Make sure the pivot bearings are bolted securely before you begin. I started drilling and the bearings flew apart because the manufacturer barely put the nuts on the bearing bolts. Without the support wheels I had no guidance and the bit was free to move. Luckily I was able to stop the drill in time without damaging the glass table I was cutting through. I had to tighten the nuts and adjust the guide to the exact position it was in when I started, which was more of a guess. Luckily I guessed right and after about 3-5 minutes of gentle pressure the drill bit cut through 1/4" glass. So it worked after careful testing due to the manufacturer's poor quality control.