Alternator woodruff key

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rvich said:
The drive sprocket has 1/4-inch key but I was wondering about the rotor. I thought it was supposed to be 1/8-inch? Just checkin.

Russ
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Russ, that was what I was thinking when I asked my my original question, rather than just filing one down to fit. If anyone can definitely say what size the key should be would be helpful.

L.A.B. said:
Alan W said:
the keyways in the rotor and the crankshaft are only 1/16" deep each (total 1/8") so no way is the rotor going to fit on the shaft over the key.
Click to expand...

A rotor keyway only 1/16" deep in the crankshaft doesn't sound quite right somehow?
Alternator woodruff key


Can you be certain there isn't a piece of old Woodruff key still in there?

What does the key that you removed look like (photo?)?

Or wasn't there any Woodruff key?
Click to expand...

LAB, no the woodruff key wasn't there when I took the rotor off and the rotor had turned on the shaft. From your picture are you saying the slot in the shaft is also half round in profile to take the key? If my old key has broken, and is still in the shaft, then it has broken off leaving a very smooth flat surface in the shaft keyway (sorry no photo to show at the moment).
 
Oh oh My Combats have curve shaft key cut outs, ... so serious DIY pecking key apart or pay a pro with special equipment. Normal difficult keys are child's play compared to the keys blacksmith welded into one with the crank. Keys are harder than crank metal so can be broken up, ugh, but also the slot buggered up so best wishes maintaining mechanic sanity.
 
hobot said:
Oh oh My Combats have curve shaft key cut outs, ... so serious DIY pecking key apart or pay a pro with special equipment. Normal difficult keys are child's play compared to the keys blacksmith welded into one with the crank. Keys are harder than crank metal so can be broken up, ugh, but also the slot buggered up so best wishes maintaining mechanic sanity.
Click to expand...

OK so now we may be getting to the bottom of the problem. My bike is a '74 850. I don't want to start hammering what may or may not be a broken key out of the shaft without being really sure.

bad_friday said:
............I have used one a few weeks ago and it did fit without any problem.
Fritz
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Can Fritz or anyone who has got their rotor removed at the present time confirm the shaft profile?
 
Hi Allen ,
the key to your problem the key way cut in your shaft should be a semi circle shape hence woodruff key . If as you say your key way in the shaft is flat it may well be the previous key has broken off .You want to hope if that is the case it was not an alloy steel woodruff key 8630 that is 40 - 50 Rockwell almost file material , hope it has a plain steel key . And if that is the case you could carefully drill and tap the broken key and using a suitable bolt jack it out . You will need to measure it first to be sure , if not you have a modified shaft hope not lots of luck .
 
An 850 MkIII crank, but it has the same rotor key/keyway as earlier models, and hopefully it gives you an idea of the shape and depth of the slot.
Alternator woodruff key
 
Thanks LAB, that is exactly what I wanted to see. Unfortunately it would appear that my key has snapped off 1/16" below the circumference of the shaft :cry: . For all the world it looked like the bottom of a flat keyway. I will try to tap it out, looks like this could be fun!

Thanks all
Alan

PS good job I didn't just file a key flat to 1/8" high & slide it in, eh?!
 
Norton Dave said:
And if that is the case you could carefully drill and tap the broken key and using a suitable bolt jack it out .
Click to expand...

I usually drive the more stubborn specimen of this breed out by using a thin pin punch and a relatively light hammer and place the pin close to one end of the half circle, giving a moment around the circle center. Relatively light force on the punch will turn the woodruf key in its place, lifting the rear part up, especially if a little pen fluid and some heat cycles are applied. One punch and you should at leat see whether the groove is shaped as it should be and that there is something left in there.


Tim
 
Tintin said:
Norton Dave said:
And if that is the case you could carefully drill and tap the broken key and using a suitable bolt jack it out .
Click to expand...

I usually drive the more stubborn specimen of this breed out by using a thin pin punch and a relatively light hammer and place the pin close to one end of the half circle, giving a moment around the circle center. Relatively light force on the punch will turn the woodruf key in its place, lifting the rear part up, especially if a little pen fluid and some heat cycles are applied. One punch and you should at leat see whether the groove is shaped as it should be and that there is something left in there.


Tim
Click to expand...
This is the correct answer, millwright 101.
 
concours said:
Tintin said:
Norton Dave said:
And if that is the case you could carefully drill and tap the broken key and using a suitable bolt jack it out .
Click to expand...

I usually drive the more stubborn specimen of this breed out by using a thin pin punch and a relatively light hammer and place the pin close to one end of the half circle, giving a moment around the circle center. Relatively light force on the punch will turn the woodruf key in its place, lifting the rear part up, especially if a little pen fluid and some heat cycles are applied. One punch and you should at leat see whether the groove is shaped as it should be and that there is something left in there.


Tim
Click to expand...
This is the correct answer, millwright 101.
Click to expand...

I'd try this too.
 
The purpose of the Sunk Woodruf key being to transmit torque and hold in place during high speed operation. The Shear is another interesting thing. If something in the train destructs the key will Shear , preventing catastrophic damages. Easy enough to put one in ,occasionally a nightmare to remove. Penetrating oil , pinpunch , vice-grip lock, side cutting pliers (dykes) ,Tig welding a slide hammer arrangement to it , or a miniature cutting wheel down the center ,up to you.
 
Torontonian said:
The purpose of the Sunk Woodruf key being to transmit torque and hold in place during high speed operation. The Shear is another interesting thing. If something in the train destructs the key will Shear , preventing catastrophic damages. Easy enough to put one in ,occasionally a nightmare to remove. Penetrating oil , pinpunch , vice-grip lock, side cutting pliers (dykes) ,Tig welding a slide hammer arrangement to it , or a miniature cutting wheel down the center ,up to you.
Click to expand...

My understanding from my training days, is that keys are more to locate rather than drive. Especially in this instance where the timing marks are on the rotor.
The nut is there to retain.
It was a long time ago though (my training)
JohnT
 
JohnTy said:
Torontonian said:
The purpose of the Sunk Woodruf key being to transmit torque and hold in place during high speed operation. The Shear is another interesting thing. If something in the train destructs the key will Shear , preventing catastrophic damages. Easy enough to put one in ,occasionally a nightmare to remove. Penetrating oil , pinpunch , vice-grip lock, side cutting pliers (dykes) ,Tig welding a slide hammer arrangement to it , or a miniature cutting wheel down the center ,up to you.
Click to expand...

My understanding from my training days, is that keys are more to locate rather than drive. Especially in this instance where the timing marks are on the rotor.
The nut is there to retain.
It was a long time ago though (my training)
JohnT
Click to expand...
Yes, and if the rotor to sprocket spacer is put on wrong, the rotor will not be secured and will spin without a key, no matter how much you tighten the rotor nut. This may have been the root of the issue.
 
hello All best wishes to everyone

regarding woodruff keys, I would humbly point out the following in relation to bad fitting. this is purely info for those un aware. it can cause problems that are non existant.
On Inch based system:
with every thickness, a woodruff key also comes in differing radius. if a bigger radius is attempted to be fitted, it will not seat correctly and there fore appear to sit higher. the reverse also applies.

there is a table of woodruff keys and numbers available from many sources. machinery handbook (any edition) is a good reference to have for all manner of engineering standards.

if the replacement key is the same thickness AND radius it will fit.

good fortune to all
Bradley
 
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