy imperial ones.
Or am I not understanding your problem?
 
all i,m saying is, why cant i buy plans in metric ??

its 2013..... why cant we move on..
 
I'm currently building Gerry's Beam Engine metric version, but I'm changing all the screws to BA as I'm finding it impossible to get small size metric screws with hex heads. Cap screws just don't look right for the era of the beam engines.

Paul.
 
I live and work in the metric world, but I don't have an issue with imperial plans. After all, at the end of the day you're just aiming for a mark on the micrometer, it doesn't matter if that mark is 12.00mm or something silly like 9.57mm.

Converting the plans to mm first saves having to grab a calculator while working, although those letter and number drill bit designations are a pain.
 
it doesn't matter if that mark is 12.00mm or something silly like 9.57mm.
Click to expand...

That is right, to some extend. It starts with stock material, reamers and threads.
If you need a shaft 6.35 mm in diameter, 100 long, you won't turn that down from a 7 mm. Or some rectangular bar with 6.35 by 9.675 mm. Then you start to adjust the plan. And that's where the pain starts and it ends in that nothing matches.


Nick
 
It's a weird situation when it comes to metric vs imperial that's for sure. I was schooled before and after my country's transition to metric so I am conversant with both systems of measurement. It's interesting to note that most bar stock here is still made to imperial dimensions but sold as a metric size. Although, very slowly, we have been changing to purely metric sizes.

The problem is that bar stock in either system of measurement has reasonably large tolerances, so buying a 6mm piece of x material may yield a bar that measures anywhere from 5.5 to 6.5 mm and the same goes for imperial, a 1/4inch round bar may measure from .225 to .265 inches. Metric drill bits and reamers are just as much of a problem also, a 6mm drill bit may actually measure 5.8 to 6.2 mm, ditto for imperial.

Whether the plans are in metric or imperial, you are still going to encounter the same problems. If the plan calls for a 6.25mm hole that is just as much of a pain as an imperial plan calling for a .252 inch hole. Cutting anything to length, metric or imperial is not a problem as we normally use filing, grinding or sanding or some other method to bring it to a suitable length, not necessarily the length that was called for, but one we can live with.

The argument of metric vs imperial really is mute, neither system offers anything better than the other and you may convert in either direction, willy nilly, you are still going to encounter the same problems in either system and as Murphy's law states ... If it can go wrong .... :D

IMHO, anyone who can deal with any of the above is a craftsman by any sense of the word and should command respect simply for being able to deal with the nightmare that is metal working ... wouldn't you agree?
 
Last edited:
When I buiild my Hoglet I used an app on my phone
called Simple Unit Converter.
Works fine for me, just fill in the lenght of Inch and it show it in mm.
Ove
 
AlexW91 said:
never mind bloody 3/16th and all that nonsence...
Click to expand...

careful with your wording, I quite like all that nonsence *club*

I work in imperial mostly but use metric bar stock as it allows me to take a light skim down to the exact size i.e. 5mm > 3/16 etc.

There are plenty of metric plans available but you have to look at the history of the hobby in the UK/US and in what period of time most of the traditional drawings, using castings, come from.

Unless you look at plans from europe ->
http://www.ateliermb.ch/shops/gussteile/ch/contents/en-uk/d9.html which use castings or at more modern bar stock engines being designed on here and in the model engineer magazine, you will find yourself realising that most plans are just a guide anyway :p and it doesn't matter what system you use aslong as it fits!

Ps. Imperial is wayyy better.
Rob. :)
 
this subject has been beat around a long time, passionately .
the only correct solution is the one that works for you in your shop. and the only answer is helping anyone who asks find the best solution for his shop and his needs.

supposedly the US was to be metric by now. When I was in school the big push was to learn metric. And were were supposed to complete the transition by 1985 or 1990 or something like that. It did not happen. Yes there are us manufacturers that make things to metric standards , I calibrate scales mostly in avoirdupois system but I do carry and Use metric weights.
If I buy a name brand measuring tape it is in feet and inches I would be looked at crazy if i went to a hardware store and asked for a meter stick. Much of the import machine tools from china are in US standard . that is what I am used to.
I will not knock someone who grew up with metric for liking the metric system and wanting plans in metric. but if I want to build an engine from Jann ridders and I hope to soon then I need to deal with a print in metric. and if someone from the Netherlands or OZ wants to build a Elmer Versburg engine it is in fractional inches. And machine tools measure in decimal inches or decimal millimeters. se le vi . May as well blame it on the french as they invented the metric system or at least were one of the first countries to adopt it.
The point is there are two widely used systems and we need to either learn to be comfortable with both or comfortable adapting or translating one to the other. If I only build to imperial standard prints with UNC or UNF stadard fasteners I am limiting myself. And if someone else only uses metric plans they IMHO limit themselves. this hobby is all about learning new things and overcoming obstacles and adapting. using a plan set that is outside ones comfort zone is part off that. However if one is building a first engine that is not likely the time to have to worry about conversion from one system to another. Remember rule # 1 this is for FUN.
Tin

for those in the US there is company in Maryland calle Maryland metrics they specialize in import metric items tools fasteners etc. and they carry BA standard taps and dies as well.
 
The problem is that bar stock in either system of measurement has reasonably large tolerances, so buying a 6mm piece of x material may yield a bar that measures anywhere from 5.5 to 6.5 mm
Click to expand...

??? Hot rolled?
If you buy blank drawn steel, it has a tolerance of h9 or around that. Swiss lathes wouldn't work at all with +/- 0.5 mm.


Nick
 
Your problem is you are not looking in the right places, if you use google to search it will throw up english speaking results which will either give you UK or US plans which are generally in imperial, start looking on the continent and you get metric plans like the german ones linked to above.

Also have a look at this french site that has a nice looking barstock bean if you like the look of barstock engines.

http://jpduval.free.fr/
 
I convert metric plans to imperial plans quite frequently. I use the correct conversion factor, 25.4. The trick is knowing what purchased materials can be easily changed and what can't. I use imperial cold rolled shafting, knowing that I don't want to be turning shaft diameters to some bastardized size. I use Imperial fasteners, as they are more common here and match my Imperial drills and taps. Anything that is going to be machined to size anyways gets directly converted to the equivalent imperial size, even if it doesn't conform to any Imperial size srandard. For 3mm shafts I convert to 1/8" even though that is not an exact conversion, In the same vein, 5mm=3/16",6mm=1/4" , 8mm= 5/16" and 10mm=3/8". These are not "exact" conversion factors, but knowing that, I can drill, bore, or ream the bushings to match the shafting. I try and use only two fastener sizes, 5-40 which is close as damn to 1/8" or 3mm, and 10-24 which is 3/16" or 5mm.---Brian
 
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