Fitting a ball valve to a Buffalo 40l boiler

[Dave S]

I've had this ball valve since Santa called by and was getting round to fitting it when I discovered that the tap hole is too small.Can anyone suggest the best tool for increasing the hole size without causing damage?

Thanks for any pointers.

[Fil]

for a 1/2" bsp or 15mm compression type fitting a 20mm qmax punch is the tool you need Dave,

a slightly cheaper tool is a stepped drill bit, but its no where near as clean a finish as a qmax punch, and at the wider diameter bores when it catches a stepped drill bit has some significant kick..

[Dave S]

Thanks Fil, I'll consider that.

EDIT: Measured at 20.5mm so just order a 21mm one - £10.78 delivered. Could have got for a couple of quid cheaper, but I prefer to deal with Amazon where possible as their customer service is so good.