Announcement

Collapse
No announcement yet.

dimension for T-nut to lock when turned 90deg

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • dimension for T-nut to lock when turned 90deg

    Hi

    Somewhere, recently, I saw a simple drawing with a dimension that is a constant value. This drawing shows a T-nut that will fit through the T-slot on a slotted table and this t-nut when turned (by the clamping bolt) will rotate only 90deg thus "locking" the nut in the slot.

    So, the T-nut has end corners cut at an angle that will allow the T-nut to rotate clockwise but the remaining portion of the T-nut end presses against the sides of the slot in the table.

    Kind of like this...

    |\
    ||
    \|

    The dimension is the constant that is used to calculate the length of the side, or how much longer to make the T-nut so that it performs the action described above. I remeber the first digit of the value, it was 1 point something

    Did I see it here on the forum, or was it in a magazine? I knew I should have written down that value!
    Kind regards

    Peter

  • #2
    Back when I worked the trade they called what you describe as "suicide bolts" because their propensity for coming undone and popping out was a frequent topic whereever they were used. Also when it comes time to back off the nut the bolt head would turn n the slot and the clamp spring off the work with a hellova clatter.

    Most of the problem came from wear and overloading. The once-flat surface of the head became cam shaped. I don't know if there is a standard for suicide bolts - or T-nuts for that matter. OK use to make them but I don't know if they are in business anymore. Look for "quiick release T slot bolts." Seems to me that the T slot dimensions of non standard would play an importan part in their design. The ones I used to avoid didn't trun 90 gedrees but somewhat less, more like 60.

    I suggest you saw a hunk of wood and play with its shape until you come up with something that will drop into a T slot and turn to lock into place. A T nut may be more difficult. There won't be much head left if a tapped hole runs through it. You might have to go down a nominal bolt size.
    Last edited by Forrest Addy; 12-01-2008, 05:03 AM.

    Comment


    • #3
      Hi

      Thanks for the feedback.

      In the process for search for something else, I cam across this...

      http://rick.sparber.org/Articles/tn.pdf

      This article (not the one I saw recently) showed the size required. I'm off to the w/s to try it out
      Kind regards

      Peter

      Comment


      • #4
        Re Mr Sparber's parallelogram T nut

        Suggestion; use stock the same size you would make a normal T nut from. Turn or mill a cylinder on the top side of the nut blank to the same depth as the key portion of the normal T nut. Make the cylindrical portion a close but manageable fit in the upper part of the T slot. Drill and tap for the bolt, and cut the wings to the required length and angle. This should give some added stiffness.
        Jim

        Comment


        • #5
          J&L sells them, and they have all the dimensions also. PN GIB-00460 should get you to the page of the catalog.

          I've ground them out of a standard T-nut in a pinch, really not that difficult, burn your fingers up pretty good though(Thats why they make visegrips). Finally got smart and just bought a few for emergencies.

          Comment


          • #6
            Electricians use the same thing with unistrut nuts but they have grips on the flange for reducing slippage and they are not being constantly taken off and on again. Wear might be a problem unless heat treated.
            Looks like with enough wear and, like Mr. Addy said, they coud release with a bang. Liven things up a bit in the shop, I suspect.
            Pat

            Comment


            • #7
              Originally posted by Peter Sanders
              Hi

              Thanks for the feedback.

              In the process for search for something else, I cam across this...

              http://rick.sparber.org/Articles/tn.pdf

              This article (not the one I saw recently) showed the size required. I'm off to the w/s to try it out
              So 1.414 which ironically is the value you multiply AC voltage by to get DC smoothed.

              I always thought that Beaver milling machine of mine was a bit AC / DC


              .
              .

              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



              Comment


              • #8
                Actually, its very easy........ flat-to-flat its the distance that the t-nut would be anyway, when in holding position.

                The width of the flat is irrelevant, what is important is that the result can fit thru the slot. So just draw a regular t-nut to fit, then draw parallel lines slightly under the width of your slot, at an angle so as to include the corner of the nut, centered on the threaded hole. Done.
                2801 3147 6749 8779 4900 4900 4900

                Keep eye on ball.
                Hashim Khan


                It's just a box of rain, I don't know who put it there.

                Comment


                • #9
                  Sounds like it needs a locking feature.

                  You could drill a through hole through the stud just below table level - so that once it's all in position you could insert a pin or shaped block which bears against the slot sides, and prevents the nut rotating back to the 'release' position...

                  Or make a drop-on piece, basically a block the width of the top part of the slot, and with a hole for the T-nut stud in the midddle. Either side of that hole you have pins facing vertically down. Pins engage sockets on the T-nut top face when T-nut is rotated for full engagement. This might be better, requires no access from the side.

                  Comment


                  • #10
                    I hope Mr. Sparber quits before he takes a chunk out of his machine table. I would much prefer to see the nut yield than the relatively fragile cast iron lip of the table. Using a machine table for yield testing is risky at best.

                    I also would not get carried away putting "grippers" on the back side. I have a drill press table whose t-slots have signs of some chewing on the back side. Its a real annoyance since on a drill press, you need to be able to loosen the bolts holding the vise a little bit and slide the vise around to center the work. It does not work well if the t-nuts grab on the back side on chewed-up t-slots.

                    These t-slot nuts are a work around. As such, if they are a pain in the neck to use, so be it. They seem to be a poor alternative to the real thing and using them might encourage the use of a proper fitted t-nut.
                    Take care of your t-slots....they are a lot more valuable than a cheap nut...or even the time it takes to fish a nut in from the end.

                    Paul
                    Paul Carpenter
                    Mapleton, IL

                    Comment


                    • #11
                      Originally posted by John Stevenson
                      So 1.414 which ironically is the value you multiply AC voltage by to get DC smoothed.
                      That's not a coincidence John

                      RMS Voltage = V(Peak to Peak)/SQRT(2)

                      Diagonal of a square = X * SQRT(2)

                      SQRT(2) = 1.41421356
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                      Comment


                      • #12
                        Hi

                        Thanks for the info.

                        I really only want to be able to use these to clamp a drilling jig to a drill press table.

                        For convemience and ease of use by the teachers/students I wanted them to be able to place the drilling jig on the table and clamp it to the table from above and without having to remove and refit clamping nuts below the dp table.

                        This should work ok I will have a go at making something tomorrow.

                        This leads me to another question re clamping but I will create a new thread for that.
                        Kind regards

                        Peter

                        Comment

                        Working...
                        X