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Clutch nut torque?

Aloha everyone,

It's been a while and some of you may or may not remember me from previous posts, questions and discussions. None of you probably remember that for quite some time me and my bikes has lived on different sides of the country, 50 km apart.
Well, that has now changed and we all live close to each other!

So today I started sorting out the last little details on my -47 M21 before I will start riding it. Number one was a loose clutch nut. I am talking about the small one inside of the spring, the one that holds the basket on to the taper. It was all loose and wiggly and the bowler was scratching the tranny-cover.

Now to what torque is this nut to be tightened?

I had a look around the tech-section but failed to find the answer, maybe I was blind. If there is not a defined torque any rough approximation by at knowledgable person would be appreciated. Kinda boring nut to have go undone while riding.

Best regards,

Simon

Re: Clutch nut torque?

It happened to me once. I used Loctite thread locker and my battery operated rattle gun, it's been fine ever since. Torque settings weren't really detailed back then. Ron

email (option): ronpier@talk21.com

Re: Clutch nut torque?

Ron Pier
It happened to me once. I used Loctite thread locker and my battery operated rattle gun, it\\\'s been fine ever since. Torque settings weren\\\'t really detailed back then. Ron
I know, but I was kinda hoping someone would have a rough figure to go on. But locktite it might be in the end.

Best regards,

Simon

Re: Clutch nut torque?

I don't have a torque figure for that one...Torque figures, such at those I use for the head bolts, I arrived at by a combination of experimentation and looking at the torque figures for more modern bikes with the same diameter head bolts as a rough guide...

So, if you started off with the clutch nut torque figure for say, an A65 or T140 you might be in the right area...

I do it up (very) tight with a socket and T Bar whilst applying the rear brake to stop it moving (with the bike in gear.)...I've not had one come undone yet. I don't use Loctite....

You can apply plenty of force as both the shaft and the nut are hardened...Ian

email (option): ian@wright52.plus.com

Re: Clutch nut torque?

Thanx Ian and Ron!

Googled and found the number 80lbft -dear lord!
I cant remember but I suppose that's what I tightened the clutch nut on my Bonneville to as well.

This one now is at about 30-40 lbft, we'll se how it goes...

/Simon

Re: Clutch nut torque?

I'd have thought 80ft/lbs a bit high...but that's only a gut feeling...

There are no torque figures for the M20 as they pre date the general introduction of the 'modern' torque wrench, so any figures on the internet for a given application aren't BSA figures and should be approached with a 'critical eye' and a sensible level of caution and analysis...Ian

email (option): ian@wright52.plus.com

Re: Clutch nut torque?

Same gut feeling among us then Ian.

And yes I know about the torque figures being of later dates. I once saw a 45 minutes film from the Triumph factory that now seems have disappeared from the internet. Anyway, in the film the process of building the 500 OHV twin was thoroughly explained and not a torque wrench in sight in the entire factory.

/Simon

Re: Clutch nut torque?

Simon of Sweden
Same gut feeling among us then Ian.

And yes I know about the torque figures being of later dates. I once saw a 45 minutes film from the Triumph factory that now seems have disappeared from the internet. Anyway, in the film the process of building the 500 OHV twin was thoroughly explained and not a torque wrench in sight in the entire factory.

/Simon
Simon,

i would have thought in those days in when there were experienced fitters and engine builders around that torque wrenches would not be needed. Good fitters would know how far to tighten a bolt nut or stud up to its correct torque just by feel. You can have 2 exact size studs and nuts but made of a different grade of steel and hardening and the torque figures for these will be completely different.
I think your figure for your clutch nut will be ok as long as you have good matching tapers. I always check my tapers and if slightly out i lap them by hand with some very fine grinding paste which takes minutes. Check for top clearance on your keys as well as these can hold your centres off the taper as well.
Modern torque wrenches can be miles out as people tend to leave them loaded up from their last job, this damages the spring bar. You should always return a torque wrench back to the zero figure or the bottom figure when you have finished with it.

Tim W

Re: Clutch nut torque?

I do not have a modern torque wrench. :wink:

Re: Clutch nut torque?

[.. Good fitters would know how far to tighten a bolt nut or stud up to its correct torque just by feel. You can have 2 exact size studs and nuts but made of a different grade of steel and hardening and the torque figures for these will be completely different...']

Those two statements rather contradict each other I'd have thought...How would a fitter picking up a bolt know what steel it was made of etc.?...And if he didn't know how would he then know how much to tighten it?...

It is certainly true that you develop a feel for when a bolt is at the point where it begins to stretch (prior to ultimately snapping) or when a thread is in a similar condition (prior to stripping). However, I don't think anyone could do up a bolt, or particularly a series of bolts, to a specific torque entirely by feel..I've spent most of my life in engineering and I'm fairly sure I couldn't do that....

