Situation...
We have a part with a dimension that we check with plus .0002 gauge pins.
The only way to check this dim is with a gauge pin as the hole we're checking in midway into the part.

The spec is .133 to .137.
The first article piece accepted the .137 pin, but did not accept the .138.

what's your call?

Situation...
We have a part with a dimension that we check with plus .0002 gauge pins.
The only way to check this dim is with a gauge pin as the hole we're checking in midway into the part.

The spec is .133 to .137.
The first article piece accepted the .137 pin, but did not accept the .138.

what's your call?

Well, at first blush, I would say that the size of the hole is somewhere between .1372 and .1381, all of which range is out of tolerance. I wonder, though, why you're using + pins. If you were using a minus pin, which is customary, and the .1378 pin (nominally .138) went in, the hole would be considered oversized. Why shouldn't the same rationale apply on the + side?

Well, at first blush, I would say that the size of the hole is somewhere between .1372 and .1381, all of which range is out of tolerance. I wonder, though, why you're using + pins. If you were using a minus pin, which is customary, and the .1378 pin (nominally .138) went in, the hole would be considered oversized. Why shouldn't the same rationale apply on the + side?

Nothing that is done here is customary.
All our pins are +

Initially, I say fail. As long as the pin has not worn too much.

Nothing that is done here is customary.
All our pins are +
Not a "gauge pin kinda guy" Discordian, so I can't help you out - but I did enjoy a chuckle. Nice to know we're not alone sometimes!:cool:

-Steve

Nothing that is done here is customary.
All our pins are +

Well, the likelihood is that your customer will measure it with a minus pin. For those who aren't familiar with what we're talking about, gage pins are generally not used in their exact nominal sizes because (using the present example) a pin that's exactly .137 in diameter will not fit in a hole that is exactly .137 in diameter. The OD of the pin and the ID of the hole can't occupy the same plane simultaneously. It's customary, when gaging hole size, to use pins that are .0002 smaller than the nominal size of the upper spec limit, which provides a "cushion." In this case, where the upper limit is .1370, a .1368 pin would normally be used for "no-go" purposes, thus assuring that no oversized holes would be accepted. Although Discordian states that an alternate measurement method isn't available in this instance, that's usually the way to go when use of pins creates ambiguity.

Well, the likelihood is that your customer will measure it with a minus pin. For those who aren't familiar with what we're talking about, gage pins are generally not used in their exact nominal sizes because (using the present example) a pin that's exactly .137 in diameter will not fit in a hole that is exactly .137 in diameter. The OD of the pin and the ID of the hole can't occupy the same plane simultaneously. It's customary, when gaging hole size, to use pins that are .0002 smaller than the nominal size of the upper spec limit, which provides a "cushion." In this case, where the upper limit is .1370, a .1368 pin would normally be used for "no-go" purposes, thus assuring that no oversized holes would be accepted. Although Discordian states that an alternate measurement method isn't available in this instance, that's usually the way to go when use of pins creates ambiguity.


Our customer won't measure it.
The part goes into an assmbly here.
An external customer should never even see it... unless he want to void the warranty.

but thanks for the explanation... I'm going to ask around and see why we historically use + pins in general.
My WAG is it's because we're concerned with maximizing gas flow so it's better to err on the bigger side.

Out of curiosity, What's the hole for?

Mike

Our customer won't measure it.
The part goes into an assmbly here.
An external customer should never even see it... unless he want to void the warranty.

but thanks for the explanation... I'm going to ask around and see why we historically use + pins in general.
My WAG is it's because we're concerned with maximizing gas flow so it's better to err on the bigger side.

Your main concern should be whether or not the hole will work as is, and secondarily, changing the specification to reflect the real needs of the product.

I would have to say that the part failed since it accepted the .137+ pin (assuming no wear).

All gauging performed at my current employers is based upon the preferred gauging policy as defined in ASME Y14.43-2003: "Dimensioning and Tolerancing Principles for Gages and Fixtures", Accept most good parts, reject all bad parts (reject some borderline good parts).

So when using gage pins to measure a hole the go member is a plus pin and the no-go is a minus pin.

For tubing we use plug gages to check the inside diameter of the tube which acts the same way I imagine as a minus pin. The plug gage is made to be 0.001" smaller than the low end of the scale which allows for room for the gage to fit. If the gage were exactly the same size as the minimum ID specification then a condition could occur where the plug won't fit but the part is within tolerance.

If we're checking the outside diameter (other than using a micrometer which is standard for all parts) we will sometimes use a ring gage, which is 0.001" larger than the maximum tolerance of the outside diameter. So kind of like a plus pin I guess?

Anyway, when we use the plug and/or ring they're go/no-go gages so if the plug or ring doesn't fit we know the tube doesn't meet specifications.

But from the situation described it sounds like the dimension is above the maximum specification.

Your main concern should be whether or not the hole will work as is, and secondarily, changing the specification to reflect the real needs of the product.

yeah. And it will probably get ECO'd.
but the snap decision by QC based on history of other parts and similar situations was to accept the part.
Historically it never mattered that the pins were +. If the part took the pin for the high end it was in spec figuring this was built into the spec. But this time the QC inspector caught **** from the chief engineer....

but now we're getting into dysfunction.

yeah. And it will probably get ECO'd.
but the snap decision by QC based on history of other parts and similar situations was to accept the part.
Historically it never mattered that the pins were +. If the part took the pin for the high end it was in spec figuring this was built into the spec. But this time the QC inspector caught **** from the chief engineer....

but now we're getting into dysfunction.

Look at it like this: either way, a nonconforming condition was discovered. Either the NC was in the parts, or in the specifications. Same effect in many instances.

For tubing we use plug gages to check the inside diameter of the tube which acts the same way I imagine as a minus pin. The plug gage is made to be 0.001" smaller than the low end of the scale which allows for room for the gage to fit. If the gage were exactly the same size as the minimum ID specification then a condition could occur where the plug won't fit but the part is within tolerance.

If we're checking the outside diameter (other than using a micrometer which is standard for all parts) we will sometimes use a ring gage, which is 0.001" larger than the maximum tolerance of the outside diameter. So kind of like a plus pin I guess?

Sorry but you are at risk of producing tubes out of specification. If the minimum inner diameter of the tube is .500" and you are using a plug/pin gage of .499" you could be producing undersized tubes. Same with your ring gage for the outer diameter - if the maximum O.D. is .750" and your ring gage is .751" you could be producing oversized tubes. As in Jim's response - the "NoGo" pin is typically manufactured with a +.0000/-.0002" (depending on the precision ordered). Thus the "minus" pin mentioned. A "Go" gage would typically be ordered with a tolerance of +.0002/-.0000". Being concerned about a .500" pin going into a .500" hole should not be an issue because you probably shouldn't be running the feature at the extremes of the tolerance anyway.

Well anything is possible, but in this instance it isn't likely. In our process, the plug and ring gages are for functionality checks, not dimensional checks. I probably should have specified that. Dimensional checks are done using micrometers and calipers, which would pick up on out of tolerance conditions.

Situation...
We have a part with a dimension that we check with plus .0002 gauge pins.
The only way to check this dim is with a gauge pin as the hole we're checking in midway into the part.

The spec is .133 to .137.
The first article piece accepted the .137 pin, but did not accept the .138.

what's your call?

I would reject the part plain and simple.:bonk:

I would not reject the parts as long as the past run history has proven fit and function. What I would to do is ask the customer for an advance deviation request, engineering change order or increase of tolerance. You also might want to look into purchasing some minus gage pins.