Need thread spec for GM 9420261 nut

[Gary B.]

EFAED31F-F93D-4298-8A20-D8E1AA83CD9B.jpg

Those nuts have free spinning flanges and are sometimes referred to as Keps nuts. The Trim Parts repro tail and backup lamps came with Pal or stamped steel nuts, like this one.

98DE674E-5A82-4B19-94AC-C275D9DF64F1.jpg

[Mike M.]

Re: Need thread spec for GM 9420261 nut

of all the c-2's I've restored the past 50 years, I've never seen anything other than pal nuts on original tail lite housings. mike

[Gary B.]

Re: Need thread spec for GM 9420261 nut

Mike,

Hmmm. Interesting. Have you ever heard of Keps nuts being used?

I have to admit, it sure would be easier to use the repro Pal nuts.

Gary

[Robert P.]

Re: Need thread spec for GM 9420261 nut

I had those same nuts on my early 66 , was changing out the pitted taillights and couldn't use them on my new lights
so pal nuts where used
Bob

[David H.]

Re: Need thread spec for GM 9420261 nut

Gary

I would try first washing with soap and water to remove grease. Then a few hours (maybe more) in Evapo-Rust. Wire brush threads using a rifle bore brush attached to an electric drill.

In any case, don't use a tap to clean. A thread chaser should be all that is needed after bore brush.

Use a caliper and thread gage on the studs to determine size and threads per inch.

Dave

[Gary B.]

[Gary B.]

Re: Need thread spec for GM 9420261 nut

I had those same nuts on my early 66 , was changing out the pitted taillights and couldn't use them on my new lights
so pal nuts where used
Bob

[Joe L.]

Re: Need thread spec for GM 9420261 nut

The original nuts that secured the tail and backup lamp housings to the body on my ‘66 look like the following:

[ATTACH=CONFIG]108170[/ATTACH]

Those nuts have free spinning flanges and are sometimes referred to as Keps nuts. The Trim Parts repro tail and backup lamps came with Pal or stamped steel nuts, like this one.

[ATTACH=CONFIG]108171[/ATTACH]


I’d like to reuse my original nuts rather than the use the repro Pal nuts, but the original nuts are an absolute bear to screw into the studs on the lamp housing. The original nuts are so difficult I worry the pot metal studs will break. I’d like to use a die to pre-thread the studs. But I can’t figure out the thread spec for the nuts. The GM part number listed in the ‘66 AIM for the nuts is 9420261. From a Google search and a search of the DB archives I can find no description of the thread specs for that nut. It’s not 1/4-20. The internal threads in the nut look coarser that 20 tpi But 5/16-18 screw is too big. The closest screw I can find is 1/4-14, but that is a very sloppy fit when I test it in the nut, so 1/4-14 doesn’t seem correct. Does anyone know the thread spec for GM 9420261? This has got me stumped.

Thanks,

Gary

Gary------


As I mentioned previously I'm away and can't get at my references (which might not answer this question, anyway). However, I think that GM #9420261 was a PAL nut. If so, the ones you pictured were either some sort of substitute of unknown part number or carry-over from a previous model year. Have you checked the 1964 or 1965 AIM's for part numbers for this application?

[David B.]

Re: Need thread spec for GM 9420261 nut

Part #9420261 is described as irregular self-threading faceted flange type stamped 1/4 steel nut with sealer (type SFW sealer style). The flange dia. is .594

[Richard M.]

Re: Need thread spec for GM 9420261 nut

Gary------


As I mentioned previously I'm away and can't get at my references (which might not answer this question, anyway). However, I think that GM #9420261 was a PAL nut. If so, the ones you pictured were either some sort of substitute of unknown part number or carry-over from a previous model year. Have you checked the 1964 or 1965 AIM's for part numbers for this application?

Joe you have a very good memory......


I did some online research. Part# 9420261 was superceded to 9422265 in January of 1965. Parts History Catalog P&A 30H January 1973

Part# 9420261 was discontinued, unsure of actual date, but reference Parts History Catalog 87A December 1981


I looked in my Standard Parts Catalog, no Part# 9420261, but the 9422265 in the Standard Parts Catalog 24 June 1971 is shown ...
for 1/4" stud.

I looked through my 63-67 AIMS.

1963 Section 12 Sheet C1 Item 6 3779316 See THIS, used on 1961-1963 Corvette, 1/4" Self Threading.

1964 Section 12 Sheet C6 Item 6 9420261
Note SYM (1) 3779316 "WAS 3779316". The date is (1x-xx-63), a hole is punched over the center of the date.

1965 through 1967 used 9420261

I suspect yours shown with the rotating flange may be the 3779316. However a guess as I could find no specs in the Standard Parts Catalogs I see. My Hardcopy 1929-1959 Standard Parts Catalog is not near me at this time.

Rich

[Gary B.]

Re: Need thread spec for GM 9420261 nut

Guys,

Thanks for the research. The Keps nuts from my car definitely had some dum-dum sealant under the flange.

After experimenting on one stud, I think I can get the original Keps nuts to screw on if I first run a Pal nut on and off the stud to create some threads for the Keps nut to grab onto and follow.

Gary

[Michael G.]

[Gary B.]

[Michael G.]

[Gary B.]