[TR] Lock nuts and lock washers

[Michael Porter]

john taylor wrote:
> Listers,
>
>  In recent strings there have been several comments about lock nuts and
> lockwashers.
>
> PLEASE..... think about it... LOCK WASHERS DO NOT WORK. In order for them to
> have a spring effect the fastner must be loose.
>
>   

Well, this sort of flies in the face of a couple of hundred years of 
engineering. The lockwasher doesn't work only when loose.  Pretty much, 
the purpose of the lockwasher is to keep the bolt and nut threads 
scrubbed together to increase the friction required for the nut to 
turn.  This is no different a principle than that behind prevailing 
torque fasteners.


Beyond the theory, I have plenty of real-world examples to indicate that 
they do work, and just fine, thank you.  One of my favorites was that of 
a former boss on a farm who decided, like Mr. Taylor, that lockwashers 
had no real use, so he left them off the rake tines of the hay baler. 
There were about forty of these on the baler, and they were simply 
pieces of rod with an eye formed on the end, which slipped over a blind 
bolt and were captured by a flat washer, lockwasher and nut.  The tines 
dragged along the ground and separated the windrowed hay into columns 
which then were fed into the baler.  Because of the vibration, without 
the lockwashers, every tine had either loosened and was flopping around 
or had fallen off in less than twenty minutes. Add lockwashers, and 
everything is fine through the end of the hay season. If you want to 
understand the utility of the humble lockwasher, just work on 
high-vibration equipment such as farm equipment for a while. 


The other bit about lockwashers comes from Volvo Heavy Equipment. They 
owned 51% of a company for which I worked, and one of their 
pronouncements was that, because they had decided that Loctite was a 
carcinogen, only lockwashers would be used in their plants in 
applications which had previously used Loctite.


It was a terrible idea, because some installations just weren't amenable 
to using lockwashers (confined spaces where juggling lockwashers 
inclined assemblers to leave them off, etc.), and more so because their 
thinking was based on those old, old rat studies on saccharin ingestion 
(saccharin is an essential ingredient of Loctite), even though one would 
have to eat about two pounds of the stuff or be completely immersed in 
it for a couple of weeks to receive a median lethal dose.  But, the 
point was that Volvo's engineers think lockwashers work as advertised. I 
doubt you're going to find many mechanical engineers who would say that 
they do not.  Some may have preferences for PT nuts, but, that doesn't 
negate the principle behind the lockwasher.


Cheers.


-- 


Michael Porter
Roswell, NM


Never let anyone drive you crazy when you know it's within walking distance....