Need a Fastener Size and Type Identified

[Ron W.]

Can anyone tell me the size and type of fastener this is?
GM part number 3886921. Shown in the '71 AIM, page L157.
Secures the center air duct to the heater box.
Online search comes up with nothing.

[Joe L.]

Re: Need a Fastener Size and Type Identified

Can anyone tell me the size and type of fastener this is?
GM part number 3886921. Shown in the '71 AIM, page L157.
Secures the center air duct to the heater box.
Online search comes up with nothing.

Ron------


Unfortunately, this screw was never available in SERVICE. So, I have no specs on it. My recollection, though, is that it's a short 1/4-20, self-tapping, hex head screw with a phosphate finish.

[Ron W.]

Re: Need a Fastener Size and Type Identified

Thanks Joe.
I'll measure the hole in the plenum and see if the 1/4-20 will work.

[Rich P.]

Re: Need a Fastener Size and Type Identified

Ill look tomorrow but if not mistaken its a 5/16" hex sheet metal thread.

[Ron W.]

Re: Need a Fastener Size and Type Identified

Rich,
Thanks. I'll watch for your post.

[Alan S.]

Re: Need a Fastener Size and Type Identified

Hi Ron,
Here's that fastener from my 71. I'd size it at 10-24 x 5/8".
It is hex headed and appears to have the phosphate finish as Joe surmised, and hopefully will jive with Rich's findings.
Note the chisel tip and captured washer.
I read it as AF.
Regards,
Alan

[Rich P.]

Re: Need a Fastener Size and Type Identified

tn_IMG_0915.JPGtn_IMG_0916.JPGAlan's pics are 100% correct and what I have seen fir this application. GM used this screw assembly in dozens of locations in the 60's and 70's. The only thing is they are sheet metal thread as 10-24 is machine thread...It's hard to tell and now a days I need to put my dollar store reading glasses on to see that!!! I have included a picture just to show some of the period correct head markings.

[Alan S.]

Re: Need a Fastener Size and Type Identified

Hi Rich,
You're right.
I was trying to describe it's size and screwed up. ( A pun!…..)
So it's a #10 sheet metal thread?
Regards,
Alan

[Ron W.]

Re: Need a Fastener Size and Type Identified

Rich, Alan,
Thanks for your responses and the photos.