I think you did well Denis!
Just keep in mind that you will forever curse yourself if you don't drill them out true.
One thing you can do is replace a few studs temporarily and use the head itself as a guide.
Any fairly snug-fitting drill bit will be guided by the head, and will mark a centre on the top of the offending stud, to guide your punch &/ or drill (I think Robert Leigh suggested this above).
The Woodrow tools are great in principle, but in practice the hole sizes in the head are distinctly variable. If you can find any bolt or scrap of tube which fits snugly and drill it down the centre, it will have the same effect.
Drilling down the middle of bolts is a challenge but can be done:
(1) drill a hole in your machine vice using the tapping drill size for the bolt you want to drill (OK, I have an old machine vice - but the point is it will sit dead flat and can be bolted to the bed of the drill).
(2) start the tap in the drill chuck (turning it by hand), until it gets too tight to turn, then finish by hand (this gets you a nice vertical start)
(3) put the tapping drill back in the chuck, and lower so the bit is located in the threaded hole; in this state bolt the vice to the drill bed.
(4) raise the chuck, remove drill bit, replace with a pilot drill say 3mm dia - not too small; screw your bolt down into the vice.
(5) now you can drill down the centre of the bolt in perfect alignment - well, you stand a good chance...
Of course you could do the same trick with any bit of tube etc that will fit, as long as you can stop it spinning while you drill it.
Just keep in mind that you will forever curse yourself if you don't drill them out true.
One thing you can do is replace a few studs temporarily and use the head itself as a guide.
Any fairly snug-fitting drill bit will be guided by the head, and will mark a centre on the top of the offending stud, to guide your punch &/ or drill (I think Robert Leigh suggested this above).
The Woodrow tools are great in principle, but in practice the hole sizes in the head are distinctly variable. If you can find any bolt or scrap of tube which fits snugly and drill it down the centre, it will have the same effect.
Drilling down the middle of bolts is a challenge but can be done:
(1) drill a hole in your machine vice using the tapping drill size for the bolt you want to drill (OK, I have an old machine vice - but the point is it will sit dead flat and can be bolted to the bed of the drill).
(2) start the tap in the drill chuck (turning it by hand), until it gets too tight to turn, then finish by hand (this gets you a nice vertical start)
(3) put the tapping drill back in the chuck, and lower so the bit is located in the threaded hole; in this state bolt the vice to the drill bed.
(4) raise the chuck, remove drill bit, replace with a pilot drill say 3mm dia - not too small; screw your bolt down into the vice.
(5) now you can drill down the centre of the bolt in perfect alignment - well, you stand a good chance...
Of course you could do the same trick with any bit of tube etc that will fit, as long as you can stop it spinning while you drill it.