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| 7.62mm Crusader |
Trying to learn about torquing TTA vs TTY and cannot find anything stating markings on bolts to determine if they are TTA or TTY. How would one know the difference. Understanding TTY bolts should not be reused, I am puzzled. Is this a industry standard use for torquing bolts? I watched a German car mechanic use a torque wrench on a Audi axle shaft nut to 140 foot pounds. He followed with a piece of pipe rotating the nut 180 degrees. So the good ol fashion torque wrench cannot always apply the correct torque to all fasteners. Anyone have knowledge to share? Thank you. | ||
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Member |
Torque in some applications is a minimum, if it won’t hurt to be of the German Torque spec, “goodantight” then it simply won’t hurt to give it a quarter turn. In other applications where torque is paramount, fiberglass flanges, fine thread bolts, small bolts that you can actually stretch or break by hand, then I would never go an extra anything. In all my time working in plants we rarely replaced bolts unless it was for a precision application or they were simply eroded/stretched to shit, but most of my work involved 3/4”+ diameter bolts so we didn’t usually have to worry about overtightening. 3/4 or 1” impact and head on to the next flange. It’s also worth noting that it depends a lot on gasket types as well, when we were using spiral wound metal gaskets it wasn’t important, using some synthetic materials you can actually go beyond a good seal and squish the gasket out. If he is a professional putting a cheater bar on a nut to tighten then I would say it’s poor form. I certainly used cheaters to break stubborn bolts, double wrench, heat, he’ll I’ve had to torch hundreds of bolts, but going back together I’m not sure I’d ever do it. 10 years to retirement! Just waiting! | |||
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I thought that was German for "virgin."  . “Leave the Artillerymen alone, they are an obstinate lot. . .” – Napoleon Bonaparte http://poundsstudio.com/ | |||
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| Member |
Whoa, whoa, we talking about bolts or what?  10 years to retirement! Just waiting! | |||
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| 7.62mm Crusader |
Thank you Otto. I read that term Guten Tight. My friend replaced a starter motor for Mercedes Benz which had much like aluminum bolts. These were discarded for new. I am assuming these are TTY. If one has nothing to go by, say a shop manual, how would they know a nut or bolt gets torqued to which method? Probably Google...  | |||
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| Left-Handed, NOT Left-Winged! |
There is nothing about the bolt or markings on it that makes the difference. The size and grade of the bolt (grade determines tensile strength) are factors in the tightening process. Short answer: Torque is 80%-90% friction and thus a rather poor predictor of what you really want, which is tensile clamp load in the bolted joint as a result of elastic elongation of the bolt. In manufacturing, the goal is to control clamp load on critical joints, but the only way to do this is with strain gauges or ultrasonic measurement of bolt length before and after tightening, correlated back to the modulus of elasticity to determine load. In practice, you can control clamp load much better with torque and angle processes. You need a torque high enough to fully seat the joint and remove any springiness from gaskets and other soft parts until you have hard contact. After that threshold torque, controlling angle gets a much better correlation to clamp load than anything else, because thread pitch and degrees equal elastic bolt stretch. In marginal joints that are underdesigned to minimize bolt quantity and size, torque to yield results in the highest possible clamp load. In production we use very advanced electronic controlled systems that detect the onset of yield in the load curve and shut off. Each spindle in this kind of system is about $20K. A full cylinder head system is around $500K or more. I always advise design engineers to keep everything in the elastic region and avoid TTY because of rebuild/reuse of our products. TTY is for shit you never plan to rebuild, or for things where you can tightly control rebuild/reuse and ensure they replace any TTY bolts. Depending on bolt grade you may be able to go to yield more than once, but that is only with lower grades that have more yeild margin. High grades go from yield to neckdown failure pretty quickly and can only be used once. And when they design a joint that requires yielding the bolt, they are almost always using the highest grade bolts in the first place. | |||
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| 7.62mm Crusader |
