Bolts & Screws using friction only to hold (or fluted)

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Bolts & Screws using friction only to hold (or fluted)

Home Forums General Questions Bolts & Screws using friction only to hold (or fluted)

Viewing 17 posts - 1 through 17 (of 17 total)
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  • #27040
    Richard Rogalewski
    Participant
      @richardrogalewski21509
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      #444154
      Richard Rogalewski
      Participant
        @richardrogalewski21509

        I have a need for a screw with a round head which uses friction only to hold it whilst the nut is tightened. So, the round head has no slot or anything, just plain round head. Or something similar which is partly fluted near the head. Do such things exist? Wanting M20-ish in stainless steel.Thanks.

        EDIT: BTW, carriage bolts & screws not acceptable, well, I'd have to remove the square bit..

        EDIT: Aaah, ribbed necked carriage bolts. Except ideally I'd need a screw of that type. I could use a spacer I guess, with a bolt.

        Edited By Richard Rogalewski on 01/01/2020 13:32:31

        #444155
        old mart
        Participant
          @oldmart

          Car wheels used to be held on with headed studs with splines on the diameter just under the head. They didn't go as big as 20mm, but light commercial vehicles such as Transits might. Try a garage for wheel studs. 

          A drawing would help.

          Edited By old mart on 01/01/2020 13:39:41

          Edited By old mart on 01/01/2020 13:41:02

          #444157
          bill ellis
          Participant
            @billellis45274

            Not sure if the round head without slot/hex is available, but if they are you could cut a slot across the threaded end and use a screwdriver to hold it whilst tightening. If you use a longer bolt than is required you can chop the slotted bit off afterwards (assuming you have access). I know you can get countersunk bolts that then have a smooth head cap screwed into them (usually used for mirror fixings and suchlike).

            #444160
            Richard Rogalewski
            Participant
              @richardrogalewski21509

              Actually, I'd need 3 for my needs. If I only made 3, best I just grind off the square part of M20 x 20mm stainless carriage screws. If I made a production run, I'd try to avoid having to grind off the square parts of carriage screws, and that suggests use of rib neck carriage bolts, or similar. But, I'd need a spacer with a bolt. As the screw or bolt is passing through 1mm thick sheet metal.

              EDIT: Actually, in any case, I'd need to use a spacer given the thinness of the material the screw or bolt is passing thru.

              Edited By Richard Rogalewski on 01/01/2020 14:07:05

              #444173
              daveb
              Participant
                @daveb17630

                Reshape the hex head of a M20 machine screw and cut a screwdriver slot in the threaded end so you can hold it to tighten the nut.

                #444175
                Howard Lewis
                Participant
                  @howardlewis46836

                  If you are planning to make your own, make the diameter immediately below the head a tight fit in the hole, a fitted bolt, in fact. Once drawn into place, the slight interference between the shank and the hole should provide enough mgrip to allow the nut to be torqued up; especially with a dab of Loctite under the head and allowed to cure.

                  Howard

                  #444180
                  Martin Cargill
                  Participant
                    @martincargill50290

                    For a machine we looked after we used a straight knurl on the shank of a 12mm socket head cap screw and machined the hex socket part off, leaving only a small part of the bolt head. The screws were then pulled into a tight fitting hole in the holding part using a 12mm nut and washers. They worked pretty well and were only ever removed (by punching the bolt out) if the screw snapped during use.

                    Martin

                    #444188
                    Richard Rogalewski
                    Participant
                      @richardrogalewski21509

                      pin assy.jpg

                      Here is the item I'm wanting to make. I could use a M16 carriage bolt with square removed if I just made 3. But, if I made in production quantities maybe I'd need something else. Not easy to obtain 30mm M16 carriage bolt I imagine.. Would have to cut down a longer bolt/screw I suspect.. I would probably need a spacer between the nut and the 1mm thick sheet.

                      Ideally the screw/bolt head would be very hard – not susceptible to filing.

                      Edited By Richard Rogalewski on 01/01/2020 17:24:35

                      #444193
                      Phil P
                      Participant
                        @philp

                        Richard

                        I am curious as to what you are trying to make here, would you tell us what the purpose of the assembly is please.

                        Thanks

                        Phil

                        #444196
                        Richard Rogalewski
                        Participant
                          @richardrogalewski21509

                          On the issue of production: Let's say a few hundred of these "pin assemblies" were to be made. Would it be perfectly reasonable, in terms of production efficiency (or whatever) to buy in carriage screws and use a lathe to remove the square features? As oppossed to getting someone else to produce the screws without the squares. I imagine buying in carriage bolts and modifying might be what most people would do.

                          #444197
                          Richard Rogalewski
                          Participant
                            @richardrogalewski21509
                            Posted by Phil P on 01/01/2020 17:43:54:

                            Richard

                            I am curious as to what you are trying to make here, would you tell us what the purpose of the assembly is please.

                            Thanks

                            Phil

                            It's a "pin assembly" for a lock where a hooked bolt engages with said pin.

                            #444200
                            Tim Stevens
                            Participant
                              @timstevens64731

                              The problem you may face with a 'dead hard' bolt (pin, etc) is that extreme hardness comes at the expense of toughness. So, a firm tap with a decent hard-faced hammer is likely to knock the head clean off – rather defeating the excercise, I suspect. That is, if you could solve the problem of hardening the head while keeping the threads from being equally fragile. Or distorted.

                              Sometimes there is a good reason for not being able to find a novel part.

                              Sorry – Tim

                              #444203
                              Nimble
                              Participant
                                @nimble

                                Hi Richard,

                                Could you take a standard coach bolt and reduce the depth of the squqred part then counte-rbore a standard nut to fit over the square reducing its depth if necessary..

                                Regards, Neil

                                #444212
                                Jeff Dayman
                                Participant
                                  @jeffdayman43397

                                  If you are making a lock and want cheap but strong construction, consider the design below. If the pin ends could be identical dia and length or at least the same dia, costs would be kept low due to minimal machining and simple workholding.

                                  lock pin idea.jpg

                                  #444214
                                  JasonB
                                  Moderator
                                    @jasonb

                                    You are likely to need a spacer or counterbored nut anyway as almost impossible to thread right upto the underside of the head. Also having a dead square internal corner between head and shank will be a stress raiser

                                    #444221
                                    Keith Long
                                    Participant
                                      @keithlong89920

                                      Richard have a search on the web for "rivbolt" or "clinch bolt". I think one of those would serve your purpose if they come in the sizes to suit.

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