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Posted by Michael Kelly on August 15, 2000 at 07:28:32:

I need a setup for a Barber Coleman #3, 12/N, (feed index is either .175 or .075 whatever is standard I am not at the shop right now and cant look at the machine)
Picture if you will a tight wound extension spring with a wire diameter of .375" the outside diameter of the spring is 2". I need to make an insert to fit in each end
which will act like a screw thread to fit the end of this spring. Both ends of the spring are ground flat. I have a milling cutter with .1875 radius and o.d. of 1-7/8" with a 3/4" bore.
My problem is the number of teeth to set the gear machine to along with the feed gears. I would like to cut this at a very slow feed as the depth of cut is large for this machine.
I had the machine setup for .375" feed per revolution of workpiece. Then i set the number of index at a high number of teeth to alow for slow revolution of workpiece. I had the index set for 250 teeth
and the cutter speed as low as possible. I could scratch the surface but for a full depth of cut, this will not work. material being cut is 303 stainless, cutter material m-2 tool steel. I plan on cutting a bar form blank and holding the end with a bracket
as have no room for a snap center fixture. The single thread is a problem. I know it can be done but the book says you have to cut 3 teeth minimum. please advise. The cutter is a simple milling cutter with no helix angle. I need to get this job out this week.
I think the helix angle is about 5.62 degrees. The insert has to fit inside, it does not have to be perfect as it will be tag welded after insertion

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