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making a grade 8 bolt

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  • #16
    Originally posted by fxkl47BF View Post
    thanks guys
    i am in the us and mcmaster-carr has part number 6628K25
    a 3 ft stick only $6.88 and shipping

    Ultra-Strength Easy-to-Machine 1144 Carbon Steel Rods
    Yield Strength: 125,000 psi
    Hardness: Rockwell C30 (Hard)
    Heat Treatable: Yes
    Max. Hardness After Heat Treatment: Not Rated
    Specifications Met: ASTM A108

    Also known as Fatigueproof, these rods have enhanced strength and resistance to breaking from repeated impact compared to High-Strength Easy-to-Machine 1144 Carbon Steel Rods. Containing more carbon and manganese than other easy-to-machine carbon steels, 1144 carbon steel offers higher yield strength and hardness, even without further heat treatment. Use it to fabricate parts that require stress resistance.
    Did you know that Mc Master also has hi strength grade-8 threaded rods already made for you, for a reasonable price?
    https://www.mcmaster.com/threaded-ro...readed-rods-8/
    25 miles north of Buffalo NY, USA

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    • #17
      Originally posted by Richard P Wilson View Post
      You guys can slag off McMaster all you like, but you don't know how insanely jealous it makes me here in the UK to read of this one stop store that seems to sell EVERYTHING a machinist needs. We've got nothing like that over here.
      Who was slagging off McMaster? I absolutely LOVE them for just those reasons... its one-stop shopping!
      I'm sure they would be happy to sell to you, but the shipping might be a bit much....
      Bear in mind they *are* a large industrial supplier after all..
      25 miles north of Buffalo NY, USA

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      • #18
        Originally posted by Doozer View Post

        Maaaaannnnn........... I would love to have a Pratt & Whitney thread miller.
        But hey, since I am in a loving mood, I would really love to have an Excello thread grinder.
        So awesome. Maybe some day. Watch this space.

        --Doozer
        You could make some $$$ off the guys on PM with that
        25 miles north of Buffalo NY, USA

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        • #19
          Originally posted by MattiJ View Post
          34crnimo4 (34crnimo6) is another common prehardened steel in europe, close to AISI 4340.

          Using something like 4340 would allow you to slow down the quench enough to avoid quench cracks.

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          • #20
            Originally posted by johansen View Post
            And what happens when it fails?

            you will need to roll the threads
            this. Rolled threads are stronger and that's what it'll need. Excellent coverage of that topic in Carroll Smith's "Engineered to Win"
            in Toronto Ontario - where are you?

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            • #21
              What others have alluded to- for anything critical it makes more sense to buy it. Critical meaning anything aviation, anything where failure could hurt somebody, or cause damage, that kind of thing. If you can buy gr 8 threaded rod you can make a custom length bolt, and it will most likely be stronger than what you will machine. Your decision must be tempered by the application.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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              • #22
                Originally posted by Doozer View Post
                I would really love to have an Excello thread grinder.
                So awesome. Maybe some day. Watch this space.
                Would you know how to dress the wheel? The wheel obviously has to be tilted to match the helix .....but thread profiles are not tilted, i.e. they're in a plane aligned with the axis. So how do you dress the sides of the wheel, to what angle? I've pondered grinding threads but wonder about the wheel geometry and dressing
                in Toronto Ontario - where are you?

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                • #23
                  I think Brian at VersaMill has a thread grinder or 2...
                  He might be able to give you the skinny on it,

                  --D
                  DZER

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                  • #24
                    Originally posted by darryl View Post
                    What others have alluded to- for anything critical it makes more sense to buy it. Critical meaning anything aviation, anything where failure could hurt somebody, or cause damage, that kind of thing. If you can buy gr 8 threaded rod you can make a custom length bolt, and it will most likely be stronger than what you will machine. Your decision must be tempered by the application.
                    i agree 100%
                    i repair/fix/upgrade old/antique devices/machines that will not be put to work full time
                    none of my work is critical
                    with a small lathe and mill i enjoy making the parts that i can

                    it was stated in one of the post that o-1 is overkill
                    but if one was to use o-1 what would the tempering temperature be to achieve the tensile strength of grade 8

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                    • #25
                      When I need a special high strength screw or bolt I make it out of a larger/longer grade 8 bolt. A handy source of pre-hardened material of known quality.
                      Joe B

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                      • #26
                        Originally posted by nickel-city-fab View Post

                        Who was slagging off McMaster? I absolutely LOVE them for just those reasons... its one-stop shopping!
                        I'm sure they would be happy to sell to you, but the shipping might be a bit much....
                        Bear in mind they *are* a large industrial supplier after all..
                        Not in this thread certainly, but theres been another thread on here recently complaining about them.

                        'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                        • #27
                          Originally posted by Mcgyver View Post

                          this. Rolled threads are stronger and that's what it'll need. Excellent coverage of that topic in Carroll Smith's "Engineered to Win"
                          AFAIK rolled threads are not requirement for grade 8 per se. And the rolled thread is stronger than machined thread only if the thread is rolled before heat treatment. Many? manufacturers heat treat after rolling as it is cheaper…just like thread rolling is lot cheaper than cutting in large volumes.

                          Original UN threadform is bad start anyways, IIRC whitworth threadform with rounded crests shows bigger improvement than rolling vs machined.

                          best of the best is rolled thread after heat treatment with modified UN(xyz) thread form. But this is not your bog standard grade 8 hardware store bolt, more like costly aerospace fasteners or expensive head studs.
                          Last edited by MattiJ; 09-15-2021, 03:12 AM.
                          Location: Helsinki, Finland, Europe

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                          • #28
                            Originally posted by fxkl47BF View Post

                            i agree 100%
                            i repair/fix/upgrade old/antique devices/machines that will not be put to work full time
                            none of my work is critical
                            with a small lathe and mill i enjoy making the parts that i can

                            it was stated in one of the post that o-1 is overkill
                            but if one was to use o-1 what would the tempering temperature be to achieve the tensile strength of grade 8
                            I would temper it at between 450 to 550 degrees F, basically a 45-50 RC temper.
                            For a high strength application I would actually mirror-polish the threads, like a clockmaker.
                            Last edited by nickel-city-fab; 09-15-2021, 09:02 AM.
                            25 miles north of Buffalo NY, USA

                            Comment


                            • #29
                              Originally posted by MattiJ View Post

                              AFAIK rolled threads are not requirement for grade 8 per se. And the rolled thread is stronger than machined thread only if the thread is rolled before heat treatment. Many? manufacturers heat treat after rolling as it is cheaper….
                              I think you'd heat treat afterwards to save the rolling dies. I won't go to the mat (haha) on this as I haven't enough direct knowledge, but what you says is contrary to what I've read and contrary somewhat to experience in that metal does have a grain that doesn't start to go away unless you normalize. Cutting threads interrupts the grain, rolling does not.

                              whats your source that that rolled is only stronger if heat treated after, and why? A friend runs a good size fastener manufacturer, i'll see if he has any insight
                              Last edited by Mcgyver; 09-15-2021, 08:31 AM.
                              in Toronto Ontario - where are you?

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                              • #30
                                There are two issues.... One is the potential stress riser unless you cut rounded threads. That can be fixed by using a full profile threading insert for the thread concerned.

                                The other is the grain and the increase in strength due to work-hardening from rolling the threads. That is not as easily handled for cut threads. Rolling is somewhat like forging in how it works with the "grain", and some sort of heat treatment may be needed to attain the same added strength.
                                2730

                                Keep eye on ball.
                                Hashim Khan

                                Everything not impossible is compulsory

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