What Steel for a BXA tool holder - Page 2
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  1. #21
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    Ahhh.... do youse guys really mean that all that costly aircraft alloy forged material that our country has been using to make all that real strong and real expensive gear COULD OF BEEN MADE WITH eLCheapo steel??????

    Freekin amaizing... why doncha call Boeing, and General Electric, and a few others and offer your expertize...

    Now here's another id fur ya ... replace the bolts in your car engine wid the bolts from the corner hardware store... you know the ones that have the stuff made in China...
    WTF...it's steel aint it???

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    Not trying to whip a dead horse, but here is a quote from Sandvick about a new material that is extremely ridgid.


    "Because of the combination of properties, Sandvik Nanoflex is ideally suited to mechanical applications where lightweight, rigid designs are required. A high modulus of elasticity combined with extreme strength can result in thinner and even lighter components than those made from aluminium and titanium."

    The point I get from this that the rigidity is a COMBINATION of ME and "extreme strength" which I would assume high tensile or high yield. This is kind of what I', basing my "theory" on.

  3. #23
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    I was inspired by the same magazine article to make up an AXA tool holder with built-in rake. I went to the local community college, found a suitable piece of 4140 in the scrap bin (they AREN'T that big!) and easily machined it out in a couple of sessions. I was strongly advised by the instructor NOT to harden it for fear it would develop stress cracks at the points of the dovetail as had one he had made, so I will let you know in a few years how long this one lasts if we are still arguing about the modulus of elasticity and hardness versus rigidity.

    Froggie ** [img]tongue.gif[/img] **

  4. #24
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    Hey Cruze...

    Maybe you can save a lot of $$$ by making that new milling spindle from rebar...
    WTF ...it's steel

  5. #25
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    I was strongly advised by the instructor NOT to harden it for fear it would develop stress cracks at the points of the dovetail as had one he had made
    That's very true, and good advise!

    Hardening steel doesn't increase its stiffness, but it does increase its yield strength. But the increased yield strength generally comes at the cost of reduced toughness.

    A good compromise would be to caseharden it, which would make it resistant to "bite marks" from the tool clamp screws, but still leave the core with the original toughness of the annealed 4140.

    Not surprisingly, most commercial toolholders are case-hardened, and not through-hardened.

  6. #26
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    flame war!

    ha ha. took me a while to get this beat throug my thick skull...

    equal sized bars of (almost any) steel will bend the SAME AMOUNT per unit of force until they yeild.

    the HARDER material will only continue to take more force well AFTER the softer material has begun to teild.

    so the HARDER material is STRONGER... but NOT STIFFER

  7. #27
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    Ok... so all youse guys can save a ton of $$$$
    just dont tell your customer that you made his parts from rebar instead of the alloy he spec'd....

    WTF... it's all steel ..aint it???

  8. #28
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  9. #29
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    Gary E, you just flat don't "GET IT", do you?

    Un hardened, vs hardened, same steel.

    Both have equal deflection under load, if not overstressed.

    But, the hardened one will have a higher BREAKING STRENGTH (ultimate strength).

    Not only that, it will have much less yield (permanent stretch) before breaking.

    What does that mean?

    It means that the soft stuff will break at a lower load. Before it breaks it will stretch, at an even LOWER load.

    The hard stuff will stretch LESS, and at a HIGHER load, and will break at a HIGHER load. It is "stronger".

    But BOTH will deflect essentially the same amount under loads less than the yield strength of the unhardened.

    in fact, they will deflect about the same as for 1018.

    That is completely different from comparing "strengths", which is what your hypothetical customer is specifying........ :rolleyes:

    NO, rebar won't work, we are talking about steel, not parakeet poop on a stick....

  10. #30
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    dsergison .....

    Enter at your own risk!!!!

  11. #31
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    J Tiers
    Gary E, you just flat don't "GET IT", do you?

    Un hardened, vs hardened, same steel.

    Both have equal deflection under load, if not overstressed.
    Your another one that should call Boeing and John Deere... WTF...call GM and FORD too...and tell them how you have this wonderfull idea on how to save them a ton of $$ by not using heat treated alloy steel.....

    Spend some time in strength of materials class sometime...

