Subject: Re: [Mgs] Mgs Digest, Vol 68, Issue 5

From: Glenn Schnittke <[email-masked]>
Date: Mon, 07 Jan 2013 21:13:37 -0600

I've been working on this same question on an XPEG. The response from 
the old hands I've talked to has always been ' rearrange the nuts to 
best fit and  then shave the bottom of the rest on  a glass plate to fit'.

My thought on that is 'what keeps the stud itself in place'? There's 
never a torque value for bottoming the stud into the block. And there's 
no mechanical device to keep the stud from backing out, so what's 
keeping the whole assembly from backing out even with the cotter pin 
through the castellated nut or nylock or whatever you're using on the 
top side?

It's just one of those things that has puzzled me through the years - 
what keeps a stud from backing out when the nut holding whatever it is 
in place has a VERY specific torque value?

Moss's answer seems to be nylock nuts. I don't trust them. On top of 
having to figure the friction value onto the eventual torque value, I'm 
concerned about how the heat will affect the nylon over time. If I have 
to go to a locking nut I should rather trust an aircraft nut which has a 
metal-to-metal contact and I'd still have to factor in the friction to 
the eventual torque value.

I've seen all kinds of discussion on specific torque values for heads, 
main caps, conrods, etc. I've found nothing in any manual or discussion 
about the proper torque for bottoming a stud. I'm sure I'm going to 
excite all the engineers on the list by bringing this up, but why can't 
I just back off the stud just a little bit to move the cotter pin hole 
to meet the castle nut?

Glenn

> From: Duvall Video Productions<[email-masked]>
> To:[email-masked]
> Subject: [Mgs] loctite question
> Message-ID:<[email-masked]>
> Content-Type: text/plain; charset=us-ascii
>
> Anyone use red loctite instead of mechanical fasteners on main cap nuts?   I
> have an MPJG engine from a TA when I torque down the mains, the holes don't
> line up to the castle nuts for the wire.   I don't want to over torque and if
> I back them up to match the hole, I loose my torque.
>
> Suggestions?
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From: Barney Gaylord <[email-masked]>
Date: Tue, 08 Jan 2013 08:40:56 -0600

The answer for seating torque on the stud (any stud) is finger tight, 
not to exceed 5 lb-ft of torque.

The recpetical is a deep threaded hole, and the stud has a shorter 
thread.  The stud screws in until it runs out of threads on the stud, 
at which time the last incomplete thread on the stud will bind in the 
first thread on the receptacle.  Applying more torque at that time 
will damage the top female thread, raising a burr and possibly 
damaging a casting.  Too much torque on the stud could crack the casting.

Most studs (not all) will have course thread on the bottom end and 
fine thread on the top end.  The steeper ramp angle on the bottom 
thread will prevent the stud from turning while the nut is being 
tightened.  Otherwise prevailing torque on the last incomplete thread 
is all that prevents the stud from turning.  Binding on the 
incomplete thread is also all that keeps the stud from unscrewing 
when the nut is being removed.  This is why self-locking nuts have a 
tendency to unscrew the stud when being removed.  That also makes it 
difficult to back the nut off 1/4 turn if you want to re-torque it later.

If you back the stud out a little in attempt to synchronize location 
of a cross pin hole, chances are pretty good that the stud will 
rotate again and end up in a non-predictable final position when 
tightening the nut.

Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com

At 09:13 PM 1/7/2013 -0600, Glenn Schnittke wrote:
>I've been working on this same question on an XPEG. The response 
>from the old hands I've talked to has always been ' rearrange the 
>nuts to best fit and  then shave the bottom of the rest on  a glass 
>plate to fit'.
>
>never a torque value for bottoming the stud into the block. And 
>there's no mechanical device to keep the stud from backing out, so 
>what's keeping the whole assembly from backing out even with the 
>cotter pin through the castellated nut or nylock or whatever you're 
>using on the top side?
>
>It's just one of those things that has puzzled me through the years 
>- what keeps a stud from backing out when the nut holding whatever 
>it is in place has a VERY specific torque value?
>
>having to figure the friction value onto the eventual torque value, 
>I'm concerned about how the heat will affect the nylon over time. If 
>I have to go to a locking nut I should rather trust an aircraft nut 
>which has a metal-to-metal contact and I'd still have to factor in 
>the friction to the eventual torque value.
>
>I've seen all kinds of discussion on specific torque values for 
>heads, main caps, conrods, etc. I've found nothing in any manual or 
>discussion about the proper torque for bottoming a stud. I'm sure 
>I'm going to excite all the engineers on the list by bringing this 
>up, but why can't I just back off the stud just a little bit to move 
>the cotter pin hole to meet the castle nut?
>....

