718 surface finish problems

[WillB.1026]

I am currently drilling and boring inco 718 bar stock on a horizontal lathe. I've got the drill going no problem, but when I go to semi and finish cuts my surface finish is horrible. The part I'm making has a .025" thick wall and I'm using Walter cnmg 431 wsm01 as my inserts. The feeds and speeds are s130 with a feed of .001. Any suggestions?

 

[Seesecurity]

With a 0.025 wall it could be ringing/chattering. A drawing would help...

 

[WillB.1026]

Can't give a print, the company won't allow it. I've tried explaining to them that it's due to deflection but they believe it's a speeds and feeds problem.

 

[Mr.Chipeater]

.001 IPR with a .016 radius insert? I'd say you'd need to be around .005, that being said, if you're trying to turn a .025 thick wall it ain't going to happen with a CNMG a negative insert will just push on the wall too much. You'd be far better off using a sharp positive aluminum grade insert to reduce tool pressure but be prepared to change edges after every part.

 

[WillB.1026]

.001 IPR with a .016 radius insert? I'd say you'd need to be around .005, that being said, if you're trying to turn a .025 thick wall it ain't going to happen with a CNMG a negative insert will just push on the wall too much. You'd be far better off using a sharp positive aluminum grade insert to reduce tool pressure but be prepared to change edges after every part.

Should I keep the spindle at 130 with the .005 ipr?

 

[Seesecurity]

Can't give a print, the company won't allow it. I've tried explaining to them that it's due to deflection but they believe it's a speeds and feeds problem.

Surely you can do a hand drawing with the detail you're having trouble with, the rest of the part doesn't have to be per your actual part?

 

[guythatbrews]

Surely you can do a hand drawing with the detail you're having trouble with, the rest of the part doesn't have to be per your actual part?

We can only guess the overall configuration of your part. Without more info just wasting everyone's time. Although I agree it ain't happening with cnmg431 in any config.

 

[Micmac1]

Not sure what the size or tolerence is but ive had luck with just carbide drilling to size with a thru coolant drill. Dial in speeds for surface finish....with an .025 wall theres no chance you are going to bore that unless you just get lucky.

 

[bradleyk]

You're asking for a speed recommendation without giving us the diameter your turning. The carbide should be able to handle about 150 sfm in Inco 718, but that means squat when your turning with a wall thickness of .025". A positive insert with smaller nose radius will help reduce tool pressure...TCMT or TPMT 3(2.5)0.

Have you tried finishing first and then drilling? That will bring its own host of problems, of course, with that wall thickness. You may need to drill a smaller hole then rough ream and finish ream.

 

[guythatbrews]

Not sure what the size or tolerence is but ive had luck with just carbide drilling to size with a thru coolant drill. Dial in speeds for surface finish....with an .025 wall theres no chance you are going to bore that unless you just get lucky.

Maybe he can. The bore may only be .050 deep. We just don't know!

 

[guythatbrews]

The feeds and speeds are s130 with a feed of .001.

s130? Do you mean 130 SFM?