Lathe taking a deeper cut then dialed in on the DRO.

[Just for fun]

I watched the video, great info.

Thanks

 

[Just for fun]

I haven't been trying to make any exact cuts on this piece, just trying to learn how the lathe operates. I only have maybe 2 hours operating experience, so I have a lot to learn.

I will start using the technique in the video.

I guess I was mainly curious if the .004 extra was normal on a .050 cut. There is a few things for me to check. And make a way to lock the cross slide. Along with making sure my setup is right and following the technique in the video, I should start to get ahandle on it.

I guess for a roughing cut a little extra bit a big deal.

Thanks again for all your replies. It all helps.

 

[benmychree]

After watching the video, one comment; he takes his last cut to finish size without any measuring before taking his cut on the whole length of the finished surface; as an apprentice, I got a pointed lecture from the foreman (after cutting a workpiece a bit under the stated tolerance; his suggestion to avoid such in the future was to cut a short distance into the cut, long enough to take an accurate measurement and make sure it was not undersize, if it was, make adjustments to bring it on the proper size, he said few parts would be ruined by a very short undersized portion.. I cannot say that this foreman has a particularly fond place in my memory, he was a particularly rigid man, raised in a railroad shop, a pretty brutal place and he reflected that; he did not particularly like me and the feeling was reciprocated, but I do owe him for several appropriate suggestions.
RIP Elmer Richards. When I told him in later years that I was opening my own business, he told me that I had nowhere the necessary experience to do so, I guess he was wrong!

 

[DavidR8]

After watching the video, one comment; he takes his last cut to finish size without any measuring before taking his cut on the whole length of the finished surface; as an apprentice, I got a pointed lecture from the foreman (after cutting a workpiece a bit under the stated tolerance; his suggestion to avoid such in the future was to cut a short distance into the cut, long enough to take an accurate measurement and make sure it was not undersize, if it was, make adjustments to bring it on the proper size, he said few parts would be ruined by a very short undersized portion.. I cannot say that this foreman has a particularly fond place in my memory, he was a particularly rigid man, raised in a railroad shop, a pretty brutal place and he reflected that; he did not particularly like me and the feeling was reciprocated, but I do owe him for several appropriate suggestions.
RIP Elmer Richards. When I told him in later years that I was opening my own business, he told me that I had nowhere the necessary experience to do so, I guess he was wrong!

Jeeper, he sounds like a real ray of sunshine!

 

[mksj]

Similar to what benmychree mentioned, whether using the dial or DRO, when I am getting close to my final pass, I take a diameter cut close to my last cut DOC and then measure the diameter. Typically the actual DOC will be slightly less than expected due to deflection/rigidity, I then compensate for that difference in the last cut. Rigidity of the lathe and locking the cross slide/compound and possibly a rigid tool post helps. Sharper cutters/inserts will typically have less deflection and cut cleaner close to expected, the blunter the nose and negative rake tooling, will push the work a bit more, so cutter geometry/type is a significant factor. Also use a live center when possible, typically when the stick out is more than ~4-5X the diameter of the work or with thinner flexy stock. I mostly use a CNC extended point live center for the smaller diameter work, in particular when threading.

I recall at my graduation one of my professors at medical school saying he thought I wouldn't make it to graduation, I graduated in the top 10% of the class and was determined to prove him wrong. Later when I became a professor and had students, as long as they tried I would push them forward to succeed rather then say they will never make it.

 

[Larry$]

then take fairly light finishing cuts to size

If you are going to take light cuts with an insert, make sure it is designed for that. Otherwise it might be inclined to skate/burnish rather than cut. After watching Stefan's video I started using that method. It works! It is especially true when using inserts that normally require some depth of cut to work well. If your insert is at all worn it will require more depth of cut to work well. All this is likely even more true if your lathe isn't super rigid.

 

[benmychree]

Jeeper, he sounds like a real ray of sunshine!

He had previously worked as a boss at Hall Scott Motors in Berkley as a boss, he had such problems with his subjects that he had a nervous breakdown, came to our shop to mend, said he never wanted to boss again, couldn't help himself, I guess.

 

[benmychree]

If you are going to take light cuts with an insert, make sure it is designed for that. Otherwise it might be inclined to skate/burnish rather than cut. After watching Stefan's video I started using that method. It works! It is especially true when using inserts that normally require some depth of cut to work well. If your insert is at all worn it will require more depth of cut to work well. All this is likely even more true if your lathe isn't super rigid.

This is why I prefer positive rake ground inserts for all but roughing.

 

[snoopdog]

After watching the video, one comment; he takes his last cut to finish size without any measuring before taking his cut on the whole length of the finished surface; as an apprentice, I got a pointed lecture from the foreman (after cutting a workpiece a bit under the stated tolerance; his suggestion to avoid such in the future was to cut a short distance into the cut, long enough to take an accurate measurement and make sure it was not undersize, if it was, make adjustments to bring it on the proper size, he said few parts would be ruined by a very short undersized portion.. I cannot say that this foreman has a particularly fond place in my memory, he was a particularly rigid man, raised in a railroad shop, a pretty brutal place and he reflected that; he did not particularly like me and the feeling was reciprocated, but I do owe him for several appropriate suggestions.
RIP Elmer Richards. When I told him in later years that I was opening my own business, he told me that I had nowhere the necessary experience to do so, I guess he was wrong!

"Hey Onee!

 

[compact8]

I guess I was mainly curious if the .004 extra was normal on a .050 cut. There is a few things for me to check. And make a way to lock the cross slide.

You may check if the DRO reading changes after the cut. If it does not change, it means the cross slide has not moved so locking it will not help. Something else is loose / flexing allowing the tool to be pulled towards the workpiece. An extra of 4 thou is too much to be acceptable.