CV or Constant Velocity Joint Bolt

[CrRusty]

Can anyone explain why VW used recessed hex or recessed 12 point heads on the bolts that attach the axles to the vehicles? Why not use grade 8 bolt? Thx. ---R---

[KTPhil]

I don't know, but in general one advantage of the type they used is a larger, full circle surface to press on the washer and boot cap. A regular hex bolt might have to have a larger head, and the clearance is tight there. The same clearance issue means you can use a 12-point bit on an air ratchet, where a socket probably won't fit.

[cellobus1]

The 12-pt. "triple-square" bolts give you more options to put the torque wrench on, if it's not a ratcheting torque wrench. Twice as many as an Allen head bolt or regular bolt.
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1976 unrestored daily driver Standard bus, "Stella"
formerly, 1959 Standard bus
formerly, 1973 transporter which was 4 years old when it taught me to drive

[Wildthings]

A Class 12.9 bolt is a step up from a Grade 8 bolt. Why VW didn't use a larger diameter bolt is the question.

[Abscate]

Much better strength in the head on an internal hex, torn, or triple square than a bolt , too.
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.ssS!

[timvw7476]

The VW Group has been engaging in a love affair with internal drive cap
screws for some decades now...
I even retrofitted some to a Honda CT-90 crankcase so I'm infected too.

[Abscate]

6 M8 bolts probably have a total shear strength of 2000 kg, way over the force they feel,

Engineering is using sufficient plus margin size fasteners, not the largest fastener that will fit.
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.ssS!

[Glenn]

The head size is smaller with a triple square than a hex bolt.
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Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

[Jetfxr69]

Almost lost another shaft the other day. Luckily decided to get under and adjust brakes up a little and noticed it. All 6 bolts (triple squares) on the trans side were backing out and 3 of 6 on wheel side were as well. Probably only a few miles from slinging it right off. I did NOT locktite them earlier, so my fault. Retorqued with the proper bit and when they come out this winter for rebuild, will locktite upon reinstalling. My new predeparture check item now. Oil, lights, battery cable tightness, any drips or puddles, and now shaft security. Clear prop- contact!
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You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer. Zappa

‘77 westy Seamus
‘76 tintop Crusher
‘77 westy The Judge
‘72 tintop bastard westy Hudson

[Spike0180]

not sure, but it makes drilling them out once they strip at 48yrs old really easy. And the mk4's use the same bolts, so you can find them new. Which is awesome.
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Brutis Patches Izabich: 1970 VW Transporter - 1776cc DP
Current State: Projects never truly end...
Location: Grosse Pointe, Michigan
Other cars: 2003 F150, 2003 Jetta GLI vr6-6sp

Sambastic: adj; the quality of being nit picky, elitist, expecting everyone to do things the way they believe is best with no regard to situation, "sambastic"

[Abscate]

[Wildthings]

[Randy in Maine]

[SGKent]

just as a side note, Grade 2, 5, 8 bolts are SAE measurements. They are not metric. Metric uses a different grading system. Since VW are metric the first observation would be that a grade 8 bolt would not thread into a metric bolt hole.

Metric use (strength # / then size of metric thread used):

4.6 / M5 - M36
4.9 / M1.6 - M16
5.8 / M5 - M24
8.8 / M1.6 - M36
9.8 / M1.6 - M16
10.9 / M5 - M36
12.9 / M1.6 - M36

Equivalent:
US Grade 2 = approx metric 5.8
US Grade 5 = approx metric 8.8
US Grade 8= approx metric 10.9
US Grade above 8 (A574) = approx metric 12.9

There are also different kinds of bolts. Meaning some hold two things together so the force is lengthwise in the bolt, and some are shear bolts, where they take a load where two things slide or hang. A sheer bolt usually has a smaller threaded area but is very beefy where the load is. Say you have two pylons and a piece hangs between them. That would take a shear bolt.

When I told my machinist mentor Bill that I wanted to learn the automotive machinist trade from a race engine builders perspective, he said he didn't have any openings. The guy was known all over the racing circuit, building Indy engines, Vee and SuperVee engines, CART engines, drag engines both for unlimited and unlimited marine racing. I went in a couple times and swept up the shop as a volunteer, and while doing it one day noticed Bill looking thru all his bolt bins for a specific kind of bolt. I took it upon myself to reorganize and sort thru all the fasteners he had to save the shop time. After about a day Bill came over and started going thru all the different kinds of markings, pitches, shanks etc., so that by the time I was done after 10 days he had given me a pretty good lesson on fasteners. Then he offered me a job. When he passed away a couple years ago he did so peacefully in retirement. But everyday I miss that shop and the people in it. They turned out the best engines in the world. When Bill was done training me after about 3 years, my masterpiece was to restore a Ferarri Dino motor for a friend. Restore means making it as good as the day it left the Ferrari factory.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Wildthings]

[Zed999]

[SGKent]

Golly gee Ma. I thought I schorr tightn'd those bolts. Maybe I shud a thrown them in the clothes washer after fixing it like Pa was talking about. He said something about the washer not having torque or something like that. Not sure what he meant but maybe the motor was weak or somethin'. What time lunch be ready? I sure am a hungry. You see who Daisy Mae is a being courted by these days? Some guy picked her up in a VW bus making a clanking as it drove off. Daisy Mae isn't that kinda girl. Boy is he in for a surprise when he reaches for her and she a wallops him with that a rollin pin.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Wildthings]

[SGKent]