I bought the 1/4-20 along with a 5/16, 3/8 and 1/2 inch combination drill and taps. So far I haven't had any problems. I have a milling machine with thread cutting mode. In aluminum I drill a hole, then reduce the speed to 50 rpm and tap it. With steel, I turn several times to remove the chips. They cut good, clean threads and are much quicker than drilling a hole and then tapping. I use thread oil and recommend it, especially for steel.