Im building a 2x72 grinder and it uses 1.5" solid steel bar for the arm. I have drilled one of two holes. The second hole just wont drill. At first I thought it was the cheapo Harbor Freight drill bit set (though they have acutally worked great) so I sharpened the couple bits. After sharpening...it still wont drill. Any ideas? Im using cobalt HSS bits. Did a 1/4" pilot, stuck on a 3/8" opening and need to open it up to 1/2".