Machine head drill size p bass

[Slappindabass]

Hi guys, having a go at making a few necks. What is the size of the machinehead holes on a p bass? 18mm? 11/16?

 

Is a forstner bit the way to go. Thanks

[Jabba_the_gut]

Hi,

I've used (sharp) flat bits to cut machine head holes and they turned out fine. The only thing you must do in my experience when drilling these holes is to have a pilot hole and clamp the neck to another piece of wood so there is no tear out when the drill passes through the back of the headstock. Takes a little longer to do but results are worth it. As usual, always good to give this a try on a bit of scrap first.

I haven't used a forstner bit for this (yet) but I think the Axcaliber ones that Axminster tools do are really good. I've used a few of these for other bass related jobs and have been very pleased with them. I might just buy one for doing machine heads as the cut from these is very clean.

Cheers

[Slappindabass]

Thanks very much jabba. 👍

[fleabag]

I thought the holes on a P were 17mm,  but may be wrong

[Slappindabass]

18 and 17 ordered. Thanks

[BigRedX]

Surely the hole size depends on the machine heads you are intending to fit?

As others have said, drill a pilot hole first. I'd want to be using a pillar mount drill to guarantee that the holes were at exactly 90° to the surface of the headstock. I've also see build videos where the luthier will drill the full-sized holes half way through and then flip the neck over and drill from the other side to prevent tear out. You will definitely need pilot holes and a pillar mount drill for this method.