odd size chuck key

[rmcphearson]

I bought an old Cushman 4 jaw off fleabay and it requires a chuck key bigger than 1/4", smaller than 5/16". The i.d. of the socket is about .290 across the flats. Is there such thing as a 9/32 key?

I may make one from a hardened pin but I don't have a mill so it will not be a quick and easy job for me.

Regards,
Roland

[JCHannum]

Chuck keys do not necessarily follow any dimension standard. To make it more complicated, they are often tapered to boot. It is a good learning project for file work.

[digr]

I built this one and didn't have a mill yet. Used a side grinder with a cut off wheel.

[Mcgyver]

I may make one from a hardened pin but I don't have a mill so it will not be a quick and easy job for me.

as a general principal, make the part you want wear soft....better to have the key get messed up over time rather than the chuck...I'd make the key from mild steel.

its an easy job to file a square section on the end of a round bar of mild steel

[Ken_Shea]

Or turn a piece about the right size then beat it into the chuck key hole with a big hammer, wiggling it from time to time so it don't get stuck, kinda like broaching in reverse.

Just kidding, just kidding

[Doozer]

That's a good way to break a pinion or worse.

--Doozer

[Ken_Shea]

That's a good way to break a pinion or worse.

--Doozer

Hard to believe any one could take that seriously Doozer, especially with the "Just kidding, just kidding "
at the end.

[Doozer]

Sorry, as soon as I read about hammering........my eyes totally glanced over the "just kidding" part. Sorry bout that.
--Doozer