Drilling/boring aluminium in the lathe

[kong]

Hiya guys, I am in need of a faster way to create a large bore in aluminium. I need to make a hole 53mm diameter, 40mm (ish) deep in 6082 ali. I usualy bore it in the lathe after drilling a 20mm diameter clearance hole.
Unfortunately I am having so much trouble boring it afterwards, what with the nasty long chips inside that deep bore, I need an alternative.
I don't know a lot about drills, and have come across u-drills. Will these be a useful tool to use, or is there a better drill for my application? Any help appreciated here, thanks Jason.

Oh yeah, I need to keep the hole flat-bottomed too!

[DAB_Design]

Are you wanting to drill straight to finish? Or is a 2nd boring operation going to be used?

[kong]

There will need to be a boring op afterwards.

[DAB_Design]

Have you looked into a Metcut (brand) style indexable drill? We use these alot in all types of material. In aluminum, speeds and feeds can be quite high if the setup is rigid enough.

We also use one of their counter-bores to go straight to finish on .785 +/- .005 holes. Repeatability is excellent. We get about 90 holes before rotating inserts (6-4 tit.).

[kong]

Thanks, these look like the u-drills I am on about. U-drill is probably the trademark name from sandvik that make them. They look the same.
So I take it these drills will drill without a pilot hole, or at least without a large pilot hole? At the moment, using standard drills, I work my way up the sizes, which is obviously time consuming.

[DAB_Design]

No pilot needed. Make sure you don't use one too close to your finish dimensions. They do have a problem with going big if the feeds/speeds aren't just right. That's why we don't use them for finish (the drills not c-bores). However, if you need to drill close to your finish dimension, a pilot hole wouldn't hurt.

The biggest one I've used is approx. 2.3", on stainless. It did already have a hole in the center from a previous operation(apoprox. .68"). Pretty cool to watch. If you drill through, they push out a nice little disc great for frisbee.

[kong]

Thanks Dab, I just bought a couple on ebay. Expensive, but hopefully worth it

[raylht]

Hi

any bros can help me to solve how to drill dia 18mm depth 190mm using drill bit? i ve tried using cnc lathe with long series drill bit, but hole taper at the extreme end. thks

[ImanCarrot]

having so much trouble boring it afterwards, what with the nasty long chips inside that deep bore

You need to break that chip- drill a hole off centre just inside your final diameter, that way long chips can't form when you bore it, after you've done the centre 20mm hole stick an end mill in (a drill would deflect) and mill a hole connecting that centre 20mm hole with just inside the outside diameter. No stringy chips

[edit]Do two or three if you want to be sure[/edit]