Machining and hand-reaming a hole?

Question

I need to ream out a 1/4" hole in a 3" aluminum block. I plan on making the rough hole on a drill press. What is the best way to do this? Use a 15/64 drill (.234) and then the reamer or is that too much material to remove? Or should I drill with a 1/4" and ream with a 1/4"? Thanks. Tips are welcome as well. I need a accurate, smooth finish.

Answer 1

I would definitely drill an under size hole and ream to the final bore size but .016 inch would be a lot to ream out of a 3" long hole by hand. They make drill bit sets with letter designations A-Z which you should be able to find at a specialty tool store. The letter "D" drill bit has a diameter of .245 inch and the letter "E" drill bit has a .248 inch diameter. You may want to buy both sizes and drill and measure test holes. Because a drill bit will tend to make a hole larger than it's diameter due to runout of the bit and runout of the drill press a letter "E" drill might actually be too big. If so the letter "D" size should be just right.