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Lathe question- where does the tool meet the work?

PostPosted: Tue May 29, 2012 5:06 pm
by Rickbaro
Trying to think back to my High school shop classes, but it was a few years ago. Does the tool meet just below the centerline of the work? Or does it depend on the work and the tool? I'm playing with aluminum and using a carbide bit. I also tried a HSS tool as well.
The tool has a sharp corner, and I'm using the point.
I don't seem to get a smooth cut on my Grizzly 4000.

Thanks for any help.

Rickbaro, who is convinced that if I only had a nice vintage Southbend...

Re: Lathe question- where does the tool meet the work?

PostPosted: Wed May 30, 2012 9:56 am
by Phil Morris
Here is a page out of the tlas book:



Re: Lathe question- where does the tool meet the work?

PostPosted: Thu Jun 07, 2012 10:33 pm
by Richard-TX
I do lots of cutting of aluminum and if you want a good finish using HSS, the most important part to attaining a good finish is the rounding of the corner of bit. Some refer to it as honing but it is more of creating a radius instead of a sharp point. After grinding take a piece of 300-600 grit sandpaper and break the sharp point. It usually doesn't take a lot. Aluminum is funny stuff. It also requires a steeper angle on the bits than steel and the bits should be really sharp. In short you want the cutting edge to taper into and out of the work.

The cutting edge should be at or slightly below center, never above. Above leads to severe problems.

What aluminum alloy you are using makes a big difference. I have a chunk of aluminum here that is impossible to turn and make look reasonable. It is too soft.

One more item. If someone says that the finish they get from a lathe is mirror smooth, they are exaggerating/lying. It is impossible to get a mirror finish on a lathe.

PS. None of my bits look like the book.

If you come by and bring a couple of your bits and some aluminum stock, I will help you.

It isn't who made the lathe that makes the difference. It is the machinist running the lathe. Having said that, few things are more miserable than a worn out lathe no matter who made it.