Home » Public Forums » GMCnet » Re: [GMCnet] 12pt inner drive bolt torque
| Re: [GMCnet] 12pt inner drive bolt torque [message #327817] |
Fri, 05 January 2018 13:19  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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I think that the bolts that Manny supplies with his 1 ton kits are highest
known grade, with special lockwashers. We have been using blue threadlocker
with squeaky clean threads and torquing to 55 foot pounds. BUT, THE DRIVERS
SIDE BOLTS PARTICULARLY NEED TO BE PERIODICALLY CHECKED after break in
miles. I have found quite a few on both the 1 tons and OEM front ends that
loosen a bit after some mileage.
We have experienced owners losing all the bolts on the drivers
sidewhen shops unfamiliar with front wheel drive systems have worked on
them.
Check those bolts regularly.
Jim Hupy
On Jan 5, 2018 10:44 AM, "John R. Lebetski" wrote:
Looking at charts for 3/8-24 I told him to stop at 50 with blue and split
spring washers
--
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] 12pt inner drive bolt torque [message #327819 is a reply to message #327817] |
Fri, 05 January 2018 14:06  |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Back in the day, this was discussed a lot. I don't think it's appropriate
work from torque charts for these special bolts, but rather to understand
the design intent. These bolts will experience fatigue as well as
loosening, and one reason to overstress them slightly is to relieve
internal stresses. Those internal stresses (left over from manufacturing)
yield, which results in more even stress and strain across the bolt. That
makes it more resistant to fatigue, and also a bit stronger. Also, it keeps
it from ever being unloaded. A bolt that loosens does so because part of
its loading cycle unloads it to the point where normal strain in the parts
can unscrew it. We learned about this with spoked wheels over the
years--the spokes have to be overstressed to relieve internal stresses at
the head, which is formed by swaging. Doing so minimizes fatigue failures.
I tightened mine to 62 ft-lbs when I installed Manny's kit, and I will
indeed check them when they've had some miles put on them.
I've never heard of one of these Grade "10" bolts breaking or stripping
threads either when being installed or subsequently, but I have heard of
them getting loose. And the book recommends quite high torque. I suggest
there's more to fear from under-torquing than over-torquing.
Rick "GM didn't use Loctite and the bolts didn't become loose with driving"
Denney
On Fri, Jan 5, 2018 at 2:19 PM, James Hupy wrote:
> I think that the bolts that Manny supplies with his 1 ton kits are highest
> known grade, with special lockwashers. We have been using blue threadlocker
> with squeaky clean threads and torquing to 55 foot pounds. BUT, THE DRIVERS
> SIDE BOLTS PARTICULARLY NEED TO BE PERIODICALLY CHECKED after break in
> miles. I have found quite a few on both the 1 tons and OEM front ends that
> loosen a bit after some mileage.
> We have experienced owners losing all the bolts on the drivers
> sidewhen shops unfamiliar with front wheel drive systems have worked on
> them.
> Check those bolts regularly.
> Jim Hupy
>
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| Re: [GMCnet] 12pt inner drive bolt torque [message #327860 is a reply to message #327817] |
Sat, 06 January 2018 08:19 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I think you're correct. I had to get 10 + rated cap screws with the same head surface as the twelve point bolts, they've worked fine after chasing the flange threads and putting a bit of blue LocTite<tm> on them. I used 65 ft-lbs and worried not for the bolts, but for the flange itself. Strip it and you have a problem. What are the chances of the flange threads giving up before the bolts?
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] 12pt inner drive bolt torque [message #327888 is a reply to message #327819] |
Sat, 06 January 2018 12:07 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Richard Denney wrote on Fri, 05 January 2018 15:06Back in the day, this was discussed a lot. I don't think it's appropriate work from torque charts for these special bolts, but rather to understand the design intent. These bolts will experience fatigue as well as loosening, and one reason to overstress them slightly is to relieve internal stresses. Those internal stresses (left over from manufacturing) yield, which results in more even stress and strain across the bolt. That makes it more resistant to fatigue, and also a bit stronger. Also, it keeps it from ever being unloaded. A bolt that loosens does so because part of its loading cycle unloads it to the point where normal strain in the parts can unscrew it. We learned about this with spoked wheels over the years--the spokes have to be overstressed to relieve internal stresses at the head, which is formed by swaging. Doing so minimizes fatigue failures.
