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Making heavy hex bolt to finished hex bolts

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  • Making heavy hex bolt to finished hex bolts

    I have a customer who requires ASTM B8M spec for hex bolts, but in finished hex head pattern. To make it more difficult, the source of the steel must be either domestic or DFAR's compliant, or as an exception no India, China, Taiwan or Indonesia.

    So I am down to having heavy hex bolts in B8M machined down to finished hex sizing. Quantities are not big, 70 to 300 a month, but the customer does not want to commit to a bulk manufacture, but would rather pay as the need arises..

    Using a 1/2 bolt as an example:

    Per IFI,
    heavy hex bolt head size:
    Width across the flats: .875 to .850
    Head height: .323 to .302

    Finished hex size :
    Width across the flats: .750 to .725
    head height .364 to .302


    So for 5/8 and 3/4 I will have to reduce the head height some, and for sure the width across the flats.

    I need to either pay a shop to do this or do it myself. I do not have a mill, but I do have a lathe.

    Is a mill the best way to do this?
    Last edited by cuemaker; 08-19-2011, 10:02 AM.

  • #2
    Is he aware that will reduce the strength of the bolt?
    It's only ink and paper

    Comment


    • #3
      Are you talking ASTM A193 or ASTM A320 here? Big difference here, the first could be met with cut thread, the latter less likely. If you're planning on thread rolling then you're OK either way.

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      • #4
        Why would your customer want high grade bolts which have had the markings removed from the heads?

        You could machine the flats on the lathe if you made a fixture to hold the bolts on the tool post, and put a milling cutter on the spindle. You'd need a mill to make the fixture, though.

        I'd farm them out, but I'd be very careful who I asked to do the work because of the fact that the bolts you get back will be indistinguishable from lower grade bolts without expensive testing.
        Any products mentioned in my posts have been endorsed by their manufacturer.

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        • #5
          I've done hex on my lathe. Impossible to get plug for my truck so I made one. Mill the top and bottom of the hex, turn bolt and repeat.



          Andy

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          • #6
            Originally posted by Carld
            Is he aware that will reduce the strength of the bolt?

            I am working with engineers drawings, so yes, I assume they understand what they are doing.

            Comment


            • #7
              Originally posted by rkepler
              Are you talking ASTM A193 or ASTM A320 here? Big difference here, the first could be met with cut thread, the latter less likely. If you're planning on thread rolling then you're OK either way.

              ASTM A193.. not A320.. sorry... but you bring up a point of which I may not know of.. Does A320 not allow thread cutting and only roll threading for stainless?

              I do know that B7M and L7M do not allow any mechanical work done after final heat treat...is that what you are thinking of?

              Comment


              • #8
                Originally posted by cuemaker
                ASTM A193.. not A320.. sorry... but you bring up a point of which I may not know of.. Does A320 not allow thread cutting and only roll threading for stainless?
                The difference is in the spec strength, a weaker spec usually allows cutting of the head and threads, stronger specs usually require forming to meet the strength spec. I think in this case the heads are likely to be cold formed in either case. As long as you're not cuttng the head down far enough to affect the pull strength I'd expect that you're fine.

                As to the method I'd setup an indexer for the flats and attempt to rig something to align the flats for the cuts. Precision of alignment depends on how much you're taking off - if your new size hex is less than the original flats then alignment doesn't matter at all. Not sure about thinning the head - you might actually need to take off the bolt markings with all the changes and might need to remark them, most of that depends on the use.

                Either way I'd expect a bolt with a cold formed head to be pretty tough, a 316 cold formed head is going to be really fun to machine.

                Comment


                • #9
                  Originally posted by winchman
                  Why would your customer want high grade bolts which have had the markings removed from the heads?

                  You could machine the flats on the lathe if you made a fixture to hold the bolts on the tool post, and put a milling cutter on the spindle. You'd need a mill to make the fixture, though.

                  I'd farm them out, but I'd be very careful who I asked to do the work because of the fact that the bolts you get back will be indistinguishable from lower grade bolts without expensive testing.

                  Winchman,

                  Customer dont care who makes them or markings, as long as we provide the MTR's and certify the county of origin.

                  As for tagging and separation, you bring up good points. The original bolts will arrive in a bag with proper labels indentifying the parts with heat codes. Those parts will then be inspected, re-packaged and re-labeled. Since all material will be B8M, I dont foresee the machine shop mishandling the product to much unless they happen to mix other jobs that require stainless and machined heads..

                  The parts will arrive back to me here, we will then again inspect insuring the head dimensions and then ship. Lots of hassle for 70 to 300 bolts a month. But if they are willing to pay for it, we are willing to do it.

                  Comment


                  • #10
                    You will need a mill or a lathe with polygonal cutting.

                    Or possibly a die that will shave off an outer ring of the head. But that is the most expensive option (Initially)

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                    • #11
                      This would be dead simple on a cnc mill, even my converted BP. I see a setup like a vertical 5C for the bolt, align off one flat, program to cut the top and sides to spec.

                      Given cold rolled 316, if surface finish is an issue, your head height may be a problem if it's just a whisker off (low depth of cut).

                      Are you going to manually debur/polish?

                      Maybe you can just send them out as a batch each month, and mark up the result?
                      Last edited by lakeside53; 08-19-2011, 01:05 PM.

                      Comment


                      • #12
                        Well, I just got back from a meeting with a nicely equipped shop who is setup for this kind of thing.

                        They had 4 or 5 small hardinge chucker lathers, 2 big Warner Swasey lathes setup as chuckers, 2 (dont remember the name) old machines that were automated for similar operations and 2 CNC lathes with bar feeds...

                        They will be more than capable to handle the work based on who their current clients are (pump manufacturers) with the availability to do the odd rush jobs we get.

                        Only caveat is I have to provide material due the exactness, but thats only a slight pain in the ass compared to a capable shop.

                        Comment


                        • #13
                          Originally posted by cuemaker
                          Well, I just got back from a meeting with a nicely equipped shop who is setup for this kind of thing.

                          They had 4 or 5 small hardinge chucker lathers, 2 big Warner Swasey lathes setup as chuckers, 2 (dont remember the name) old machines that were automated for similar operations and 2 CNC lathes with bar feeds...

                          They will be more than capable to handle the work based on who their current clients are (pump manufacturers) with the availability to do the odd rush jobs we get.

                          Only caveat is I have to provide material due the exactness, but thats only a slight pain in the ass compared to a capable shop.
                          So are you modifying existing bolts are having new ones made?
                          Last edited by tdmidget; 08-19-2011, 08:18 PM.

                          Comment


                          • #14
                            Originally posted by cuemaker
                            I am working with engineers drawings, so yes, I assume they understand what they are doing.
                            Never, never, ever assume that an engineer knows what they are doing.

                            I once had one that wanted me to take 3" x 3" x 1/4" angle and mill off one leg to 2". I asked him why we couldn't just use 3" x 2" x 1/4" angle. Dead silence on the phone, and then do they make that?

                            I kid you not.

                            Scotty

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                            • #15
                              Originally posted by ScottyM
                              Never, never, ever assume that an engineer knows what they are doing.

                              I once had one that wanted me to take 3" x 3" x 1/4" angle and mill off one leg to 2". I asked him why we couldn't just use 3" x 2" x 1/4" angle. Dead silence on the phone, and then do they make that?

                              I kid you not.

                              Scotty
                              Hahaha. All engineers need to be pointed to MCmaster.
                              Not because I think its a good place to buy parts.. Especialy if you don't live in the USA.. But it is a wonderful site to quickly determin if something 'exists' in a commonly made state.
                              Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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