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Hard to machine alloys myths

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  • J Tiers
    replied
    WHICH "common stainless"?

    Some are an absolute dream to cut, clean and easy, others are a real pain.

    Then some ordinary-seeming stuff, like hot-rolled high carbon materials, will humble you if you let up for an instant......

    4140 will dull HSS in one pass of a few inches, especially if you are pulling blue chips, but thankfully doesn't harden as badly as some other materials.

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  • Martin0001
    replied
    It is not claimed that "hard to machine alloys" dont exist.
    It is claimed that few common (and less common) materials, namely stainless 304 or 316 or titanium (Ti6Al4V), Monel, Hastelloy, in particular B3 hastelloy and few others are not in this class, despite of tons of whining in professional community.

    Usual reason of such sad experience is:

    1. I cannot be bothered to sharpen my tools.
    Machine is strong, I can turn with a nail.

    2. Stubborn, often mindless application of rules known to be correct for a carbon steel.

    3. Air gap bearings

    4. Carriage sliding down its bedways like a drunk man in the fog.

    5. These materials are very tough, everyone says that they are tough, even my customer knows it, so he will pay more and I will laugh all the way to my bank.

    Of course few materials are troublesome and Inconel or Steallite are between such (as mentioned by others).
    But common stainless?
    Last edited by Martin0001; 10-16-2013, 01:14 PM.

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  • J Tiers
    replied
    Despite all warnings about "mystery metal", the reality is that we ALL have it and we ALL use it. We do not need material certs for most all of what is done in our shops for our own purposes.

    As for "myths", I deny that the idea of hard to machine material is a myth. It depends on the machine you have, however.

    And I declare that anyone who says it's easy if you do it right is boasting! (Either about their machine, or their expertise)

    Of course if you do everything right it is better. But some materials will wipe that wonderful hand-honed sharp edge right off of your HSS cutter in a short while.

    If you EVER let the now-dulled cutter "rub", and it WILL rub as soon as it dulls enough, then many materials will become as hard as the hobs of hell, perhaps even "laughing at" the puny carbide you think may cut through. The cutter can dull very quickly in some materials, HSS may last less than one "pass" across the material, no matter HOW sharp you make it.

    If the cutter ever DOES rub, most likely you will find out about it when you decide to sharpen it, and find that it dulls and rubs AGAIN in 2 seconds, because of the hard area you just created.

    Now, if you have a large and powerful machine, this will not be a problem for you, because with enough power, you can cut some materials with a factory-fresh unsharpened HSS blank. Dulling is a nuisance, of course, but you have many more choices. And you will not have any problems with "spring" of teh machine, which can cause issues in work-hardened areas of the piece.

    With a large and heavy machine, you dial in the cut, and the cutter moves in that far, no questions, no problem. Not so with the usual Atlas, Southbend, Logan, or maybe some Sheldon machines.
    Last edited by J Tiers; 10-16-2013, 08:56 AM.

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  • Rustybolt
    replied
    There's a difference in cutting this stuff in a home shop and having to do production on thousands of pieces. The people that make inserts have done yeoman research so that a factory running exotic alloys isn't changing inserts or grinding tooling every tenth or 100th part. This is important when there are tens of thousands of parts to make.

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  • Martin0001
    replied
    As previous poster have said, F/C i s freecutting steel, type of mild steel and contains lead or/and sulfur to make it such.
    Nice material in the shop.

    I might add that due to various regulations use of lead is discouraged and there is a different type of freecutting steel which contain tellurium instead.
    It is rather a higher shelf product.

    On the other hand freecutting steel doesn't weld well.

    Leave a comment:


  • flutedchamber
    replied
    [QUOTE=boslab;880123]
    Originally posted by flutedchamber View Post
    Free cutting mild steel, ive only made resulpherised and leaded, we used to get a couple of tickets to present in the canteen for free milk when making leaded steel!, as if that would help. Either way makes small chips. Adding sulphur to steel is fun too, make sure your up wind of the ladle, very nasty fume.
    Mark
    Thank you.

