Thread: Mill/Lathe
View Single Post
Old 06-25-2011, 05:35 PM
42blue15 42blue15 is offline
Motorized Bicycle Elite Member
Join Date: Sep 2008
Location: St Louis metro, USA
Posts: 135
Default Re: Mill/Lathe

Originally Posted by Dan View Post
...LOL, rambled there and really just wanted to ask, any thoughts on material for the bushing? Most mass produced ones seem to be steel? Also, will be mighty thin. Am a bit worried about that but it will have no wiggle room.
... So, I want to make a shaft increase-er (5/8 to 3/4) Is not enough room and need a 7/8s drive. ...
5/8" to 3/4" would be 1/16th thick, that's not real thin. Any kind of structural steel should work. Mild steel too, maybe even cut it down from a piece of black pipe. But you need to cut the black pipe down from BOTH directions, to expose clean smooth metal. So, if you could find a piece of pipe that is 1/2" ID and 13/16" OD that would work--but a piece of black pipe that is 5/8" ID and 3/4" OD but a little lumpy will not.


First question I have is how will the CVT be rotationally-secured on the engine's shaft? is there a keyway in the engine's shaft and in the CVT input, and are the two keyways the same width? The key may need to retain the bushing from working out, meaning that you may need to cut a closed slot into the bushing. To cut the keyway you will need the vise & vise hold-downs, the 3/8" mill collet and drawbar, an end mill (or two) in the smaller of the two keyway widths, and a drill bit that is about 75% of the diameter of the end mills.

The key itself you may need to make, since it will need to be extra-tall (not square). You can use aluminum or brass, just put a bit of anti-seize compound on it before assembling things.


The second problem gets back to the 3-jaw chuck.... they don't really center well. Which to a machinist, means within .001" or so. You would need the first item I mentioned (the dial indicator w/magnetic base) to check that.

Here is the problem that happens with cheap 3-jaw chucks: if you make cuts on a part, take it out of the lathe to test-fit it, and then want to put it back in the lathe to cut on it again,,,,, the second cuts are NOT going to be coaxial with the first.

If you tighten all three of the lathe chuck pinions gradually and equally, that helps with centering. You may get the error down to .003" or less if you're lucky--but still doesn't guarantee it will be perfect. And you cannot just eyeball things, since being just .005" off can make many parts unusable.

If you want to try to make this bushing without a 4-jaw chuck and without a dial indicator, you can do that but you should not remove the part from the lathe chuck to test fit it to the engine & CVT. You will need to hold the engine and CVT up to the part still clamped in the lathe chuck to test-fit them.

The dial or vernier calipers would help a lot here also.... what I do is cut a part to .01" too big (for an outside measurement) or too small (for a hole), and then start working it down in very light cuts until it is the exact size needed.
Reply With Quote