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Monel 500 vs monel 400

Virtually no hands on experience with either but have a horror story from a customer. Set up to trepan K500 bars. First couple of batches went smoothly. Next batch ate tools screamed and squalled and just was a friggin' disaster. After much hair pulling, metallurgist determined that there was about one and a half percent more copper in the batch, making the material unmachinable even though the copper was within the acceptable range..
 
I ran Monel the one and only time damn near 30 years ago, no idea what type. Pretty small tight tolerance Cnc Swiss parts, I still have nightmares. I was handcuffed to one machine for a couple weeks.
 
Monel 400 machines very similar, as far as speed/feed goes, as 300 series SS. Biggest difference is its greater tendency to tear on some machined surfaces.
I have never run alloy 500, but plenty of 400. I would expect it to be more difficult based on the following from specialmetals.com

MONEL® alloy K-500 (UNS N05500/ W.Nr. 2.4375) is
a nickel-copper alloy which combines the excellent
corrosion resistance of MONEL alloy 400 with the
added advantages of greater strength and hardness. The
increased properties are obtained by adding aluminum
and titanium to the nickel-copper base, and by heating
under controlled conditions so that submicroscopic
particles of Ni3 (Ti, Al) are precipitated throughout the
matrix.
 
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We run both occasionally but often enough that we keep a fair amount in our material inventory. Personally I liken monel 400 to a 304 or 316 in that it can be stringy and gummy, build up on inserts, chip control can be an issue. But good news for you if you have had success with 400 I, at least, find 500 easier to deal with. It cuts more like a hardened 17-4 in that it forms a reasonable chip, I'm not sure what inserts you are using but with what I use I have found good results with my sfm at or around 200. We turn, drill, tap and mill with no trouble. We make valve parts and probably 70% of what we run is 316 or 17-4 running on late model Mazaks so my views on machinability may be a bit skewed, lol.

P.S.
Take it slow, it's high nickel so heat build up is a concern, it is a predictable material at least, it's stable and not prone to tearing or random weirdness like on incoloy that suddenly work hardens. Drill with carbide, tap with new, sharp, high quality taps and plenty of oil. I love working with both as I find that 400 and 500 take a shine and polish and have a beautiful luster like no other material I work with.
 
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Thanks, from what I am hearing, it shouldn't be a problem. I'm shocked at the cost of a 5" diameter by 52" piece. Couldn't find any 3 1/2 square so I guess we will have to mill it square. Anyone know a source for 3 1/2 square?

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RJT
dont sweat Monel it cuts like butter just slow, if your doing alot of milling then run a rougher and finisher tool make sure the tools stay sharp. if you can run oil do it cause your tool life will increase by over 150% easy.
we mainly did small lathe parts and hundreds of thousands of them for a customer years ago Actually was my 1st customer in 1993 , long skinny parts with small holes drilled through usually around 1/8-.250 dia with .050 dia through hole and a .090 counter bore and up to 3" long. on occasion we did plates thickest I think we done was around 3/4".
we ran the lathes on barfeed (non swiss at the time) matter of fact all omniturns for 10+ years. the mill we used was a fadal and acrolocs. again keep the tools sharp. if you can get away with it use a small rad on the rougher it will help save the finisher. dont over feed it either.
 
I suspect that without needing enough to have a mill run of the 3.5" square, you'll have to cut from round bar. Just be careful and don't screw the part.

An open die forging would likely be too expensive to be worth the fuss.
 








 
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