Laser cut large Campagnolo pattern sprockets - Update

[alexnharvey]

It won't be a significant change. Have you considered only treating the teeth?

[fausto99]

... Have you considered only treating the teeth?

...and what would be the advantage of that? If any, how would I keep the carbon off of the rest of the sprocket?

[alexnharvey]

They're the only part that needs hardened.

[fausto99]

They're the only part that needs hardened.

I think it would be advantageous to harden the centre part which engages with the splines on the freehub too. In which case, it's only practical to do the whole thing.

[531colin]

Hold the sprocket with a couple of bits of wire? Doesn't matter what happens to the wire.

Isn’t red hot wire likely to break?

Well, if I was going to tow a car, I wouldn't go out of my way to get the tow wire red hot, but how much does your sprocket weigh?

The biggest problem with silver soldering stuff is holding the parts together.....you have to get it all red hot for the solder to run, you need to juggle blowtorch, stick of solder, and flux as well if you need to re-apply flux halfway through....you don't have enough hands to hold the parts in position; one way of doing this is to wire the bits together.

I have never quenched in powder, only in oil or water. ...for either of those, you could heat up the sprocket on a brick. pick the brick up and tip the sprocket into the oil.

Powder arrived in the post today but I don't have a small metal tray sorted out yet so won't be attempting the hardening just yet. Does any one know if case hardening will result in any significant change of dimensions? Should I be filing and polishing for a slightly looser fit before the event?

Foil dish from the takeaway or from an oven-ready pie?

[alexnharvey]

They're the only part that needs hardened.

I think it would be advantageous to harden the centre part which engages with the splines on the freehub too. In which case, it's only practical to do the whole thing.

Do the splines show any wear or deformation currently?

[fausto99]

Do the splines show any wear or deformation currently?

No. None at all. I think that's because they were a very tight fit. In fact, I had to file to fit because I had erred on the tight side with my drawing. I could not find a dimensioned drawing or CAD file online, so I drew the centre from caliper measurements.

[fausto99]

I have never quenched in powder, only in oil or water. ...for either of those, you could heat up the sprocket on a brick. pick the brick up and tip the sprocket into the oil.

I think we must be at cross purposes here. The powder is to get carbon into the mild steel. I will be quenching in water.

[alexnharvey]

Do the splines show any wear or deformation currently?

No. None at all. I think that's because they were a very tight fit. In fact, I had to file to fit because I had erred on the tight side with my drawing. I could not find a dimensioned drawing or CAD file online, so I drew the centre from caliper measurements.

So, that part probably doesn't need hardened but it probably doesn't do any harm too, worst case is that the dimension changes and you have to file it a little.

If you do want to i think you can pack the centre with sand and then put the case hardening powder around the teeth.

[cycle tramp]

If you pop onto www.iforgeiron.com there's at least one thread about case hardening. Having not done it in practice, but it could be that only the bit of red hot metal that you put the hardening substance on may become case hardened... a bit like when samurai sword makers made the edge of the blade very very very sharp and hard by covering the edge of the blade (rather than the whole blade) with certain types of clay.

[SporranMcDonald]

I suspect my Campy 8 speed setup is not going to last much longer. In the long run, I may swap the whole lot out for some Claris 8 speed shifters and levers; then I'll have my pick of large Shimano sprockets.

Just to say that I have brought and fitted some Claris STIs [ R2030-L / R2000-R ]to go with a Shimano 8-speed rear end setup. Still early days but it's great to return to precise shifting.
The purchase was due to the Campag Chorus Ergo lever ( circa 2001 ) was having problems shifting on (both) :-
- full Campag rear end
- Shimergo

I just couldn't face another Ergo lever rebuild, especially as spare parts are seemingly unobtainable.
. . . . only 20 years pah ! ( possibly 80,000 miles . . . . 100,000 shifts maybe ? )

[fausto99]

I suspect my Campy 8 speed setup is not going to last much longer. In the long run, I may swap the whole lot out for some Claris 8 speed shifters and levers; then I'll have my pick of large Shimano sprockets.

Just to say that I have brought and fitted some Claris STIs [ R2030-L / R2000-R ]to go with a Shimano 8-speed rear end setup. Still early days but it's great to return to precise shifting.
The purchase was due to the Campag Chorus Ergo lever ( circa 2001 ) was having problems shifting on (both) :-
- full Campag rear end
- Shimergo

I just couldn't face another Ergo lever rebuild, especially as spare parts are seemingly unobtainable.
. . . . only 20 years pah ! ( possibly 80,000 miles . . . . 100,000 shifts maybe ? )

Good to know. Thanks for the recommendation. My Veloce 3 x 8 set up dates from 1997; not done badly, methinks.

BTW I tried a Shimano 8 speed hub rear wheel in my Campy 3 x 8 bike a while ago, without thinking about spacing, and it worked absolutely fine, with just a tweak to the derailleur end stops. I had tried it before but with shims on the spacers to match Campy 8s spacing. This time it was a stock Shimano 8s cassette sraight out of the box and it just worked! I know the two are only 0.1 mm different but over 8 speeds it adds up and Murphy's law it always waiting in the wings to trip you up - so - a pleasant surprise.

[fausto99]

Update. I have now had a go at case hardening my 32T sprockets. As suspected, it has resulted in some dimensional changes! I had to persuade them back to flat, which took a while, and they no longer fit onto the freehub splines. Perversely, the centres are harder than the teeth tips, as they remained red hot for longer, so I'm probably going to need the Dremel to ease out the centre indents.

[alexnharvey]

Update. I have now had a go at case hardening my 32T sprockets. As suspected, it has resulted in some dimensional changes! I had to persuade them back to flat, which took a while, and they no longer fit onto the freehub splines. Perversely, the centres are harder than thethe teeth tips, as they remained red hot for longer, so I'm probably going to need the Dremel to ease out the centre indents.

Maybe you should have only hardened the teeth! Or made the whole thing from hard steel in the first place.

[531colin]

I can see a Heath-Robinson contraption where the sprocket is mounted on a substitute freehub, slowly turned by a crank handle so that only the teeth pass before a (fixed) blowtorch before passing through a trough of the magic powder........

Am I the only one to be surprised that application of a powder to the surface of red hot steel allows carbon to become part of the steel?

Is this how (eg) hub cones and BB axles are case-hardened? For those, the hard layer appears to be quite thick (when its worn through)