Machining T-nut

After you make the facing cut, run a dial indicator from the outside edge to the center and see if it stays zeroed. Then you will know if the cross slide is the cause, or other factors at play. If it traces the cut perfectly, proceed across center to the other side and see if it still traces with zero TIR. If it stays zero on the front, and moves on the far side, then you have a problem with cross slide squareness.
 
anytime i have a problem such as this, its usally movement. I would lock the carriage down first(if it has a lock) and see if problem persists. I usally mount an indicator on the carriage and another on the compound to find where the movement is coming from. It could be that your tool is pulling into the work as you cut. Usally the carriage will push away, so unless your starting at the center and feeding out it shouldnt concave. determing where the movement is makes it easier to fix the problem. Hope this helps you.
 
Are you moving the cross slide to face off the material or are you using the compound? Use the cross slide and you should get a straight cut! Make sure your toolpost is tight also!
 
I think that the pounding is moving my carriage away. I have stopped for the moment. I need to revisit. Work the outside until I catch up with the inside. I also need to check on locking the carriage. There must be one, but I haven't found it. It is a learning process. I know that there is wear in the apron and I need to rebuild it.

I was not using the compound, and made sure that it is set on zero degrees. Perhaps I can change my method such that my hand mantains contact with the carriage. I will work on this.
 
I have also ordered better measuring equipment so that I can better determine the setup. My lathe is older, but in what appears to be decent shape. It is a South Bend 9A built in 1952. It came with lots of tooling and I think that I need to rebuild it over time and it will teach me. I really agree with Ron below, that the interrupted cut was "driving" the carriage away. If there is not a problem there is no reason to learn...

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papermaker said:
Are you moving the cross slide to face off the material or are you using the compound? Use the cross slide and you should get a straight cut! Make sure your toolpost is tight also!
Click to expand...

I noticed that the interrupted cut did loosen the toolpost. It also drives the cutter down. I am glad that I bought a better toolpost, but I'm working for it!

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Tony Wells said:
After you make the facing cut, run a dial indicator from the outside edge to the center and see if it stays zeroed. Then you will know if the cross slide is the cause, or other factors at play. If it traces the cut perfectly, proceed across center to the other side and see if it still traces with zero TIR. If it stays zero on the front, and moves on the far side, then you have a problem with cross slide squareness.
Click to expand...

Bought better dial indicator and magnetic base...
 
geraldsd said:
I think that the pounding is moving my carriage away. I have stopped for the moment. I need to revisit. Work the outside until I catch up with the inside. I also need to check on locking the carriage. There must be one, but I haven't found it. It is a learning process. I know that there is wear in the apron and I need to rebuild it.

I was not using the compound, and made sure that it is set on zero degrees. Perhaps I can change my method such that my hand mantains contact with the carriage. I will work on this.
Click to expand...

This may not be the same for your 9" but here is a drawing of an older 9" carriage:

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See the square-headed bolt just above the way wiper on the top side of the carriage? That is the carriage lock.

-Ron

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img14.gif
 
I do not own a SB but is there a chance that the spindle head is misalligned? Do you get a taper when doing a normal turning cut with the work mounted in the chuck?
 
I have sat back and looked and read and I can see that the cut is good until I get the the "interrupted" part. I have figured out how to lock the carriage btw. I can see now that where the cut is interrupted I will have to lock the carriage and take small bites. I can't thank everyone enough for all of the effort that has been made to help me. I have learned a lot, though!
 
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