Bolt size clarification...

[329s]

When looking at bolt A-20740 Engine rear support bolt IN THE PARTS PRICE LISTS, which gives the size as 5/16-24 (2 x 1-3/8)...what does the "(2 x 1-3/8)" mean?

I know it has to do with the length of the bolt, 1-3/8 I think...but what does the "2" mean?

These are the bolts that attach the Engine rear support to the frame...three (3) per side.

Thanks.

Pluck

[Bob C]

Pluck,
If this is for the AA the 1932 parts book shows bolts are 21492-S2 5/16" -24 x 1 7/8" for 28-30
and 22245-S2 5/16"-24 x 1 1/2" for 30-31.

Bob

[Tom Wesenberg]

I think the "2" is the class of fit.

[Dan in MI]

The S2 is the finish of the fastener. I believe S2 is just oiled. Ford still uses the same way of calling the finish today.

[jimvette59]

Just a guess. Could it mean 5/16 x 24 tpi x 2" long with a 1-3/8" shoulder. Ya think ?

[329s]

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Originally Posted by jimvette59

Just a guess. Could it mean 5/16 x 24 tpi x 2" long with a 1-3/8" shoulder. Ya think ?

NO...the bolt is 1-3/8 inches in length.

Pluck

[329s]

Originally Posted by Dan in MI

The S2 is the finish of the fastener. I believe S2 is just oiled. Ford still uses the same way of calling the finish today.

Dan,

It has nothing to do with the finish of the bolt.

Pluck

[329s]

Originally Posted by Tom Wesenberg

I think the "2" is the class of fit.

Tom,

What do you mean by "class of fit"?

Pluck

[Marco Tahtaras]

Here is a link to a thread you started more than 18 months ago.

http://www.fordbarn.com/forum/showthread.php?t=29804

[Preacher]

could it be 'quantity 2 required' my July1, 1931 parts price does not show the 2 in the description only: 5/16-24 x 1-3/8

[Tom Wesenberg]

I recently had to buy some spare taps and bought class 3 taps, which gives a threaded hole much more precision than the Craftsman tap I was using, which I'd guess might have been a class 1 tap.

[329s]

Originally Posted by Marco Tahtaras

Here is a link to a thread you started more than 18 months ago.

http://www.fordbarn.com/forum/showthread.php?t=29804

JEzzzzz...I forgot about that one...heck, I can't remember what happened yesterday let alone 18 months ago...Thanks Marco.

Pluck

[KR500]

I believe Tom is correct that the 2 is a class fit. When buying and using taps for example we would use GH3 taps which are designed to give 75% thread when used with the proper tap drill size. When building tooling which would get heat treating we would tap with GH5 taps which cuts the thread oversize. Class 1 fits would be a fit where the bolt or stud would be a tight but, useable thread and would appear to give an unshakeable type fit. Years back Champ used to market oversize studs to be used on rear axles because the originals would be too loose after a time in service. Always examine your taps or when purchasing taps. I have seen guys trying to start left hand taps and get nowhere, remember some A horns use a left hand nut on the armatures.