The Hudy cuts the comm from right to left.
McMaster sells some diamond bits for 50 something USD and the are perfect. I have one on my Cobra lathe and I can get cuts "almost" as good as the Hudy.
The PN from McMaster (http://www.mcmaster.com
AL-4 3316A42 $51.67
The L stands for Left Cutting, but we use the diamond part facing down, so this means we need the opposite cutting bit (not the right one as it should be logical). Trust me I know because I had to buy two of them (LOL).
The Hudy Part number for the cutting bit is:
HU101081 Hudy Commutator Lathe Diamond Tip
And it's almost the double of the price.
(EDIT) I almost forgot about the carbide bits that fit. Here goes:
AL-4 3367A341 $3.57
AL-4 3367A131 $3.42
I understand that C2 is better for our uses (don't ask me why, but I guess it is)
Grade C-2— The best grade for general purpose use on cast iron and nonferrous materials. Grade C-2 tool bits provide very good shock and abrasive wear resistance along with high load and edge strength. Comparable to Kennametal K68, Carboloy 883, Sandvik H13A, Valenite VC2, and Wesson 2A5.