Drilling a 11mm head to accept 12mm studs

[chrischris]

I would like to drill my 11mm head to accept my new 12mm arp studs.

I can't seem to find a 12mm drill bit, but I do have a 31/64 inch bit that is just over 12mm. Will this bit be a problem? Should I do this on a drill press or will a steady hand with a hand drill work?

Thanks guys,

[arb]

Well, that's 12.3 mm.  

Do you have a 29/64 bit too? That's 11.5mm - half way there. I'd use the drill press and do it in 2 steps so they will be more precision... use the 29/64 first and them the 31/64 to finish.

[chrischris]

Cool, I will use my neighbors drill press. Will drilling it out to 12.3 mm be a huge problem? I want to ensure a proper seal, but with my idiotic limited knowledge I have found that sometimes I sweet the small stuff....

[blkboostedtruck]

drill slow!
Duane

[arb]

If you were to Mic the 11mm holes you'd find they were larger than 11.0 mm- maybe in the realm of 11.2 or 11.4 mm. I think 12.3 mm is not a problem. Infact, when you are done, 12.3 will not be the final size, maybe 12.34 or so


 YES !!!  SLOW that press down. You want a slow rate. Aluminum is VERY VERY soft  - part of the reason I said to step it.... take it slow and easy. Ideally you would not drill at all but broach it !!!  Google broaching if you haven't heard of this more precise method.

[riddleyo]

In addition to drilling the holes, you will have to enlarge the flat washer recesses in the top of the head. The washers that go with the 12mm bolts/studs are larger than the 11mm washers.

I suppose you could use 11mm washers with 12mm bolts, but I have never tried this.

[Fisher]

I've used 11mm Washers with 12mm Head Bolts, works fine.  I used a Dremmel Tool to cut the 12mm Washers off.

Bolts need to extend 1.25" from Head Surface.