    Leave a comment:


  • boslab
    replied
    [QUOTE=flutedchamber;880114]
    Originally posted by Martin0001 View Post

    "Particular troubles are with securing good surface finish
    These observations do not apply to F/C steel."

    For the life of me, I can't place F/C steel. Please help!!

    I know I'll think of the answer an hour after I post this.
    Free cutting mild steel, ive only made resulpherised and leaded, we used to get a couple of tickets to present in the canteen for free milk when making leaded steel!, as if that would help. Either way makes small chips. Adding sulphur to steel is fun too, make sure your up wind of the ladle, very nasty fume.
    Mark

    Leave a comment:


  • flutedchamber
    replied
    [QUOTE=Martin0001;879851]

    "Particular troubles are with securing good surface finish
    These observations do not apply to F/C steel."

    For the life of me, I can't place F/C steel. Please help!!

    I know I'll think of the answer an hour after I post this.

    Leave a comment:


  • Guest's Avatar
    Guest replied
    Started out as a machinist in the Navy and consequently machined a lot of Monel & Kmonel using HSS cutting tools. We had a very good supply of Momax blanks, but a very limited amount of cemented/brazed carbides and carbide inserts were unheard of. As the OP said Monel & Kmonel can be machined very successfully with HSS tooling as can stainless. One just needs to pay attention to tool conditions and cutting speeds/depths.

    Another poster cited a job where he could not see the surface he was cutting. It sounds like he had one of those nasty set-ups that was going to give him grief no matter what the make-up of the material or cutting tools.

    Of note we made cutting tools using a nickel based spray welding process which we used to cut Stelite (sp?) valves & valve seats. They were suppose to only be ground, but we did quite a few with our shop made tooling.
    Last edited by Dr Stan; 10-16-2013, 09:28 AM.

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  • Jaakko Fagerlund
    replied
    Ah, AMPCO coppers <3 Have had the pleasure of turning and threading that stuff a few tens of times, making die casting machine pistons. Machines just like prehardened stuff, but oh the fun of getting an inside thread in to it...

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  • Zero_Divide
    replied
    Originally posted by TOOLZNTHINGS View Post
    AMPCO bronze ( trade name ) contains iron and is slightly magnetic. It comes in various grades. AMPCO 18 is a popular grade and cuts
    fairly well. Other grades not so much. A good magnet will identify these bronze types , but not the grade. Some of these bronzes are very difficult to work with.
    Arghhhh.
    You beat me to it guys!
    Ampco surely fits that description.
    They market bronse and copper super alloys under the same name. Which makes them a little confusing.
    Softer ones machine very close to mild steel.
    Yes those alloys can go upwards of 300 HB, whoch is not fun anymore.
    It has superior heat transfer abilityes and is often used for cooling rods and mold inserts.

    Btw turni g is about the easyest things you could do to work hardenable materials.
    It is easy to keep the proper chipload and tools are sturdy.
    In milling you often have to compromise and many people compromise on feedrate which is wrong.
    Last edited by Zero_Divide; 10-14-2013, 11:49 PM.

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  • Spin Doctor
    replied
    Ampco 45 maybe ?

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  • toolznthings
    replied
    AMPCO bronze ( trade name ) contains iron and is slightly magnetic. It comes in various grades. AMPCO 18 is a popular grade and cuts
    fairly well. Other grades not so much. A good magnet will identify these bronze types , but not the grade. Some of these bronzes are very difficult to work with.

    Leave a comment:


  • KiddZimaHater
    replied
    I noticed INCONEL wasn't mentioned, for good reason.
    Probably the worst crap I've had the displeasure to machine.
    I had the unfortunate job of drilling and tapping 3/8 NPT holes alongside 10-32 holes in 12 plates of INCONEL.
    Torn threads in the NPT holes, and broken taps in the 10-32's.
    Horrible stuff.

    Leave a comment:


  • lazlo
    replied
    Originally posted by Martin0001 View Post
    Will get chemical analysis in friendly lab but that will take some time.
    Just about every scrap yard and gold/silver merchant has an XRF gun these days. Ask nicely and they'll zap it for free

    Leave a comment:

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