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Old 09-06-2012, 01:34 PM   #1
329s
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Default Bolt size clarification...

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

Last edited by 329s; 09-06-2012 at 03:12 PM.
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Old 09-06-2012, 02:16 PM   #2
Bob C
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Default Re: Bolt size clarification...

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.

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Old 09-06-2012, 05:01 PM   #3
Tom Wesenberg
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Default Re: Bolt size clarification...

I think the "2" is the class of fit.
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Old 09-06-2012, 07:18 PM   #4
Dan in MI
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Default Re: Bolt size clarification...

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.
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Old 09-06-2012, 09:19 PM   #5
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Default Re: Bolt size clarification...

Just a guess. Could it mean 5/16 x 24 tpi x 2" long with a 1-3/8" shoulder. Ya think ?
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Old 09-06-2012, 09:59 PM   #6
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Default Re: Bolt size clarification...

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Quote:
Originally Posted by jimvette59 View Post
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
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Old 09-06-2012, 09:59 PM   #7
329s
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Default Re: Bolt size clarification...

Quote:
Originally Posted by Dan in MI View Post
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
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Old 09-06-2012, 10:00 PM   #8
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Default Re: Bolt size clarification...

Quote:
Originally Posted by Tom Wesenberg View Post
I think the "2" is the class of fit.
Tom,

What do you mean by "class of fit"?

Pluck
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Old 09-06-2012, 10:19 PM   #9
Marco Tahtaras
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Default Re: Bolt size clarification...

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

http://www.fordbarn.com/forum/showthread.php?t=29804
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Old 09-06-2012, 10:33 PM   #10
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Default Re: Bolt size clarification...

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
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Old 09-06-2012, 10:47 PM   #11
Tom Wesenberg
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Default Re: Bolt size clarification...

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.
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Old 09-06-2012, 11:02 PM   #12
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Default Re: Bolt size clarification...

Quote:
Originally Posted by Marco Tahtaras View Post
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.

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Old 09-07-2012, 07:27 PM   #13
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Default Re: Bolt size clarification...

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.
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