Woodruff key questions?

[AquaManAndy]

What is a good material to craft a woodruff key for the drive sprocket on a 66cc skyhawk engine? The original woodruff key along with a spare one from a spare flying horse engine both broke while riding and the sprocket would then come off the crankshaft. I then cut off the end of the largest pin punch I had and used that to form a woodruff key, now I'm not entirely sure what kind of metal the pin punch was made of nor am i sure or not if it will be strong enough to hold up to the engine. Granted however when I installed the last woodruff key i made myself i had to tap the drive sporcket on with a hammer it was so snug, I only had to slide on the first woodruff key i replaced. I can ride my bike again but after the last 2 incidents I am not confident to take the bike outside my neighborhood. so yes to reiterate what my question is what would be a good material to use for making a woodruff key? I want to be confident with my bike again. Thank you

 

[crassius]

fitting tight is usually more important than the material it is made from

 

[FurryOnTheInside]

I'm no expert having not even got all the parts for my build yet, lol; but just for something to talk about..

The woodruff key is sacrificial, meant to protect the shaft. Making it from stronger material will just be risking damage to the shaft or breaking the more awkward to replace keys further up the drive train.
I think I would investigate the possibility of a bad chain line or a problem with the chain itself that may be locking up, breaking your drive sprocket key.

 

[AquaManAndy]

Hmm Ill look at the chain today though I did have another problem free ride this morning when it was sunny out

 

[skyash]

If you're pin punch is for steel then it would be hardened and probably the best stuff for the job .if your sprockets got play or not up against the key it will pull in to the key and brake it .so make sure the sprockets hard up against the key when you it put on .

 

[Steve Best]

I am an expert on the topic (machinist and mechanic) and I'd suggest Furry gave a pretty good answer.
If the woodruff key keeps getting sheared, there is a problem somewhere else. It is only a location device.
Bolts not tight, grease on a taper, wear, something else is wrong.

Steve