Lock Washers

[glippert]

It's no secret that all of you are probably a lot smarter than me about such things, so I'll ask my question here. Cleaning up a little today, sorting nuts, bolts washers, etc, and it occurred to me that I don't know the proper use for various lock washers. Inside star vs outside star? Star vs spring? I presume the stars are for lower torque situations like electronic assemblies & cicuit boards. But I've been known to "mis-presume" more than a few times in my life.

(I also presume that wondering about such things may indicate too much free time...)

 

[PACub100]

Well hot dog, sitting here on lunch break and you got me wondering the same thing... so I had to find out.

 

[kmcconaughey]

Greg, McMaster-Carr is a great resource for info like this. I can't link directly to it but follow the link then click where I show in the screen capture.

 

[glippert]

Thanks guys. I knew I came to the right place!

 

[Greg Riutzel]

I don't use them. About 15-20 years ago I noticed they didn't do much except gouge the mating surfaces with the split style being the worst. I still use the toothed ones for electrical, especially grounding; and soft material as in hard plastics or maybe wood. The best defense against loosening is correct torque. For extra guard against loosening as in areas of vibration good 'ol Loctite , prevailing torque nuts, Ny-lok, Belleville washers, etc. Carroll Smith, race car driver and engineer, wrote a really good guide on fasteners especially for safety and high performance.

 

[dgeary]

I don't use them. About 15-20 years ago I noticed they didn't do much except gouge the mating surfaces with the split style being the worst. I still use the toothed ones for electrical, especially grounding; and soft material as in hard plastics or maybe wood. The best defense against loosening is correct torque. For extra guard against loosening as in areas of vibration good 'ol Loctite , prevailing torque nuts, Ny-lok, Belleville washers, etc. Carroll Smith, race car driver and engineer, wrote a really good guide on fasteners especially for safety and high performance.

I agree with Greg. I've worked on a lot of equipment over the years and always noticed that the split lock washers were nearly always broken. Like he said, use a good flat washer (hardened if available) to spread the load, proper torque and Loctite if you need the extra insurance. I do recommend using the Bellville spring washers mentioned above for high torque applications, particularly on 1/2" or larger fasteners.

 

[gary noblit]

Greg,how's that for sharing knowledge? So now how about the reasons behind torques ,allen, phillips, straight, screw/bolt heads..And quite often on the same engine....A cause of many curses over time...

 

[glippert]

Greg,how's that for sharing knowledge? So now how about the reasons behind torques ,allen, phillips, straight, screw/bolt heads..And quite often on the same engine....A cause of many curses over time...

Puts my brain close to overload! This forum continues to amaze me.

 

[kphill]

I don't like split lock washers.. Under vibration they can crack on the opposite side and fall away.. I use a double nut for vibration points or critical applications like a clutch rod.. Just run the first nut on and tighten it where you want it then run the second nut on and use it as a jam nut and while holding the first nut in place with a wrench, tighten the second nut tight against it.. It will not loosen until you back them apart..

 

[Everettlee]

The company I work for uses Nord-lock washers……they simply stay tight under all conditions
https://www.nord-lock.com/nord-lock/products/washers/

 

[Rgausman]

Agree with everthing said above...

I am a fan of flanged nuts and bolts torqued to proper spec. I vibration situations, use nylock fasteners or Loctite.

 

[kphill]

I only use locktite when necessary.. The blue locktite is ok as you can loosen it without heat but be careful using it on small parts or fasteners made from aluminum as you can snap them off.. Also the red locktite must be heated to 400+ degrees to break the bond so it has its limitations.. Also if you remove a fastener that has had locktite applied you should chase the threads with a tap to clean the threads so you can retorque the bolt to the proper spec as old loctite on the threads add friction..

 

[kphill]

I was taught to think of a bolt as a spring, as clamping force is what holds the two parts together.. When you torque a bolt you are stretching it and creating the clamping force like a spring... If you overtorque it you overstretch the bolt and it can cause it to break over time and also damage the threads when you overtighten it.. If a bolt or nut is properly torqued you really should be good..

 

[Greg Riutzel]

All good info which brings up matching the bolt/fastener grade to the job. Going to swap meets and oldies car meets I occasionally see owners scratching their heads over why grade 8 bolts on engine accessory drives are breaking. If the bolts are too strong for an application in that if the correct torque/tension for a grade 8 was used something in a part or drive can give or yield such as a tension bar, a timing cover attachment point, or an aluminum housing on an alternator losing the clamp force. If it's just tight enough for the job but not full bolt tightness the clamp force decays because the bolt is not in it's elastic range to resist movement and now that grade 8 bolt is "getting hammered" in the hole until failure. Put a grade 5 in and the torque with stretch for it is what keeps things clamped but not deform the joint. Bolt stretch is what keeps things together. As to Lock Washers; I went to the source that being the ASME spec. It's B18.21.1. There's nothing in it about "locking" fasteners but it is about providing a bearing surface under nuts or bolts and distributing forces and taking up looseness. It only mentions a possible benefit of resisting loosening but they go flat anyway. In 1969 a German guy, Gerhard Junker, came up with a machine to test bolt/joint tightness and found that split washers actually aided loosening. It has since become part of an arsenal of testing machines used by manufacturers. Here are some handouts: a good source for anyone's library, right up there with service manuals Carroll Smith's Nuts, Bolts, Fasteners and Plumbing Handbook (Motorbooks Workshop): Smith, Carroll: 9780879384067: Amazon.com: Books A good rundown on mistakes. Don't let the graphs and tech get in the way, lots of readable stuff : Case Study (vibration.org) Lastly this one has lots of pictures and if you explore the site, you can find cool stuff on head bolts Helical Spring Washers

 

[Greg Riutzel]

,allen, phillips, straight, screw/bolt heads..And quite often on the same engine....A cause of many curses over time...

Different ways to skin the same cat. Better control, ease on the assembly line, more torque without camming out. I recall a 1946 article in Automotive and Aviation Industries, an old trade publication, where auto makers, Ford IIRC, was adopting Phillips drive for trim screws. It was to reduce the tool slipping out and marring finishes and paint work.

 

[dware]

I have always liked what I have heard referred to as airplane nuts , slightly squashed so that they will not come off without a wrench.
You only need a flat washer .

 

[Everettlee]

Lots of talk about proper torque and I agree but I rarely use a torque wrench. Only (mostly) for engine bolts
Loctite requires the surfaces to be clean and oil free to work, without cleaning you certainly are not gaining the advantage of the retaining qualities. I use loctite always on optics on firearms, great product