On Sat, 20 Jun 2009 20:57:14 -0400, "John"
wrote:


"Wes" wrote in message
...
Mark Rand wrote:

Woodruff keys were not designed for transmitting torque and should not be
used
for such. It causes the keyseats to self destruct.

I'm curious about your comment, I've seen woodruff keys in many things.
The most notible
thing is the handles on a bridgeport. That may be a case of location
being primary over
torque since those are not stressed.

I'm tempted to just cut it for a pocketed square key and be done with it.

I *thought* there might be some sort of rational to the woodruff key that
made it better
than a square key.

Wes



A square key usually is held by a setscrew. I cant think of a time that a
woodruff key had a setscrew on the shaft.
A woodruff key cant work out of the slot. they are used when the part has to
slide along the shaft.

John
They are also used on tapered shafts. Look at the flywheel on your
average single cyl air cooled engine. (where they also transmit torque
- starting torque as well as, in many cases, accessory drive torque.

Just blew two so-called "facts" about woodruff keys with one example.
Not a sliding fit, and delivers torque.

Then go to the harmonic ballancer (front pulley) on many car engines -
Woodruff key there too - definitely not a sliding application, and
definitely delivers torque - runs the alternator, air conditioning,
and power steering loads.

It is also used to hold the drive pulley on many
alternators/generators/etc as well as keying timing gears to both
camshafts and crankshafts..

A woodruff key is used where the loss of the key through lateral
movement is to be avoided. It is also used where a controlled torque
shear is required. They fail very predictably under high impact shear
loads, providing a certain level of mechanical protection to
drivelines.