Drill The "Keeper" Hole in the Front Sprocket?

The stock front sprocket on my KZ 750 B4 has the small hole in it to accomodate the tang on the lock washer that you bend over the edge of the nut to lock it from turning.

I just got a replacement sprocket from Z1 and it doesn't have the small hole.

Should I drill it to match the old sprocket?

If you don't feel comfortable doing this I'd imagine a local machine shop can do it for you.

It will take a centerpunch and hammer(after measuring where the new hole will be),drill press, cobalt drill bit of the correct size, cutting fluid(Rapid Tap is a good one or Tapmatic))a drill press vise to hold the sprocket, and slow speed and firm pressure as the sprocket is probably hardened and is tough to drill.

Don't forget to break the burr(chamfer) with a drill bit or file after drilling so parts fit together.

I don't have a drill press anymore, I do have several sets of bits, spring ceneter punches, and a good hand drill. I guess I'll just go for it.:laugh:

I was wondering how hard the steel would have to be given that the rear sprocket is aluminum and has lasted for many years (and maybe 20k miles) with very little wear.

I guess I'll find out how hard it is when I try to drill it.......:ohmy:

It's hard, as in surface hardening, be a lot easier to drill if you use a Dremel with a grinding stone and grind down about .025"-.030" to get through the hard part.

steell wrote:

It's hard, as in surface hardening, be a lot easier to drill if you use a Dremel with a grinding stone and grind down about .025"-.030" to get through the hard part.

Interesting, I think I have some diamond tipped cutters for my Dremel. Maybe I'll start the hole with the drill and if it won't cut, I'll try the Dremel.

steell wrote:

It's hard, as in surface hardening, be a lot easier to drill if you use a Dremel with a grinding stone and grind down about .025"-.030" to get through the hard part.

HARD doesn't begin to describe it.... I flattened the tip on a steel nail set punch trying to put a dimple in it. The drilles would not even put a shiny spot on the metal. I was able to remove some with the cone shaped stones with my Dremel, but it is not surface hardened it goes all the way through. I did not get a hole all the way through, but I got a flat bottomed hole about half way deep using diamond impregnated cutting cylinders and my Dremel. Hope that will work.

Forking ridiculous they made that thing out of something from the planet Krypton.

Different manufacturers may do it differently

Solumnruss (think I spelled that right) was trying to cut a sprocket on his lathe and ran into that, but I'm pretty sure he just had to get below the surface hardening to cut. Could be wrong though, that was a while back.

Generally, you can anneal (make it soft again) hardened steel alloys by heating it till a magnet won't stick, then letting it cool slowly in the air.

You'd have to harden at least the teeth before using it again, and that's more complicated

steell wrote:

Different manufacturers may do it differently

Solumnruss (think I spelled that right) was trying to cut a sprocket on his lathe and ran into that, but I'm pretty sure he just had to get below the surface hardening to cut. Could be wrong though, that was a while back.

Generally, you can anneal (make it soft again) hardened steel alloys by heating it till a magnet won't stick, then letting it cool slowly in the air.

You'd have to harden at least the teeth before using it again, and that's more complicated

I am used to working on gun hammers and triggers that are case hardened, but that sprocket is one hard SOB. Funny to lean on a drill for about 15 seconds then lift up and see you didn't even POLISH the point you were trying to drill a hole in.....:ohmy:

I suppose that means the teeth shouldn't wear too fast.

I still can't figure out why the front sprocket has to be so flinking hard when places like Sprocket Specialties have been making sprockets out of aluminum for many years. I have had one on the back for at least 15 years and it shows virtually no visible wear. With the roller spreading the force over a long curved area, it doesn't seem like it would need to be hardened to Rockwell Ten Million......