I had these for a few months and had just used them on wood when needed. Recently I repurposed a trailer hitch insert making my own bike rack for my camper. The 2x2x1/4 inch tube had a 1 1/4 steel ingot tack welded inside for extra support. I needed to drill 2- 3/8 inch holes for bolts and I used the bit on my drill press to do this. The bit cut right trough the thick metal with no problems. I didn't have cutting oil but the press was on low speed and no issues other than that usual bind up when you get to that last little bit of steel, but I blame that on the low speed rather than the bits.