Knurling

[gr8life]

First time I have ever posted a question. I have some 1.50 inch 6061 aluminum that I am knurling. I use a scissor type tool and have pretty good results. The knurls need to be very deep. I work at 125 rpm, the slowest speed I have, with flood coolant. My question is how close can I come to that 1.50 inch diameter to reduce stress on the headstock? My fear is getting too close to the top and having the tool roll over the stock. Any advice would help.
thanks

[timlkallam]

You want the knurls to be exactly on top. I put a 1/4 inch piece of steel stock between the workpice and the knurls and move the knurls in until they stop . Now you can figure how far you are from the center.
If your knurls are 3/4 inch dia figure
3/8 +1/4 +3/4=1.375 from center , move your knurls in
2.75 and you will be on center.