Design for multi-country manufacture - Metric vs. inch stock 14

[BobVo]

We are a US company which recently merged with a European company. How do we design 'common' products, when we can't but metric stock economically here, and they can't buy US gage, or fractional, stock there?

We certainly aren't the first in this situation. What do other companies do? Any suggestions appreciated.

Thanks.

 

[KENAT]

What do you mean by stock, just 'stock fasteners' or do you mean 'stock material' such as sheet or plate of a certain thickness or both.

On the fasteners issue, I willl say that metric is probably easier to get in the US than Unified is in most other places.

So it may be you have to look at each category and see if one way or the other has advantages.

I'd be interested in seeing what others post as we have some similar issues and haven't yet forged a clear path forward.



KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[DiamondDave]

Although I prefer imperial i'd say stocking metric would be the best course of action since it is more widespread. Uness it is a UK company where you might be more likely to come across imperial sizes.

 

[CoryPad]

Perhaps you can list what kinds of items you need (either in this thread or in a new one). You may find that the membership can help you find economical metric items.

 

[TheTick]

We had trouble with some metric hardware. Clevis pins, weld nuts, cap nuts and retainers in particular. Good luck finding metric structural tubing in the U.S.

My boss likes to point out that the U.S. is one of only three countries that isn't metric, and another of those is Libya.

 

[eromlignod]

Contrary to what most of the world seems to believe, the United States is not "non-metric". We are both metric and imperial equally. Any American engineer under the age of about 60 is utterly bilingual with regard to measurement systems. You can get virtually any metric part you want here, though they might cost a little more, be a little harder to find, and require the additional purchase of a metric tool.

So, as has been mentioned, it is no big deal to specify metric equipment for use in America, though it might be a bad idea to use imperial elsewhere.

We don't hate the Metric System in America, we just think it's overrated.

Don
Kansas City

 

[KENAT]

Oh real minor issue but look out for some screw head types. North American metric pan-heads are apparantly taller than the rest of the world, it's the Canadians fault apparanly. Bit me in the proverbial on my first significant project in the States.

eromlignod, I think you may slightly everestimate how 'bilingual' many US engineers are, but certainly agree they're probably more bilingual than anyone except Perhaps Brits, Canadians and maybe a couple other commonwealth places.

I'd almost be more concerned about things like stock material sizes such as scructural tubing, plate etc.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[Metalfixer]

TheTick wrote <<Good luck finding metric structural tubing in the U.S.>>
I buy from Parker Steel Company.

http://www.metricmetal.com

They have everything metric, no minimum orders, and sales people are very helpful. If you can use short pieces, they sell cut-offs at reduced prices.
Larry

 

[TheTick]

Nice! Thanks.

 

[romke]

what exactly do you mean with "common products"? Components that can be incorporated in products on both locations or products that can be used "as is" and need not be linked to other machinery? In the latter case you can either use metric or imperial. As i understand it designing is not the problem, but manufacturing. If particular materials in certain sizes are difficult to obtain or costly then manufacture should take place where they are readily available - and perhaps shipping cost then becomes the problem. it is also possible to build a complete metric or imperial unit and equip it with an interface in the other system so it can easy be connected to other machinery.

the automotive industry in europe has put up with such a scheme for years (brakehosecouplings and tapered roller bearins only have become available in metric sizes only in recent years). still engines are sold with a SAE size bell housing flange and trucks with fifth wheels that require an imperial size kingpin....

it all illustrates that in a global world global standards are more then ever needed.

 

[SomptingGuy]

Tyre/Tire sizes!!!

A mix of imperial, metric and then a ratio thrown in for good measure.

Does anyone manufacture metric wheel rims?

- Steve

 

[CoryPad]

All OEM wheels are metric.

 

[SomptingGuy]

Metric as in sensible rounded numbers, or just inches converted into the nearest mm equivalent?

- Steve

 

[CoryPad]

What is a sensible rounded number?

