Power Antenna Lower Mount Thread Size?

[Richard M.]

1965-1966 I couldn't see it in a search.....

This is stripped badly so I need to Heli-Coil it. It's appears it is a 1/4 inch bolt that is used. Please, could someone look it up for me? I have no reference AIMs available. I just need to know if it's course or fine thread.... 1/4-20 or 28?

This one at the pick pointer.....

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Thanks, Rich

[Richard M.]

Re: Power Antenna Lower Mount Thread Size?

A buddy notified me it's..... 1/4-20.

I'm all set.
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[Gary B.]

IMG_9120.jpg

That screw is GM 9418423, which is 1/4-28. It says qty=3, which must include the one that goes up into the bottom of the motor case.

Gary

[Richard M.]

Re: Power Antenna Lower Mount Thread Size?

Thanks Gary,

Ahhh, Yes the underneath one up into the case. Interesting, this had a 1/4-20 round head, my buddies had same, so maybe both were corroded and they did a switcheroo.

Is your antenna mounted in the car? Is it a hex or round head? AIM shows hex, but just curious.

My 1938-1966 P&A has no such number in Standard Parts, so it must've been a assembly line only part. Maybe Delco supplied them as part of the antenna "assembly".

[Gary B.]

IMG_9121.jpg

Mine has an indented hex head, anchor headmark, Gr. 5.1.

Gary

[Gary B.]

Re: Power Antenna Lower Mount Thread Size?

Rich,

PS: I think there is some issue about making sure that that screw going up into the motor case is not too long so as to interfere with something internal to the motor case.

Another interesting tidbit is the engineering print says the “use and shape of indentation optional” for that screw. At one time I owned a 65/66 power antennae that was restored by Dale Smith at OEM Glass. That one came with a trimmed hex head bolt, not indented.

Finally, I’ve never heard of anyone finding a slotted screw at that location.

Gary

[Richard M.]

Re: Power Antenna Lower Mount Thread Size?

Gary, Thanks for this detailed information. It's one area I never thought of as I've not ever researched this hardware.

I'll have to borrow a 1/4-28 Heli-Coil kit as I don't have one.

Rich

[Gary B.]

[Richard M.]

Re: Power Antenna Lower Mount Thread Size?

Gary a while ago I was reaching for my caliper to measure it and got distracted. I'll get the depth next trip back to the shop, like in half hour or so. I need to do something else too.

[Richard M.]

Re: Power Antenna Lower Mount Thread Size?

Here are some numbers...

Depth of casting hole. 0.600"
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Depth before hitting gear. 0.825"
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[Gary B.]