Finish direction of OD

[Rory]

I am in the process of showing some guys at work how to use the lathe package, they grew up using Fanuc's FAPT system. When we got into doing a finish profile they wanted to finish from the chuck outward towards the tail stock (from big Diameter to small diameter). It doesnt seem as though MC is set up to easily work this way. I was able to get it to work, but needed to make at least three changes to the operation and lead in / out parameters.

Has there ever been any debate in the form about which direction to finish? Does anybody prefer one over the other?

 

Rory

[Trevor Bailey]

It really depends on the material, shape and tooling you are using. When I turn anything that will produce "stringy" chips and I need a good finish, I will work from back to front. I will also make sure that my coolant line is orientated so that it will push the chips to the front of the part also.

 

Just one example.

[Mattingly]

Mastercam will easily do chuck to tailstock turns by changing your plunge parameters then the lead in lead out is just personal preference

[chris m]

Let me preface this by saying I'm assuming you are talking about "back-dragging" not using a cutting tool actually designed for back turning; if I'm wrong please stop reading right now.

 

Typically inserts and cutting heads are made to cut in the -X and -Z directions. For example you cannot turn away from the chuck with a wiper style insert [which can work very nicely for good surface finishes, by the way].

I feel that turning the "wrong" way leads to cratering of the insert due to chip buildup behind the cutting edge, and tool deflection due to improper tool geometry. You are also, strictly speaking, loading your Z axis ballscrew the "wrong" way, although finish chips generally don't produce enough cutting load for this to be an issue.

 

Just my opinion