pushing metal

[hard hat]

getting some practice in with the metal lathe, and having an issue. while turning tubes for a navigator/jr gent out of 60/40 nickel copper (monel) with a carbide cutter and power feed, I noticed the metal was pushing toward the headstock end. after trimming off the bulge, it was undersized. the cap came out fine.
yesterday at the pen turning group meeting I asked some questions and tried again today, using a HSS cutter with plenty of lube. the results were much better.
what guidance can you provide on this? is it something that can happen with other materials?
sorry for the bad pics, they are ipad mini pics under LED lighting.

here is the body


and the cap


todays work


heres the whole pen

 

[Rich L]

You picked a tough metal to work with. What is the geometry of your cutting tool. Your lead angle should be shallow so you're not pushing metal into the workpiece and the tool tip radius should be small. Is your lathe solid and rigid? Carbide is preferred. Did you use an indexable tool? what insert did you use. What RPM and feed rate? Can you take a picture of the tool?

Cheers,
Rich

 

[hard hat]

The indexable turning tools are made by AR Warner Co in the USA. These Warner precision tool holder kits use carbide inserts. They include three styles of tools; AR right hand tool, E Neutral threading tool with 60° included angle, and AL left hand tool.

The kit includes three tool holder styles with TCMT inserts, one extra TCMT-21.52 carbideinsert, one extra Torx screw, and one wrench.

The change gears are set to cut at 64 tpi. Rpm was about 1000.

With the HSS, it had about 10 degrees each of top rake, side rake and front relief. The nose was rounded over moderately. The cutting lubricant is castrol syntec 5w-30. Speed was about 1000 with the same cutting speed. I noticed that too light of a cut with the steel resulted in chatter.

 

[Rich L]

OK. Estimating your diameter that's about 150 SFM and that's probably OK. Your feed is probably OK at ~16 IPM. You don't say what your lead angle is. The insert is triangular but how is it mounted in the holder? If it's just sticking out like a threading tool then that's not good. I presume you're using the right hand holder. Your insert also has a 1/32" tip radius which is too big (IMO).

One other thing - your depth of cut is important. You should not be taking too light a cut (finishing operations) as that material will work harden and make a mess of things. Take a minimum of .010". If any one of your turning operations takes too light a cut and hardens the surface then subsequent turning will be difficult unless you cut deep enough to break through.

I went to the AR Warner web site and I can't find a kit with the holders you mention and I don't even see that they offer the TCMT inserts. I can't imagine the threading tool using an insert with 1/32" tip radius unless you're making really big threads.

On the HSS cutter - still need to know the lead angle. Your reliefs are workable if not a little big but I don't know what "moderate" rounding of the cutting edge means. The only thing I might do to a freshly ground cutting edge is hone it with a couple light swipes of an super fine arkansas stone.

Could you take another iPad Mini pic of the tool?

Just trying to help.

Cheers,
Rich