do some research on machining soft materials with standard twist drills....
tri-lobed holes are really common when not drilling through thick materials(under 1/2") with high helix twist drills.
And carbide drills with straight flutes are in a sense reamers.
a reamer has straight flutes for a reason, and that is to avoid the odd-shaped hole that twist drills tend to make.
I have drilled through hasteloy, nimonic, duplex and a whole host of other exotic stainless steels few peop[le know exist.
Harder materials will exhibit this effect to one extent or another, just not to the extent of say aluminum or brass.
Even using 3000psi thru-coolant carbide twist drills the holes never really make a "perfect" hole.
There is a reason holes in jets are made with reamers.
Besides boring the pants off of you(you really should wear belts ladies and gentlemen)
I've drilled out jets before as well.
Worked OK, but ended up buying jets in the end.
Lots of sets in fact... too many looking back on it now. 10 sets is more than any 1 bike needs... now I need more bikes.......
From the engineer at I had a conversation with about fluid dynamics going through a reamed jet orifice VS a tri-lobed(or otherwise non-round) hole, he mentioned that the drilled jet probably acts like 1-2 sizes smaller than it measures due to turbulence restricting flow through the opening.
So you may be running as if you had 120-130's....
Dunno, I machine things like a madman, but have no degree in anything past a BS in BS'ing.
l8r
