The chain stay crimper I made came from an aluminum kickstand. I cut and shaped it to mimic the crimps on a Miyata 1000. When I need to use it I silicone it to one jaw in a vise. Cure for 24 hours and then crimp the stays. Have not tried it on a built frame, only unbrazed tubes. It works very well and people comment that the crimps look production. The Vise is a Wilton 4" bullet vise, about 40 or 50 years old.
Tried using a vise grip, but my hands cannot manage the leverage.