Bicycle Mechanics - Need help with cones for Ofmega rear hub
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07-31-12, 12:41 PM
I was repacking the hub bearings on my 1984 Bianchi Nuevo(a!) Racing, and found that the cones were destroyed both front and back. I was able to get some campy front cones for my Ofmega hubs (nine 7/32 bearings) but am having a devil of a time finding rear replacement cones. They are 10x26 with nine 1/4 inch bearings each side. I was told by a number of people that the Campy rear cones work, but the local shop had 3 or 4 different types of campy cones and none fit. All had the problem that the narrow end of the cone was too wide to fit inside the circle formed by the bearings. Looking at the original cones, the cone was ground such that on the narrow end it tapered almost to a sharp edge, whereas the Campys seem to have more meat and be larger on this end.
Anybody have experience with this? Are these cones really different, or did my local shop show me the wrong parts, and should Campys really fit?
If Campy's don't fit is there another solution? I don't want to just buy something off I'net or ebay and find that I have the same problem that I had at my local shop.
07-31-12, 12:48 PM
Aaron's bike repair [Seattle]had a demonstration of how to combine
a variable speed drill to spin the cone on an axle,
and a die grinder to re face pitted cones.. as they spin..
07-31-12, 01:22 PM
Do you know if they have a youtube of this or anything? I would like to see how they set this up and what they did for a fixture to hold everything. I suppose I could do it on the drill press or in a lathe. Do you know if they ground in the same direction as the rotation of the cone or counter rotation? Or does it even matter? Also, do you know what kind of stone they used?
This is actually a feasible idea, thanks - I was thinking about getting the bigger cones and grinding them down, but hadn't thought of refacing the existing ones.
All that said, this is a great plan B - I would really like to replace with new if possible/available.
07-31-12, 01:47 PM
Use your Shao-lin Google-Fu., grasshopper .. Aaron has a Website.
07-31-12, 02:15 PM
Yeah yeah... dropped them a note! hope the cones are thru hardened otherwise I am going to have to figure out how to case harden them!
07-31-12, 02:25 PM
If you can keep the steel cool it won't lose its tempering.. keeping it rotating helps that,
Bench grinders in shops, had a water cup near them to keep cooling the piece being ground.
07-31-12, 04:29 PM
So Aaron replied and I got good info from them. To your point above - if the parts are case hardened, there is only a thin skin (several thousandths of an inch) of hardened steel on the outside of the piece, and if you grind through that you are to the softer stuff inside. In that case I may have a problem If the whole piece is through hardened (like if it is drop forged), that is a different matter. You are absolutely right about losing temper though when grinding serious amounts and heating up your piece.
Good lead - just joined this forum today and it is already paying off. Hope I can contribute to the collective good - Cheers!
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