Keys for keyways

[Antman]

Trying to crank my homemade rotab, I completely distorted the key in the keyway. I'm using a lathe change wheel and a mod1 worm I made. Most of the backlash was in the key. The gear fits closely with the shaft. Please give some advise about material for a 4mm keyway and how best to make and fit a key.
Ant

 

[MuellerNick]

Keys are made out of C45 (US name 1045).
I'd just buy a key before waisting time to make one … well, waisting time to buy 10 if I can't find the right size in that drawer and stock up for the next one that doesn't fit.

Nick

 

[MachineTom]

Having had issues with worn keyways before, The easiest way is to buy a slightly larger piece of keystock, like 5mm instead of 3/16, then just file it to fit the shaft then to gear. I do this by filing the key in a vise set so that only the area the fits the shaft is cut, then insert the key into the shaft and file to fit the gear, very likely one is worn more than the other.

Of course the best way is to recut the shaft and gear for a larger key.

 

[rodw]

I recently bought a selection of various sizes for AUD $16. I only need one or two

 

[Antman]

Thanks guys can't buy key steel here, I'm at the end of nowhere over here, the nearest place I know where you can sometimes get it is 200km away. I've started making the key from some nice mystery metal, a scrap steering shaft, in the shaper. The stub of stock gives me something to hold on to when I file to fit. And thanx again Tom, I see I must cut the keyway in the shaft deeper before I carry on with the key.
Ant

 

[Philipintexas]

I encountered a similar problem with a large 10" flywheel on a small 1/2" shaft on an IC engine and it would loosen the key no matter how tightly I fitted it. As a last resort, I drilled/tapped a hole into the wheel and shaft on the joint and put in a socket-head Allen bolt. I thought it was an original idea but I later learned this is a common solution. It has never loosened.

 

[Tin Falcon]

Ant: you can make a key from just about anything lawn mowers often have an aluminum key. If the operator hits something hard it shears the key. the mower stops running as the timing is now out of sink pull it aprt replace the key and you are good to go. it saves the crank shaft from being bet and having to replace the whole motor. many people do not know this and replace the mower rather than fixing.
Tin

 

[Entropy455]

1045 is a good key-stock steel. This is the material of choice for fabricating guide pins to join pump casings and steam turbine casing halves together.

However unless you are heavily loading your gears (i.e. high shear forces on the pin) any cold-rolled mild steel should work fine.

Go to your local hardware store. They’ll have pre-cut standard and metric size keys, and also cold-rolled square steel bar-stock (12 inch lengths) in standard and metric sizes.

And as others have already said - if you’re looking for a tight fit, you can get a slightly oversized key, and machine it down.

 

[Entropy455]

http://www.harborfreight.com/60-piece-key-stock-set-67606.html

http://www.harborfreight.com/80-piece-woodruff-key-assortment-67584.html

You can mail-order keys pretty cheap too. . . ..