correct hardness callout

[lfw618]

On prints I have seen hardness called out as value then scale, and as scale, then value. E.g 50 HRC, vs HRC 50. Is there one that is technically correct or is it generally up to the drafters/engineers discretion? Thanks in advance.

 

[MintJulep]

It's a unit.

 

[lfw618]

Which is how I'd thought about it and has led me spec hardness such as "50 HRC" . However I've noticed that about 80-90% of the drawings I see that spec hardness the hardness scale first. I do not know if I'm missing something on this.

 

[XL83NL]

What do the standards for hardness call out for? I don’t have any standard at hand but that’s what I would look into.

 

[3DDave]

I see the specification as prefix as the most frequently used.

It's been discussed before:

https://www.eng-tips.com/viewthread.cfm?qid=403385

 

[dgallup]

I've always put the value first, the way it's shown in the quote from ASTM E18-15 in the link above.

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[tbuelna]

Probably should specify a hardness range, like 48-52 HRc. Very hard to meet a specific hardness number. Should also specify exactly where the hardness requirement applies, at what point in the manufacturing process it should be measured, and what needs to be tested (ie. 100% of parts, one part per HT batch, a test coupon processed with each HT batch, etc).

 

[dgallup]

Agreed, you need a range or a MIN or MAX qualifier.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[lfw618]

Yes I agree about the range or min vs max. I was mainly just asking whether the value(s) precedes the scale or vice versa in terms of formatting. It looks like according to that quote from ASTM E18-15 the value generally goes first, but I'm not sure it's something I'd actually mark up on a red line, since it seems to be so often used the other way with no issue.