I tightened mine to 62 ft-lbs when I installed Manny's kit, and I will indeed check them when they've had some miles put on them.
I've never heard of one of these Grade "10" bolts breaking or stripping threads either when being installed or subsequently, but I have heard of
them getting loose. And the book recommends quite high torque. I suggest there's more to fear from under-torquing than over-torquing.
Rick "GM didn't use Loctite and the bolts didn't become loose with driving" Denney
Rick,
As usual, you are largely correct, but to compare the drive axle capscrews to spokes would not be a good idea. The spokes of a spoked wheel have to be stressed to yield to, as you said, normalize the residual internal stresses. It also imbues an internal tension to make the part act as a spring over the extent of its expected working load.
I cannot locate the actual specification for the 12 point capscrews (394777), but the Mcmaster parts are a common aircraft fastener of the ASTM A574 grade. This makes them a heat treated high alloy part and as such, if you try to over stress one, it will fail in an almost glass fracture. The can be loaded to elongation only a very little bit, and I would be surprised if the 75#ft called for in the assembly manual will do that.
The lockwasher called out in the build book is not a common part, and the parts manual says "Procure Locally". Mine were a hardened part. A lockwasher is supposed to work by both locking into the burr that they cause on the mating surfaces and by supplying additional load when making the joint up. It is my experienced opinion that in this assembly, that is a lost cause.
Years back, I went around on this subject just for myself. I carry these fasteners as spares and a torque wrench because they could be very difficult to source on the road. We have a 23' coach, and my capability to carry spares is very limited. I tried, but I could not effectively cross-drill the heads. I wanted to safety wire those guys. If I could find drive on lockers, that would be good to, but those are kind of a specific part.
Fred and Emery....
The assembly manual calls out 12ea of the single part number.
Matt - working hard at not freezing his buns off -
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: [GMCnet] 12pt inner drive bolt torque [message #327892 is a reply to message #327888] |
Sat, 06 January 2018 12:36 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Matt,
Yes, you’re right, we won’t be micro-yielding these bolts. My point with
the example is that there are cases when threaded fasteners and assembled
parts are loaded to higher than usual levels to overcome particular strain
activity in the assembly. That only the bolts on one side loosen
demonstrates to me that the problem stems from strain activity. That said,
these bolts are specifically supposed to be replaced when removed and not
reused, which indicates to me that they are expected to be loaded close to
the yield strength of some part of the assembly.
Those ASTM A574 bolts have a rated strength of 170 ksi, and McMaster calls
them “Grade 9”.
The washers I have used are “high-collar” lock washers. I agree they won’t
really bite into the bolt.
Rick “who used what Manny sent for this year’s project” Denney
On Sat, Jan 6, 2018 at 1:08 PM Matt Colie wrote:
>
>
> Rick,
>
> As usual, you are largely correct, but to compare the drive axle capscrews
> to spokes would not be a good idea. The spokes of a spoked wheel have to
> be stressed to yield to, as you said, normalize the residual internal
> stresses. It also imbues an internal tension to make the part act as a
> spring
> over the extent of its expected working load.
>
> I cannot locate the actual specification for the 12 point capscrews
> (394777), but the Mcmaster parts are a common aircraft fastener of the ASTM
> A574
> grade. This makes them a heat treated high alloy part and as such, if you
> try to over stress one, it will fail in an almost glass fracture. The can
> be loaded to elongation only a very little bit, and I would be surprised
> if the 75#ft called for in the assembly manual will do that.
>
> The lockwasher called out in the build book is not a common part, and the
> parts manual says "Procure Locally". Mine were a hardened part. A
> lockwasher is supposed to work by both locking into the burr that they
> cause on the mating surfaces and by supplying additional load when making
> the
> joint up. It is my experienced opinion that in this assembly, that is a
> lost cause.
>
> Years back, I went around on this subject just for myself. I carry these
> fasteners as spares and a torque wrench because they could be very difficult
> to source on the road. We have a 23' coach, and my capability to carry
> spares is very limited. I tried, but I could not effectively cross-drill
> the
> heads. I wanted to safety wire those guys. If I could find drive on
> lockers, that would be good to, but those are kind of a specific part.
