Dramas with 5/16 head fasteners

Mark F · Nov 19, 2011

I was refitting my 850 head last weekend. Got it on o.k. and was bringing every thing nicely up to torque. Got to about 18 ft/lbs on the front right 5/16 nut when I got that sinking feeling that all is not well. All of a sudden it starts turning without getting any tighter. Ugh!!!!!! You know what that means. So anyway I left it over the week and then this morning I pulled the nut out to check it and it seemed o.k. so put it back in tightening it up and ping. It had snapped the stud. Bugger. :cry: Anyway pulled the head got the broken stud out and took it to our local Norton man and got 2 new studs to replace the old originals(?) Get home put everything back together and I am getting back up around 20 lbs again when it all starts to get a bit slack. :evil: This time the damn stud had stripped! :evil: :evil: The new studs were about 3 mm shorter than the ones that came out and I could see that on the one that was o.k. the thread was not all the way through the nut.
Anyone had similar problems? What the heck is going on here. :?

Matt Spencer · Nov 19, 2011

Bu**er . Its bu**ered , Whats wrong ? youre going Nuts .

. Er .

Pulled the thread out of the nuts when the first studs gave out , or half the thread .
so , approaching a decent tension , it turned to Custard .

Unless you used New Nuts too . . . in which case , you Have got a Problem . . :lol:

Being all methodical , it pays to pre trial fit nuts etc , lubed . And feel if all the threads are to 3 microns tollerance or the like .
No binding or wobble .Particularly if its not a quick off / on replacement opperation .

Plus , theres all differant grades of steel & bolts / nuts . El Cheapo fittings from the local hardware arnt realy necesarilly ' Engineering ' standard.As regards Engine Fastenings .

Then theres the Olde ZEN , & the Finger Tips Art . Often doesnt pay to work on em when in a mood of dark dudgeon , or inbibeing excess Ale . For some reason .

Save that for the Football . :wink:

bmwbob · Nov 19, 2011

I've seen where the studs are a tad long and can strip threads when the studs are installed from hitting bottom.

Guido · Nov 19, 2011

If you are talking about the 2 studs in the front which thread into the cylinders then you'll notice that the threads are longer on one end of the stud. The short side goes into the cylinders, if you put the long threads into the cylinders then you'll be short of threads for the head nuts.

RennieK · Nov 19, 2011

Check that there aren't extra washers pressed against the head from before. They can get stuck there and forgotten about.

rpatton · Nov 19, 2011

Guido said:
If you are talking about the 2 studs in the front which thread into the cylinders then you'll notice that the threads are longer on one end of the stud. The short side goes into the cylinders, if you put the long threads into the cylinders then you'll be short of threads for the head nuts.

+1 DAMHIK :roll:

Mark F · Nov 20, 2011

Thanks for the replies.
I'm thinking it's more a case of bad luck than anything else.
Matt no el cheapo local hardware fittings. Genuine Norton stuff. To be honest I didn't know you could get Cycle thread nuts and bolts from the local hardware. :lol: All fitted well. Not too loose not too tight.
Bob they weren't too long that's for sure.
Guido I know what you mean about the short and long thread. The originals were around the right way and the new ones were about the same each end, but flat on the end that goes in the barrels. They weren't bottoming out either. The one that snapped did so about 5mm from the end directly under the nut.
Rennie the head has been reconditioned by the local Norton man. The original washer recesses were machined out to take thicker stainless washers. Nice stuff. I hope deep enough to allow for the thicker washers.
The one thing I did notice is that he new ones were slightly shorter than the originals which wouldn't have helped with the stripping out.
It's just a big PITA to have to pull the head off again and I don't particularly like all the additional stress I am putting the rest of the hardware through. :evil: :evil: :evil:

Rohan · Nov 20, 2011

When you take them out, just out of curiousity clamp the base of one in a vice or whatever and see if you can bend it, easily ? (wear eye protection, just in case).

Torontonian · Nov 20, 2011

Genuine new studs.No Stainless.

Rohan · Nov 20, 2011

Yes I read that.
Be interesting to see if they are soft though....

(Or how accurate the torque wrench is)(remember that aircraft mechs have their torque wrenches checked/calibrated, very regularly.)

bwolfie · Nov 20, 2011

Rohan said:
Yes I read that.
Be interesting to see if they are soft though....

(Or how accurate the torque wrench is)(remember that aircraft mechs have their torque wrenches checked/calibrated, very regularly.)

FAA requires annual certification checks of calibrated equipment used on aircraft. 9 times out of 10 adjustment is needed. If in doubt, a new HF torque wrench is cheap insurance.

Torontonian · Nov 20, 2011

Stainless for pretty and anti-rust applications but not best for serious torquing down .Torque readings no longer accurate.

rpatton · Nov 21, 2011

Maybe Joe could look into these studs. They seem a little hinky, add them to the list?

http://www.andover-norton.co.uk/Pirate%20Parts.htm

Mark F · Nov 21, 2011

Here's a pic of the little varments!

Original nuts top and bottom.
New replacement stud. Genuine. Stripped end. Slightly shorter than original.
Old original. O.K.
Snapped original.
No stainless hardware other than machined washers.
I bought a new certified torque wrench on the way home from picking up the new studs.
I haven't given them the bend test yet. I want to see what our man here thinks first.

Matt Spencer · Nov 21, 2011

They mayve employed the bloke that designed the japanese wireing looms ,
they've figuerd 2 mm short , means every 500 they save a metre of steel .
its called the economy of scale . :roll: :lol:

Rohan · Nov 21, 2011

Should we be a trifle concerned that the replacements are not black.
That says they haven't been heat treated ??

So the torque wrench that snapped that one was new ?
Or that was with a previously owned wrench ?

Mark F · Nov 21, 2011

Rohan the one that snapped was done using an old torque wrench. It had not done a lot of work though.
I wondered about the color difference.

Matt Spencer · Nov 22, 2011

Is it possible / rational to fit oversize 3/8 and drill barrel . Were Domi 3/8 . Whats the world coming too .

8)

rpatton · Nov 22, 2011

Mark,
Can you tell whether the threads on the new stud are rolled or cut?

Mark F · Nov 22, 2011

rpatton said:
Mark,
Can you tell whether the threads on the new stud are rolled or cut?

Hmmm. Good question that. No I am not really sure. I''ll have a closer look and see if I can tell.

Dramas with 5/16 head fasteners

Similar threads