If you have a 16,000# machine on 6" of concreteit is moving more than you think.
Not too many gunsmiths are running 16,000lb lathes.
I agree, but most smiths don't have over a couple thousand pound rigs.
It's not a lathe. It's a vertical machining center. cnc controlled. My lathe weighs about 4500 lbs. I'm not a gunsmith per say either but a self employed tool maker. I've done some gun work over the years though. If you have a decent machine whether it's a lathe, mill etc. it should not be prone to vibrate. A lathe might if what you're cutting has more weight on one side of the chuck than the other or if you have something on a faceplate that's not round and the weight isn't centered. Vibration on a mill is usually a sign of a poor cut unless you're using a boring bar/head. They will vibrate due to the out of balance tooling but even that can be curbed by rpm. Bad bearings in the spindle can lead to vibrations and even the gears on a lathe but these are mechanical issues that need fixing. My machines run smooth and I avoid out of balance things putting extra stress on the spindle.
So with that being said the problem with any floor is the base. Our friend in Alaska is dealing with an entirely different situation than most of us here. Where I live even the big manufacturing facilities don't require anything over 6" thick. All concrete should have rebar in it and a good base. It also matters how many bags of cement are used per yard. Footers usually are 5-5 1/2 bag mix. Good floors are 6. It's been mentioned that if your floor takes a pounding it needs to be thicker. Why put expensive machines in an area like that. We want precision from them and that's not a good way to get it. It's hard on the ways of any machine to be jolted.
