On Oct 29, 12:37*am, dave wrote:
oops, thanks, does helicoil have that?

Not sure, it might be ex-catalogue. These guys used to sell the taps
and repair coils (in fives) which I believed were Helicoil:
http://www.framebuilding.com/economy...mebuilding.htm
but it seems they've stopped and offer the traditional block insert
repair. With the helicoil style, reaming was not necessary, the
remaining old threads mostly removed with a normal drilling bit in a
drill press. The tap would align with the old thread and remain true
as long as you didn't freehand the drilling with a portable drilling
machine. It might be that the reaming operation is necessary with the
block insert but I'd say there's a fair chance you wouldn't get it
precisely aligned with a hand tool. I'm surprised in the withdrawal
of sale, I know there was a preference for the coil style by my local
professional frame builder and mechanic and he'd had plenty of
experience with the older block insert.

It might just be that the coil style requires a better cut of thread
and many dont want to have to learn the skill of hand cutting a good
thread.