Quote:
|
They are very difficult to drill.
|
Did you notice anything printed on the side of that bar before you cut it up?
like 2024-T6 or 6061-T6 or 7075? IF the drill chips are long and stringy (they wrap into the flutes of the drill bit), it is because you have a soft grade of Al.
Put rubbing alcohol (isopropyl alcohol) in a squeeze bottle, put some in the hole regularly. For a 3/8 hole, try a drill rpm of about 750. Take the drill bit out of the hole every 3 seconds or so to clear the waste and add more alcohol. With the waste cleared and the hole lubricated it should go pretty fast, you can use a feed rate that is fast enough to produce a continuous drill chip.
There should also be a distinctive but faint noise from the drill bit when everything is set up right and the bit is cutting well, like a hiss or a sizzle.