Drill/tap question

[ian_uk1975]

Got a couple of failed Helicoil repairs to deal with and have decided to just go oversize rather than attempt another thread insert repair. The original holes were M10x1.5 and the Helicoil drill was 10.25mm. The holes were then tapped for the Helicoils. What is the closest next size up I can goto? Could I just go straight in with an M12 tap, or will I need to go bigger?

[The Black Flash]

looks like you're just ok at m12:
http://www.simetric.co.uk/sidrill.htm

[one eyed mick]

It will be marginal tapping size drill for m12x1.5 is 10.20mm you will have to be abs spot on withline up HTH

[Pumaracing]

You're already at 12mm which is what the o/d of a 10mm helicoil tap is. You'll now have to either fit a helicoil for a 12mm bolt or drill and tap directly for a 14mm bolt.

I've never seen a properly fitted helicoil fail so I suggest you find out why these did first.