Boring out 3 brg crankcase for 2 brg crank

[Austin in the Shed]

Anyone know what diameter cutter I need to use to machine out the centre bearing to clear the crank?

[Peter Clayton]

You could give VINCE LEEK a call he doesn't do this mod any more (now semi-retired) but may be able to give some advise.

[Robert Leigh]

I have just measured the one Vince Leek did for me a few years ago; as near as I can judge it's 4.75 inches diameter. I took a picture which I hope is of some use.     Vince also put diagonal grooves in the camshaft centre bearing so that splash would spread oli into it.
I think it is unlikely that I shall use this crankcase, so I am open to offers.

[Austin in the Shed]

Thanks for the reply Robert.
In the end I measured a two bearing case,well the thickness of the aluminum casting surrounding the bearing sleeve and took that away from the crank / cam centres and got a similar figure to you.
I did speak to Vince for his advice which was very helpful,I’ve never machined one out before in thirty odd years.I’ll post a picture of the set up of how it was done when in the workshop.

[Austin in the Shed]

Here in the lathe,I did consider doing it on the Bridgeport as I can get around 2’ between spindle and bed if necessary but settled for this.    

[Robert Foreman]

Good work with the flying nail Dave.