Drilling 1mm holes through cap head bolts

[greybeard]

I suppose the title says it all, but a bit of background might modify the possible answers.
I'm prototyping a new style of tuning pin for a multi-stringed musical instrument.
I want to keep the costs rock bottom as I'm proposing to donate them to local schools to encourage an interest in music making.
Part of the tuning arrangement has finished up as a M5 x 25mm cap headed bolt, with a 1 -1.5mm hole drilled sideways just under the head.
This is the primary anchor point for the steel string.
Stainless would have been nice, but the near impossibility of drilling 25 bolts per instrument rules that out.
The bzp bolts I have tried seem to be case hardened, but that seems to be the only way I can go forward.

I'm thinking along the lines of either using a small grinding wheel in a dremel type drill to make a small flat, and cut through the outer layer, or heating the whole batch up red hot to anneal it, but then that would mar the appearance somewhat.

Any ideas would be welcome, along with any information that seems to fit the problem.

John

[mactec54]

greybeard

The Cap screw you want to drill, is not a problem, make a small fixture, (flat Plate) with the 5mm hole in it, then drill the 1mm hole through the edge of the fixture, were you want it to go in the cap screw, put the cap screw in the 5mm hole & drill away, it's just like having a drill bush, this will give the drill a guide

[greybeard]

greybeard

The Cap screw you want to drill, is not a problem, make a small fixture, (flat Plate) with the 5mm hole in it, then drill the 1mm hole through the edge of the fixture, were you want it to go in the cap screw, put the cap screw in the 5mm hole & drill away, it's just like having a drill bush, this will give the drill a guide

Hi mactec.
That's the method I used for some of the bolts in the first instrument I made, the proto-prototype
However, I did find that the pilot hole quickly opened up, but that might indicate I need a more rigid set up.
Also, the difference in the hardness of the bolt and the metal I used, did tend to give a shock to the drill as it hit the bolt thread, and I still blunted the drills fairly rapidly.
I got through five drills in drilling about 50 holes, some broken some blunted.
This was just trying to drill straight through the case hardening, of course, hence my post here.
Regards
John

[greybeard]

Just remembered that at the time I realised that there would be a high spot of the thread going across the hole, which the drill bit would hit.
I did wonder if I could arrange matters so that the hole in the jig came down into a valley in the thread, but that didn't seem a realistic possibility.

[mactec54]

greybeard

Your cap screws are not case hardened, they are heat treated, but quite tough, try a cobalt drill it should last better,You will need to hold the cap screw in tight, so it can't move in the fixture, put a nut & washer on it to clamp it in the fixture, if it is not held tight in the fixture, it will damage the drills quite fast

[greybeard]

Thanks mactec, I'll give the cobalt drill a go.
John