Tony,

I have bought a dozen or two slitting saws from Ebay here in England. All have been English made and they seldom cost me more than 50p each (US $0.75 cents) The Arbour came from Axminster Tools U/K and will accomodate a range of different centre hole sizes. I use them in my small bench mill. The screw head to be slotted fits into a 'V' shaped channel on the end of the mill vice jaws so you can slit dozens of screws without adjustment once you have it set up.

Harry

Biology is the only science where multiplication can be achieved by division.