by James Morikawa
I will write briefly on "Mitering the Front Triangle".
Above, an example of a mitered front triangle. Tubes have been mitered to fit the frame jig.
Measuring to establish where the headtube-bottom should be
A very important reference-point is the knowing, and "marking out" the location of headtube-bottom. From this reference-point I can locate where the headtube-top, toptube-joint, and downtube-joint should be — as they should be on the frame jig — as based on the frame's design specifications.
Good to have the fork and headset that's going to be used, to get a precision wheelbase-line to headtube-bottom length.. Best to calculate it using measurements obtained from the actual fork, and the headset lower stack height. Not always possible, so I'll just use what I know will work, which have been most of the time.
Having the headset's spec-sheet is nice to have. Having the fork's spec-sheet is nice to have. Having a million-billion dollars to waste would extremely nice to have! Duh!
A way to establish the toptube mitering angle.
A way to establish the toptube mitering length. I'm using that antenna tool to I wrote about previously. I can then tranfer this length and mark it out on the toptube — reference marks for the mitering process. Process works similar for downtube mitering.
Above, I've already mitered the toptube-joints. I'm in the process of obtaining angles for the downtube/headtube joint.
A method for setting the miter-angle on the beltmiter. The beltmiter's tube holding fixture can be easily lifted off the beltmiter. Pretty cool, eh?
I'm "into" the cutting, mitering, and honing the toptube to fit the frame jig. The joints can also be rough cut to shape using aircraft snips.
I think I've come up with a workable way to miter tubes for custom frame building, though not for mass production building. This is a personal opinion. I think I had better create a section just on my beltmiter and the process of how I use it. Give me some time. I'll write a section dedicated to it.
That's it for now. Goodbye.