Anybody know of a sprocket source?
Looking for #40 roller chain (bicycle) sprockets with an 11mm bore (keyed).
I need more than 9-11 teeth, more like 20.
runaway_pancake:
Anybody know of a sprocket source?
Looking for #40 roller chain (bicycle) sprockets with an 11mm bore (keyed).
I need more than 9-11 teeth, more like 20.
There is a standard size of chain out there that matches bicycle chain in pitch, but is wider than bike chain (I don't recall specifics - I'll try to look it up tonight when I get home); you can easily find such sprockets to match this chain (as it is an industrial and standard spec size). What you do is purchase such a sprocket to the spec you need, then you take it to a machine shop (with a bit of your bicycle chain), and have the shop face-grind/mill the surface of the sprocket to the proper thickness (they should also re-chamfer the sprocket teeth so the chain will ride properly). This won't be cheap for a single sprocket (depending on the shop, of course), but it likely will be your only real option (short of having a custom sprocket made - which will probably cost even more than doing the above).
Another option:
Take the rear cassette off a multi-speed bicycle and remove the smallest chain ring sprocket. Then have a machine shop weld up a disk/collar for the 11mm keyed bore you need, and have that welded to the chain ring. This is something that could be home-brewed if you're handy with a welder...
That's going to be a tough find. #40 is an ANSI (U.S.) spec, and the standard sprocket bores are inch, not metric. Easiest way might be to get 20 tooth sprocket with 3/8" bore and drill it out to 11mm, shouldn't be too hard. McMaster-Carr, McMaster-Carr #2737T132, $7.13 for the sprocket in steel. I use McMaster a LOT for all kinds of hardware and materials.
Oh, forgot about the keyed part. If it has to be keyed, you're going to have to find a step-up bushing. In inch sizing a 1/2"x5/8" bushing for keyed shaft is pretty common, but for an 11mm shaft, that's going to be very tough. I would just grind a flat on the shaft and use the sprocket hub setscrew.
Since 11mm (.433) is close to 7/16" (.437) the inside dia. could be 7/16" although that size is not commonly available(@McMaster).To do away with any major machining just get the 5/8" bore sprocket and get a 7/16" to 5/8" bronze sleeve bearing (6381K465) and with a hacksaw cut away for the key. Don't know how much of the key will be engaged or if there would be a size mismatch.
Thanks for the replies.
The sprocket is an odd duck, the teeth fit well with the chain. I guess it's a scooter thing.
The sleeve bearing idea seems sound. 7/16-to-11mm, close enough. I'm hopeful that it won't crumple up in there under stress. If I get a steel finished-bore sprocket, maybe I can use its set screw/s in place of the key bit. I'll have to order the stuff up, the layouts on the mcmaster catalog page aren't detailed in that regard. I won't know till I know.
Here I was wondering about J-BWelding the original sprocket to another and....
Good.
I have to come up with a platform to mount the motor on, too. J-BWeld is not out of the running, yet. 
More challenges lay beyond.
justone:
...get the 5/8" bore sprocket and get a 7/16" to 5/8" bronze sleeve bearing (6381K465) and with a hacksaw cut away for the key.
I would suggest cutting all the way through one side and then grinding a tall key that reaches between the motor shaft and keyslot on the sprocket.
If you try cutting a keyway without an arbor press and keyway broach I think you'll find it nearly impossible. You can't do it with a hacksaw and trying to file it is incredibly painstaking.
Ok - I found my notes:
ANSI #40 chain and sprockets have the same pitch as bicycle chain (1/2 inch), but the sprocket (and chain) is "thicker" than a standard bicycle sprocket and chain (almost twice the thickness, IIRC). So - I had purchased a 9-tooth sprocket (with a 1/2 inch bore for the shaft of a motor I was going to use) and had the sprocket face ground and chamfered to the size needed for the bicycle chain.
Now, if you are using #40 chain with the #40 sprocket, no need - just know that the chain won't fit a bicycle sprocket well (it will probably work, but it will have a bit of side-to-side play on the sprocket itself, which could lead to issues).
Chagrin:
justone:
...get the 5/8" bore sprocket and get a 7/16" to 5/8" bronze sleeve bearing (6381K465) and with a hacksaw cut away for the key.I would suggest cutting all the way through one side and then grinding a tall key that reaches between the motor shaft and keyslot on the sprocket.
If you try cutting a keyway without an arbor press and keyway broach I think you'll find it nearly impossible. You can't do it with a hacksaw and trying to file it is incredibly painstaking.
The 5/8" bore sprocket would already have a keyway so there is no need for an arbor press or keyway broach. The hacksaw was just to remove the part of the sleeve where the key would be,like turning a "O" cross section into a "C" cross section .
justone:
The 5/8" bore sprocket would already have a keyway so there is no need for an arbor press or keyway broach. The hacksaw was just to remove the part of the sleeve where the key would be,like turning a "O" cross section into a "C" cross section .
Whoops my bad; I misunderstood what you meant. Turns out we were both saying the same thing.