How to combine flat and split lock washers on a bolt

So I'm assembling a pull up bar and its assmebly instructions look like this In the parts list it mentions only one type of spring washer (quantity 4). But it actually came with two types of washers (quantity 4 each), type1 and type2. Am I supposed to use both of them? And in what way? Any help would be appreciated!

Lock washers have been proven to not provide any benefit at all, it's amazing to me that they are still produced and used. NASA had this to say about them: “The typical helical spring washer … serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking.”

@GregNickoloff: here or here is a start but if you just google "Do lock washers work" you will find a ton of tests and data showing they do not.

@jesse_b: I get it. But the thought is that someone already "googled" that to get here. For "completeness", etc. You quoted NASA so you should provide a link back to the source. All good.

@GregNickoloff I don't have a link handy, but I do recall reading in some NASA design standards that lock washers are explicitly disallowed.

5 Answers 5

They gave you four lock washers instead of 4 locking nuts. No problem. Install the bolts as shown in the instructions. Then install a flat washer on each bolt followed by a lock washer and then the nut. Tighten as specified.

On a tangent, a lock washer basically does nothing close to a lock nut. Do regular checks with this pull up bar, because your lock washers will loosen MUCH faster than a real lock nut. Replace with a real lock nut if you can; you don't want to break your neck over $10 worth of nuts. Info about lock washers

@DaMike The lock washers will be fine, I've used them in heavy machinery for 55 years and never had a problem. You will find them in probably every car built. Maybe NASA doesn't like them but you're not mounting your bar in the space shuttle. Looking at the position or your bolts if the nuts should ever loosen up you'll feel it long before they fall off. you should be doing regular checks on a bar like this anyway.

Put the flat washer on first then the split lock washer and finally the nut.

The advice from the German military shock testing establishment is to NEVER use any washer except a flat one.

It is the bolt that should be under tension and the bolt that provides the force that keeps the joint together. Spring washers, split washers and crinkle washers will eventually yield and the tension in the bolt will be lost. The joint WILL open up. At best the nut will fall off, at worst the bolt will experience shear or bending moments and fail.

That's very true for structural applications where the bolts are close to their capacity. However, for a pull-up bar even a single bolt with loose nut should be able to support the weight of a person. Though just to be safe, it's of course better to have a lock nut there.

Some of the contents of your statement seems to be accurate but others don't make any sense. For example, bolts are often in shear, that's what they are designed to do, and that is completely separate from the nut or even how tight the bolt.

They are normally installed so the split-ring "lock" washer is against the nut, and the flat washer is between the split-ring washer and the surface. This is to prevent damage to the surface. It appears they did not provide any flat washers, is that correct?

It appears they provided locking nuts, the kind with a piece of nylon or fibrous material in it. So you should be good.

However, I'd like to add some content about split-ring "lock" washers.

Both the Germans in the (I think) 1930s and NASA in the (I think) 1960s determined that split-ring spring washers, aka split-ring "lock" washers, actually speed the loosening of a nut under vibration when no other method is used of locking the thread in place.