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do boring bars need hardening?

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  • JoeLee
    replied
    I made these little bars out of 12L15. I don't think you can really harden that material. They work fine as long as you don't try to take too heavy of a cut. If I had made these out of any other material they would have never come out as nice as they did...... insert pocket and 4-40 screw hole would have been tough to cut.

    JL....................


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  • mike4
    replied
    I have made a couple from annealed torsion bars , machined the pockets and cleaned the body back to give some clearence and then just hardened the first 50-70 mm so that the inserts dont chew the pockets out and to reduce the wear that Sir John described .
    These are about 250mm long and 19mm diameter.

    They should outlast me as they only get 8-12 hours use every six months.
    No pics as they are packed away waiting for the next job.
    Michael
    Last edited by mike4; 06-12-2012, 07:11 AM.

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  • oldtiffie
    replied
    Originally posted by beanbag
    I would like to use this thread to express my opinions of others as well.
    Quite some others seem to be using it as a vehicle to have a shot at or to try to shred some others.

    There is any amount of precedence for you to join in.

    For what its worth, the OP's heading is:

    do boring bars need hardening?
    the text for which is:

    Originally posted by lowcountrycamo
    Making a couple of 3/4" boring bars out of hardened rod. Annealing now. Should I re-harden after machining. Bars will be 10" and 6". Thanks.
    It seems to be a simple question that after all the number of times that this thread has been hashed around over time that there should easily be a short concenus answer without any of the "side issues".

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  • beanbag
    replied
    I would like to use this thread to express my opinions of others as well.

    Leave a comment:


  • oldtiffie
    replied
    +1

    This seems to be one our annual "storm in a tea cup" threads with a lot of people talking at but not to each other.

    http://www.google.com.au/search?hl=e....0.mBgGchfARBc

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  • John Stevenson
    replied
    Now this is one of those posts that's heading for a lock if for nothing more than AK likes to hear echo's

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  • A.K. Boomer
    replied
    Originally posted by lazlo
    Your missing my point about why that's a red herring

    Mild steel has a yield strength of ~ 60 Kpsi, whether it's hardened or not. 4140 is 50% stronger than mild steel when annealed (95K yield strength), and wildly stronger when quenched and tempered (240K yield strength).
    But even mild steel is 50% stronger than Class 40 Grey -- you'd be better off with a cast iron boring bar and a steel top-slide
    Lazlo I think im seeing your point on it being a apples to oranges comparison ----- so just take annealed 4130 and put it up against heat treated 4130,
    The heat treated is both more durable and resilient. It has a higher yield strength...

    Sorry AK -- it;s tough wading through the pissing contest
    Don't be sorry - just realize that I generally don't have pissing contests all by myself -- I mean I may get a little lonely sometimes but I draw the line there...

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  • A.K. Boomer
    replied
    Sorry Flathead just trying to get through

    did maybe all this talk make resilience sound better than "wholesome" lol

    I could say you like to waste peoples time - but then it would be noticed that I have time to waste...

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  • oldtiffie
    replied
    As I said earlier - I buy my boring bars and clamps (as a set) new and whatever material they are made of does the job. If the boring is not satisfactory then I reduce speed and/or feed or re-grind the boring tool or re-think or re-adjust the set-up.

    "Stiffness" and "rigidity" are not restricted to the boring bar but to machine stiffness and set-up - to mention a few.

    If I need to make a boring bar I use plain old cold (or hot) rolled mild steel. I prefer round HSS stock as all I need are round holes - no square ones.

    On occassion I will MIG or silver braze a tool to a boring bar.

    I have a quite good but "light" lathe is so I neither push it to its limits nor do I try.

    I have plenty of time and my "tear-ar$ing" days are long gone and they are not coming back

    Leave a comment:


  • flathead4
    replied
    "Is this the right place for an argument?"
    The argument is fun but the personal attacks are tiring.

