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What is this item? Sharpening fixture I assume, but for what?

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  • What is this item? Sharpening fixture I assume, but for what?

    R.H. Clark, with a "CC" logo. Square hole suggests lathe tooling, but I thought R H Clark was primarily woodworking stuff.

    CNC machines only go through the motions

  • #2
    What size is that square hole?


    • #3
      That might help!

      Hole is approx 0.660" square.

      Angles are (compound ones on side) about 15 and 30 deg, but are compound relative to other faces. Back angle is about 10 deg relative to front face.
      CNC machines only go through the motions


      • #4
        It's a fixture for grinding 29 degree threading bits.

        Probably from the 1940's.


        • #5
          I have a similar one for eclipse square and round 1/4 HSS toolbits, the rep gave them out, stick the bit in, grind the side and face angles, flip for top rake handy and saves burning your fingers!, im guessing thats the same thing
          You dont see them about anymore but great on a toolgrinder with table, not so good on a bench job unless you have retro fitted a proper toolrest
          Shove a bit of keystock or door square rod in and see what angles you get


          • #6
            US 2385902 A

            Google patents found it, but the text is so corrupted that it hardly makes sense. Not uncommon for Google. I'll have to try the USPTO to look it up for real.

            "Fixture for grinding thread cutting tools" is the title.

            However, it is for Acme OR regular V thread tools, it is not limited to 29 deg tools, according to the patent.

            I suspected that the fixture would be useless on any manual grinder, the facets are too small, you'd need a mag table. And, indeed, the patent drawings show it on what can only be a mag table.

            However, the patent clearly shows what the two little ramp-shaped pieces I also found in the toolbox are for... they are part of the fixture.
            Last edited by J Tiers; 08-24-2014, 11:19 AM.
            CNC machines only go through the motions


            • #7
              Link below, clicking the PDF link will get you a scan of the original docs.

              Central Ohio, USA


              • #8
                Thanks, I did go to the USPTO already, but I had forgotten about the "freepatenstonline" site. Thanks for reminding me.
                CNC machines only go through the motions


                • #9
                  A while back, in the course of my day job, I made a couple of grinding fixtures for tungsten resistance welding electrodes that were similar in function but somewhat different in form.
                  Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                  ~Practitioner of the Electromechanical Arts~


                  • #10
                    I've got an electric cheddar cheese sharpener.
                    No good deed goes unpunished.


                    • #11
                      Yes but this one is cordless!
                      Kansas City area


                      • #12
                        I just made one similar (in use only) on the weekend to pass the time while babysitting a CNC on saturday at work. Took pictures to upload to the shop made tools thread, but can't figure the new phone out enough yet. I'll post that and a few more things over there when I get the chance.

                        Mine can do 55*, and 60*, with a 10* side clearance angle, and hold bits up to 3/8"

                        Edit: Here's mine. and in use

                        Worked pretty good. I roughed out 3 new bits (one double ender) by hand on a bench grinder, then finished them with the jig, in about 20 minutes. Touching them up after the fact now will be really easy. This was made using a scrap of 4140 that has been kicking around my desk for about 6 months looking to be made into something, so that's why it's the size it is. If I make another (and i will) it will be larger so as not to need blocking in on the surface grinder. Took about 30 minutes of my time to make, maybe less, maybe more, wasn't really paying attention. I ball cut the angles in the cnc (cheated, ), so it did all the work.
                        Last edited by Dan Dubeau; 08-25-2014, 04:14 PM.