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making a grade 8 bolt

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  • making a grade 8 bolt

    i need a grade 8 bolt 5/16-18 7 1/2 inches long with 1 inch of threads on each end.
    i know i can probably buy the critter but where's the fun in that.
    what material is best?
    i have some oil quench silver steel.

  • #2
    And what happens when it fails?

    you will need to roll the threads

    Comment


    • #3
      So a stud really....

      No reason why not. But you'll need a forge or oven that is long enough to heat the whole thing up to hardening temperature. For many of us this would be the stumbling block since something to heat that long a piece up in one go isn't a common shop tool. And if you had one I doubt you'd be asking and would be doing already.

      You MIGHT be able to make up a little trough forge which can then be set up with a couple or three propane torches shooting down into the gap. You'll need firebrick or some other good heat insulator to keep in the heat and get the whole length up to non magnetic on one go.

      Sneaking up on the blue spring/tough temper by contrast is pretty easy. That could be done in free air with a little care.
      Chilliwack BC, Canada

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      • #4
        A couple suggestions: Precipitation hardening stainless steel can give good tensile properties. Hardening temps are much lower than quenching from red heat required with regular carbon steels.

        If you can, switch to fine thread for a larger thread root diameter.

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        • #5
          McMaster Carr sells 4130 bar that is Rc30 hard.
          Cuts OK with high speed steel, but with carbide
          threading on the lathe is cake. No hardening necessary.
          1144 bar is in the Rc25 range. Not sure the tensile corelation,
          but it threads super well with HSS.

          -Doozer
          DZER

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          • #6
            McMaster also has 4142 bar that is Rc30 or more. The 4142 alloy is the half hard version of 4140. It also machines nicely.
            Kansas City area

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            • #7
              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.
              '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

              Comment


              • #8
                In the U.S., pre-hardened 4140 or ETD-150 are your best choices. Your reference to "silver steel" suggests you are not in the U.S. If so, what you need is a pre-hardened 42CrMo4.
                It's all mind over matter.
                If you don't mind, it don't matter.

                Comment


                • #9
                  Originally posted by johansen View Post
                  And what happens when it fails?

                  you will need to roll the threads
                  I did this not long ago with O-1. The "bolt" I made and hardened lasted about 10 torqueing cycle before it failed. Yes - I heat treated and then tempered (draw back).

                  I can post pictures if you want. It appears the quench created a small crack at the bottom of a thread. Since I cut the thread with a die - the threads had sharp corners which is where the quench crack started. The 'beach marks' are visible so you can see where the crack started.

                  Like johansen said - for high strength and fatigue resistance you need to roll - not cut - the threads.

                  Comment


                  • #10
                    Originally posted by MrWhoopee View Post
                    In the U.S., pre-hardened 4140 or ETD-150 are your best choices. Your reference to "silver steel" suggests you are not in the U.S. If so, what you need is a pre-hardened 42CrMo4.
                    34crnimo4 (34crnimo6) is another common prehardened steel in europe, close to AISI 4340.


                    Location: Helsinki, Finland, Europe

                    Comment


                    • #11
                      Originally posted by cxagent View Post

                      I did this not long ago with O-1. The "bolt" I made and hardened lasted about 10 torqueing cycle before it failed. Yes - I heat treated and then tempered (draw back).

                      I can post pictures if you want. It appears the quench created a small crack at the bottom of a thread. Since I cut the thread with a die - the threads had sharp corners which is where the quench crack started. The 'beach marks' are visible so you can see where the crack started.

                      Like johansen said - for high strength and fatigue resistance you need to roll - not cut - the threads.
                      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
                      DZER

                      Comment


                      • #12
                        Originally posted by fxkl47BF View Post
                        i need a grade 8 bolt 5/16-18 7 1/2 inches long with 1 inch of threads on each end.
                        i know i can probably buy the critter but where's the fun in that.
                        what material is best?
                        i have some oil quench silver steel.
                        Most all of the grade 8 bolts my previous employer purchased were made of 1045 according to their supplier
                        Quenched and tempered to ~32 hRC before machining
                        IMHO using a tool steel like o-1 is way overkill.
                        The highest strength bolts that I know of are made of
                        4340 Modified (also known as 300M) and have rolled threads
                        somewhere in the neighborhood of 280,000 PSI.
                        Nope you can't afford them.
                        Drag racers use them for crankshaft bearing bolts.
                        Last edited by nickel-city-fab; 09-14-2021, 05:19 PM.
                        25 miles north of Buffalo NY, USA

                        Comment


                        • #13
                          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.

                          Comment


                          • #14
                            EDIT: 125ksi is not 150 ksi, so presumably you do not actually require a true grade 8. That is a hair over grade 5. I'm leaving the rest of the post as originally typed.

                            Originally posted by fxkl47BF View Post
                            i need a grade 8 bolt 5/16-18 7 1/2 inches long with 1 inch of threads on each end.
                            i know i can probably buy the critter but where's the fun in that.
                            what material is best?
                            ...................
                            "Grade 8 bolt" (stud).

                            Is that "just because", or because those specifications are required? Reason being, if the properties are required, meaning the thing is critical, you may want to think again.

                            OK, just to get it out of the way, yes I think you could do this. However, I am not necessarily thinking you ought to, if the grade 8 is needed.

                            Grade 8 is specific. It isn't that fancy, 150ksi minimum tensile, 130ksi yield, C33 to C39 core hardness. Proof test 120ksi. "Alloy steel". Quite possible that 4140 would fill the bill if hardened, or even in the prehardened state. I'd need to look that up, and see what treatment gets the required spec.

                            The real question is can you be sure that you have made a "grade 8" part (assuming you actually need that)? I am the last thing but a safety nanny, it's not that at all. But if you need what you asked for, you need to know you have it, when you have finished.

                            Of course, if it is not a "need", but a "want", not required by the use to which the part will be put, then never mind.
                            Last edited by J Tiers; 09-14-2021, 05:13 PM.
                            2730

                            Keep eye on ball.
                            Hashim Khan

                            Everything not impossible is compulsory

                            Comment


                            • #15
                              Originally posted by J Tiers View Post

                              "Grade 8 bolt" (stud).

                              Is that "just because", or because those specifications are required? Reason being, if the properties are required, meaning the thing is critical, you may want to think again.

                              OK, just to get it out of the way, yes I think you could do this. However, I am not necessarily thinking you ought to, if the grade 8 is needed.

                              Grade 8 is specific. It isn't that fancy, 150ksi minimum tensile, 130ksi yield, C33 to C39 core hardness. Proof test 120ksi. "Alloy steel". Quite possible that 4140 would fill the bill if hardened, or even in the prehardened state. I'd need to look that up, and see what treatment gets the required spec.

                              The real question is can you be sure that you have made a "grade 8" part (assuming you actually need that)? I am the last thing but a safety nanny, it's not that at all. But if you need what you asked for, you need to know you have it, when you have finished.

                              Of course, if it is not a "need", but a "want", not required by the use to which the part will be put, then never mind.
                              IIRC minimum elongation before break was hardest part to fullfill in grade 8 spec and 1144 and etd-150 both came short on this requirement.
                              Location: Helsinki, Finland, Europe

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