Socket Head screws
Socket Head screws
(OP)
Came across statement recently that read "lock washers are not used with socket head screws." I hadn't heard of this before so I'm curious...Anyone know if this is true? And why?
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RE: Socket Head screws
Best Regards,
Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
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Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.
RE: Socket Head screws
So then, a socket head screw then by itself (no locking inserts etc) could potentially vibrate loose over time when fastened mated with a nut, pem nut, or simple threaded hole. I was curious if there was something about the geometry of the socket head that would explain that statement I had seen.
Mel
RE: Socket Head screws
I personally don't trust the split-type lock washer. The spring force exerted by them is not sufficient to maintain the friction coefficient of the preload to prevent the screw from loosening during vibration. Lock washer don't buy much more than what a good torque value will get you.
--Scott
http://wertel.eng.pro
RE: Socket Head screws
This can be got around by using extra flat washers between the head and the split washer.
Wave washers are a little better for some applications.
RE: Socket Head screws
Any bolt or screw, with or without a lock washer can eventually vibrate loose. If vibration loosening is the underlying issue, try using a thread adhesive, nylok insert, or a self-locking threadform for the tap (or nut) such as Spiralok.
Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca
RE: Socket Head screws
Don
Kansas City
RE: Socket Head screws
Best Regards,
Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)
Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.
RE: Socket Head screws
Ralph
RE: Socket Head screws
A better solution is to make sure that you tighten the bolts up to their designed load carrying capacity (this may be quite a bit more than you think) and desing the joint so that it doesn't suffer embement and collapse at that load. Make sure that the bearing surface that you are using is hard enough to carry the design load for a SHC (most LCS will yeild if not heat treated).
Also be aware that at the high hardness levels used in SHC there is a very real possiblity of Stress Corrosion Failures if there is any possiblity of corrosion in the joint. I don't like to use PC 12.9 bolts in any application that is exposed to the environment..I have fixed to many SCC failures over the years.
RE: Socket Head screws
Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca
RE: Socket Head screws
Like Screwman notes, they don't work.
See FAQ404-1257
RE: Socket Head screws
RE: Socket Head screws
RE: Socket Head screws
socket head capscrews even for our military
applications. What does not work is split
lock washers.
RE: Socket Head screws
The information posted above about the hardened SHCS tearing up the landing are is very true. Even though we DAG all the fasteners they will still score the landing area over time to the point that it has to be touched up.
One point about the use of star washers is they can also tear up a landing area in make and break situation especially with hardness below Rc35.
RE: Socket Head screws
of socket head capscrews. I assume they
are the same as the starr washers that
you were referring to. Search on
Schnorr Washers to see these.
RE: Socket Head screws
One area where toothed washers work very well is for grounding (earthing). The teeth dig through surface coating and corrosion products and give a good low resistance connection. By the same token, you don't want to use them where surface finish is important, since they dig up any kind of finish on the bearing surface.