  12. #32
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    Ha, I love it!
    Sorry I didn't get in on it earlier.
    I agree with case hardening, to help prevent "buggers". But case hardened 1018 will stress relieve itself over time, possibly causing your perfect dovetail to not fit any more. It'll probably curl up as you machine the dovetail.
    Better yet is flame hardening, when the steel quenches itself (need stl with enough carbon- third number 4 or so).
    4140 annealed would be a good choice, ht to mid 30's, might need to be ground.
    ETD150 would be good.
    Even more better - A2

    But was it a toolholder or a toolholder the guy wants to make?

  13. #33
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    Gary E,

    You are making a fool of yourself. Resistance to deflection is the same for all steels. 4140 and 1018 both have the same spring rate (stiffness)up to the point at which 1018 yields. 4140 can be pushed much farther without bending, but the initial stiffness is the same for the two alloys.

    Look it up. It is called Young's modulus. It refers to a material's stiffness, not yield strength.

    You seem like a pretty smart guy to get tripped up on something as basic as this. Or perhaps you are misunderstanding what it is that we are trying to say.

  14. #34
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    What the man is asking, I think, is what stl to use to prevent the piston from wearing the toolholder he makes.
    He needs some surface hardness in the dovetail area, that's all.
    So, when you have that ridiculous set-up chattering like hell, the piston won't wear a slot in the toolholder, causing the toolholder to fly out.
    If you provide a radius (even an undercut radius, like a drilled hole in the corner), in the the dovetail, I doubt it would ever be a problem with breakage even with thru hardend glass hard steel.
    Hot rolled and Kasint would do the job well.
    But, a big block to heat w/ torch..
    Lighten up

  15. #35
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    Actually the BXA is a wedge type toolholder. A guy I know just uses aluminum for most of his light to medium duty toolholders. He says you dont notice a difference until you really start to cut, thats when he has the stock aloris holders.

  16. #36
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    The toolholders themselves are interchangable with the wedge or piston type toolpost...
    I am planning to make a dozen BXA tool holders for my Aloris piston tool post
    He says you dont notice a difference until you really start to cut,
    when else would it matter?

  17. #37
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    Sheesh!

    Everybody's right here!!!!! All the engineers are right about the Young's modulus, and Gary E is right that you need to make a rear axle out of some special stuff.

    Back to the boring bar example.

    The 1018 and the 4140 boring bar will behave exactly the same way while lightly loaded... but once those loads pick up, they will behave very differently.

    It is important to note that a bar of 1018 will not yield every where at once. There will be portions of the bar that will experiance very high tensil loads, very high compressive loads, and virtually no load at all. Thus portions of the 1018 bar will move into plastic mode well before the whole bar moves into plastic mode, and this can have real effects on the performance of the bar.

    Cruzinonline is quite right that he can push a 4140 boring bar a lot farther than a 1018 bar... even if he doens't push the 1018 bar to the point of castrophic failure it will still end up providing a lot less ultimate ridigity in his app.

    Gary E is quite right that a rear axle made of rebar is not going to perform very well.

    And, lazlo is right that in the case of a tool holder that will see primarily compression and shear loading and will be build like a brick **** house anyway... it just doesn't matter than much.

    B

  18. #38
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    Mike K
    Gary E,

    You are making a fool of yourself. Resistance to deflection is the same for all steels. 4140 and 1018 both have the same spring rate (stiffness)up to the point at which 1018 yields. 4140 can be pushed much farther without bending, but the initial stiffness is the same for the two alloys.
    Mike you said it yourself......
    "4140 can be pushed much farther without bending,"

    If heat treating material to higher PSI Tensil gave no advantages, why is it done?

    Please join the gang and demonstrate to all those engineers that spec heat treated parts for your car, aircraft, and even your wifes kitchen mixer that they are not only wasting money buying the alloy material, but also in heat treating it.

    Have any of you guys ever cut off a Kennametal Bar? aint eazy is it?.. if it was 1018 it would be eazy. So, since it's made of something a lot stronger than 1018, why do you think they spend the $$$ on something that you say is not any better?

  19. #39
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    boring bar: the case acts as a cylinder, stronger than a shaft.
    They used to push lead or shot filled hollow bars for anti-chatter.

    toolholder for a small QC toolpost: your main concern is you just need enough surface hardness to keep the swarf you missed when cleaning from damaging the tool holder on the contact faces.

  20. #40
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    OK, that didnt come out right!

    What I meant to say is take very heavy cuts versus general machining and finish work.


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