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Posted (edited)

Hi All, i'm new here. I had a strange problem removing the vaccuum gauge from the dash frame on my 93 520H. The threaded studs appeared to be rusty. I cleaned them up but the nuts that retain the bracket were extremely hard to undo. It's like they were cross threaded. Eventually I had to hold the studs with locking pliers to get the nuts unscrewed. The nuts themselves screw onto the studs on the other gauges just fine so it's not a problem with the nuts. It's almost like the thread on the mounting stud was incorrect, metric eg, with an imperial nut forced on. Unfortunately the thread on the vacuum gauge studs is damaged and the studs rotate inside the gauge body now. Can I open up the gauge and possibly change the studs? Anyone else had this problem?

Cheers. 

Edited by tbirdsteve

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Hi,

 

Welcome to Red Square! Probably the easiest thing to do is find a used gauge to replace yours. But shipping to Oz would probably be the same or more for what you pay for the gauge. You might be able to use a gap-filling superglue to tighten the studs (Bob Smith brand is a good one) and then chase the threads with a die.

 

If the gauge was ever removed, there is the possibility that someone did use an Imperial nut.

 

Cheers,

 

John

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Posted (edited)

:text-welcomeconfetti: T-Bird.    I am surprised your gage even works. Most of them have the plastic hose fitting broken off.  I assume yours is OK and you were removing it to repaint the dash.

 

Not sure if there is enough room under the gage clamp to do this ,  but my idea is to cut off the damaged studs leaving enough to hold them with pliers while you screw on a  rod coupling nut.  Then screw in a new threaded rod jamming the old and new inside the coupling nut.    The stud would still turn inside the gage, but you would have a hex nut to hold it. 

12411.jpg

Edited by Ed Kennell
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The first 520's used a 915551 replaced by 3219-14 nut which I have recorded as having a 10-32 thread.

 

1993 and later list the nut as 915564 replaced by 3217-27 and don't know the size. Have in my notes it may have 8-32 threads.

 

A 10-32 nut will go onto a 8-32 screw and grip but very loose and would easily strip.

 

8-32 has a major diameter of .164"

10-32 has a major diameter of .190"

4.5mm has a major diameter of .177" and with a .75mm pitch equals about 33.86 threads per inch.

5mm has a major diameter of .196" and with a .80mm pitch equals about 31-3/4 threads per inch.

Wonder if the studs are metric on this gauge with a 10-32 nut on it?

 

Garry

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Wow, Garry you are amazing, sorry for getting off topic but some things need to be said! Thanks Garry

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I think you are correct Garry about it having metric threads with an imperial nut. All the other gauges have bronze coloured studs and nuts, this vacuum gauge has silver coloured studs and also the mounting bracket is different to the others. The bronze coloured nuts screw easily onto the other gauges. I bought this mower to use but I like it so much it's getting a resto before I use it. The previous owner really made some very poor repairs and mods and it needed a new dash frame and plastic cover which I found on US ebay along with lots of other parts. Yes the shipping was killer. I like Ed's idea about the coupling nut and might go down that road. 

Oh and thank you for the welcome gentlemen. 

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I'd get a set of thread gauges out , both imperial and metric along with a good master tap and die set . With a bit of work - those studs could be re-threaded a smaller size such as going down from 5mm to 4mm , ect. If the gauge case will come off (most are a die crimped outside lip , not easy to remove) the studs could be replaced with all-thread and locking nuts . Just some ideas .....

 

Sarge

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On 10/03/2017 at 5:07 AM, gwest_ca said:

The first 520's used a 915551 replaced by 3219-14 nut which I have recorded as having a 10-32 thread.

 

1993 and later list the nut as 915564 replaced by 3217-27 and don't know the size. Have in my notes it may have 8-32 threads.

 

A 10-32 nut will go onto a 8-32 screw and grip but very loose and would easily strip.

 

8-32 has a major diameter of .164"

10-32 has a major diameter of .190"

4.5mm has a major diameter of .177" and with a .75mm pitch equals about 33.86 threads per inch.

5mm has a major diameter of .196" and with a .80mm pitch equals about 31-3/4 threads per inch.

Wonder if the studs are metric on this gauge with a 10-32 nut on it?

 

Garry

Well done Garry, the stud size is indeed .164" and is 8/32 unc thread. Somebody mentioned that they have a plastic hose fitting, well this one has a brass fitting so may be a later replacement. Many thanks for your assistance. 

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