TOPIC: angle of cut

I know Ron impresses highly about a 15 deg. angle
and have figured out with a business card between throttle plate and bore
the bit flat against plate the angle is appox. 15 deg.

However as you go up from the 6 oclock position to 3 o clock and then on the other
side to 9 o clock , if you follow the plates surface you will not get the 15deg. cut to the surface
your cutting over.(or 15 deg to flow of air)
So my question is do you keep cutter 15 deg. from bottom (6 o clock) or 15 deg from surface cutting on?
also as some GGuys have posted pics with material left between cuts or should there be no material between cuts??

Hi Greg the technique is a combination of the bit angle relative to the bore wall of the throttle body, and the "aim" of the bit. By aim I mean mark the center of the throttle shaft, either w/ a magic marker or just visually. Keep the centerline of the bit shaft aimed at the center of the throttle shaft, also maintaining the bit angle relative to the TB bore wall. The Groove is formed by a series of chop cuts, each cut overlapping the last. Ridges in the resulting groove are removed by moving right to left w/ bit, a "sweep".
Challenge is to clean up the Groove yet not overdo it. I often have to say "stop!" to myself even as I'm doing the left sweep clean up pass--it's tempting to want to make it pretty. The bit needs to fit the groove as tight as possible. Most of my Grooves don't turn out pretty. They work nonetheless.

Takes some practice of course!

Tracy G