Boring bar index insert shape choices?
Hi,
I've been learning the basics of working a metal lathe. I joined a maker space club that has an old Craftsman 101/Atlas 618 and they have left me to teach my self how to use it. I am currently working with a 2-1/2" dia. aluminum rod that I want to carve into something similar to a cup. It has side walls and a bottom.
Last night I plunged a drill into the face and began the process of hollowing out the interior. I worked at a low RPM and the drilling went very smooth.
I have purchased a kit of the imported brazed carbide tip boring bars and tried to use them to enlarge the hole. I didn't have much luck with those tools. They seemed to cut crudely.
I did find that an old HSS bit that I was using for facing did a great job of cutting the face down. I also use a cheap brazed carbide tip cutter which worked well, and finally I tried a indexed carbide tip tool I had purchased and it worked pretty good.
My general observations was that the boring bars I just bought should be returned and that I should find a better product.
I would like to avoid a carbide vs HSS debate, but it seemed like the HSS worked great and I was surprised at how the carbide, even the ones that worked well, seemed to cut the Aluminum less gently. I tried various SFM looking for a sweet spot.
Which brings me to; I have found two boring bars with HSS index inserts and I am considering ordering one of them.
One uses Diamond shaped inserts and the other uses Triangle shaped inserts.
It seems like the triangle would be ideal for a plunge cut while the diamond might be good for a both a plunge cut and a bit of facing where the wall meets the base.
I'm hoping to get some comments about real life practical use of the two shapes.
Thank You.