>>....
>>....

[email-masked]

---

From: "Clayton Kirkwood" <[email-masked]>
Date: Tue, 8 Jan 2013 12:01:10 -0800

That's interesting. But so often the stud or bolt in similar applications
gets chemically welded in - rusted. Nuts the same way. So, should the
threads be coated with an anti-seize or oil, or should they be "dry"? I
don't think loctite works very well with any anti seize.

Clayton

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Barney Gaylord
Sent: Tuesday, January 08, 2013 6:41 AM
To: Glenn Schnittke; [email-masked]
Subject: Re: [Mgs] loctite question - (Mgs Digest, Vol 68, Issue 5)

The answer for seating torque on the stud (any stud) is finger tight, not to
exceed 5 lb-ft of torque.

The recpetical is a deep threaded hole, and the stud has a shorter thread.
The stud screws in until it runs out of threads on the stud, at which time
the last incomplete thread on the stud will bind in the first thread on the
receptacle.  Applying more torque at that time will damage the top female
thread, raising a burr and possibly damaging a casting.  Too much torque on
the stud could crack the casting.

Most studs (not all) will have course thread on the bottom end and fine
thread on the top end.  The steeper ramp angle on the bottom thread will
prevent the stud from turning while the nut is being tightened.  Otherwise
prevailing torque on the last incomplete thread is all that prevents the
stud from turning.  Binding on the incomplete thread is also all that keeps
the stud from unscrewing when the nut is being removed.  This is why
self-locking nuts have a tendency to unscrew the stud when being removed.
That also makes it difficult to back the nut off 1/4 turn if you want to
re-torque it later.

If you back the stud out a little in attempt to synchronize location of a
cross pin hole, chances are pretty good that the stud will rotate again and
end up in a non-predictable final position when tightening the nut.

Barney Gaylord

At 09:13 PM 1/7/2013 -0600, Glenn Schnittke wrote:
>- what keeps a stud from backing out when the nut holding whatever it 
>is in place has a VERY specific torque value?
>
>to go to a locking nut I should rather trust an aircraft nut which has 
>a metal-to-metal contact and I'd still have to factor in the friction 
>to the eventual torque value.
>

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---

From: Charley & Peggy Robinson <[email-masked]>
Date: Tue, 08 Jan 2013 14:17:45 -0600

Now, that's darned interesting!  I have always wondered why some head 
studs were coarse thread on the end into the casting  and fine thread 
for the nut.  Just never bothered to look it up.

Thanks for the post,

CR
On 1/8/2013 8:40 AM, Barney Gaylord wrote:
> is all that prevents the stud from turning.  Binding on the incomplete 
> thread is also all that keeps the stud from unscrewing when the nut is 
> being removed.  This is why self-locking nuts have a tendency to 
> unscrew the stud when being removed.  That also makes it difficult to 
> back the nut off 1/4 turn if you want to re-torque it later.
>
> of a cross pin hole, chances are pretty good that the stud will rotate 
> again and end up in a non-predictable final position when tightening 
> the nut.
>
> Barney Gaylord
>> what keeps a stud from backing out when the nut holding whatever it 
>> discussion about the proper torque for bottoming a stud. I'm sure I'm 
>> going to excite all the engineers on the list by bringing this up, 
>> but why can't I just back off the stud just a little bit to move the 
>> cotter pin hole to meet the castle nut?
>> ....
>
>
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From: "PaulHunt73" <[email-masked]>
Date: Wed, 9 Jan 2013 08:38:53 -0000

Torque specs are usually given for oiled threads.

----- Original Message ----- 
> ... So, should the
> threads be coated with an anti-seize or oil, or should they be "dry"?

[email-masked]

---

From: "PaulHunt73" <[email-masked]>
Date: Wed, 9 Jan 2013 08:37:52 -0000

Coarse one end and fine the other is normally used in alloy blocks, can't 
see why cast iron would need a coarse thread.

