The number is the manual will be for dry studs - if that is ever achievable. Lubricated studs / nuts will require less torque to avoid over tightening.
48's point is interesting though. I have twisted off rusted bolts where there is so much friction that you are actually twisting the bolt rather than stretching it. You would need quite a lot of twist on such a long stud to fail it in torsion rather than tension.
Interesting......
Despite all this we hear that people are going up to 20 lbs/ft on these.
Although the front corner studs look thinner they are effectively pretty much the same working diameter. No less than the thread root of the 8mm portion.
http://www.dansmc.com/torque_chart.htm
G
1964 Honda Dream CA78 Rebuild-storationRight, 48. I should be prudent. Would anti-seize be appropriate for lube or a drop of oil, or some of my Lithium compound grease (white, blue, or red)?
Mine: '74 CB750 K4 -- Hers: '64 CA78
Had: '75 CB550 K, '79 CT90 I'm in a quandary. All of these variables are causing me perplexity. I'd like to know (rhetorically speaking) what Honda specified on the studs themselves. Did Honda use studs that could only handle a few more psi than they'd get at the max specified torque? Or did they, like bridge engineers, specify something that would handle three times the max tension they imagined would be possible? Or is it somewhere in between? That's really the question.
How much more tension, at 16.6 lb-ft, would be imparted by lubing the threads? What is the cost/availability of new studs, should one be destroyed? How many of you are thinking to yourselves, "Why are you talking about this instead of just getting a thicker gasket in there?" Hmmm. G-Man, In looking at the link you provided, what grade are our studs? Or do they pre-date this grading system?
Mine: '74 CB750 K4 -- Hers: '64 CA78
Had: '75 CB550 K, '79 CT90 I like to avoid "stiction" where possible so I have always just used a dab of motor oil and never had an issue. The motor oil won't eliminate friction, but it will give the studs a more consistent tension and you better enjoyment while torquing. You won't fail them in tension at the stated torque values. I wouldn't use anti-seize or anything more slippery than plain old motor oil.
-48 Bob
They say that you can tell if you are talking to a genuine Engineer when you ask him a question. The answer will usually come back - "It depends". I only have 32 years as a professional Engineer so that is what you might get. Yes - there will be a factor of safety. On that chart I linked to, I'm guessing that Honda studs will be either 8.8 or 10.9. But, don't forget that these studs will have been torqued up several times before by people with various degrees of skill and / or knowledge. If you break one it may not be your fault, although it would be your problem. High risk fasteners such as big end bolts on plain bearing engines will be given 'wet' torque figures and you would be expected to use new bolts at each rebuild. These bolts are not in that category so there is a bit more leeway. For really high performance engines the "torque" value is not specified but the bolt stretch is. That is a much more reliable way of determining the tension in the bolt which is what the design engineer is trying to achieve. Because the bolts are steel and the barrel and head are aluminum the working tension will be higher than the cold tension in the bolt too. That will be factored into the design (one would hope). That can be calculated by the expansion coefficients of the two metals and their cross sectional areas. An expert like LM will have developed a feel for this but even he cannot know the history of the bolt before he got there. There is an element of pot luck. I would stick with the book value (dry) which is about 16 foot-lbs and work up from there with caution. The 'thin" studs measure about 6mm where the minor diameter of an M8 thread is 6.3 to 6.6 so the thin studs are probably a little more vulnerable. Any nicks or dings on the stud or previous bends (I have seen a few bent ones) add to the risk of breakage. I have some new studs and you see them on eBay from time to time. Don't forget that they are in aluminium at the bottom and in theory this is the weak point. Again that doesn't seem to be borne out in practice. Not sure what the extra tension will be by lubing the thread but "it depends" on which lube you use and where you put it. Lubricating the thread is one thing but lubricating the interface between nut and washer is another. That's where a proportion of the friction force (the thing that prevents the nut undoing) will come from. An all you wanted was a yes-no answer!!! Can you guarantee that your torque wrench is calibrated? In railroad workshops in the UK, torque wrenches have to be tested on a calibration fixture every time they are used. Some of those take two guys to heave on. Don't forget to have fun. G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
Bob, absolutely have fun!
Now, I know everyone wants to know where I got the 21 ft/lb figure. NOT from the book, which I've read - and yes, it's what 48 says it is. Ed told me he always torques the heads he works on to 21 ft/lbs. As you can imagine, being inexperienced and a girl to boot, I went with his figure. Here's hoping your retorque works, Bob! Hey, half the fun of these bikes is trying to decide "what's gonna go wrong next?" ;) 1965 CB77 305 Super Hawk
1989 NT650 Hawk GT 1981 Yamaha XJ550 Seca Bob
This is quite nice. http://www.cncexpo.com/MetricBoltTorque.aspx This suggests a) a lubed bolt will need to be torqued at around 20% less than a dry one or conversely will give a higher clamp load (33%) b) the values shown are about 75% of the proof load of the bolt. The proof load is the load is the load at which the bolt ceases to behave elastically. i.e. extension becomes permanent. G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
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