Otto, I believe my friend applied the correct method for Audi axle shaft nut being 140 foot pounds via wrench then turn 180 degrees. He is Jordanian and speaks less than perfect English. He worked on heavy equipments, oil and gas drilling rigs in the UAE for many years. He was in charge of 22 mechanics. His passion is German cars but he repairs everything gas or diesel. Motor cycles included. | |||
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| Left-Handed, NOT Left-Winged! |
If that is the service spec then it should be good, as long as he replaced the bolts if required. | |||
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| Member |
Eah, maybe that is the spec. I’ve done some where it was a 1/4 turn after torquing, the cheater pipe is what gets me though. I’ve NEVER put a cheater pipe to tighten something. 10 years to retirement! Just waiting! | |||
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| 7.62mm Crusader |
That made my head hurt but was darn awsome. Do you work in engine manufacturing plant? . I will need to reread your post to make a better mental note. Thank you. | |||
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| 7.62mm Crusader |
Understood Otto. His methid tells me the axle shaft nut is torqued up near or over 300 foot pounds. Thats why the bar. It wouldnt matter so long as he only goes 1/2 turn correct? | |||
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| Member |
1/2 turn after 300 lbs sounds to me like WTF is there a torque spec lmao. But I don’t know the engineering sides of it either. The cheater bar isn’t about overtightening, like I said some things can’t be, it’s more about right tool for the job. I’ve used a 1” impact, then followed it up with a 3.5” hammer wrench with a 12 lb beater. Talk about tight. I can confirm tight lol, not always great with the precision work. But yes, 1/2 turn is a 1/2 turn, using a cheater to simply tighten is different, you’re right. 10 years to retirement! Just waiting! | |||
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| Left-Handed, NOT Left-Winged! |
Yes I did in the past, but now I oversee many of them around the world, and start up new ones... | |||
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| Left-Handed, NOT Left-Winged! |
Most service specs have 60, 90, 120, or 180 degrees because it correlates to one full or one half point/flat on a hex nut. In production we can use any angle we want so we just use what gets the required statistical process capability. | |||
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| 7.62mm Crusader |
Thank you Lefty. I have learned a bit more from you sir. And Otto, JR as he is known, torqued to 140 foot pounds with a wrench capable of 250. He then applied leverage to 1/2 turn. He stated 1/2 turn yields around 200 foot pounds. 140 + 200=? I have no idea what a Audi axle shaft nut gets torqued to but JR does. He is a extremly talented and knowledgable mechanic. I just watched him rebuild all hydrolic cylinders for a vintage Mercedes convertable top sports coupe. It was labor intensive. He was paid just over 2 grand where a Mercedes dealer garage would have charged between 4 and 5 thousand for the job. I personally would have never touched that car. Hydrolic rag top, why?  | |||
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| Member |
Man Lefty Sig is like Bill Gates and I’m the guy that says turn it off then back on. Two different levels man lol. But…but…I do know how to make some stuff tight lol. My cousin always gives me a hard time for not torquing my scope mounts, I always just do it by feel. 10 years to retirement! Just waiting! | |||
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| 7.62mm Crusader |
JR was telling me of rebuilding hydrolic cylinders for some huge machine which extended out 4 lengths. The giant cylinders had hex nuts to the tune of 2 feet across their flats. He explained his way of breaking those nuts loose and retightening. I could not find such huge cylinders on line. He is a interesting fella. | |||
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| Member |
We used to have a hydraulic torque wrench, was fantastic when it worked and saved lots of time but man, watch out for your fingers!!! Pretty sure it was made by the same people who make McDonalds ice cream machines. 10 years to retirement! Just waiting! | |||
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| Left-Handed, NOT Left-Winged! |
A good rule of thumb is 1 Nm per degree angle on most bolts you will see on a passenger car. So 180 degrees will result in 180 Nm or about 130 ft-lb on top of the torque you already applied. Bigger bolts are more like 2 Nm per degree but that's more appropriate for things our friend Powermad works on. | |||
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| 7.62mm Crusader |
There's them newton meters. To correct myself, that axle shaft is a bolt taking a 17mm hex key wrench. This is why JR used that length of pipe. That Audi is built like a take up front. Everything large and strong. Good quality. I also breifly read something about speed of torque but will just pretend that doesn't apply here. Me lil brain couldn't take it.. | |||
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