Enlarging Tuner/Machine head holes?

m_c

What's the best way to enlarge vintage sized machine head holes, so I can fit modern machine heads?

I'm currently thinking, machine up a block of steel with appropriate hole spacing to create a drill guide, clamp it to headstock, then drill using a nice sharp drill bit. Tear out on the bottom side could be a problem, but would another block of solid wood clamped tight be enough to avoid any tear out?

Or is there another more suitable method, that doesn't involve too much expense?

Funkfingers

Never mind any of that. How are you going to keep the neck rock steady on the work bench?

munckee

I've seen people do it on youtube and they did it with a hand held tool called a reamer I think to avoid damaging the finish.

paulnb57

Do yourself a favour and get a reamer, I did exactly what you describe on a new Allparts neck, the drill grabbed and split the headstock almost from end to end, the glued up split is now hidden behind a black painted face, bit is still just visible from the back and end, I initially thought I had ruined a £150 neck.......lesson learned......

ICBM

m_c said:

What's the best way to enlarge vintage sized machine head holes, so I can fit modern machine heads?

I'm currently thinking, machine up a block of steel with appropriate hole spacing to create a drill guide, clamp it to headstock, then drill using a nice sharp drill bit. Tear out on the bottom side could be a problem, but would another block of solid wood clamped tight be enough to avoid any tear out?

Or is there another more suitable method, that doesn't involve too much expense?

The best way to avoid tear-out is to go from the back and *not* all the way through - only deep enough to take the tuner bushing. That way, the hole in the front is not enlarged - and can also be put back to the original collar size should you ever want to.

I use a reamer to enlarge the hole until it's large enough at the surface, then a drill of the right diameter to open out what is then a conical hole to parallel. This also avoids chipping on the back.

SteveRobinson

I have a counterbore I found on eBay. The guide fits an 8.5mm hole and the cutter cuts 10mm concentrically, just deep enough for the collar of the tuner.

streethawk

Swap the neck for one with preferred tuner holes. It can be a bugger of a job. 

m_c

Thanks for the suggestions guys.
I think a tapered reamer followed by a drill as per @ICBM is probably a safer option, possibly with the neck suitably clamped in a vice to provide extra support to avoid it splitting. The last thing I want to do is split it, given how nice it looks!

I'll wait until I get the tuners, so I can some proper measurements, as the Schaller technical drawing doesn't include any details for the securing fastener.

ICBM

SteveRobinson said:

I have a counterbore I found on eBay. The guide fits an 8.5mm hole and the cutter cuts 10mm concentrically, just deep enough for the collar of the tuner.

That's very neat. I could have done with one of those in the past.

To be honest I haven't needed to do this job for quite a long time though - the fashion for chunky sealed machineheads seems to have passed, more or less - so I'm not sure if it would save me a lot of work now...

FatPete

Or get a set of Hipshots - they do modern locking tuners that fit the vintage size holes