Checking .701 to .703 slot with gage pin

[RMARCH]

Hi Everyone,

I am looking for everyone's opinion on what size gage pin should be used to check a .701 to .703 wide slot ? Should a .701 pin fit snug or freely in the slot?

I recently did a job for a new customer and they rejected my parts. I have been a machinist for over 30 years and i never had a problem with the way i make my parts. So i wanted to see what you guys think.

Thanks in advance !!

[307startup]

Well, if the slot is actually .701", a .701" gauge pin shouldn't fit at all. Simple physics...two bodies cannot occupy the same space at the same time. Unless you gauge using a press... .702" would be a tight fit with that pin, and .703" would be a slightly loose fit...I mean .002" is generally the tolerance for a press fit anyway...

[RMARCH]

So what size gage pin should fit in the .701 slot to check the min. size?

[307startup]

For minimum tolerance= .700" would be a go, .701" would be a no go

For maximum tolerance=.702" would be a go, .703" would be a no go

I'm assuming your gauge pins are +/- .0002" or better? If they are ZZ gauge pins, they should be.

[DJPLAST]

As stated earlier, what is the pin size? If you are using minus (-) pins, a .701" is actually .7008" . If you are using plus (+) pins a .701" is actually .7012".
How deep is the slot, and how straight are the walls? What is actually being rejected? .701 should fit loose, figuratively speaking, .703 no go. How are "they" (the customer's QC team of yahoos) inspecting the part? You need to do the same. Comply, it makes life much easier.

[RMARCH]

As stated earlier, what is the pin size? If you are using minus (-) pins, a .701" is actually .7008" . If you are using plus (+) pins a .701" is actually .7012".
How deep is the slot, and how straight are the walls? What is actually being rejected? .701 should fit loose, figuratively speaking, .703 no go. How are "they" (the customer's QC team of yahoos) inspecting the part? You need to do the same. Comply, it makes life much easier.

I am using a .701 deltronic gage pin , It measures .701, not plus or minus. The slot is .171 deep.

The QC inspector rejected them saying the .701 pin should move freely in the slot. I can slide the pin in the slot but it did not fit freely.

I Reworked the parts to make him happy but i think they were ok the way they were, I just wanted to see how other people check their parts.
I always believed that for a .701 hole you need a .7008 pin and it does not have to move freely, you can push it thru with your hand as long as it's not like a press fit.

Thanks for you input !!
Ray

[NC Cams]

When you start to reject parts over 0.001" based on "feel", you are dealing with SUBJECTIVE judgement as opposed to OBJECTIVE assessment.

Whey you MEASURE a dimension, you can document a tolerance. When you GAGE a dimension on GO/NO GO, you literally have to agree upon the "feel" that can ONLY be deemed acceptable/non-accepatable via negotiations and careful gage corelation agreements.

We had a situation just like that recently - only we were dealing with a 0.0005" tolerance. The problem was that our shop was cooler than the customers and the thermal difference resulted in totally unnecessary rejection of the parts. It took a sit down between their QC and ours to work out the problem - plus a lot of buffing and spit shining of parts.

I'd contend the someone was 'inspecting to reject' as opposed to the more preferred "inspect to accept" - big difference it you're on the short end of that political battle.

Forget what size pins you use for the moment as this is somewhat of a red herring. Rather, take your inspection pins and some "good" and "bad" parts to the client. Adk for a sit down with thermally stabilized parts. Then, you and their QC folks agree on what is good and bad and base it on STANDARDS of acceptance/rejection. Then, your good part will match theirs and vice versa.

Parts measured in a A/C'd QC office can/will not conform to the stuff that is being hot shot looked at on a recieving dock with god knows what size/grade of go/no go pins - especially when you're fighting over 0.001" in a slot.

You'd be amazed at what a bit of face to face communication in a formal meeting will do to the clarification of your procedures will do for a quality rating and customer/vendor relations - you'd be surprised and may also learn smometing about the client's special needs re: the part.

We have, over and over.