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Type: Posts; User: Bob Doering

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  1. Replies
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    I would calrify the error issue for the rule of...

    I would calrify the error issue for the rule of 10 as it allows for sufficient resolution to not only determine "what the true value is" but also how close. Simple analogy: you need to go 5 miles. ...
  2. This is a nice gaging opportunity, because we...

    This is a nice gaging opportunity, because we actually know what the usage of the part is. For fitting two parts together, MMC is the key issue. So, to make a good decision, you need to find the...
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    The point of drawings is to communicate. Some...

    The point of drawings is to communicate. Some communicate better than others, and some people may not listen closely to what they are saying. But, their point is to communicate.

    I am familiar...
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    Threads are a pain, pipe threads are a worse pain...

    Threads are a pain, pipe threads are a worse pain - usually create a lot of arguments between suppliers and customers. But, it sounds like they need to have a first piece, last piece inspection at...
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    The conversation goes to show that there are very...

    The conversation goes to show that there are very few gages as easily influenced by operator skill and/or bias than the micrometers. The very screw that amplifies the measurement also amplifies the...
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    It really depends on the size and weight of your...

    It really depends on the size and weight of your parts, as well as how much CMM training you are willing to endure. You need to have a generous measurement envelope to allow for fixturing and growth...
  7. Thread: Spc ???

    by Bob Doering
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    11
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    6,731

    Problem is, most books are wrong when it comes to...

    Problem is, most books are wrong when it comes to SPC for precision machining (especially short run) - so this approach is likely to confuse both you and the customer, make useless work and cause lot...
  8. Thread: Spc ???

    by Bob Doering
    Replies
    11
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    6,731

    No problem. I have run this past some tough...

    No problem. I have run this past some tough audiences- including Japanese customers, Master Black belts, union operators, statistics gurus and ASQ sections around the country. If you sit through...
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    Sticky: Resources for correct SPC for precision machining

    Resource for information on the correct SPC for linear and circular features in precision machining.

    Learn why X-bar R is the worst - bar none - charting methodology for precision machining, and...
  10. Thread: Spc ???

    by Bob Doering
    Replies
    11
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    6,731

    CorrectSPC - SPC for Precision Machining - Stop...

    CorrectSPC - SPC for Precision Machining - Stop the X-bar R Madness! - YouTube
    1) The point of SPC is to seek out special causes and react to them. here, you would be looking for special causes...
  11. Thread: Spc ???

    by Bob Doering
    Replies
    11
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    6,731

    Actually, there is a good statistical reason why...

    Actually, there is a good statistical reason why for most short runs in machining SPC is of virtually no value. Warm-up and start-up are special causes (that can not be eliminated economically),...
  12. Thread: Spc ???

    by Bob Doering
    Replies
    11
    Views
    6,731

    For precision machining - where tool wear is the...

    For precision machining - where tool wear is the primary variation - X hi/lo-R charts with control limits set at 75% of the tolerance is the best recommendation. The problem is a sampling error. For...
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