Originally Posted by
unterhausen
I was a bit worried about the ones you have to face, but my lbs has the facer for that too. I was thinking about getting an external cup tapered head tube for a gravel bike frame.
The Columbus MTB tapered HT is 56mm at the fat end. Do you get hand facers that big? Even if you assume the fat end is square from the factory (which it did seem to be) the cut end is 46mm.
It's a dilly of a pickle because it's also too fat and thin-walled to hold in a lathe to attempt to face it before making the bike.
I took mine to a place that makes custom motorbikes and he got it really flat with a belt sander and checking the squareness on a machined table. He said that the only way to lathe it would be to machine a bit of aluminium to go inside it to support it so you could grip it properly.
I don't think any of the LBSes near me have any of these tools or would even know what they were.