Parting off question

[steamcar]

I think on a big lathe there is not a lot of difference from parting from the front or rear apart from the fact that with rear parting the tool is upside down and the swarf can fall away easily.
On a smaller lathe it depends on how the bearings are set up.
On a Myford ML7 for example rear parting puts downwards pressure on the spindle which pushes it into the headstock casting which is nice and solid.
Front parting pushes the spindle up and into the top bearing caps which are held in place with 4 bolts.
OK for most things but not as solid as pushing down.
The same difference in performance will be noticed when using form tools.
They work better if mounted upside down and brought in from the back. Lathe runs same way for both.

 

[swatson144]

Certainly what works is good. Previous posts were arguing that backside and upside down tooling pushes the saddle down when in fact it lifts the saddle. I have yet to experiment with my 12x36 Jet and see how it likes it since it parts so well from the front.

As you mention lifting the saddle would put a whole different load on the spindle. Forward backwards or upside down you can't argue with success!

Steve

Steve

 

[8ntsane]

I see Im a little late to this thread, But I think there is a few things worth mentioning. The poster is new to this, so I would check to ensure your blade is installed correctly. Meaning the blade is usually tapered. Wider on the top cutting edge, and as it heads toward the bottom it gets more narrow. I have seen newies not realize this, and grind the blade the wrong way, yes this happens. The next thing also worth mentioning here, is the tool holder used to hold the blade. If the tool holder is made properly, when the blade is installed, wide at the top, narrow at the bottom, the blade should be standing vertical, straight up and down, and not leaning to one side or the other. I have re machined a few part off tool holders to get the bade to stand vertical, and not lean over. If by chance he has the blade up side down, or has a tool holder that has the leaning blade, it will sqeele, big time. When your hearing this, is it chatter, or is it getting excessively hot? Easy way to check, with draw the tool, and a quick touch will tell you the story. I know there is many different opinions on parting, and I have a very heavy lathe that doesn't care much how fast, or what feed. I would suggest that you hand feed in, and watch for the chips curling off. If it starts to scream at you, back out, feel the blade, is it too hot, if so, you may be just going in too slow, or not enough cutting oil. If you think your getting to much chip build up, back out and clear the chips out. Just thought these might add to your things to double check. Good Luck

 

[ScrapMetal]

I am new to the craft and I have a concern with parting off parts that I have turned. When I do this I am being very careful to line up perpendicular to the work piece and lock the carriage so it cannot move. When I do the part it make a lot of screeching noise and for parts that are bored out internally, they grab and deform as the tool starts to cut through. Is there a special way to sharpen the parting tool that I might not be doing correctly? Where should it be set up - at the center, above center or below center?

As others have mentioned... Getting back to the OP's issues...

I have a couple questions about your setup. What material are you trying to part, steel, brass, aluminum, etc? How far away from the chuck are you trying to part? When I am parting off "tubes" I try to use a live center in the tailstock to support the work.

I assume that you are using a HSS type parting tool. Is it a self-made or is it an actual parting blade? How far does the cutter extend from the tool post/holder?

Are you using a power cross-feed or are you feeding it by hand?

Finally, have any pictures of the setup you are using?

All kinds of little details that can have a big affect on how well parting goes.

-Ron