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Machining Hardened 17-4 Rings

Brett W

Aluminum
Joined
Jan 10, 2014
Location
Huntsville AL
I was ask to quote, (and pretty sure I am going to turn down) a job today. Part is a 2.25in ring .170 thick, with 16UN thread on the OD, 1.650 ID. This is some sort of retaining nut for inside a tube/bore/etc.

Customer ask for 17-4 heat treated to HR1025 and passivated. So I get to looking at the part and in my mind making this involves the following steps:

Rough machine each ring (20), leaving .050 or more material oversize.
Send out of heat treat
Receive Taco chips back and possibly surface grind flat both sides
Grind ID back to shape to use as a reference for OD threading and finishing operations
Then clamp in fixture and use Mill to thread mill threads into perimeter of said ring.

As I have been told HR1025 is about 40Rc? Being that it is stainless, it will be brutal on tooling if trying to finish machine threads in a single point fashion, assuming I could get it straight enough after heat treat to actually thread within tolerance.

Option 2 rough cut threads and have them finish ground?

Obviously I am out of my depth here on this project, but looking to learn at least the process, not necessarily to do the job.
 

TeachMePlease

Diamond
Joined
Feb 11, 2014
Location
FL
I think 1025 is only a little less machineable than 17-4 H900.... If I could only cut one material for the rest of my life, it'd probably be 17-4 H900. It's 38-45 HRC, but doesn't machine like it. Quality carbide tooling has no problem with it. I dunno about the thickness though, never done anything that large/thin out of H900...
 

Booze Daily

Titanium
Joined
Sep 18, 2015
Location
Ohio
I’ve machined lots of 17-4 that got heat treated by the customer. Parts were made to print with no post HT machining required.
 

plastikdreams

Diamond
Joined
May 31, 2011
Location
upstate nj
17-4 pretty much doesn't move after heat treating. I've made many net parts then heat treated with flatness and parallelism unaffected.
 

mhajicek

Titanium
Joined
May 11, 2017
Location
Minneapolis, MN, USA
I prefer to machine 17-4 in the hard. Very stable, good tool life, good surface finish. It threadmills well too. Just order your material pre-hardened, cut the part, passivate, and ship it.
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
17-4 pretty much doesn't move after heat treating. I've made many net parts then heat treated with flatness and parallelism unaffected.
I would probably either do them hard or rough, then finish hard ... 17-4 doesn't usually distort much but if this happens to be the one time it does, you're screwed.

As I get older I get to be more of a coward ... and the stuff machines fine hard, even threads. 40 is not that hard, for carbide.
 

Brett W

Aluminum
Joined
Jan 10, 2014
Location
Huntsville AL
Why would I need to passivate if it wasn't oxidized due to the heat treating process? I was under the impression passivation was to fix heat staining on parts?
 

Dave G.

Cast Iron
Joined
Mar 24, 2005
Location
Clev, OH
Why would I need to passivate if it wasn't oxidized due to the heat treating process? I was under the impression passivation was to fix heat staining on parts?

Passivation is to remove any surface iron contamination from machining and handling. A smear of iron on the surface can cause breakdown of the passive film and result in pitting.
 

MaxPrairie

Hot Rolled
Joined
Jul 9, 2015
17-4 machines really well in the 1150 1025 and 900 conditions. I think you would be kicking yourself next time you machine the material and see how crisp the chips are and the surface finish you get. Passivation takes away free iron on the surface. The part will be noticeably more shiny after the process. You could do op 1 and leave a couple on the backside to grind to final thickness. I would quote it if it were me. You could stack parts on the grinder to, it grinds pretty nice as well.
 

dian

Titanium
Joined
Feb 22, 2010
Location
ch
as ph 17-4 is martensitic it doenst workharden during machining like an austenitic type would.
 

Mtndew

Diamond
Joined
Jun 7, 2012
Location
Michigan
1)Saw the raw stock into 10" chunks
2)Send to HT
3)Part them off in your cnc lathe
4)Make big monies.
 
As said above, depending on the type products you make, 17-4 is a dream material. in pretty much any condition. Also magnetic, so easy to grind. Barely distorts in HT if at all, etc.

You should no-quote so someone with a big number on it can look like a hero. :)

Course OTOH it is definitely not 12L14.

smt
 

plastikdreams

Diamond
Joined
May 31, 2011
Location
upstate nj
as ph 17-4 is martensitic it doenst workharden during machining like an austenitic type would.

It's not the work hardening of the part per se but what happens is you get a worn tool which causes a built up edge and the material quickly clogs the flutes or cutting insert and boom goes the tool.
 








 
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