You guys use those? I know they're suppose to put upward pressure against the screw head, but whenever I remove the screws, the split lock washers are almost flat. I can't see how they'd be putting much upward pressure on the screw head if they're almost flat.
Split Lock Washers
- Thread starter Merkava_4
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Possibly a split washer may prevent a very loosely tightened soft nut or bolt from backing out due to vibration. I have seen split washers in some automotive applications. Other than where specified, I normally use a flat washer or sometimes a serrated or a conical Belleville spring washer. Washers and bolts have to be matched in terms of required torque.
Never really liked split lock washers. However, they may have some benefit.
The edges of a split lock washer are supposed to cut into the bolt head and surface of the fastened object to prevent backing off. If the materials are hard it's no better than a flat washer.
Originally Posted By: pcoxe
The edges of a split lock washer are supposed to cut into the bolt head and surface of the fastened object to prevent backing off.
uhmm, no; that's not how they're supposed to work. And besides that, a lot of applications require a flat washer to go on before the split washer if the split washer is on the nut side.
The edges of a split lock washer are supposed to cut into the bolt head and surface of the fastened object to prevent backing off.
uhmm, no; that's not how they're supposed to work. And besides that, a lot of applications require a flat washer to go on before the split washer if the split washer is on the nut side.
You would be happier finding an Aggressive External Tooth Lock Washer.
They have various styles, including Internal Tooth.
If a Split Lock washer is correctly made with proper materials (not Chinesium) the do work really well but IIRC they require a Flat Washer under them as well.
I only see them used as a stand-alone washer in instances where they interface with a hard plastic.
But, even then, I spot them with a Copper Flat Washer under them very often.
If they are used for an anti-vibration purpose there are Anti-Vibration screws as well, where you can skip the split lock.
They have a bit of a Flange built into them, and under the Flange it is serrated to help keep the screw from loosening.
They have various styles, including Internal Tooth.
If a Split Lock washer is correctly made with proper materials (not Chinesium) the do work really well but IIRC they require a Flat Washer under them as well.
I only see them used as a stand-alone washer in instances where they interface with a hard plastic.
But, even then, I spot them with a Copper Flat Washer under them very often.
If they are used for an anti-vibration purpose there are Anti-Vibration screws as well, where you can skip the split lock.
They have a bit of a Flange built into them, and under the Flange it is serrated to help keep the screw from loosening.
Originally Posted By: Merkava_4
Originally Posted By: pcoxe
The edges of a split lock washer are supposed to cut into the bolt head and surface of the fastened object to prevent backing off.
uhmm, no; that's not how they're supposed to work. And besides that, a lot of applications require a flat washer to go on before the split washer if the split washer is on the nut side.
I am a mechanical engineer and probably installed my first lock washer 50+ years ago. I just figured the tension on the washer caused the nut not to back off. And without researching it on Wikipedia, I have no doubt that pcoxe is correct. The small tension that the washer would offer to the much higher clamping force already developed by tightening the nut would be insignificant.
And note that the lock washers are always designed so they don't "grab"when tightening. They are like a little ratchet device. As far as installing both a split and plain washer...perhaps the designer didn't understand the concept. Disclaimer....lock washers have probably outlived their usefulness with the advent of locking nuts...which were unheard of many years ago.
Thanks pcoxe.
Originally Posted By: pcoxe
The edges of a split lock washer are supposed to cut into the bolt head and surface of the fastened object to prevent backing off.
uhmm, no; that's not how they're supposed to work. And besides that, a lot of applications require a flat washer to go on before the split washer if the split washer is on the nut side.
I am a mechanical engineer and probably installed my first lock washer 50+ years ago. I just figured the tension on the washer caused the nut not to back off. And without researching it on Wikipedia, I have no doubt that pcoxe is correct. The small tension that the washer would offer to the much higher clamping force already developed by tightening the nut would be insignificant.
And note that the lock washers are always designed so they don't "grab"when tightening. They are like a little ratchet device. As far as installing both a split and plain washer...perhaps the designer didn't understand the concept. Disclaimer....lock washers have probably outlived their usefulness with the advent of locking nuts...which were unheard of many years ago.
