Questions about rear brake drum removal

[Keith_M]

Thanks for the suggestions. I usually use the 6-point sockets, but haven't ground the tip on any, which will require a grinding wheel due to the steel hardness. I am probably wrong, but I was under the impression that an impact wrench is less prone to rounding the nut because it delivers micro-blasts of energy rather than the sustained leverage achieved with a cheater bar...sort of like the difference between trying to slide a heavy piece of furniture into position in one motion vs giving it lots of little nudges.

I'm with you on this one. I don't know about rounding, but the continued impacts tend to loosen the rust; plus, I think a breaker bar can put other (sideways) forces on the bolt which could tend to break it. An impact wrench delivers the torque evenly. With a nice tight-fitting 6 pt socket I really doubt that you'll round the nut.

 

[TR3driver]

I could be wrong, of course; but that hasn't been my experience. Those "micro-blasts" have to be really strong impacts, or the nut won't turn. If they are strong enough to deform the nut, then it's a race between whether the nut rounds first or comes loose.

I've also had a lot of cases where the impact wrench just wouldn't move the nut; and a breaker bar would. Keith probably has a point, though, about rusty fasteners being different than those that are just incredibly tight.

 

[CLEAH]

As TR3 suggests, an impact wrench that is not powerful enough to budge the nut simply won't do anything--and it won't round off the nut as long as you are using a quality impact wrench socket that is not worn. As long as the socket is correctly sized and snug, there is little possibility an impact wrench will round the nut before it loosens the nut. But again, your wrench/compressor may not be powerful enough, in which case it will just stutter away. A couple pulls of the trigger will tell you on short order if it is going to come off with the impact wrench. That's my experience.

 

[British_Recovery]

My 2 cents: Anti-seize on the studs with reused nuts? Wouldn't that make it easier for them to come off on their own? Bob

 

[Bob_Spidell]

My 2 cents: Anti-seize on the studs with reused nuts? Wouldn't that make it easier for them to come off on their own? Bob

Theoretically, no. It's a common misconception that the strength of a threaded attachment is due mostly, if not entirely, to friction between the threads on the bolt and nut (or threaded hole). That's partly true, but the majority of the strength comes from stretching the bolt or stud so that it exerts a clamping force on its counterpart (steel is quite flexible). The amount of stretch is generally proportional to the torque on the bolt, but it's not precise and will vary greatly depending on the condition of the threads and what, if any, lubricant is used. That's why specified torque values are often given as 'dry' or 'wet'--or 'lubricated,' etc.--and may even specify the exact type of lubricant to use to achieve the desired stretch and resultant clamping force of the attachment. ARP, for instance, sells a special grease for use with their bolts and studs and testing with a load cell shows that the clamping force is greater for the same torque value--and more correct--when the proper (their) grease is used.

So, torquing the nut to, say, 90lb-ft with the threads dry will not stretch the stud and provide as much clamping force as lubricating the threads with grease or anti-seize (anti-seize is a lubricant, though not a particularly good one). That's also why some critical applications specify a 'torque-to-yield' value achieved by torquing to a certain value and then rotating the bolt or nut a specified number of degrees. Then, the bolt has been stretched to it's maximum length and tensile strength and hence clamping force is maximized (and it's why torque-to-yield fasteners should never be reused).

I usually use anti-seize on non-wire wheel lug studs and torque to value--most new cars specify 100lb-ft--since I know I'll be removing the nuts to rotate the tires, etc. When I reuse one of the nuts that hold a Healey rear drum assembly together I either use a new locknut or threadlocker--and sometimes both--since I don't want nor expect that assembly to come loose often. Even with (blue) threadlocker I've never had any trouble getting those nuts off when I need to.