Diamond Shaped Pins for Molded Plastic parts

[Renshu]

Hello All,
Is there anyone out there who uses or has used diamond-shaped go/no-go gauge pins to check injection molded parts? If so, have you had any success? We are presently using them, but not having great success as we have found that it is really difficult to make a perfectly round hole in plastics. I would appreciate any feedback from anyone who has experience with these.

thanks much,

Frank (frustrated)

 

[ralphsulser]

I think Summit Polymers in Kalamazoo/Portage is/was using diamond shaped pins for locating datum holes. Try contacting their Quality Engineering Manager there. I talked to him a few years ago. Sorry, don't remember his name or number.

 

[Ron Rompen]

Diamond pins should be readily available from any gauge and fixture supplier. If I recall correctly (don't have the catalogue handy) Carr-Lane stocks these in most imperial and metric sizes as a standard stock item.

 

[Paul F. Jackson]

Renshu,

If you are using the plug gages as go, no-go for the size of the hole you should be using a round pin at the minimum size as the go gage and the diamond shaped pin (max size across two points and min size or less across the other two) as the no-go gage. So if the diamond shaped pin doesn't fit that is good.

 

[Renshu]

Thank you for your reply


I thank you folks for your reply to my question. To give you a little more detail, the plant manager has mandated that we will use diamond shaped no-go pins for round holes on plastic molded parts. We are using Capron, glass-filled nylon, and molding some complicated parts for automotive. My experience so far is that it is almost impossible to get a perfectly round hole in molded plastic, perhaps I am wrong. In most cases the diamond shaped pin will not go in, but if you turn it slightly the right way, it will go in. That's a problem for me and I wanted to know if anyone else was experiencing this problem, and if so, what they did to rectify the problem. I am sure we could get fairly perfect round with a lot of time and investment in the tooling, however, no one wants to pay that cost. Thanks for your input.

Frank