Woodruff key size

R

RandyWhite

New Member
I had a cracked small bevel gear and a missing woodruff key. After reading on the site here I bought a new gear from Pistonbikes, but cannot find the correct sized key.

I was told to get one 1 size too large and file it down. No problem until I look at the size onthe shaft and the gear. The slots are 2 different sizes!

I have 1 woodruff key that fits sloppily into the gear, has wiggle room from side to side, but that same key does not fit the slot on the shaft.

is the woodruff key supposed to be 2 different sizes or is it made to fit sloppily in the gear slot.

What the ****is going on? Not to mention no one sells the small bevel woodruff key.
 
i was gonna make a how-to post about this, as a bike i built lost the key in the 10t gear.

i didn't have any keys on hand, or an extra motor i could steal one from, so i took a pin out of a bicycle chain and ground it down to fit on my grinder.

it took me about 5 minutes and it's a lot harder steel than the original.

after a few months, it's still working fine.
 
Thinking along those lines, perhaps the unfluted end of a drill bit would work as well, cut to size using a Dremel tool.
On the other hand, it might be too hard and shatter under stress, but you could always heat it with a torch to de-temper it.
 
First off Rohmell, non of the keys in that set fit the gear, let alone the shaft.

Second, I don't have anything other than a dremel to try sizing one down. The issue that is driving me nuts is the slot in the shaft and the slot on the gear are NOT the same thickness.

To make it fit, it would either have to fit sloppy as **** in the gear (Which I hear is a bad thing) or look like this from the side view.
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If sloppy fitting isn't an issue, I can file one down to fit the shaft and be done with it. Woodruff keys go for around .09 - 2.00 here locally. Screwing one up isn't too big an issue money wise, I just don't have the tools to do it. Still can't find out what the stock sized one is either.
 
what did you end up doing for the different sized key slots?
i just broke 2 teeth on my 10t sprocket and all the ones im looking at online look like the key slot isnt the same size as the one i had on
 
I went to a local store and bought a small selection of keys to fit the shaft, and left the gear side alone. Apparently they are made 2 different sizes to help gets things broke.

Only option I found was to remove the shaft and make a bigger woodruff slot on both the shaft and gear so they both match. That means if the gear or key ever breaks again you have to modify the replacement gear again.

I didn't have the tools to do it so I found one that was close, used a dremel to take some height off the key and put it all back together. Put about 50 or so miles on it and no issues. Dax has a nice set with the gear and key provided if you need them both.

Side note: I didn't "lose" my original key. When the gear cracked the key got lose and ended up behind the big gear, causing a lot of heat and clutch issues. Ripped that apart and tried placing the original key back into the shaft and it wouldn't fit. I have no idea how it fit together in the first place, with 2 different key widths.
 
ok wait so is your key fitting tight in the shaft and gear or does one has some wobble, i bought 2 keys the other day because i originally broke the key in there and the gear was spinning without the shaft so i replace it and then i mounted my engine on un straight and the chain broke the teeth on the sprocket, so yea, i was thinking if there not the same size maybe put the key in a bench vise and leave half of it sticking out and file the side of that half down to fit both shaft and sprocket snug.
 
My key fits in teh shaft like a glove, It even needed a tad bit of force to get it in. The gear side is lose as ****. Think penny size difference on the gear side.

The filing would probably work. Especially if you have calipers to measure, But I didn't have any of that.
 
ok so yours is running with that loose gap and your fine? ill probably file down the bottom half to fit better and keep the top half thick, because the key i have is already to thick so i hope i dont have problems.
 
Mine works fine for now, but you are going to need to get a key bigger than the gear side ad file it down as well. There is no woodruff key in standard size that fit the gear.

At least not that I could find.
 
Nikko said:
ok wait so is your key fitting tight in the shaft and gear or does one has some wobble, i bought 2 keys the other day because i originally broke the key in there and the gear was spinning without the shaft so i replace it and then i mounted my engine on un straight and the chain broke the teeth on the sprocket, so yea, i was thinking if there not the same size maybe put the key in a bench vise and leave half of it sticking out and file the side of that half down to fit both shaft and sprocket snug.
Click to expand...
Are you just going to use a metal file by hand or a drimmel?
 
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