| [ Total Views: 724 | Total Replies: 17 | Thread Id: 67096 ] |
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 sikdub
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| posted on January 20th, 2008 at 03:35 PM |
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HELP! 1800 Clutch Bolts
Hey All,
I'm getting ready to put my 1800 into my 74 camper but have been held up by a problem. I have got 7mm 1.0mm thread Grade 8 high tensile bolts and
when I try to tighten them up to 24ft/lb they will snap a few mm down from the head. What am I doing wrong?
The ones on the clutch beforehand were done up without washers so I have tried both with and without washers. I have tried lubricating the underside
of the heads on the bolts with oil to reduce friction but no success. I am tightening the bolts bit by bit from side to opposite side but still
manage to break at least one if not more. I have tried this with 2 different clutches also. The bolts will screw all the way into the flywheel
without the clutch but break once they get some pressure on them. I have removed the burrs on the clutch bolt holes as well.
Any help is appreciated. I've never come across this before.
Steven
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Andy
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| posted on January 20th, 2008 at 09:21 PM |
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Only thing I can think of is check the torque is correct? (can you cross check with other books, or check your torque wrench?).
The only book I have handy covers the 1700 motor and calls for 18ft/lb.
Secondly high tensile bolts generally come in grade from 8 to 12, so perhaps try a stronger bolt. Just don't strip the flywheel.
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1303Steve
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| posted on January 20th, 2008 at 10:22 PM |
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Hi
I cant find any data on the 7mm bolts, but the 8mm ones that were used on 1700 & 2 litres only needed 2.5 mkg or 18 ft. lb.
Steve
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 vw54
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| posted on January 21st, 2008 at 05:52 AM |
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they should be 8mm x 1.5 thread same as on a stock Beetle 1600
use the washer as it spread the load and acts as a locking mechanism as well
the heads of the bolts should have the number 8 or similar stamped on them
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dangerous
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| posted on January 21st, 2008 at 06:55 AM |
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For M7 x 1 fasteners:
8.8 grade should not exceed 11 ft.lbs with a drop of oil on the thread.
I would estimate:
10.9 grade 14 ft.lbs
12.9 grade 18 ft.lbs
If you use ANY lube you must REDUCE the torque or the bolt will stretch or break.
Any excess lube should be removed, I like brake Kleen.
Even on 10.9 grade 8mm bolts I would be scared to use 24 ft.lbs.
...perhaps with 12.9 grade, but never with 7mm diameter.
| Quote: | Originally
posted by westi
That's mad Alan.
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1303Steve
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| posted on January 21st, 2008 at 10:15 AM |
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| Quote: | Originally
posted by vw54
they should be 8mm x 1.5 thread same as on a stock Beetle 1600
use the washer as it spread the load and acts as a locking mechanism as well
the heads of the bolts should have the number 8 or similar stamped on them
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Hi
1800 cc Kombi motors only used the 7mm bolt, all other air-cooled VWs used 8mm.
Steve
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type3lover
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| posted on January 21st, 2008 at 10:44 AM |
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Are they too long perhaps?
.
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sikdub
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| posted on January 21st, 2008 at 11:18 AM |
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Interesting, thanks for the replies. The bolts aren't too long as they will screw all the way into the flywheel without the clutch attached. Can
someone please have a look in their manual to check torque settings definitely for me. I may have misread it. I considered grade 12 bolts but
qustioned whether or not this was necessary due to the old bolts being grade 8 also.
Cheers
Steven
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1303Steve
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| posted on January 21st, 2008 at 01:37 PM |
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Hi
I have Bentley Kombi manual, it doesn't list the 7mm bolts, only the 8mm ones. I always used 18ft. lb. on the ones on my old bug, which used a 215mm
1800 flywheel.
Steve
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dangerous
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| posted on January 21st, 2008 at 02:01 PM |
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11 ft lbs is what I found for grade 8.8 as posted above.
this is for 7mm x 1mm pitch.
That came from a workshop manual.
| Quote: | Originally
posted by westi
That's mad Alan.
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sikdub
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| posted on January 21st, 2008 at 05:46 PM |
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Ok i now have got the Gregorys in front of me and can see where I went wrong. 18ft lb is 24Nm. Don't i feel like a dumbass..
Thanks for the help
Steven
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1500S
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| posted on January 21st, 2008 at 07:48 PM |
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| Quote: | Originally
posted by vw54
they should be 8mm x 1.5 thread same as on a stock Beetle 1600
use the washer as it spread the load and acts as a locking mechanism as well
the heads of the bolts should have the number 8 or similar stamped on them
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Just for reference, do you mean M8 x 1.25 Dave?
DH
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vw54
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| posted on January 22nd, 2008 at 06:21 AM |
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yeah i can never remember the pitch on metric threads
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1500S
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| posted on January 22nd, 2008 at 07:47 AM |
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A good chart to have hanging in the workshop! Below is the ISO coarse. The link to the ISO fine is at the bottom of the page.
DH
http://www.newmantools.com/tech/threadm.htm
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dangerous
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| posted on January 22nd, 2008 at 09:09 AM |
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| Quote: | Originally
posted by sikdub
Ok i now have got the Gregorys in front of me and can see where I went wrong. 18ft lb is 24Nm. Don't i feel like a dumbass..
Thanks for the help
Steven
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That still sounds high.
It is correct for 8mm bolts.
Is that what Gregories quotes for 7mm?
What grade is on the heads, and where did you get replacements?
Might be handy to know.
| Quote: | Originally
posted by westi
That's mad Alan.
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dangerous
A.k.a.: Dave Butler Muffin Man
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| posted on January 22nd, 2008 at 09:10 AM |
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http://dodgeram.org/tech/specs/bolts/M_bolts.html
| Quote: | Originally
posted by westi
That's mad Alan.
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vw54
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| posted on January 22nd, 2008 at 10:08 AM |
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good work charts
Ive got a thread gauge around here somewhere
i proberly have been overtightening them for years just do them up with a socket n bar never broken one yet I have broken a flywheel bolt
must have been a weak spot LOL
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sikdub
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| posted on January 25th, 2008 at 12:52 PM |
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| Quote: | Originally
posted by dangerous
| Quote: | Originally
posted by sikdub
Ok i now have got the Gregorys in front of me and can see where I went wrong. 18ft lb is 24Nm. Don't i feel like a dumbass..
Thanks for the help
Steven
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That still sounds high.
It is correct for 8mm bolts.
Is that what Gregories quotes for 7mm?
What grade is on the heads, and where did you get replacements?
Might be handy to know.
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The grade listed on the heads is 8.8 and the bolts were purchased from Coventry Fasteners. They are the same as the ones that were holding the clutch
on beforehand. Am just waiting for some more to turn up now.
Steven
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