Surface finish callouts on drawings
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  1. #1
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    Default Surface finish callouts on drawings

    One of our local vendors (ex-vendor now BTW ) recently did some 303 SS parts for us. They were just simple stepped reducers that were turned down. The tolerances were fine but surface finish was the worst I EVER saw. I mean, you could see the tear marks where the tool was plowing the material off. The parts worked but since it goes into another part that is sold to the end user, I was reluctant to use them.

    So my question is, at what point do you decide to call out a finish? Would you (as a vendor) raise your price just because the print asked for an 80 rm finish?

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    If you expect the surface finish to meet a minimum standard you need to call out that surface finish on the drawing. A global note would probably be fine.

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    Is a torn surface finish even something a surface finish call out would cover?

    You can have some really shitty looking finishes that will come out pretty
    good on the #'s.

    You can have some really good looking surface finishes that don't meet the #'s.

    Is there anything in ANSI 14.5 that specifies "Can't look like shit?"


    Doesn't sound like you really care about the actual profilometer #'s, but
    you care that it functions and looks decent. I don't know how to quantify that.

    Put right on the PO "Must not look like shit"

    Maybe a check32 and a little talk with your vendor. Anybody can hit a 32 on a lathe,
    and the 32 alone tells you it has to at least not look like shit.

    If its ±.030" and a 250 or even a 125. You know that nobody cares.

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    We had customers that had one-page cheat sheets for us at the old day job - examples of what they actually expected the surface to look like for certain calls. It was a continuum from saw cut all the way to electropolished.

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    The finer the size or finish the more it cost, (ie takes more time and a higher skill level to acheave the spec) also a higher chance of making scrap....Phil

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    tear marks will violate a surface finish that is suppose to be at 125 or better.The inspectors at our customers shop considers them a 250 or worse. we had some very small parts that were about .187 in dia. a few years back on the face there was a few tears around the .050-.100 dia part of the face. we lapped them all but you could still see minor tearing but couldnt feel it. They were rejected. it was 303 ss as well. we ended up reworking them
    under a microscope they looked huge and if you compared them to a certified 250 turning surface gage you could see they were 250 or worse.

    most of our print require a 125 or better. our customer wants a 63 or better, even got a spec sheet for it from them with some other inhouse specs.
    in all honesty doing a 125 63 even a 32 on a lathe takes no more time that doing a 125 finish. Unless there very big parts. our parts are small.

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    My calibrated finger nail will tell me if it's a 63 finish or something higher than that.

    If I feel tool marks, it's greater than 63, no tool marks, it's at least 63 finish or better. Just saying.

    Tear marks, chatter in threads, especially in tapered threads, it's rework or scrap. Or is it a "appearance" cosmetic call? Scrap a many of parts over the years just for cosmetic reasons.

    Engineer does have privileges... at accepting or not accepting, but they need to know what they are doing and have the experience of knowing how important a surface finish is in the application it is used in.


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