Drilling aluminum rod

[Dale Allen]

This is as basic as it gets and the results are acceptable to me.
I use an HF 36" lathe that has a .002" runout in the headstock.
I used a 2.5" piece of aluminum rod, 6061 I think, and drilled a 7/16" hole through it. The drill bit is a jobber bit made by Irwin.
The wall thickness is about .027" on either end. It varies from .026 to .029 which is largely due to the runout.

Don Davis posted about having problems drilling soft metals.
http://www.penturners.org/forum/f166/need-help-drilling-metal-rods-center-153638/

I think the most important part is to get the stock centered as precisely as possible. I use a dial indicator to get the stock turning in the pin jaws of a G3 chuck so it is spinning as true as possible. Then I make sure the bit starts with absolutely no wobble and stays that way throughout the process.
It took about 6 plunges to get through. The shavings were getting built up a lot toward the last.

 

[magpens]

It seems you are an old hand at this, and I am not sure why you are posting but happy to read your report.

I assume the Al rod you used is nominally half-inch.

0.500" - 0.4375" = 0.0625". Divide by 2 and you get the wall thickness of 0.03125" ... pretty close to what you measured. I suppose that your rod might be a little undersize, which is unusual, or that your drill bit might be a little oversize, or a bit of both, or something else ....

You seem to be giving appropriate attention to detail in your setup.
Of course, centering is one key aspect of this, but alignment between headstock and tailstock is also obviously critical, not to mention the quality of the drill bit and the center bit you start the hole with, as well as the initial squareness of rod end. . And then there is your Jacobs chuck and its arbor and the healthiness of your tailstock taper. . So many things play a role.

Irwin drill bits are not the most precise, and if you want better results you might try Norseman.