[KSky]

Posting this here as we are all familiar with rigidity and capabilities of the Tormach.

I need to drill lots of 3/8 holes through 3 inch aluminum blocks. Currently, I spot drill and then go right to a size W drill. Regular HSS that I use only for this and keep sharp. It works ok, but towards the bottom of the hold it sometimes shrieks even though I am spraying coolant right at the hole and it's well flooded. It also wanders slightly and that happens no matter what bit I use. I bought one of these from McMaster but it does the same. https://www.mcmaster.com/catalog/129/2759/3021A41

Running at 4100 rpm and 9 ipm. I suspect I need to plunge faster, but near the bottom I really bog down the tormach and I am worried it will stall.

Any suggestions appreciated.

[ToolHIT]

It does sound like the chips aren't evacuating causing the drill to load up/shriek and then walk. There are a couple ways to fix this:

-Decrease the peck depth on the drill cycle. Generally you want to peck at half the drill diameter with HSS or Cobalt Drills so you would want to be at a peck depth of .1875" but I would try a peck depth of .100" to make sure chips evacuate.

-Increase your Chipload. You are currently at .002" IPR which is light for a 3/8" diameter drill and could be causing too thin of a chip that doesn't break. In Aluminum you want to be around .006"-.008" IPR. Try running it at 3,500 RPM & 20 IPM if the tool pressure isn't too great or 3,500 & 14 IPM (.004" IPR) would also help. The thicker chip will help it break and evacuate better

-Or change your drill to a Parabolic Flute drill as it gives extra chip clearance in aluminum and will also reduce your tool pressure. I really like the YG Gold P Parabolic Flute Cobalt Drils, below is a link to the one we recommend:
3/8": https://www.toolhit.com/collections/...cts/dlgp511024
W: https://www.toolhit.com/collections/...cts/dlgp513123

Hopefully this helps!

Mike

[KSky]

Thanks for the advice, it worked very well. No more shriek and the holes are staying on center. I also added a coolant jet to help flush out the hole. Thanks a bunch.