i just got a 1-3/4" bit if you need to borrow im in downey. i just drilled 8 holes in my 3/8" thick tank. when i ran it slower it got hot. therefore i ran water on it. i ran it at a higher speed and before it could get hot, it got through the hole alot smoother, cooler, and the hole came out clean.
drill at a speed that when the shavings come out they are as long as possible. they will look like a corkscrew. for me that was at a higher speed and pressure.