Dimension on the high limit with a plus gauge pin - YOU MAKE THE CALL!

[ScottK]

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?

 

[Jim Wynne]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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?

 

[ScottK]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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 +

 

[BradM]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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

 

[Steve McQuality]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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!

-Steve

 

[Jim Wynne]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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.

 

[ScottK]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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.

 

[CycleMike]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

Out of curiosity, What's the hole for?

Mike

 

[Jim Wynne]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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.

 

[e006823]

Re: YOU MAKE THE CALL! Dimension on the high limit with a plus gauge pin.

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.