I need to drill a 2" wide hole 7" deep in hard maple end grain. I used a 1/2" 3 flute 4" long spiral bit in a 2 1/2" bit extender and 3 holes. Now I'm getting a lot of vibration from what may be imbalance at high speed. I have tried Forstner bits, but they won't cut through end grain. Maxi-cut bits made in Germany were made to cut through end grain but are discontinued. Has anyone had success with creating a hole this size in hardwood end grain?