Thanks pcoxe.
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I spoke to a Loctite field rep once. He said the most ridiculous thing you can do is put a flat washer under a split lock washer. The flat washer cancels any benefit from the lock washer. Of course, he was promoting Loctite products as well.
The front wheel axle on my Harley has a flat washer with a lock washer. It works very well for that application, as it seems to grip the nut until the tension is all the way off the lock washer.
A well-designed fastener application won't need any sort of lock washer, it's a kludge for those that are marginal, or for extra safety.
Under a screw head I like the serrated Belleville washer and for a nut, a Nyloc.
Under a screw head I like the serrated Belleville washer and for a nut, a Nyloc.
Originally Posted By: supton
Hmm, never thought of this. I often have a flat washer on the surface being clamped (aluminum or wood) then a split washer then the bolt head. Never stopped to think about it.
Yea..we are all creatures of habit.
Hmm, never thought of this. I often have a flat washer on the surface being clamped (aluminum or wood) then a split washer then the bolt head. Never stopped to think about it.
Yea..we are all creatures of habit.
JHZR2
Staff member
So the question is if the flat washer does anything if it bends flat?
Im sort of surprised at this. A split washer is bent like a spring. The spring under compression might flatten, but my first guess is that a fully flattened lock washer with no spring back was overtorqued.
No idea if that is right or not...
Im sort of surprised at this. A split washer is bent like a spring. The spring under compression might flatten, but my first guess is that a fully flattened lock washer with no spring back was overtorqued.
No idea if that is right or not...
Flat washers are for protecting the surface from the bolt head when tightening down or when used with lock washers they spread out the force on the material. I always just use lock washers once and then throw them away. SS ones are particularly bad about loosing tension.
Is the bolt loose on the ones with the flattened out washers? I would assume any tension applied when originally using them would remain until it is loosened.
Is the bolt loose on the ones with the flattened out washers? I would assume any tension applied when originally using them would remain until it is loosened.
Alright pcoxe, here's my source:
Standard Aircraft Handbook
Enlarged 4th Edition
Copyright 1952, 1958, 1980, 1986
by AERO PUBLISHERS, INC.
ISBN 0-8306-8812-9
Page 38
"Plain Washers
The plain washer, AN960, Fig. 2-10, is used under hex nuts. It provides a smooth bearing surface and acts as a shim in obtaining correct grip length for a bolt and nut assembly. It is used to adjust the position of castellated nuts in respect to drilled cotter pin holes. Plain washers should be used under lock washers to prevent damage to the surface material.
Lock Washers
Lock washers (AN-935 and AN-936) may be used with machine screws or bolts whenever the self-locking or castellated type of nut is not applicable. They are not to be used as fastenings to primary structures, or where subject to frequent removal or corrosive conditions."
Standard Aircraft Handbook
Enlarged 4th Edition
Copyright 1952, 1958, 1980, 1986
by AERO PUBLISHERS, INC.
ISBN 0-8306-8812-9
Page 38
"Plain Washers
The plain washer, AN960, Fig. 2-10, is used under hex nuts. It provides a smooth bearing surface and acts as a shim in obtaining correct grip length for a bolt and nut assembly. It is used to adjust the position of castellated nuts in respect to drilled cotter pin holes. Plain washers should be used under lock washers to prevent damage to the surface material.
Lock Washers
Lock washers (AN-935 and AN-936) may be used with machine screws or bolts whenever the self-locking or castellated type of nut is not applicable. They are not to be used as fastenings to primary structures, or where subject to frequent removal or corrosive conditions."
True, a flat washer will protect a soft surface from the cutting edges of a split lock washer, but what prevents the flat washer from turning and allowing a nut to unwind? A split lock washer has to dig into both surfaces to work.
Originally Posted By: pcoxe
but what prevents the flat washer from turning and allowing a nut to unwind?
The force of compression. It's supposed to be under a compression load like a spring.
but what prevents the flat washer from turning and allowing a nut to unwind?
The force of compression. It's supposed to be under a compression load like a spring.
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