Here is a video of a guy building a stand alone tubing cutter, and he sells the plans. I think it could be modified to work with square tubing tool. I don't think it need all 3 motors for the linear movement of the tube. IMHO
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Nice design Tom! Thanks for posting. I think if I were building it, I would go ahead and use all 3 motors for the feed. If you modified it for cutting square tubing, then I expect would need 4 motors for the feed. Very cool machine!!