Everybody (many is more accurate) complicate tools with a sine function. Distance between rolls is immaterial knowing their spacing is what makes it work dependably. Do a couple calculations at say 3.500, 5.000, or 10.000". Then insert a actual inspected length, say you determine the planned 5.000" turns out 5.006. Depending on work you do that amount will result in a small percentage, and why longer bars are more accurate. I think right here on HMT.net, Marv did one in wood or cardboard that still worked. With one or two nice plates of material you can go to town. And ignore a machining process using two vee's; takes a degree of additional sophisticated tooling. [swivelhead mill, relieving cutter, angle wheel dresser, surface grinder, and some way to generate accurate spacing, and you'll still be compelled to determine the result]
Here's a little gift.....
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