DarkSpeedWorks wrote:
beston wrote:
I added bosses to the top tube of my P4. Although nerve-racking, it really isn't a difficult to do following these
instructions from tririg. Of course, you wouldn't be adding the bosses, but rather following the part about drilling holes.
The process looks pretty easy. But there is one question l have: is there a precise and straightforward way to determine where the exact top or center of a round top tube is? Just so l can get the bento holes at the very apex(?) of the top tube. Any thoughts?
Nick (TriRig) has a lot more experience with this than I do and may have more insights than me on this.
The short answer is 'No'. The slightly more flexible answer depends on how 'precise' you really care to be. My approach was to;
1. mask off the area for the two holes and a stripe down the top of the top tube
2. use calipers to measure the width of the tube.
3. as carefully as I could, use calipers to then mark the center of the tube (=width of tube/2).
4. check the 'centering' of both holes by extending a line through the two 'drill' marks all the way to the seat post (any deviations of straight-ness or centering my be highlighted by doing so).
5. recheck all measurements, adjust.
6. recheck all measurements
7. recheck all measurements
8. Starting with the smallest drill bit I had, making small holes in the top tube and progressing stepwise to larger bits.
I was very happy with the outcome / alignment of the two bosses. However, I'm sure there are more precise ways of doing this than I have explored.