They work just fine. BE SURE to do a dry run before cutting. This squares the machine up with the pipe. Also when you think you have enough tension on the chain tensioner give it a little more. If your doing gas pipe you can run the machine right on the epoxy coating, when making the dry run fire up the torch and burn the coating off as you go. If it's plastic coating you must remove all the plastic and adhesive where ever the machine will travel. Ted