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Calling Pedantic Mechanic(s) [message #261573]

Thu, 11 September 2014 09:36

cbryan

Messages: 451
Registered: May 2012
Location: Ennis, Texas

Karma: 3

Senior Member

Rob, et al,

ARP fasteners say, I think, that for accurate torque, we should lubricate the threads in a cleaned environment. Be sure to lubricate under the head of the bolt if it is a cap screw.

I think that the engine builders on the assembly line just use the as-machined threads and hardware, with residual cutting oil and assembly lube on the threads and don't pay attention to the underside of cap screws.

So, what is the correct way? And what happens to torque when Loctite is used? That means clean threads.

Or does it make a particle of difference?

Thanks for your kind response.

Carey

Carey from Ennis, Texas 78 Royale, 500 Cadillac, Rance Baxter EFI.

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Re: [GMCnet] Calling Pedantic Mechanic(s) [message #261577 is a reply to message #261573]

Thu, 11 September 2014 09:48

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

Lubricant will affect torque a great deal. It also will affect the cure
time on thread lockers. Most GOOD torque charts will give values for
specific fasteners wet or dry. Loctite also has a primer in a spray can
that smells like MEKP but we all know that stuff is on the banned substance
list in most places, so it probably is not.(grin). When you spray fasteners
with it, they dry completely devoid of any lube oil. Is this good or bad?
Beats the heck out of me. I torque the drive flange bolts to 75 foot
pounds, and I use BLUE THREAD LOCKER. I prefer Loctite brand, but there are
others out there a bit cheaper. The really expensive stuff is their
pneumatic line sealant. $65.00 a bottle. I use the stuff on all air line
fittings instead of teflon tape. Makes me cringe when I drip even a small
amount on the floor.
Jim Hupy
Salem, OR
78 GMC Royale 403

On Thu, Sep 11, 2014 at 10:36 AM, Carey Bryan wrote:

> Rob, et al,
>
> ARP fasteners say, I think, that for accurate torque, we should lubricate
> the threads in a cleaned environment. Be sure to lubricate under the head
> of the bolt if it is a cap screw.
>
> I think that the engine builders on the assembly line just use the
> as-machined threads and hardware, with residual cutting oil and assembly
> lube on
> the threads and don't pay attention to the underside of cap screws.
>
> So, what is the correct way? And what happens to torque when Loctite is
> used? That means clean threads.
>
> Or does it make a particle of difference?
>
> Thanks for your kind response.
>
> Carey
> --
> Carey from Ennis, Texas
> 78 Royale, 500 Cadillac, Rance Baxter EFI.
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> GMCnet mailing list
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Re: Calling Pedantic Mechanic(s) [message #261591 is a reply to message #261573]

Thu, 11 September 2014 10:47

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

cbryan wrote on Thu, 11 September 2014 08:36

Rob, et al,

ARP fasteners say, I think, that for accurate torque, we should lubricate the threads in a cleaned environment. Be sure to lubricate under the head of the bolt if it is a cap screw.

I think that the engine builders on the assembly line just use the as-machined threads and hardware, with residual cutting oil and assembly lube on the threads and don't pay attention to the underside of cap screws.

So, what is the correct way? And what happens to torque when Loctite is used? That means clean threads.

Or does it make a particle of difference?

Thanks for your kind response.

Carey

We routinely measure clamp loads with lubricant in various spots and dry as well. Interestingly the sweat off your nose and simply the fact that you have touched the part with your fingers supplies enough lubrication to make a big difference in torque required.

Bob de Kruyff
78 Eleganza
Chandler, AZ

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Re: Calling Pedantic Mechanic(s) [message #261604 is a reply to message #261573]

Thu, 11 September 2014 11:33

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

cbryan wrote on Thu, 11 September 2014 10:36

Rob, et al,

ARP fasteners say, I think, that for accurate torque, we should lubricate the threads in a cleaned environment. Be sure to lubricate under the head of the bolt if it is a cap screw.

I think that the engine builders on the assembly line just use the as-machined threads and hardware, with residual cutting oil and assembly lube on the threads and don't pay attention to the underside of cap screws.

So, what is the correct way? And what happens to torque when Loctite is used? That means clean threads.

Or does it make a particle of difference?

Thanks for your kind response.

Carey

Oh Judas Priest...

Carey,

You have just pried open a can of worms that has plagued manufacturing since threaded fasteners were first used.
I still have the ASTM report that delineates the fifty six (Yes - 56) variables that significantly affect the torque-tension relationship.

Lubrication in the fasteners is critical. Cleanliness is critical. When an engine line receives a bin of fasteners, those fasteners were cleaned and sprayed with a specific lubricant at the supplier. I have worked on a few of these.

Fastener tension is what it is all about. Tensioning by torque and torque alone has about a +/- scatter of 35%. GOT THAT? So the scatter is 70% of the total? Yeapers, it sure is. This is why almost all production is done as torque and turn. This is why I always tell people, if you feel like it is going poorly, stop. If a manufacturer has a specified method. Stay with it, even if you think it is in error. To say that everything matters is an understatement of the actual situation.

This is a lot of what I am going to try to explain in the paper I am trying to put together for a future tech session. It is taking a lot longer to put together than I had initially expected because I keep having to go back and put things back in that had hoped I could leave out so as to make the entire picture less daunting.

I hope this was some clarification. If I have raised another question, I will be back after a short stop.

We are at the Quad-cities Botanical in Rockford Il right now.

Matt - Ex - International Fastener Institute and ASTM Fastener Technology Committee

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: Calling Pedantic Mechanic(s) [message #261616 is a reply to message #261604]

Thu, 11 September 2014 14:38

Otterwan

Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...

Karma: 0

Senior Member

Don't overthink it. Most GMC parts are not rocket science. Torquing to specs should be fine 99% of the time, as long as you didn't dip the bolt in 90 weight first.

1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."

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Re: Calling Pedantic Mechanic(s) [message #261669 is a reply to message #261616]

Fri, 12 September 2014 02:19

Bullitthead

Messages: 1411
Registered: November 2013

Karma: 5

Senior Member

'Tis very simple: lubricate where binding surfaces must slide against each other, and if the fastener is to be glued in place(Loctite, etc.),use no oil on portion of threads that will be glued. The glue will provide the lubricant for those threads--like Bob said, it doesn't take much.
If you don't want the fasteners glued together or stuck in their bores or corroded from dissimilar metals with added water:
One of the best lubricants we used on the Lear Jet wheel bolts was a spray on gray metal coating that allowed the bolts and washers to slip enough to get accurate tightening torque without coating the whole bolt with goopy anti-seize that would fly off on touchdown/takeoff spin up and get in the brakes, even if applied as thinly as possible.

Terry Kelpien ASE Master Technician 73 Glacier 260 Smithfield, Va.

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