Woodruff key questions
 

I managed to weld up the clutch basket / shaft for the lathe I am repairing okay fine.
Didn't damage the threaded sections and it is still straight if we can trust my tenths
indicator.

I used the fiberglass tape suggestion in an earlier threads, wrapped tin foil around
mounted bearings that I couldn't get of non destructively.

Welding, I put opposite strips weld on the fill and non fill side to keep distortions
minimized. I took my time too.

I used the short bapps of weld on opposite sides.

One trick that helped was I set my 3W LED maglight positioned so that I could really see
what I was doing from under the hood.

Decided the section could stand losing 0.015" on diameter, I have to bush the pulley
anyway so I'm taking the easy route on this.

Now I'm down to putting a woodruff key in. I can't exactly tell what was in it due to the
damage. The pulley groove is 3/16" and a fragment of key was 3/4" long but I wouldn't bet
it wasn't 7/8" or 1" too, those see to be sizes I can get a key in.`

So I started calculating things. A 3HP motor puts out ~4.4 lb/ft of torque at 3600,
doubled if the motor is half that rpm, I can't remember what it is atm.

There is a pulley ratio of 1:2 motor:driven clutch so now I have 8.8 lb/ft at the pulley /
shaft interface that is a ratio based on diameter of shaft of 24.34 giving 214 lb of force
on the key at the shear line.

A 3/4 x 3/16 key has .140 sq/in in shear. Using 60Ksi that would mean I'd have to
generate 8437 lbs at the shear line to shear the key.

So the questions a

Is there a standard shear value in KSI for woodruff keys? I'd think we would want them to
give rather than the expensive parts but my assumption could be wrong.

What kind of safety margin is typically used in this kind of application?

Thanks in advance,

Wes

Woodruff key questions
 

On Fri, 19 Jun 2009 17:50:05 -0400, Wes wrote:



So the questions a

Is there a standard shear value in KSI for woodruff keys? I'd think we would want them to
give rather than the expensive parts but my assumption could be wrong.

What kind of safety margin is typically used in this kind of application?

Thanks in advance,

Wes


Don't know the answer, but the numbers in your sums look pretty safe.

RANT
Woodruff keys were not designed for transmitting torque and should not be used
for such. It causes the keyseats to self destruct.. They are for location
only. If a designer wants to transmit torque they should use a proper taper
key. Preferably gib headed for easy extraction.

God Save the King!
/RANT

Woodruff key questions
 

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.. They are for location
only. If a designer wants to transmit torque they should use a proper taper
key. Preferably gib headed for easy extraction.


I haven't seen a gib head since I repaired Sheridan double crank die cut press(s).

Wes

Woodruff key questions
 

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

Woodruff key questions
 

"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

Woodruff key questions
 

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.

Woodruff key questions
 

Woodruff key questions
 

Woodruff key questions
 

David Billington wrote:

Actually in that situation the taper handles the torque and the woodruff
does alignment. The woodruff key or some method of alignment is required
to position the flywheel and the magnets for the ignition, the friction
fit on the taper handles the torque unless severely overloaded. I've
never seen an aluminium woodruff key but wouldn't deny their existance
if required for an application. I've dismantled a few small engines in
the past and have never seen other than a steel woodruff key used.

Ace Hardware thinks the keys in a Briggs and Stratton is aluminum.

See

http://www.acehardwaresuperstore.com...y-p-58407.html




technomaNge
--

Woodruff key questions
 

On Sun, 21 Jun 2009 16:10:38 -0500, technomaNge wrote:

David Billington wrote:

Actually in that situation the taper handles the torque and the woodruff
does alignment. The woodruff key or some method of alignment is required
to position the flywheel and the magnets for the ignition, the friction
fit on the taper handles the torque unless severely overloaded. I've
never seen an aluminium woodruff key but wouldn't deny their existance
if required for an application. I've dismantled a few small engines in
the past and have never seen other than a steel woodruff key used.

Ace Hardware thinks the keys in a Briggs and Stratton is aluminum.

See

http://www.acehardwaresuperstore.com...y-p-58407.html




technomaNge
A service manual from 1984 mentions a zinc key.
Gerry :-)}
London, Canada

Woodruff key questions
 

I can assure you that the torque for a flywheel to tapered shaft
connection is handled by the taper and a BIG flywheel nut to seat the
taper. I used to do an 40 hp outboard engine every other week where
someone had hit a rock and spun the flywheel. Sheared the key but
destroyed both the crank and the flywheel. The secret to not doing
rework was to torque the flywheel nut to the specified 175 foot pounds.

wrote:
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.

Woodruff key questions
 

David Billington wrote:
wrote:
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.

Actually in that situation the taper handles the torque and the woodruff
does alignment. The woodruff key or some method of alignment is required
to position the flywheel and the magnets for the ignition, the friction
fit on the taper handles the torque unless severely overloaded. I've
never seen an aluminium woodruff key but wouldn't deny their existance
if required for an application. I've dismantled a few small engines in
the past and have never seen other than a steel woodruff key used.

Briggs and Kohler use aluminum or Zinc keys on most of the small (under
7hp) engines. All the ones on push mowers are zinc.


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.

Maybe the previous poster got sliding wrong, the part located by the
woodruff is slid into position, but is not necessarily a sliding part.
The main load transfer for items like crank pulleys is via friction due
to the clamping load and not via shear loads on a locating key.


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..

I wouldn't argue against that but the loads are somewhat lower
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.

Woodruff key questions
 

Aluminum or zinc keys are the vast majority, also in my experience. Nearly
all the small engines' flywheel/crankshaft keys I've seen, which include
probably a hundred or more, Toro, Tecumseh, Briggs and a few other names,
plus some chainsaws, but I believe all the vertical and horizontal shaft
engines were zinc or aluminum keys.
The ones that I'm not entirely certain about are the chainsaw engines.

These engines included some older ones, but they were mostly 1970s or 80s
models.

The blade hubs or output shaft sprockets had steel keys.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Steve W." wrote in message
...

Briggs and Kohler use aluminum or Zinc keys on most of the small (under
7hp) engines. All the ones on push mowers are zinc.

Woodruff key questions
 

I know this topic is many years old but I've recently bent two 1" diameter crankshafts on a Honda push mower because they use a steel Woodruff. The first crank bent when i hit a low stump from a bush. I had it replaced to the song of $250 parts and labor. The second I bent back straight this afternoon with a 3lb hand maul, after hitting a fist sized rock that bent the crank to a runout of 2.5mm (I was using a metric dial indicator). My hands wwre numb for 30min after using the vibrating mower. Anyway why would Honda use steel keys? Just to provide their service centers with hundreds of dollars of repair work and many angry customers? I got my shaft runout to about 0.6mm and it runs very nice now. But I'm shopping for zinc/aluminum keys right away.

Woodruff key questions
 

On Mon, 28 May 2018 18:08:15 -0700 (PDT),
wrote:

I know this topic is many years old but I've recently bent two 1" diameter crankshafts on a Honda push mower because they use a steel Woodruff. The first crank bent when i hit a low stump from a bush. I had it replaced to the song of $250 parts and labor. The second I bent back straight this afternoon with a 3lb hand maul, after hitting a fist sized rock that bent the crank to a runout of 2.5mm (I was using a metric dial indicator). My hands wwre numb for 30min after using the vibrating mower. Anyway why would Honda use steel keys? Just to provide their service centers with hundreds of dollars of repair work and many angry customers? I got my shaft runout to about 0.6mm and it runs very nice now. But I'm shopping for zinc/aluminum keys right away.
Make one from a penny?