In the case of M20 head bolts for example it is difficult to do up all 10 bolts to exactly the same tightness, particularly if a composite head gasket is used which by it's nature has some misleading 'give' in it as it is tightened...
There is also the facet of human nature that dictates you will probably give the bolts a little extra 'tweak' rather than risk them not being tight enough...

Personally, I always use a torque wrench to get an evenly applied 28-30ft/lbs on the head bolts...Single fasteners or fasteners where even tightening is not so important I do tighten by 'feel' but I have no idea how many ft/lbs have been applied....Ian

email (option): ian@wright52.plus.com

Re: Clutch nut torque?

The old school mechanic in the Garage workshop where I trained as a motor mechanic would continually say "Tight is tight" Anything over that and you're probably stretching the threads. Like Ian, probably one of the few times I use my torque wrench is on the head bolts, which is more about getting them tightened evenly. Ron

email (option): ronpier@talk21.com

Re: Clutch nut torque?

Ian Wright
[.. Good fitters would know how far to tighten a bolt nut or stud up to its correct torque just by feel. You can have 2 exact size studs and nuts but made of a different grade of steel and hardening and the torque figures for these will be completely different...']

Those two statements rather contradict each other I'd have thought...How would a fitter picking up a bolt know what steel it was made of etc.?...And if he didn't know how would he then know how much to tighten it?...



Maybe i did not word this correctly, could be something to do with my education. Maybe i should not have mentioned its correct torque, i would have thought that garages in the 30s and 40s would not have had access to any kind of torque wrench or torque figures to what they were working on. The fitter or engine builder would have learned through experience how far to tighten a bolt nut or stud before it stretched. He also would be able to tell that a stud or nut was made from better grades of steel then others, just like we can tell the difference from fixings from China made from chocolate compared with our graded fixings.
I was lucky at the time but did not know it. I left school and got a job at a large engineering company in the early 70s. Went through the standard 5 year apprenticeship making the usual scribing blocks engineering jacks, clock stands, scrapers made from old files you know the stuff. I still have most of these and it set me up for the rest of my working life. I do have a couple of accurate torque wrenches but don't use them often unless an important torque is quoted. I have over the years built a feel on how the tighten a fixing but like you Ian if i was to tighten 10 bolts on a composite head gasket i would not be able to gauge unity of the fixing.
Aso in my original post i wonder just how accurate our old torque wrenches are these days, at least using them you can get everything up to a figure but is that figure really what it says.
Hope this corrects my post.
Tim W

Re: Clutch nut torque?

I can't argue with that..As it happens I followed a very similar trajectory, starting my apprenticeship in 1970 with Brown and Sharpe, the machine tool manufacturer...

Unfortunately, all the 'apprenticeship tools' I made were stolen along with a lot of other stuff when someone broke into my garage in the late 70's...

I have a couple of torque wrenches but only really use one for the BSAs...That's a 0-50ft/lbs one that I purchased specifically to tighten M20 head bolts as I felt I wasn't doing a good enough job 'free hand'....

The 1970 Triumph T120R that I built a couple of years back had quite a few specified torque settings and I tended to follow those as I didn't really see a reason not to whereas I haven't used one at all on the Gold Star I've just finished....

As the bulk of the bikes I've had were from the 40's through to the early 60's (the end of pre unit in BSAs case) torque wrenches haven't figured that much over the years and I have relied mainly on experience and 'feel'.

Twin cylinder big end bolts and a few fasteners on the Square Four were notable exceptions...

Regarding the accuracy of torque wrenches I tend to accept that if they aren't old and have been treated well, they should be reasonably accurate...When I worked at British Aerospace for example, everything was subjected to testing and calibration on a regular basis but I guess in the private workshop you have to stop somewhere!! :laughing: ...Ian.

email (option): ian@wright52.plus.com

Re: Clutch nut torque?

Ron Pier
The old school mechanic in the Garage workshop where I trained as a motor mechanic would continually say \"Tight is tight\" Anything over that and you\'re probably stretching the threads. Like Ian, probably one of the few times I use my torque wrench is on the head bolts, which is more about getting them tightened evenly. Ron
Wow, Ron, that brought back a rush of memories. My late father said 'tight is tight,' all the time when we worked on cars together. He'd served in the Netherlands' Marine Corps in the motor pool. After the liberation, he was 'reassigned' from resistance work to fight the Japanese in the Pacific. When the bomb dropped some months later, the government sent him to fight the rebellion in Indonesia instead of back home. Anyway, I always thought 'tight is tight' was his own. I had no idea it was an old school expression.

email (option): moatjon [ at ] aol.com

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