Rim thickness = 3.75 mm [&plusmn;] 0.25 mm
Flange thickness = 5.5 mm [&plusmn;] 0.5 mm
Lug hole diameter = 16 mm [&plusmn;] 0.5 mm

I suppose the wheel width from bead seat to bead seat is "noncompliant" at 216 mm, as is the wheel diameter from bead seat to bead seat (436.6 mm).

The solid model, drawing, calculations, dimensional measurement, and testing are all metric, so I think it is safe to call it metric.

 

[SomptingGuy]

As I said, it's a sad mix.

- Steve

 

[IceStationZebra]

At my last job, making off-road equipment in USA and EU, with some sales in Australia and Asia. This was our approach wherever feasible.

Hydraulic fittings - Imperial, O-ring face seal
--Metric fittings are hard to get and $$$ in North America, whereas imperial can be found in EU and to a lesser extent Asia.

Fasteners - Metric
--Watch the differences in head sizes of cap screws between EU, Japan and North America.
--Many of the large components will be metric anyway (transmission, engine, axles, etc.)

Steel - Try to design with thicknesses which can be interchanged with minimal effect. Make sure the design can accept either, and specify either on the drawing.
--This depends on what you can live with, but <0.005" should be OK.
example: 3mm (0.1181") vs. 11 gage (0.1196")
6mm (0.2362") vs. 3 gage (0.2391")
8mm (0.3150") vs. 5/16" (0.3125")
16mm (0.6299") vs. 5/8" (0.625")

Batteries - designed to accommodate either
-- was a pain, but is doable

Tires - Off-road tires aren't an issue, pretty much the same worldwide.

ISZ

 

[BobVo]

Sorry for not specifying in the original post.... I was referring to sheet metal, tubing and bar stock. We do use metric fasteners on all our products, as it makes international field service easier. While metric fasteners are, generally, available in the US at a reasonable cost, the sheet and bar stock seems limited. I did recently find Parker Steel (metricmetal.com) and plan to talk to them about stock, but as they are in Ohio I'm concerned about shipping costs for materials. And as we have multiple sheet metal and machine shop suppliers they would all be buying independently in the volumes they need to support our products.

 

[juergenwt]

The notion that most US engineers are bilingual is a not true.
Many say so but they do not know what they are talking about.
Unless you are brought up in the metric system from your first day in school, you are not capable of thinking in metric - you are constantly converting, no mater how hard you try. The Obama administration should make the hard choice:" First day in the new school year - all metric!!!Period. No transition over 5 and 10 years - that is a bunch of crap.They will just nickel and dime it to death. If we fail, we will just raise another generation of young people who are practically illiterate,as far as being able to converse with the rest of the world when it comes to engineering and manufacturing. If you need any proof, look at what happened to the conversion of TV to digital. Years of preparation and than- politics.
Yes, it is a handicap for US manufacturing trying to manufacture to metric dim's because materials like sheet and bar sizes are bought at a premium price and if you buy inch sizes you have to machine it down to the next metric size. So anybody out there rooting for the continuation of our present situation is just secretly trying to keep the inch system in place.

 

[Longinthetooth]

I was interested in Kenat's comment about the UK and Canada. Both the UK and Canada have been metric for many years. Having worked in Canada for a long time, the problem in refining and petrochem was that most of the equipment/technology comes from the US and we found that it was imperial units or nothing a lot of the time. Maybe that is changing now. Since relocating back to the UK 2 years ago I now work exclusively in metric (on new plant) although, as Juergenwt said, I constantly convert, especialy when doing things in my head and I want to get a "feel" if something sound's right.
I do think that metric (or SI) is overated although the advantages of 1 global system are obvious.
I did junior school in Imperial, senior school in SI, and unversity back in Imperial. No wonder I am mixed up!

 

[eromlignod]

I started learning the metric system in fifth grade (1974). It has been shoved down my throat my entire life. I know it forwards and backwards and so do all the engineers I have ever worked with (I have been in industry for 22 years).

I can think in metric all I want. When I estimate the metric size of an object, I picture a metric ruler in my head, just like I do with imperial. There is no conversion to it. I know the temperature in my office right now feels about 22C. I can pick up an object and tell you approximately how many kilograms it weighs. What do you want?

...and it's still overrated.

Don
Kansas City