I believe that a breaker isn't supposed to be used as a regular "disconnect"...they are not meant for constant on/off cycles. The OP is going to be better served with a true disconnect switch to "drop power tool" power in his shop. I've never installed them, but it should be pretty straight forward...the disconnect needs to be rated for a minimum of what the feed to the sub-panel is built to. It may need to be sourced from an electrical supply house to get one that's a lockable switch rather than a pull-disconnect like is typical for an HVAC setup.