G'day,
Here's some info from "back in the day."
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-----Original Message-----
From: gmclist-bounces On Behalf Of Rob Mueller
Sent: Thursday, August 28, 2008 9:56 AM
To: gmclist
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! ;-)
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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
