Fasteners are measured for length from the surface of the material being joined to the end of the fastener. For hex head bolts that means from under the head to the threaded tip of the bolt.
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Length
How fastener length is measured varies based on the type of head. As a general rule, the length of fasteners is measured from the surface of the material, to the end of the fastener.
For fasteners where the head usually sits above the surface such as hex bolts and pan head screws, the measurement is from directly under the head to the end of the fastener.
For fasteners that are designed to be counter sunk such as flat head screws, the fastener is measured from the point on the head where the surface of the material will be, to the end of the fastener.
For more information please see our Measuring Fastener Length page.
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Step 3 - Measure Length of Bolt
Since the length of the bolt is the last number in a metric measurement, you should measure for it last. Start from right below the head, including only the shank, and measure to the tip. This rule for bolt length holds true for most types, including cheese, hex, pan, socket, button, and low socket head types. Only measure the entire length if you are working with an oval or flat head variety.
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Tue Oct 03, 2017 9:55 am Post subject:
As Johnny used to say, more to come,
but here's what I have so far:
I have two flywheels. One came with a T-block disassembled,
the other is still in my jeep. Its apparent mine is thicker, so probably has not been ground to death.
First the Auburn clutch cover that came off my jeep.
Thickness at the bolt holes (not measured at the edge, and not where the washers deformed the edges of the bolt holes: .120
Was it .125 when new?
Flywheel #1 that came with truck engine. Thickness at the bolt holes: .942
Depth to thread from the pressure plate side: .260-.272
Flywheel #2 still in my jeep. Thickness at bolt holes: .980
Depth to thread from the pressure plate side: .288
The 5/8" lockwasher was measured at .0625 thickness.
It appears from these in the field, rudimentary, and amateur dimensions that the grip availability or total depth to thread from the clutch cover to the threads are as follows:
Using the worst case scenario I have which is the least worn flywheel,
Takeout bolt 1-1/16" long under head, looks to have .592" threaded into the flywheel.
The new, replacement bolt. .875 long under head, looks to have .4045" threaded into the flywheel.
Keep in mind the flywheels are tapered on the front side of the engine so care must be taken to ensure a decent reading at the bolt holes.
Also, the grip length is factored into the measurements, but is not considered a problem for either bolt as the .4425 grip availability with the most worn flywheel is deeper than the length of the grip on the longer bolt, being .375.
It would be greatly appreciated if anyone able to measure their clutch covers and flywheels could do the same so we could have a more comprehensive set of data to go by. And please feel free to check my figures. I'd actually feel better with someone checking my work.
By the way, is everyone feeling good about having .4045" of threads holding the pressure plate on as opposed to.592?
I'm wondering if somewhere back in the dim,
foggy someone screwed up and began using
that dimension as total length instead of length
under the head.
Only the "Someones" completely unfamiliar with the technical aspects of bolt measurements.
Anytime you call or email a hardware supplier and the person on the other end of the phone only offers you their list of bolts with overall lengths just hang up and call the next one on your list. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Wed Oct 04, 2017 7:07 am Post subject:
Hi Wes,
Yes, good advice.
What I did was order a set of bolts from a supplier by the Willys part
number. What I received were .77" long under the head. Until I saw the
length did not match my takeouts and the specs I had no reason to ask
about length. Or so I thought.
I am compiling a list of suppliers and what they offer versus the 1-1/16"
spec. I will post what I find when I receive the results.
It's quite possible Willys/Kaiser's internal supercedure list allows the later shorter bolt to sub for the earlier longer bolt. When their internal engineering folks agree to that it happens. But the new bolt they provide will have the new part number!
Now if the vendor you are using has decided to issue standard hardware sourced bolts that are incorrect in dimensions and labeling them with the original Willys PN and is not telling you this up front then that is fodder for legal action.
Have you contacted a Chrysler dealer yet to determine if any valid supersedure's have occurred to that original Willy/Kaiser part number 630129? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
What is appropriate thread engagement for something like
this application?
Full. The general industry standard is a minimum of 1 1/2 threads showing on the exit side of the joint. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Thu Oct 05, 2017 10:57 am Post subject:
Hi Wes,
Even using my takeout flywheel which has been turned to .980 at the bolt holes the later G740 and G758 specs at 1-1/16" do not match the thread engagement you noted.
The only bolt seen so far that matches was the original Ord 9 G503 at 1-1/4".
This is adding .0625 washer thickness and .120 cover thickness to the takeout flywheel thickness above = 1.1625
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Sat Oct 21, 2017 11:49 am Post subject:
This will probably wrap up my search for factory pressure plate bolts.
The previous chart referred to three bolts I took measurements from.
I had to renumber them below to match up with the lengths.
Below is a photo of four bolts.
#1 is an offering from RJ Fitzpatrick under WO-630129.
#2 is a Mr. Gasket offering #911.
#3 is an Army Jeep Parts offering under WO-630129
#4 is the takeout bolt from my M38.
Bolt #1=
Total length=1.05
Thread length=.625
Grip length=.215
Grip length in flywheel=.0325
Length of threads in flywheel=.38
Bolt #2=
Total length=1.215
Thread length=.66
Grip length=.32
Grip length in flywheel=.1375
Length of threads in flywheel=.53
Bolt #3=
Total length=1.195
Thread length=.665
Grip length=.335
Grip length in flywheel=.1525
Length of threads in flywheel=.53
Bolt #4=
Total length=1.315
Thread length=.68
Grip length=.4
Grip length in flywheel=.2175
Length of threads in flywheel=.61
A few notes.
I did not contact every vendor, assuming a representative sample would do for purposes of discussion.
Kaiser Willys replied to my query by sending their bolt measurements,
which match Ron's.
Midwest Military replied and John advised he only supplies takeouts, no new ones.
So there you have it. Good luck finding the G503 1-1/4" bolts,
as well as the factory spec 1-1/16" bolt, but you have several options
once you drop the the thread length requirement of 1-1/16"
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