By James Morikawa
I will briefly describe the mitering of the Chain Stays.
Pictured below are the tubes and stays mitered to fit the frame jig.
On this build the customer wants "S" bends.
I used my Hammil Engineering Fork Blade Bender that I purchased from Nova Cycles a number of years ago. I've done some modifications to the bender to better suit my personal use.
On this build, I'm using socket type dropouts.
I'm measuring for the inside diameter of the drop-out socket. I use this measurement for marking a reference-points on the chainstay. Notice the reference mark I've made. I will cut and miter to around this area. This is approximately where the dropout will be brazed.
Above I'm using the "antenna" measuring tool to get an idea of chainstay length for the mitering process. I've written about this tool on a previous page.
Transfering and marking the length onto the chainstay. I will use these marks as reference points in the mitering process.
Getting an idea of the approximate angle for mitering. I've written about this simple tool in a previous page.
Having reference marked the miter length, and knowing the miter angle, I proceed with the belt-miter process.
The belt-miter — I think of it as a high speed "filing", or "honing" process. The tube or stay can be quickly removed and remounted onto the belt-miter. Minor adjustments to angle and centering can be made during the miter process; usually as I near the desired dimensions. The markings I described above let me know when I'm nearing the desired lengths. I monitor the mitering process by removing the tube/stays from the miter and checking the fit on the frame jig. The idea is to miter and fit the tube/stays to the frame jig without changing any of the jigs angles, nor lengths. I quess as in machine shop talk, "I'm honing for a precision fit".
It's not a precision one-cut mitering operation such as done on a milling machine/hole-saw set-up. It'a process very similar to what's called, in machine shop jargo, "honing", or "hone" — definition from my American Heritaage Dictionary: "A tool with a rotating abrasive tip for enlarging holes to precise dimensions". In this case the tip would be the rotating belt-roller, and the hole would be the miter shape.
Enough said, I'm going to talk someone in a confusion.
Have a good day.