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What thread is this?


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  #1  
Old 03-14-2019, 01:58:59 AM
cobbadog cobbadog is offline
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Default What thread is this?

On the front steering arm of our David Brown Cropmaster tractor the threads are an unusual size. I bought new ball joint a LH and Rh thread and the old ones screwed off by hand and the new ones went on by hand. My problem is I simply want to know what thread this is.
It measures 11/16" OD and my thread gauge using Whitworth 55' shows it is 18TPI G - 5/16" as stamped on the gauge.
My thread chart does not identify it as Whitworth or UNF or anything. Any help in identifying is much appreciated. I am not in any trouble with the threads or anything, I just want to know what thread it is.
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Old 03-14-2019, 07:01:03 AM
QuickJ QuickJ is offline
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Default Re: What thread is this?

It is 11/16th -18 UNS A standard Special thread.
You can buy Taps and dies for it at McMaster Carr. and find out all of the details on it in machinery's handbook.

Jim in Minnesota
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Old 03-14-2019, 06:23:05 PM
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OTTO-Sawyer OTTO-Sawyer is offline
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Default Re: What thread is this?

Threads can be almost any size & pitch imaginable.

Small factory I worked in making parts for Harley Davidson and several other companies had a few oddballs like 1"-32 and 2 1/4"-32 which is Really Fine for a 2 1/4 inch end-cap. (I think That might have gone on the end of the cylinder for some automatic door closers we made other parts for).

Strangest Taps I have is a 3/8-32 I picked up at an auction someplace 25+ years ago, and an old 1/2-12 where the norm is 1/2-13 or 1/2-20

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Old 03-14-2019, 06:28:36 PM
cornbinder89 cornbinder89 is offline
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Default Re: What thread is this?

Quote:
Originally Posted by QuickJ View Post
It is 11/16th -18 UNS A standard Special thread.
You can buy Taps and dies for it at McMaster Carr. and find out all of the details on it in machinery's handbook.

Jim in Minnesota
I may be wrong, but I think that is the thread Cummins used on the 855 head bolts, Odd size and TPI
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Old 03-14-2019, 07:54:05 PM
Pat Barrett Pat Barrett is offline
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Default Re: What thread is this?

Cummins thread is correct. It's also the thread on the arm, end of a 8N Ford generator. It's not too odd a thread. Also, Harley used a 1/4"-24 thread somewhere up on the handle bars on something. 1/4-24 was once a common thread. As stated, so many thread pitches on various things.
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Old 03-14-2019, 08:11:01 PM
eddie bedwell eddie bedwell is offline
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Default Re: What thread is this?

Hi Team,
my guess would be that the Thread is an SAE Standard form selected for Tie Rod Ends.
The SAE have laid down many standardised sizes for engineering components over the years.
Link is to a Chart from a supplier of such items--the thread similarities for various sized tie rod ends can be noted.
The tractor designer would select a determined/calculated size end suitable for his application from a given Standard set of ends offered by outside makers.

http://www.bareco.com.au/files-tierod-un1

Hope this helps.
Cheers,
Eddie B.
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Old 03-14-2019, 09:14:34 PM
bartlett0815 bartlett0815 is offline
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Default Re: What thread is this?

On my 1944 Harley-Davidson WLA that odd 1/4" thread is used to hold the voltage regulator on the front, right half of the engine casing. If I remember correctly it is also used on some shifter spacer thingy or something in the transmission.
Kevin in NC
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Old 03-14-2019, 10:58:23 PM
JoeCB JoeCB is offline
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Default Re: What thread is this?

Quote:
Originally Posted by bartlett0815 View Post
On my 1944 Harley-Davidson WLA that odd 1/4" thread is used to hold the voltage regulator on the front, right half of the engine casing. If I remember correctly it is also used on some shifter spacer thingy or something in the transmission.
Kevin in NC
Be really careful when encountering what appears to be 1/4 thread on older American machines. There were two American Standard threads that can get you in trouble. #14 - 20tpi measures .242 and #16-20tpi measures .268. Both deceivingly close to the common 1/4 - 20.


Joe B
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Old 03-15-2019, 06:55:29 AM
QuickJ QuickJ is offline
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Default Re: What thread is this?

Quote:
Originally Posted by JoeCB View Post
Be really careful when encountering what appears to be 1/4 thread on older American machines. There were two American Standard threads that can get you in trouble. #14 - 20tpi measures .242 and #16-20tpi measures .268. Both deceivingly close to the common 1/4 - 20.


Joe B
Interesting, I have some #14-20 taps, but I have not seen or encountered #16-20.

Jim in Minnesota
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  #10  
Old 03-17-2019, 12:44:32 AM
cobbadog cobbadog is offline
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Default Re: What thread is this?

A big thanks to everyone who replied, it does help me to figure our what it is.
Eddie, your chart coutesy of BareCo is very interesting. The only David Brown listed is a different size to mine but the MF and Ford list as the same OD but different offsets from the end of the shank to the centre of the ball joint.
This information gives me a hint as to what has me stumped on my new ball joints against the old. The old ones when screwed all thwe way on by hand meaure 20mm overall width less than the new joints measured the same way.
I cant help thinking I have been supplied MF joints instead of lets say the Ford ones.

Again, thanks for the replies and interesting info on the different 1/4" threads mentioned too.
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Old 04-07-2019, 05:06:17 AM
Henry Maudslay Henry Maudslay is offline
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Default Re: What thread is this?

Otto-that 1/2 12 is probably a 1/2" Whit tap that has found its way across the pond!
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Old 04-08-2019, 09:29:20 PM
Mikechoochoo Mikechoochoo is offline
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Default Re: What thread is this?

1/2 12 was very common before the size was standardized at 13 threads per inch. I have a 1/2 12 tap from the Great Northern Railroad .
Mike
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Old 04-09-2019, 11:47:14 PM
tdmidget tdmidget is offline
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Default Re: What thread is this?

Quote:
Originally Posted by Henry Maudslay View Post
Otto-that 1/2 12 is probably a 1/2" Whit tap that has found its way across the pond!

Whitworth threads are characterized by the 55 degree flank angle. The threads per inch is immaterial as you could cut a Whitworth thread with any number you want, just as a unified thread can be any number of threads per inch and any diameter, as long as the thread form is a Unified thread form.
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