SAE material or metric material 3

[Jeff Trevathan]

We work for a Japanese company and deal a lot with Japanese drawings that, of course, use metric material (plate thickness, round and rectangular tubing, structural steel, etc.)Is metric material readily available in the USA or should it be converted to SAE (inch) material? I have had occasions when converting metric parts to inch, it affects the form and function of how some parts will fit together. If metric material is easily obtainable, it is sometimes best to stay metric. Please let me know your thoughts on this matter.

Respectfully,
Jeff T.

 

[KENAT]

So, properly done drawings/documentation should make it fairly clear if you can substitute similar size inch material, but may require you to find the relevant standard that defines 'STOCK' material tolerances.

Otherwise, you'll have to do some form/fit/tolerance analysis & investigation.

So, if the drawing calls up metric stock and it's readily available for reasonable cost I'd say it's plan A.

However, more I think about it you should probably look up what the STOCK tolerances are assuming that's how the material is designated on the Japanese drawings, rather than an explicit tolerance given on the drawing. If you have an explicit tolerance on the drawing I assume you wouldn't be asking this question.

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[tygerdawg]

I've been in this debate before. Stay Metric if at all possible and economically feasible to do so. If anything goes haywire, there will always be that extra well, what about conversions / calculations / yaddayaddayadda question that will confuse the path to the root cause.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[EdStainless]

There is a lot of metric material in supply in the US (CAT, Toyota, BMW, ...) so stay metric.
You will find some oddities, your drawing calls for 6mm, and people will quote you 0.236".

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P.E. Metallurgy, Plymouth Tube

 

[SwinnyGG]

I also work for a Japanese company and deal with this a fair bit. Metric HSS sections, metric plate, etc- area available but range from a few % more expensive to 10x the cost.

I make this decision on a case-by-case basis. Unfortunately, for me, that's how it must be done.

 

[drawoh]

Jeff Trevathan,

Did the Japanese specify stock, or did they specify thicknesses, with tolerances?

This is why you design sheet metal to be fairly insensitive to the actual thickness.

--
JHG

 

[juergenwt]

We had to duplicate thousands of tools when we moved some production from Germany to the US. All prints were metric and at first we started to substitute inch size material but soon had to give it up. It looked like it would not be a problem using inch size material for base plates, blocks and other tooling components, but soon became a quagmire the further we got into building tools and dies to metric prints. This was especially true when building complicated multi station tooling for CNC using a fourth axis.
This was twenty years ago and metric material was not readily available. We found it better to machine everything from inch down to the correct metric size. No more problems after that.

 

[Jeff Trevathan]

I want to thank everyone for their input on this issue (inch material vs metric material). All the Japanese drawings I have dealt with never had tolerances on material thickness unless it had to do with some machining for a fitting issue. There have been times where inch material could be used to replace a metric part. But it does make life easier when metric material can be used since it is now more readily available than back in the day.

Thanks again,
Jeff