>
> Fred and Emery....
> The assembly manual calls out 12ea of the single part number.
>
> Matt - working hard at not freezing his buns off -
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
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| Re: [GMCnet] 12pt inner drive bolt torque [message #327910 is a reply to message #327892] |
Sat, 06 January 2018 15:48 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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G'day,
Here's some info from "back in the day."
**************************************************************************************************************************
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org On Behalf Of Rob Mueller
Sent: Thursday, August 28, 2008 9:56 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] sizes..
G'day,
I stopped by the shop where I buy my nuts and bolts today and purchased several grade 8 Allen Head Cap Screws (AHCS) (3/8" x 24 x 1 1/4") and some grade 8 (8 mm) hardened washers. Eight mm washers were purchased because 3/8" washers were too sloppy a fit.
The screws were manufactured by:
Brighton-Best Socket Head Screw Manufacturing Inc.
1665 Heraeus Boulevard
Buford, Georgia 30518-3383
The washers were in a bin without any manufacturer labels.
Using a small grind stone in my Dremel tool the holes in the washers were increased to a snug fit around the AHCS threads.
The threaded end of the AHCS were machined flat so the over all length (OAL) could be measured accurately.
I've got the whole front suspension system and drive system out of The Blue Streak so the left final drive flange was clamped in a vice using copper jaw liners to protect the splines.
The inner CV joint housing was placed on top of the final drive flange and one of the AHCS was screwed in finger tight to keep them together.
A 0.300 in diameter ball bearing was inserted in the socket head of another AHCS and the OAL was measured with a micrometer (Measurement #1).
A hardened washer was placed on that AHCS and it was screwed it into the inner CV joint housing 180 degrees opposite the one already installed without any lubrication.
The 3/8" x 24 AHCS takes a 5/16 Allen wrench. I put an adapter on my torque wrench (McMaster Carr P/N 5274A12 Easy-Read Adjustable Click-Style Torque Wrench 3/8" SQ Dr, 5-80 ft-lbs/5-110 NM Torque Range) and set to 45 ft lb.
The AHCS was torqued slowly keeping my arm at an angle of 90 degrees perpendicular to the wrench until it clicked.
The ball bearing was re-inserted in the AHCS socket and the OAL re-measured (see measurement #2).
The torque wrench was re-set to 75 ft lb and the AHCS was re-torqued.
The ball bearing was re-inserted in the AHCS socket and the OAL re-measured (see measurement #3).
The AHCS was removed from the flange, the ball bearing re-inserted in the socket and the OAL was re-measured (see measurement #4).
Measurement #1 = 1.6160
Measurement #2 = 1.6180 (bolt stretched 0.0020 at 45 ft lb torque)
Measurement #3 = 1.6218 (bolt stretched 0.0058 at 75 ft lb torque)
Measurement #4 = 1.6191 (bolt stretched 0.0031 from new length)
Copper based anti-seize grease was applied to the threads and between the bottom of the head and the hardened washer of a second AHCS and the test was repeated.
Measurement #1 = 1.6097
Measurement #2 = 1.6130 (bolt stretched 0.0033 at 45 ft lb torque)
Measurement #3 = 1.6183 (bolt stretched 0.0086 at 75 ft lb torque)
Measurement #4 = 1.6133 (bolt stretched 0.0036 from new length)
NEW SUBJECT:
Steve Rourke of Cinnabar advised that the OEM bolts P/N 394777 were available for $2.00 each. They also stock the lock washers P/N MS37 at $1.25 ea.
WHAT I'M GOING TO DO:
Twenty four (24) OEM bolts have been ordered from Cinnabar to fit to The Blue Streak and Double Trouble. When they arrive the heads will be drilled for safety wire using a cobalt drill bit. If they fit snugly 3/8" hardened washers will be used under them; if not 8 MM hardened washers will be reworked. The OEM bolts will be installed using a bit of oil for lubrication.
UNQUOTE
Update:
I received the OEM bolts from Cinnabar and drilled them for safety wire using a 1/16" cobalt drill. Despite going slowly and using lubricant I burned out two drills! The OEM bolts are harder than the hinges of hell! No I don't know where that is on the Rockwell scale! ;-)
****************************************************************************************************************************
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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