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  #1  
Old 30th November 2009, 08:19 AM
Patrick Johnson Patrick Johnson is offline
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Question Tape Measures (again) Gage R&R

I have read a number of the posts on tape measures, but this is a slightly different twist. The plant where I'm at has long used tape measures ("we've always done it that way"). The problem is that most tape measures resolution is only at 1/32" or 1/16" and the tolerance ranges on what we are measuring are typically anywhere from +/- 0.016" to +/- 0.047"!! I have done several gage studies using various operators and not one has passed to date. They all fail based on the ndc, % study variation, % contribution and of course P/T ratio!!

Am I missing the boat or is this a pointless activity to measure with a tape measure? I have discussed this with my manager but the direction I got was to get a certified tape measure. I was then told to check this certified tape to other tapes to verify their accuracy. After that I was told to have the various operators check the same piece 10 times to make certain that they could accurately measure a piece with it.

This seems pointless. I still strongly believe that even though people "build houses with tapes" that they are not up to the task at hand.
Please advise if I am missing something from the outsiders point of view.
Thanks to Patrick Johnson for your informative Post and/or Attachment!

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Old 30th November 2009, 09:02 AM
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Re: Tape Measures (again) Gage R&R

Patrick:

It is so obvious that your tape measured are not used in the appropriate application. You can visually see down to 1/16 " or .060 thou yet you are trying to measure down to an tolerance of .047. It just doesn't make sense.

One always needs to look at the 10% rule. If you part tolerance is +/- .050", your gauge should have a increment to at least .005".

Your R & R values that you have already calculated show that this type of gauge is not appropriate for the application and all the King's horses will not make it better.

You now have the toughest job of any person in the Quality field - trying to convince your Supervisor that your company should look for alternative methods of measuring.

Good Luck!

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Old 30th November 2009, 09:45 AM
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Re: Tape Measures (again) Gage R&R

Quote:
In Reply to Parent Post by Patrick Johnson View Post

I have read a number of the posts on tape measures, but this is a slightly different twist. The plant where I'm at has long used tape measures ("we've always done it that way"). The problem is that most tape measures resolution is only at 1/32" or 1/16" and the tolerance ranges on what we are measuring are typically anywhere from +/- 0.016" to +/- 0.047"!! I have done several gage studies using various operators and not one has passed to date. They all fail based on the ndc, % study variation, % contribution and of course P/T ratio!!

Am I missing the boat or is this a pointless activity to measure with a tape measure? I have discussed this with my manager but the direction I got was to get a certified tape measure. I was then told to check this certified tape to other tapes to verify their accuracy. After that I was told to have the various operators check the same piece 10 times to make certain that they could accurately measure a piece with it.

This seems pointless. I still strongly believe that even though people "build houses with tapes" that they are not up to the task at hand.
Please advise if I am missing something from the outsiders point of view.
Other than GR&R, what are you seeing that makes you think that the tape measures aren't working? Is it possible that the tolerances are too tight? If there's no history of rejection that can be ascribed to measurement error and tape measures have been in use for a long time, what's to be gained by spending money at this point?

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Thanks to Jim Wynne for your informative Post and/or Attachment!
  #4  
Old 30th November 2009, 10:25 AM
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Re: Tape Measures (again) Gage R&R

I have to agree with Jim - why the GR&R exercise if there are no problems directly related to measurement? I worked in a modular home plant in a past life, and we used various kinds of tapes, all with the same problems. What I suggested (but never implemented), was a measuring range, calibrated by a surveyors steel tape (NIST) certified and checking tape measures against that. Anything found out more than 1/16" was to be tagged and removed from service. This was never done because most cheap tapes would fail, and the company supplied the tapes.
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Old 30th November 2009, 12:07 PM
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Re: Tape Measures (again) Gage R&R

I too am with Jim on this one. Do you really need such (relatively) tight tolerances? If you could give us some indication of what you are measuring and what current known field/performance problems you are experiencing we may be able to help more.

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Old 1st December 2009, 11:02 AM
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Re: Tape Measures (again) Gage R&R

Quote:
In Reply to Parent Post by Patrick Johnson View Post

I have read a number of the posts on tape measures, but this is a slightly different twist. The plant where I'm at has long used tape measures ("we've always done it that way"). The problem is that most tape measures resolution is only at 1/32" or 1/16" and the tolerance ranges on what we are measuring are typically anywhere from +/- 0.016" to +/- 0.047"!! I have done several gage studies using various operators and not one has passed to date. They all fail based on the ndc, % study variation, % contribution and of course P/T ratio!!

Am I missing the boat or is this a pointless activity to measure with a tape measure? I have discussed this with my manager but the direction I got was to get a certified tape measure. I was then told to check this certified tape to other tapes to verify their accuracy. After that I was told to have the various operators check the same piece 10 times to make certain that they could accurately measure a piece with it.

This seems pointless. I still strongly believe that even though people "build houses with tapes" that they are not up to the task at hand.
Please advise if I am missing something from the outsiders point of view.
Using a tape measure on such tolerances indicates that you are not concerned (or turn a blind eye) to products that are indicated as "out of tolerance". If this is the case, and you are receiving no comebacks from the customer, then of course the product is over specified. If you "are" rejecting product that the tape measure indicates is "out of spec" then you are undoubtedly throwing money away.
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Old 7th December 2009, 11:10 PM
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Re: Tape Measures (again) Gage R&R

Quote:
In Reply to Parent Post by Patrick Johnson View Post

I have read a number of the posts on tape measures, but this is a slightly different twist. The plant where I'm at has long used tape measures ("we've always done it that way"). The problem is that most tape measures resolution is only at 1/32" or 1/16" and the tolerance ranges on what we are measuring are typically anywhere from +/- 0.016" to +/- 0.047"!! I have done several gage studies using various operators and not one has passed to date. They all fail based on the ndc, % study variation, % contribution and of course P/T ratio!!

Am I missing the boat or is this a pointless activity to measure with a tape measure? I have discussed this with my manager but the direction I got was to get a certified tape measure. I was then told to check this certified tape to other tapes to verify their accuracy. After that I was told to have the various operators check the same piece 10 times to make certain that they could accurately measure a piece with it.

This seems pointless. I still strongly believe that even though people "build houses with tapes" that they are not up to the task at hand.
Please advise if I am missing something from the outsiders point of view.
Welcome to posting in the Cove!

Given the measurement you need to make, I must ask what is the overall length you measure? If it is say 50', then the tolenece you need is frankly impossible to achieve with a tape. If you are working under 12", get digital calipers and have them calibrated by an accredited lab, then teach folks how to use them proprly to get good results.

Even a precise steel ruler cannot give those tolerences, due to the uncertainty.
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Old 18th December 2009, 09:48 AM
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Re: Tape Measures (again) Gage R&R

Thanks to everyone for your feedback and I believe you all brought up some interesting points.

The parts are steel doors and frames of varying sizes. The main issue is trying to hold tolerances in thousandths of an inch on something that may be over several feet large.

Until we can get the tolerances right we will continue to run in circles. If the tolerances truly need to be this tight then we will have to accept the fact of the 10:1 rule and acquire a more appropriate gaging method. Since the dimensions in question rarely present an issue from the customer I believe our time is best spent on the prints first and the measurements later.

I appreciate the advise and observations.

Thanks again!!
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