----- Original Message ----- 
> studs were coarse thread on the end into the casting  and fine thread for 
> the nut.  Just never bothered to look it up.

[email-masked]

---

From: Barney Gaylord <[email-masked]>
Date: Wed, 09 Jan 2013 07:14:34 -0600

Want more confusion?  Head studs (in the block) have coarse 
threads.  Manifold studs (in side of the head) have fine 
threads.  Water valve studs (in side of the head) have fine 
threads.  Thernostat studs (in top of the head) have coarse 
threads.  In the gearbox, bolts for the remote shift extension 
housing to tail housing joint may be either coarse or fine thread 
depending on time of produvtion of the gearbox (and that's an 
aluminum housing going either way).

At 08:37 AM 1/9/2013 +0000, PaulHunt73 wrote:
>Coarse one end and fine the other is normally used in alloy blocks, 
>can't see why cast iron would need a coarse thread.
>....

[email-masked]

---

From: "Clayton Kirkwood" <[email-masked]>
Date: Wed, 9 Jan 2013 07:27:41 -0800

But can oiled threads be locked with loctite.

Clayton

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of PaulHunt73
Sent: Wednesday, January 09, 2013 12:39 AM
To: [email-masked]
Subject: Re: [Mgs] loctite question - (Mgs Digest, Vol 68, Issue 5)

----- Original Message ----- 

[email-masked]

[email-masked]

---

From: "Stephen West-Fisher" <[email-masked]>
Date: Wed, 9 Jan 2013 10:41:00 -0500

I'm not sure of the original premise, my experience is that torque specs are
given as dry clean threads unless stated otherwise. The addition of Loctite
or lubricant requires a reduction in torque or the fastener will be
over-stressed. 

--
Stephen West-Fisher
N4IK
-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Clayton Kirkwood
Sent: Wednesday, January 09, 2013 10:28 AM
To: [email-masked]
Subject: Re: [Mgs] loctite question - (Mgs Digest, Vol 68, Issue 5)

Clayton

-----Original Message-----

[email-masked]

---

From: Richard Ewald <[email-masked]>
Date: Wed, 9 Jan 2013 08:29:02 -0800

No, loctite is a glue.  Glue won't stick if there is oil present.

On Wed, Jan 9, 2013 at 7:27 AM, Clayton Kirkwood <[email-masked]> wrote:

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From: Charley & Peggy Robinson <[email-masked]>
Date: Tue, 15 Jan 2013 12:45:51 -0600

Dunno where you got your experience :-)   but every auto repair manual 
_I_'ve read specified clean, lightly oiled bolt threads, with the usual 
exception being spark plugs because they're pre-lubricated.

BTW;  how did you luck into that 1x2 call sign?

DE af5ao

[email-masked]

---

From: "Stephen West-Fisher" <[email-masked]>
Date: Tue, 15 Jan 2013 14:29:32 -0500

The standard torque values are clean and dry. Some applications specify
oiled, if they don't then they should be dry. The difference is a 25-30%
reduction in torque values if you oil them - unless of course it is
specifically stated to oil them in which case they have already taken it
into account. I have never seen a workshop manual which states that all
torque values are for oiled threads, so I'd appreciate it if you could send
me a reverence.

I believe the original question was about big end rod bolts and I believe
(without looking) the torque is specified as oiled.

The 1x2 is a vanity call, 1x2 and 2x1 calls disappeared here in the south a
long, long time ago. Previously I was N8KTZ and KQ4NO.

--

Stephen West-Fisher

N4IK

From: Charley & Peggy Robinson [mailto:[email-masked]] 
Sent: Tuesday, January 15, 2013 1:46 PM
To: Stephen West-Fisher
Cc: [email-masked]
Subject: Re: [Mgs] loctite question - (Mgs Digest, Vol 68, Issue 5)

Dunno where you got your experience    :-)           but every auto repair
manual  I've read specified clean, lightly oiled bolt threads, with the
usual exception being spark plugs because they're pre-lubricated.

DE af5ao

 
--
Stephen West-Fisher
N4IK
-----Original Message-----

Clayton
 
-----Original Message-----

[email-masked]

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