View Full Version : Setting Lathe Tool Position - Not Cutting in the center - Help.

02-28-2017, 06:12 PM
I have Mori SL1 that I just finished retrofitting. I've never used a professional cnc lathe before. I'm used to using a cnc lathe that I built with just a quick change chuck.

I've setup my first tool and it's cutting too low, not through the center, but the tool is already bottomed out in the tool holder. How do I adjust for this? Should I mill a little off the tool to get it lower in the holder?

03-31-2018, 01:28 PM
There are a few reasons why the tool would be off center. Turret base alignment, turret rotation alignment, spindle alignment, or the wrong size tool/insert/seat.
The first three are usually out of alignment due to crashes. Its fairly easy to check these by using a dial indicator. These should be checked in a certain order.
First check the spindle alignment, do this by putting a 2-3" diameter x 8-10" long piece of aluminum in the chuck and taking a cut with a sharp insert along the Z-axis. The idea is to clean up the piece and measure for taper over about 8" or so. it should be around 0.0005" or less taper over 8" or so. This will confirm that the spindle axis is parallel to the Z-axis.
Next check the turret base alignment. Do this by running an indicator over the turret face in the X-axis direction. It should be around 0.001" or less over the turret face. This ensures the turret is parallel to the X-axis.
Then check the rotation alignment of the turret. This is done to make sure the turret rotates to the correct position relative to the spindles center line. The easiest way to check this is to run a test dial indicator (0.0005" or 0.0001" graduation) on the surface that the bottom of the tool sits on in its holder (the non set screw side). This should be as parallel as possible.
If any of these things are out of alignment, they should be fixed. Mori has good documentation about correcting these procedures. Requesting the literature from Mori is the best way to obtain it. The process of correcting these issues is basically like dialing a vise on a milling machine table, same concept.
If all of these things are fine, then begin looking at the tool. Machine miss alignment is very common and is the cause of most headaches with tool on center problems. Machining down the tool to cut on center or shimming is a bandaid fix for this. Other issues will arise if the problem isn't fixed, like drilled holes not being straight, parted off pieces being conical, and poor tool life. Machine alignment can be an intimidating task to overcome, but learning how to do it yourself will save you tens of thousands of dollars compared to having a technician align it for you.
Hope this information is helpful,


03-31-2018, 10:05 PM
Very old post, but I appreciate the response. Turns out I didn't examine the tools holders, they have adjustments on the back to set cutter height. Easy peezy.

04-09-2018, 09:22 PM
Glad to hear you got it sorted out.
I realized it was an old post about halfway through typing it. To late to turn back then. :)