I'm just tired of fighting over 1/2" screws with a 1/2" marine drill. Apparently I had to always thresh through the bolts also with a new chisel. This 9/16" diameter ship's drill bit fits 1/2" bolts. A 46 foot bridge that was damaged last winter is currently being restored and this drill bit is a life saver. up to 3 plies of pressure treated DF up to a total thickness of 10 1/2". Pretty amazing. highly recommended. I also recommend the Perfect Companion tool with these wood bits. The North Mole is on a 30* grade. By no means In this case I could do a 'level' well by looking at the 'fit of the pants.' Originally bought for plumbing projects, do yourself a huge favor and get one of these. https://www. amazon.com/gp/product/B00LP417N4/ref=oh_aui _search_detailpage?ie=UTF8&psc=1 Man. what a great combo. For your health!