I already have a piece of 6/3 cable and only need 6/2 for running to a welder. Is it OK to just not use white wire and wirenut it or do something else. Thanks.
You may also want to mark it as 'unused' and why, so that 10 years down the road, there is no doubt about what it is, and why. And, agreed: do NOT cut it off, cap with a nut.