Machining cylinder barrel for Anzani Y type

[Trevorc]

I am working to the L Chenery drawings to build the Anzani Y type. I am about to start the cylinder barrels. The build notes published in the ME specify the use of a 9/33 round nose counterbore with a 3/16 pin to produce the nicely curved inlet and outlet ports.
Enquiries have drawn a blank, friends have never heard of them and an extensive internet search has revealed nothing.
Are these tools still available, if so where to purchase?
Thanks for help
Trevorc

[Jasonb]

Probably one to make yourself, a 9/32 ball nose cutter drilled for a 3/16" guide pin to go into the valve guide hole

Could probably get away with a 9/32" or even 7mm ball nose milling cutter and let it just follow the 3/16" hole

You will never machine the curve as shown

[Jo]

You need to make yourself one out of silver steel. If you are using the original Aluminium castings then make the shaft of the cutter thicker as it is a long way down to the bottom of the cylinder.

The inner corner of the port will need to be filed or dremmeled to make it smooth.

Jo