Metal Lathe Carbide Tool Choice & Contact Angle?

MaverickNH

MaverickNH

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Newbie here.

My mini-lathe came with AR, BR, AL, BL, E indexable 3/8” carbide tools, that I’m using in a QCTP.

For turning & facing steel, iron, brass and aluminum, I understand speeds and feeds matter, but I’m not sure about which tools to use when and the angle the tool should contact the workpiece at for best outcomes. The R & L, I understand as right-to-left and left-to-right operation - it’s more the A (0) and B (15) part that I’m not clear on, and contact angles.

I’d imagine this has been asked before.

Thanks for the help!

BRET
 
Hey Bret ! All these angles really depends on the application of what your are doing . Cutting angle could be straight , negative or positive . Facing off to zero doesn't really matter as there is no shoulder to machine to . Turning or facing to a journal determines the shape of the insert you use . The material would determine what inserts to use as they have different coatings , chip breakers etc etc etc . Maybe this would help ?

 
With the assumption that you've got the standard tool holder set:
The tip of the tool should be flat and intercept the work on the centerline of the spindle. You can verify this by taking a facing cut. It should not leave the little tit in the middle of the cut. Generally, you want the tool to be square to the stock, pointing straight in, but you often have to change this to reach what you're wanting to cut off.
All the other angles are built into the tool bit.
 
With a QCTP you can set any tool to any angle needed to get the job done.
Generally speaking, the A series is for turning into a shoulder and the B series is for plain turning and facing. The E series is for cutting threads.
The idea is that you can mount up the proper tool (usually with the tool shank square to the work) and do most of the turning without re-adjusting or changing tools. This makes it easier to keep track of where you are at and saves time in the long run.

As a fairly new hobbyist I generally find myself changing tools and making adjustments quite often. This means I get to re-zero or touch off much more often than real machinist. But in the end I still get the job done and have fun.

If you are really new to the lathe, have a look at the Blondihacks lathe series of videos. I found them quite informative and sometimes go back and watch a particular one over as a refresher. YMMV
 
piper184 said:
With a QCTP you can set any tool to any angle needed to get the job done.
Generally speaking, the A series is for turning into a shoulder and the B series is for plain turning and facing. The E series is for cutting threads.
The idea is that you can mount up the proper tool (usually with the tool shank square to the work) and do most of the turning without re-adjusting or changing tools. This makes it easier to keep track of where you are at and saves time in the long run.

As a fairly new hobbyist I generally find myself changing tools and making adjustments quite often. This means I get to re-zero or touch off much more often than real machinist. But in the end I still get the job done and have fun.

If you are really new to the lathe, have a look at the Blondihacks lathe series of videos. I found them quite informative and sometimes go back and watch a particular one over as a refresher. YMMV
Click to expand...
BlondieHacks is really good and if you dig through This Old Tony's old videos there is some very good info there as well.
 
piper184 said:
With a QCTP you can set any tool to any angle needed to get the job done.
Generally speaking, the A series is for turning into a shoulder and the B series is for plain turning and facing. The E series is for cutting threads.
The idea is that you can mount up the proper tool (usually with the tool shank square to the work) and do most of the turning without re-adjusting or changing tools. This makes it easier to keep track of where you are at and saves time in the long run.

As a fairly new hobbyist I generally find myself changing tools and making adjustments quite often. This means I get to re-zero or touch off much more often than real machinist. But in the end I still get the job done and have fun.

If you are really new to the lathe, have a look at the Blondihacks lathe series of videos. I found them quite informative and sometimes go back and watch a particular one over as a refresher. YMMV
Click to expand...
I learned a lot from Quinn! She's awesome, and explains everything VERY well!!
 
Janderso said:
There are so many really good Youtube machinists.
When I restarted my hobby machinist hobby back in 2016, I watched Mr. Pete. I think he is a great teacher, especially his earlier videos.

Click to expand...
I like some of Tubal Cain's vids as well. Old shop teacher. Still pretty "old school" too by the looks of it. Nothing at all wrong with that - start at the basics!!
 
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