I disassembled the shaft holding the conical clutch assembly and posted some information on my blog. Here's a picture of the seating surface that the conical clutch mates with.
The right one has not been worked on yet, so you can see the glazed surface that causes the clutch to slip. I already used emery cloth on the left one.
The cone clutch surface is shown below, along with all the other pieces that make up the assembly.
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