Go-No Go Pins

[BrianP.]

Seen this on another forum and now I have run into it here. You have a hole say .066-.067. A .067 pin goes in the hole but an .068 does not. Guy says good. I say no good a .067 pin should not go. For sake of discussion we will assume an exact size not a plus or minus pin. I believe his thought is you get to use up to .0679 and it is still a .067 hole. Not bad till it actually goes to .068.

[Newbeeee™]

Nope.

66 and 9 tenths can go, 67 is a no.

Send him back to school...

[Rocketmachinist]

I hate tolerances that are written like that anyways. I think it should be written .0660-.0670 that way you know that the tool your going to use for inspections is in tenths and .0671 is out of tolerance.

[Newbeeee™]

I hate tolerances that are written like that anyways. I think it should be written .0660-.0670 that way you know that the tool your going to use for inspections is in tenths and .0671 is out of tolerance.

Yes but implied tolerances (2, 3 or 4 decimal places) can be a slippery slope.

A 1" slip (gauge block) is an inch as we know.

And it's (within reason) exactly 1" and if you write it 1.0 or 1.0000 it doesn't change anything

[BrianP.]

Nope.

66 and 9 tenths can go, 67 is a no.

Send him back to school...

 

That's how I have always interpreted it. 067 is the high limit .0671 is out. You cannot put a .067 pin into a .067 hole. Size for size would be press fit.

 

Link to other forum.

 

http://www.cnczone.com/forums/machinist-hangout/318552-machinist.html

 

Last answer is spot on.

 

And I've never even gone to school.

[Rocketmachinist]

Yes but implied tolerances (2, 3 or 4 decimal places) can be a slippery slope.

A 1" slip (gauge block) is an inch as we know.

And it's (within reason) exactly 1" and if you write it 1.0 or 1.0000 it doesn't change anything

True but there are also gage classifications depending on how tight they held to those standard sizes.

 

 

TOLERANCE OF GAGES

The difference between a Class Z gage and Class ZZ gage is the deviation allowed in the manufacturing process for tolerance and geometry and does not define the useful life of the gage.  Helpful reference materials are as follows, below is a sample from B89.1.5-1998 ANSI / ASME Standards:

Class ZZ has an allowed deviation of .0002″, geometry of .0001″, finish 10 micro-inch Ra

Class Z has an allowed deviation of .0001″, geometry of .00005″, finish 8 micro-inch Ra

Class X has an allowed deviation of .00004″, geometry of .00002″, finish 4 micro-inch Ra

Class XX has an allowed deviation of .00002″, geometry of .00001″, finish 2 micro-inch Ra

http://www.meyergage.com/abcs-of-gages/differences-between-z-zz-classes-of-gages/

[Newbeeee™]

yes - I was talking lab grade not workshop though.

[Mjölnir]

yes - I was talking lab grade not workshop though.

 

then there's Deltronic class X gage pins in .0001" steps...

[Newbeeee™]

then there's Deltronic class X gage pins in .0001" steps...

Yes I know of them. All I was trying to (badly) say, is you have to be careful using implied tolerancing.

[civiceg]

Could put the pin dia to be used on the in process check sheet. 

 

Feature A - .066 Plus pin goes in smooth

                  .067 Minus pin does not start

[jlw™]

How is this even a debate?

[Newbeeee™]

How is this even a debate?

Because the operator who fooked it up is trying to worm his way out of a reject note

[Del.]

My gage pins are minus .0002. Technically I have understood that it takes .0003 to slide into an onsize hole.

[Guest]

 

Well, I got the final word from Vermont Gage who sent me this response to my email:

 

"Please see the attached excerpt from ISO 1938. It clearly states that the No-Go is not allowed to enter the part. You may also review ASME B89.1.7.3.1-2001, Guidelines for Decision Rules: Considering Measurement Uncertainty in Determining Conformance to Specification. This standard takes the 10% Rule (Guard Banding as used in Go/No-Go Gages) and expands upon it.

 

The bottom line is that the Go needs to pass through the entire length of the hole freely and the No-Go should not fit. Neither gage should be forced.

 

If you would like to take a deeper dive, see Mill-STD-120 and Mil-S-45662A. Both of these standards have been discontinued but, give a background for the reasoning behind these gages and others."

 

That pretty much seals the deal! Thanks to Vermont Gage for a concise and timely response.

 

D.W

 

 

BOOM!

 

Brian, write that MoFo up. Not for scrapping a part unless it's standard policy but for being a dumb@$$.

[civiceg]

I would bet the operator knows better, just making excuses. My favorite is "I couldn't find the right size pin"

[BrianP.]

BOOM!

 

Brian, write that MoFo up. Not for scrapping a part unless it's standard policy but for being a dumb@$$.

 

He is the Trak guy here and been here longer than I have. Good guy to work with. Does some really nice work. But very opinionated on many things. Not even going to try and change his mind. Have to agree with the inspector from the customer though. I would never make a part like this. .067 is the UPPER limit. .0671 is oversize.

[Guest]

Reminds me of a time I worked somewhere and they INSPECTOR told me that the Tread Go/NoGo gage could enter the treads as many turns as long as it did not go through of if there "was drag".

 

Ummmm ASME B1.2 - 1983, Section 5.2.1 and ASME B1.16M - 1984, Section 5.2.1

 

"...product thread does not pass over more than three complete turns.”

 

I refused to sign for the part. I knew the thread was bad. I got written up for not signing. This part was a big deal too. Nuke part. His contention was that he could "feel drag" the whole length of the thread gage. He was FOS. I tested it and there was no drag. The next part I changed from a tap to a thread mill... to leave no doubt. I left shortly thereafter.