I’m doing some contract work translating some German produced blue prints for machined parts in order to get them quoted in the United States.
An image of the call out is here
I believe the first third is a surface finish call-out the Ra1, 2 being measured in micrometers. To translate that to a more familiar format in the US it would be a 48 roughness (measured in micro-inches). Right?
The other two thirds of that call out is completely new to me, I have no idea what it means.
Off the top of my head . . . Surface finishes are not perfectly flat, they are in actualy wave like. I believe the second and third call outs refer to the upper and lower wave amplitude limits. Don’t have my Machinery’s Handbook at my side anymore these days so that’s the best I can guess right now.
Not seeing the call out in context, I’m not sure exactly what the last two parts are. It’s possibly defining the surface is between a certain area for a machining process The triangle on the front of the first symbol means machining required.
RA is in micrometers. Millionth. I’m pretty sure on this, that it isn’t in microns which is micro inches.
RA is Roughness Average.
RA does not give the lowest to highest range.
Yeah, sorry about that, I’m trying not to violate the non-disclosure agreement I signed with this company.
What seems weird to me (but then again I know squat about specifying finishes) is that this string of symbols, occurs spaced just like in the linked image, free floating above the title block of the drawing. I thought surface finish call-outs usually pointed to the surface they referenced.
Free floating above the title block. That generally means that it is a general overall finish callout for all unspecified surfaces. Most likely close to an industry standard for that type of material. Can’t be too certain without knowing the application.
RA is in micrometers.
Micro is millionth of whatever unit your dividing.
I’m pretty sure on this, that the RA isn’t in microns which is the same as saying micro inches. For Q.E.D.
Like Si Amigo said it’s likely a general finish call out on any surface that has a finish requirement.
OK, I got up today and broke out the Machinery’s Handbook. The first value describes the wave distance from highest to lowest peaks. The other two seem to describe the exceptable range of amplitude off of the nominal. You will have to get a more precise answer from a German Machinist as I am only familier with ANSI standards and this format isn’t totally covered by any ANSI standard that I can find.
I can tell you that this finish is typical for die cast surfaces, boring, cold rolled surfaces and reaming. That is, it's better than a saw cut or sand cast surface but not super fine like lapping or polishing.
Well, I’m no machinist, but my initial impresion was that the second and third figures represented inside and outside corner specs – and ISO 13715 does cover edge specs, just as ISO 1302 covers surface finish.
I only did a cursory Google, but I found several tutorials and summaries in English and German listed for each standard separately (I apologize if I’ve insulted your intelligence by suggesting that you may have googled them as a single spec, but I’ve see it a lot when looking up unfamiliar specs, esp in a foreign language)
I don’t know if they provide the level of detail you desire. I didn’t see any complete copies of the complete ISO specs on the first page (100 results)
Now that I look at it on my PC instead of my blackberry it makes more sense. The second and third ones have nothing to do with surface finishes. They are obviously calling out edge and corner chamfer dimensional requirements. Basically all they are saying is break all sharp corners and edges.
