All the ones I've seen and used (family is in concrete business and I'm in tool & die) have carbide inserts, but won't cut through a piece of pine. They're made for hammerdrills.
Well, I've enlarged holes in leaf springs on a drill press using masonry bits and coolant. Can even sharpen the inserts. He's not going into production, just one hole.
Well I'm in the same boat as you, With the new kit I was able to replace the top gear but the bottom gear needed a bigger opening.. Fortunately my bottom gear was ok so the jacks worked for the weekend camping trip.. I'll use them like this and when they start wearing again, i'll look for new jacks!
Youroo!! 
Linear Mode
