Woodruff Key Cutter Question

[schemer]

On a project for an edger shaft I have to make that is no longer available for purchase, I need to cut a keyway for a pulley that has a built-in (or somehow attached) woodruff key. I was originally just going to use an end mill because I don't have any woodruff key cutters but I kept wondering if it was important or not that the slot ended in a curve. The .250 slot starts on the end of the shaft and is 1 inch long so the pulley actually slides on with the woodruff key in the pulley as opposed to the normal way where the key is in the shaft. Then I read somewhere about the curved end being better when the keyway goes up to a shoulder (which this does not) due to stresses where they meet. So, I think a regular end mill cut slot will work fine, but wonder if the original design was to make it stronger, or because they were set up with a woodruff key cutter and it was not even an issue? Thoughts?
Thanks,
schemer

edit: After thinking on it, I am going to buy the woodruff cutter and use it as it is the better way to cut a keyway anyhow. An end mill with a two flute cutter works ok for the most part but I may need to start a woodruff keycutter collection to add to my tooling. :whistle:

 

[JimDawson]

Re: Woodruff hey cutter question

I suspect that the original shaft keyway was cut on a horizontal mill with a 3 inch or so diameter cutter. That is why it tapers up at the end. This would be much more efficient in a production setting than using an end mill to cut the keyway. I think you will be just fine cutting a new keyway with an endmill.

 

[schemer]

Re: Woodruff hey cutter question

I suspect that the original shaft keyway was cut on a horizontal mill with a 3 inch or so diameter cutter. That is why it tapers up at the end. This would be much more efficient in a production setting than using an end mill to cut the keyway. I think you will be just fine cutting a new keyway with an endmill.

Hi Jim,
I was thinking that may have been the case. I almost bough a horizontal mill but ended up with a Bridgeport clone instead. I was editing my post above as you were typing so I may but a $20 cutter just to add to my tooling. But I believe you are correct in the fact that it will not pose any strength issues and was made that way for no particular reason. Now I am wondering if the little 3/4 inch keyway cutter would leave a radius on the end that is the same as the 3 inch cutter if that is what they used?
Thanks,
schemer

 

[Andre]

Re: Woodruff hey cutter question

Hi Jim,
I was thinking that may have been the case. I almost bough a horizontal mill but ended up with a Bridgeport clone instead. I was editing my post above as you were typing so I may but a $20 cutter just to add to my tooling. But I believe you are correct in the fact that it will not pose any strength issues and was made that way for no particular reason. Now I am wondering if the little 3/4 inch keyway cutter would leave a radius on the end that is the same as the 3 inch cutter if that is what they used?
Thanks,
schemer

A 3/4" cutter would not leave the same end radius as a 3" cutter.

A 3/4" cutter leaves a 3/8" radius and a 3" cutter leaves a 1.5" radius.

Just use an endmill.

 

[schemer]

Re: Woodruff hey cutter question

A 3/4" cutter would not leave the same end radius as a 3" cutter.

A 3/4" cutter leaves a 3/8" radius and a 3" cutter leaves a 1.5" radius.

Just use an endmill.

Thanks for your reply Andre. I guess if I buy a key cutter with the wrong radius it would be just as good to use the end mill. I knew the radius would be different, just didn't know what was used originally. Probably could figure it out.... Ok, I am done over thinking this. )
schemer

 

[kd4gij]

In theory in high stress app. an endmill leaves a sharp corner in the keyway witch can break under high stress. A keyway cutter has a radius on each touth that makes a lot tougher slot. Has nothing to do with the end of the cut. The larger the key the larger the radius at the bottom of the keyway. Now in the op's app an endmill will probly do just fine.

 

[GK1918]

See; again history reapetes its self, you need a shaper done deal.........

samuel

 

[awander]

If the Woodruff key is attached to the pulley, the curved side of the key would be buried inside the pulley, no?

Which would make the key look like just a regular square key to the shaft.


You don't mean that the curved side of the key is sticking out off the pulley, and meant to mate with the shaft, do you?

If so, using a Woodruff cutter to cut a semicircular Woodruff keyseat would be silly, as there would be no way to get the pulley/key onto the shaft....

 

[kd4gij]

No you wouldn't cut a Woodruff key slot. I would use the key cutter to cut the slot the lingth needed to get the pully on. An endmill will leave sharp conners in the bottom of the slot. With a keycutter the corners will have a radius on them. This chart shows the radius for each key size. http://www.transeals.com.au/catalogues/files/Transeals_Keyway chart.pdf . You may be able to get endmills with the radius on them. I have just always used a keyway cutter.

 

[awander]

No you wouldn't cut a Woodruff key slot. I would use the key cutter to cut the slot the lingth needed to get the pully on. An endmill will leave sharp conners in the bottom of the slot. With a keycutter the corners will have a radius on them. This chart shows the radius for each key size. http://www.transeals.com.au/catalogues/files/Transeals_Keyway chart.pdf . You may be able to get endmills with the radius on them. I have just always used a keyway cutter.

Yeah, but I think the OP is not worried so much about the corners at the bottom of the keyway, but the radius left at the end where the keyway curves up.