I've seen this discussed/proposed on a lot of posts over the past years but has anyone successfully done it?
I need to move my front sprocket out about 0.3" so the circlip method of holding the sprocket on won't work. If i drill/tap a bolt in the end I can put a washer/retainer on to hold the sprocket from sliding off the shaft.
I ordered cobolt and carbide drill bits and am going to give it a try. I assume the shaft is hardened steel because I already tried with a regular drill bit and it didn't do anything.
Another option would be an offset sprocket but i couldn't find any for sale and figure the drilling would be easier than me making my own offset sprocket.
Are you pulling the shaft? How are you going to drill that straight and absolutely centered?
Even with a cobalt drill I bet you will have an incredibly hard time drilling it. And then how are you going to tap it? A hardened steel tap is not going to work, and you are going to have a blind hole, so you'll have to basically make a hollow shaft to get a tap in deep enough to fully cut the threads, we're talking tapping a 1" deep hole in hardened steel. You ever tried to tap even 1/4" thick plain steel? I've broken taps many times in 1/8" thick plain steel.
I think you'd be better off with a replacement countershaft taken to a machine shop and have it done there.
IMHO, but good luck anyway :)
Thanks for the reply, all good points you make, I am now skeptical:-(
I am going to do it in-place without removing the shaft. I plan to lay down my drill press and put it underneath the bike and line it up.
there is a small dimple in the center that will help me align and get the hole going.
I will try it this weekend and will report back. If it doesn't work i will move on to a different plan.
Well I drilled it successfully to about 1". Got through the first 1/4" with a carbide bit before breaking it. Luckily i was able to extract the broken pieces. Finished it off with a cobalt bit. The steel was really tough for the first 0.1" or 0.2" or so and then softened up, so must be a type of case hardening.
Weird thing, once i hit about 1" deep I appear to have hit a void? Looking at diagrams, i don't see any reason the shaft would be hollow or have an oil passage in there or anything?
Will work on the tapping next.
I've dreamed about this. You can get it center easily - the counter shaft was dimpled in the center. You could drill it and the tapping part will be very very hard. But if you manage it its a very fine solution.
The stupid circlip has bothered me for years, I want to fit a belt drive in it, but the hurdle has been the drill and tap situation as well as the fact that a poly chain belt cant be turned tighter than a 4.9" and the clearance to the stupid clutch push rod is only 4.4 at best ...
You're going to a 530 chain - all the best for your endeavor, I love it.
Cool.
Buddha.
You're right, the dimple helped in centering the hole for drilling.
My current tap is pretty old so i ordered a fresh one, should have in a few days.
Here is the setup, I laid my drill press down underneath the bike and shimmed it to the correct height.
BTW, I'm using the GS500 as a donor motor for a cafe project.
The deed is done, it went fairly smooth. I drilled about 1" deep with a 17/64" drill size (used a carbide and a cobalt). The outer part was a lot tougher than the inner. Then I put on a 5/16" cobalt drill bit and went back and drilled in only about 0.1" so my tap wouldn't have to cut through the tough outer section. I tapped with a 5/16-18, moving nice and slow. I should be able to use a 1" long bolt with a large washer to hold on the sprocket.
Brilliant work. Now I better do this and do a belt drive GS500 like I've been dreaming of.
Cool.
Buddha.