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First look at the available rpm's of the lathe and how they relate to the REAL cutting fast the material is moving past the bit. If you multiply the diameter of the blank by PI (3.14159) and then by the revolutions per second (RPS) of the lathe (which is rpm/60), you'll find out how fast the material will be moving past the bit. Think of this as the speed that you would be moving the bit through the material IF it was laid flat and you were making a straight cut. Remember that this motion will be perpendicular to the motion of the tool, though, so it's not like you'll be trying to push the ShopBot this fast. It will give you an idea of what the bit's going to have to be cutting, though.

Diameter * PI * RPS = "virtual" cutting speed through material

Try some different lathe speeds until you get something reasonable for that "material speed" value, then you can use that RPS value to calculate the move speed of the ShopBot.

The other value you'll need to decide on is the stepover, the distance that the bit would move down the length of the blank for each revolution of the blank. That would be the amount of material that was constantly being cut off the blank, just as if it was a long straight cut. Don't have a clue what that should be...I guess it depends on the power of your lathe, the kind of bit you're using, the material your cutting, and the depth of cut for each pass, how smooth of a cut you're looking for. Remember that the smaller this number is, the less bite the bit is taking on each revolution. I'd suggest starting small and shallow and increasing as you feel comfortable

Now take the RPS of your lathe that you decided on earlier and multiply it by the stepover value that you want and you should get the speed that the ShopBot should be moving down the blank...the move speed setting for your ShopBot.

(rpm/60) * stepover = ShopBot speed value (MS)

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