Can this be turned on a lathe?

[dlavery]

Yes, you can do it, but you are probably going to want to do it in two steps.

The first part of the cut will be an interrupted cutting operation. This is rather hard on carbide tool bit, so I would recommend using a "standard" tool steel cutting bit, with very light rake (you want all the support for the cutting edge that you can get). If this is one of the standard Martin gears made of 303 Steel, then you will want a surface cutting speed of about 50 ft/min. For a 2.25 inch diameter gear hub this works out to about 85 rpm. Since it is an interrupted cut, you would be safe to slow it down by another 20%. In other words, cut slowly and cut shallow (about 0.010" - 0.015" per pass if you are using a small lathe [1-1/2HP or less]). The tool steel bit should stand up under the shock loads and last long enough to get past the bolt holes.

Once you are down to a smooth cut, switch to a carbide bit. Crank up the surface cutting speed to about 150 ft/min. You should be able to increase the cut depth to 0.030" per pass. You will get through the rest of the cut a lot faster.

Since you are doing this as a "one-off" these numbers are close enough to do the job. If you were going to do 10,000 of these as a production run and were concerned about the very best optimum cutting speeds and maximizing tool life and overall productivity rates, then there would be a lot more we would have to talk about. But for this type of work you should be all set. Good luck!

-dave

[Andrew]

Another option would be to do this on a rotary table on a mill. You might want to check with the shop if they have one.