If you need to do it tomorrow, do the weld method if you have a mig. Weld a washer with a hole about same size as head of screw onto the screw, then weld a nut to washer and remove clutch screw with a socket. No welder? gotta get the bits and hope the head doesn't break off. Soak with penetrant first, with any method. Drilling out is a 80% chance of failure and real trouble with small screws. Weld method or bits are near 100% success. If you use a bit, set your cordless driver clutch to make it light to medium "hammer". Start low and work up with "hammer" frequency until something happens. Let it bang and the penetrant will finally release it. Too much clutch bang will strip even a clutch head. It might take several minutes of hammering so charge them batteries. You want 75% vibration and 25% torque, if you know what I mean.
