Lock Washers a Waste of Time?

One of the nice things about blue Loctite is that it in addition to reducing loosening, it provides something of a barrier between fastener surfaces. I don't know if it provides significant protection from rust and galling, but it probably does.
 
BGHansen said:
I was taught that torque is how clamp load is obtained. The bolts is stretched into tension which maintains the clamp load, basically it's stretched into a spring. What holds the joint together is friction between the nut/bolt head and the mating surface. If either rotate (lefty loosie), then some of the clamp load is lost. Loctite, nylock nuts and I would imagine star-washers increase the friction so the joint will be less likely to loosen.

Key to achieving clamp load is some distance between the head of the bolt and the nut. Tighten two pieces of sheet metal together with a 1/4"-20 and you maybe get one thread of stretch and little clamp load. Makes sense that a split lock washer would help put the bolt into some tension and help with the clamp load when bolting up thin materials. Don't know how much friction (if any) it adds to keep the nut from turning.

Bruce
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The trick with using torque to hold a bolt and nut together is: that the proper torque clamps the things together in such a way that under no situation (of vitration or change in load), does the threaded member end up with zero tension and loses its clamping force.
 
MrWhoopee said:
On a VW bus (the real ones, thru '67), the front wheel bearings are retained with nut, lock-nut and keyed retaining tab washer between. Rear brake drums are retained with castellated nut torqued to exactly 280 ft. lbs. (6 ft. cheater on 3/4 breaker bar, then jump on it) and cotter key (split pin downunder).

In general, metric stuff seems to use wavy washers instead of split.
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This would be a Starrett cheater and breaker bar, and a 140# jump with two feet to achieve 280 ft. lbs.? That’s how we do it!!:laughing:
 
The Bolt Science data is based on testing with a Junker machine. It created alternating shear load in the test joint. It is the clearance between the bolt and nut that allows relative motion between them leading to loosening. The reason Loctite is so effective is that it fills the gap between the nut and bolt therefore preventing relative motion.

If sufficient clamping force is applied to the joint to prevent sliding of the bolted members there can be no relative motion between the nut and bolt. In structural engineering that is called a slip critical connection. All the shear load between the members is transmitted by friction. The shear force on the bolts is assumed to be zero.
 
mcostello said:
My Eye Doctoruses a drop of clear nail polish on the top of eye glasses screws to prevent loosening, easy to remove.
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I used that when building Erector set models that would be transported. Poor man's Loctite, never had a screw back off.

Bruce
 
BtoVin83 said:
Put a pipe wrench on the nut and drive around the yard.
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I've actually had to put the socket, breaker bar and cheater on, then back up to try to break the nut loose. Raised the back end about 18 in. off the ground.
 
My old friend Reed grew up in this field. His Dad was fond of saying "Stripped threads is worth TWO lockwashers!":big grin:

The very first shop I ever drew a paycheck from used alot of Permatex #2. I use it to this day. But we did not work on airplanes:cautious:
 
What about serrated flange nuts and washers? They are what I go to for frame and suspension work, have not had any loose ones yet.
 
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