    Tom

    P.S. - I just noticed your quotes. Perfect.
    Last edited by flathead4; 06-11-2012, 10:27 PM.

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  • lazlo
    replied
    Originally posted by A.K. Boomer
    so don't heat treat neither of them and compare yield strength -- im not ascared
    Your missing my point about why that's a red herring

    Mild steel has a yield strength of ~ 60 Kpsi, whether it's hardened or not. 4140 is 50% stronger than mild steel when annealed (95K yield strength), and wildly stronger when quenched and tempered (240K yield strength).
    But even mild steel is 50% stronger than Class 40 Grey -- you'd be better off with a cast iron boring bar and a steel top-slide

    Actually that wasn't his original point -- it was my point to point that out to him.
    Any other questions?
    Sorry AK -- it;s tough wading through the pissing contest

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  • jep24601
    replied
    "Is this the right place for an argument?"

    Leave a comment:


  • A.K. Boomer
    replied
    Originally posted by flathead4
    They might have well said it was "wholesome."




    Ha!

    Tom


    Really? are you reading any of this? what planet do you live on - Hostess?

    is any switch being flicked at all? - a dim bulb? some kind of spark? are you getting anything from any of this yet?

    Leave a comment:


  • A.K. Boomer
    replied
    Originally posted by lazlo
    The AISI 1020 is a red herring, IMHO, since mild steel's properties don't change substantially through heat treat.
    so don't heat treat neither of them and compare yield strength -- im not ascared

    Evan's original point was that the tensile and yield strength of an alloy boring bar increases via heat treat,

    Actually that wasn't his original point -- it was my point to point that out to him.

    Any other questions?
    Last edited by A.K. Boomer; 06-11-2012, 08:55 PM.

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  • A.K. Boomer
    replied
    Originally posted by Arthur.Marks

    resilience. (1) The amount of energy per unit volume released on unloading. (2) The capacity of a material, by virtue of high yield strength and low elastic modulus, to exhibit considerable elastic recovery on release of load.
    p.48 Metals Handbook Desk Edition (2nd ed.). (1998). Materials Park, OH: ASM International.

    If there will be a discussion, there must be an agreed upon definition and, preferably, one that is quantifiable. Otherwise, we can turn circles all day over what is "hot" and what is "cold." The reference above is the most authoritative one I have access to. The yield strengths for the two alloys are listed as follows:

    ANSI No. 1020, cold drawn. Yield Strength = 350 MPa / 51 ksi
    ANSI No. 4130, Water quenched from 855°C and tempered at 540°C. Yield Strength = 979 MPa / 142 ksi

    p.154, 156. "

    The Modulus of Elasticity for both is constant. Given this information, I tend to follow this line of thought: For a given material, "resilience" as defined above is a ratio of "high yield strength" to "low elastic modulus." Given that the elastic modulus is constant with these two examples, a higher yield strength would be defined as having more resilience.

    Okay. So what does that matter? I guess it means that the heat-treated 4130 bar will take more stress* before being permanently deformed (changing shape). "Stress" here is being defined as, the intensity of the internally distributed forces or components of forces that resist a change in...shape of a material that is or has been subjected to external forces. p.56. " In other words, the strenth of the boring bar to "push back" before permanently changing its shape.

    The KEY to remember here is that this has NOTHING to do with the deformation characteristic of the bar BELOW the yield strength. Both bars perform identically in this regard (Modulus of Elasticity). It only means that the point at which your boring bar is ruined from a big oopsie takes a bit more force than the non-heat-treated material.

    I guess? I'm no metallurgist. Heck, I'm no "machinist!" I am just a guy that is trying to sort through the confusion in this thread with the available reference material on my shelf, a little logic and about two hours into it. I hope my "proof" was clear, correct and at least helped someone rather than fuel the argument



    Thanks Arther, very well written I might add

    But the sad thing is is it most probably will fall on deaf ears...

    appreciate the time - don't feel bad, I bet I got more in than you

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