Experience with the diamond shaped go-no/go pins - Question for all

[Renshu]

I wonder if anyone can tell me if you have had any experience with the diamond shaped go-no/go pins to check products. In my 20 some years, I have never seen these. Our new plant manager has insisted we use these and our confidence on them is low. Does anyone have any experience on these and wonder about whether you feel they are more/less accurate and reliable?

thank you.

Frank A.

[charlie broe - 2008]

This is my first post so please bear with me.

I have used diamond shaped no-go gage pins in the past. Its purpose is to detect local variations in a hole. An egg shaped hole that is within specification at any point would be found acceptable with a standard round no-go gage pin whereas the diamond shaped gage would detect oversize areas. The reason for detecting the oversize local areas is simple. A close tolerance hole designed for a light-press fit component could fall out because the press between the component and the hole is reduced by the oversize conditions.

For example a dowel pin pressed into an egg shaped hole may appear to be secure but come out after the customer has received the part.

The diamond shaped gages are as accurate and reliable as standard gage pins.

I have over 30 years in quality and have not often used diamond gages.

Charlie B.

[Claes Gefvenberg]

Welcome to the Cove, Charlie

In Reply to Parent Post by charlie broe

I have used diamond shaped no-go gage pins in the past. Its purpose is to detect local variations in a hole. An egg shaped hole that is within specification at any point would be found acceptable with a standard round no-go gage pin whereas the diamond shaped gage would detect oversize areas. .

I thought that was it but I have never used the things myself, so I decided to wait for someone who knew. Thank's.

/Claes

[Paul F. Jackson]

The diamond shaped pin is commonly used in a go-position hard gage to stop rotation in the tertiary datum feature. Where the primary datum "A" is established by a plane (or three target areas doing likewise), the secondary datum "B @ MMC" established by a "virtual condition" round pin (squareness tolerance subtracted from the MMC feature size), the wide portion of the diamond pin reflects the squareness@MMC of the tertiary datum "C @ MMC" relative to the primary (perpendicular to a line intersecting the centers of both dowels) while the narrow portion of the diamond pin verifies the position tolerance "C @ MMC" of the distance between the dowels (parellel to the line intersecting both dowels).

Its use is primarily to stop rotation in the tertiary datum with minimal clearance perpendicular to that line while providing clearence of fit for the spread deviation between the dowels parallel to that line so that all other features can be verified with virtual condition pins relative to their feature tolerances specified [position|dia. XX.XX MMC|A|B MMC|C MMC|.

[Arvind]

For those who are not familiar with part location concepts, here are some hints.

4 way location- Typically a circular pin. This pin will restrict movement of hole of mating component in X & Y directions.

2 way location- Typically an elongated slot. Slot will allow freedom in one axis but restrict movement of mating part in other axis.

Diamond pins are used for locating a 2 way of elongated slots. The major axis of diamond is bigger than minor axis.

Arvind

[Bill Ryan - 2007]

In Reply to Parent Post by Renshu

I wonder if anyone can tell me if you have had any experience with the diamond shaped go-no/go pins to check products. In my 20 some years, I have never seen these. Our new plant manager has insisted we use these and our confidence on them is low. Does anyone have any experience on these and wonder about whether you feel they are more/less accurate and reliable?

thank you.

Frank A.

In case it hasn't been done yet - Welcome to the Cove

Just from my company's viewpoint, we use the diamond concept as described by Paul and Arvind (basically - for the tertiary datum on a "virtual"/functional hard gage). For a "Go/NoGo" type of product acceptance check for size, we will take the "NoGo" pin size and mill two parallel flats on it. This allows a better feel for the operator to notice if there might be a drag or an out of round condition. We typically only use this on a hole that gets machined in some fashion (drilled, tapped, etc.) where an out of round condition could lead to noncleanup or loss of thread integrity.

[Renshu]

Thanks for the update, as mentioned, I have never used or seen diamond shaped pins before. I was told that the concept was to ensure there was no elongation in a hole, but it just didn't seem feasible. Now that I have read your answers, it sounds correct and I have confidence in the information given me. I appreciate everyone's help and input. thanks again.

Frank

[Dale D. Barnes]

Hello everyone

I have actually had our nogo sides of our pins shaved by 25% on each side and recertified. We have had problems with alot of holes being out of round and this solved the issue. The flats allowed us to find out if the hole was out of round anywhere. This was a bit cheaper than buying all new pin gages.