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2 unrelated questions

 

First looking for the Csk washers that are fitted to the screws holding the boot trim in 6's and also used to be fitted to the rear cockpit trim on side screen cars, I thought they were called cup washers but they aren't quite the same and the kits that moss sell now are all flat washers.

 

Second prop/drive shaft bolts Moss list them as being 1 3/16 long and there £2 each it on line I clean get 1 1/4 bolts considerably cheaper I'm guessing a 1/16 isn't going to make any difference but thought I would ask before all my UJ's lock up!

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Graham, Regarding propshaft/UJ bolts you must remember that S-T specified a special bolt for this application that was not a standard size. You will find that a cheaper bolt such as you describe will be of a slightly smaller diameter and will therefore not be a tight fit for its application. The use of a bolt with a specific part number such as 107960 means that the bolt has features that make it markedly different from a standard bolt. These bolts need to be fit for purpose don't fit cheap alternatives.

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Thanks Rob
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Hi Graham,

 

suggest you take note of Bob's advice, he is spot on . . . . . for the sake of saving a fiver on nuts'n'bolts you can trash your transmission.

 

Some of the S-T specific bolts and nuts are common to Land Rovers also, but stick with the better calibre suppliers not the bargain basement Landie folks if you want appropriate quality.

 

Cheers

 

Alec

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Hi Graham,

the propshaft bolts are produced for the shear strength.

If it has a special number then that is because it is special.

If you want to not use the correct bolt then you can use a high tensile bolt but it needs to be rated high enough so that its shear propertise are equal to the correct bolt.

 

Shear strength in a HT bolt is apprx 60 - 80% of the tensile strength.

 

However you don;t know what shear strength you want.

Buy the correct part - you skin flint :P:P

 

Roger

Edited by RogerH
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I had the task of re-sourcing these many years ago.

 

The plain shank length of 107960 is greater than the equivalent pound shop grade item. It is also a controlled diameter. I cannot recall what spec it was.

 

Meaning the drive flange will have a plain shank locating it the driven flange, rather than a bit of thread, which would be a smaller diameter.

 

 

 

Peter W

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Chaps many thanks for all your feedback who knew bolts could be so exciting ! and yes on examining my old bolts in the garage its clear that the shoulder of the bolt is longer than might be expected on a 'normal' bolt.

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Hi Graham,

you raise a very important point on mentioning the length of the shank.

If you look at an aerospace bolt and where it fits.

The shank (plaijn part of the bolt under the head) fits into the full depth of the hole.

That way ALL the parts that make up the joint are reacting against a smooth consistent surface.

Between the nut and the material of the joint you fit a plain washer. This gives room for all the threads to do their thing and life is happy.

If the plain shank is too short then parts of the joint will be rubbing against the threads and possibly cutting in - this could lead to cracking and or serious wear.

 

Why would the shank be too short. These b;**dy stupid automotive bolts have too long a thread. You could get almost half a dozen nuts on them

So you buy a bolt that is externally long enough and so the shank is too short.

You could cut the thread down but you then lose the plating.

OR you could do it properly and make the shank the correct length and have enough thread for the application 1.5 x thickest nut depth or so.

 

I wonder what a Saab car bolt length looks like.

 

Roger

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Looking at the head stampings, Drive/Prop shaft bolts are not 'special' in the true sense of the word but are chosen because of higher tensile/shear strength quality than 'ordinary' bolts! Oh and manufactured to tighter tolerances!

I agree with Roger, but it must be the aviation link regarding bolt shank length. I was surprised at some of the suspension bolts with the amount of thread on what could be termed a critical bolted joint.

Interestingly I've had my beemer in bits and all the bolts of the suspension on that would actually be termed setscrews where the thread goes all the way up to the head. But then again they nail something together and do not 'work' in their own right.

However back to the drive shafts rather than nyloc nuts all metal stiff nuts are much better! So, 'Aerotight' as they are called or the AN125 series. However they are wallet damaging! Personally I used Loctite on the bolt thread, just a small drip halfway down the protruding bolt thread so the nut engages with the Loctite as its wound down but it doesn't get on the nylon of the nut.

 

As for Saab .... they're just wooden pegs! :P:ph34r::P

 

 

Dave

Edited by DaveN
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