[AT] O.T. Woodruff vs straight keys

[Rena Glover Goss]

A key can be used as a safety limiter on torque so that it shears instead of breaking gear teeth, etc.  In that case, the length of the key can be used to adjust the break-away torque load.  Some small engines (like Briggs) use a particular metal for the key to get this type of safety.  In the lawnmower repair shop business, I often ran into engines where the owners had replaced the OEM key with a steel one.  I presume they thought that "any ol' key" would do the job.  Never mind that when they hit a gas pipe with their lawnmower, they twisted off the crank shaft!


Larry
---- Dennis Johnson <moscowengnr at outlook.com> wrote: 
> I think there are 2 main reasons for woodruff keys
> 1 - these keys are contained from side to side so they cannot slip. You can also use other types of key ways that enclose the keys, but the most common is to cut keyway to the end of the shaft.
> 2 - the woodruff keys may take less material out of the shaft. This might weaken the shaft slightly less.
> 
> Dennis
> 
> Sent from my iPad
> 
> > On Aug 11, 2017, at 8:13 PM, "joehardy at epix.net" <joehardy at epix.net> wrote:
> > 
> > My brother is rebuilding a corn chopper and having difficulty replacing bearings on the pick up head. Couldn't get to slide the bevel gears off drive shaft. He asked me why woodruff keys were used instead of straight keys. Thought I'd throw his question out to our group. Ref: Read discussion on Practical Machinist. Joe Hardisky, Ryman Farm, Dallas, PA
> > _______________________________________________
> > AT mailing list
> > http://www.antique-tractor.com/mailman/listinfo/at
> 
> _______________________________________________
> AT mailing list
> http://www.antique-tractor.com/mailman/listinfo/at