This guide shows different methods to measure the taper of a shaft. Thanks to orangerobin for the reference.
Tapers of common components
According to Naz: "Most of the ones I’ve done all seem to be 5 degree, except the silly french of course, which is 4 degrees."
| Taper | Small End Dia (mm) | Large End Dia (mm) | Taper Length (mm) | Taper (mm/mm) | Resulting Angle (Degrees) | Taper (Degrees) |
|---|---|---|---|---|---|---|
| Motobecane Ignition | 12.70 | 14.95 | 23.75 | 0.0947 | 2.7 | 5.4 |
| Peugeot Doppler Non Enduro (Fits Ducati CDI). | 13.04 | 15.90 | 27.50 | 0.1040 ~0.10 | 3.0 | 6.0 |
| Peugeot Doppler Enduro 441283 12/2009 "Problem Crank" | 11.4 | 15.9 | 23.0 | 0.196 | 5.5 | 11 |
| Pug MVT Premium Internal Rotor | 13.40 | 16.00 | 31.87 | 0.0816 | 2.34 | 4.7 |
| Puch, Tomos, Derbi, and Sachs 505 Ignition | N/A | 15 | 18 | - | 5 | 10 |
Cutting a Taper
Octavio: I just cut the taper for a Puch shaft last night. 5 degrees was dead on. My major ID ended up being 0.59” (15mm).
Here is the procedure for those who haven’t done this before:
- Set your compound slide angle to your taper angle.
- Square up your tiny boring bar.
- Take passes of material off using only the compound slide axis.
- Creep up to your final ID checking fit with your crank during the last 0.01”(0.25mm).
- If you’re not super confident. practice on a piece of Al stock ahead of time.
This procedure is pretty obvious to those that have a lot of machining experience, but if you like me and have some, but not loads, it takes some thinking and doing to get this all figured out. I practiced on a piece of Al stock before chucking up my actual rotor.
