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  • Automatic center punch

    I' looking for plans for an automatic center punch. I'm an apprentice machinist who also has access to machines at home and I think it would be an interesting and worthwhile project.

  • #2
    Take a Starret automatic center punch apart and copy it. Some people call this "reverse engineering." You might want to change the thread pitches, since those used by Starret are unique to Starret.
    Duffy, Gatineau, Quebec

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    • #3
      I wonder if "center punch with sliding sleeve hammer" is an automatic center punch? Project #22 in South Bend Lathe's Machine Shop Projects.

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      • #4
        Originally posted by Arthur.Marks View Post
        I wonder if "center punch with sliding sleeve hammer" is an automatic center punch? Project #22 in South Bend Lathe's Machine Shop Projects.
        See page 7 for an image of same:

        http://www.wewilliams.net/docs/1928%...%20Shop%20.pdf


        I suppose it might be thought of as a "1'st generation" automatic center-punch.

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        • #5
          Thanks for that illustration, tlfamm. Yeah... not exactly what is asked for I have a contents index for the Village Press books. I see Metalworking Book Three lists "An Automatic Punch" under shop improvements. I wonder if anyone could provide a general description of the one presented there?

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          • #6
            It's not really something you need plans for; google image search for 'automatic prick punch' or 'automatic center punch' will give you cross sectional images that outline the basic principles, then copy those as you see fit. There's even an animated gif on the wikipedia article for 'automatic center punch'. The biggest challenge will be sourcing appropriate springs.

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            • #7
              It is a sliding hammer punch in PiM book 3

              Arthur,

              I have the book and it is a sliding hammer center punch, no springs. The same design as tifamm's .pdf he pointed you to, just made a bit differently.

              - Reed

              Originally posted by Arthur.Marks View Post
              Thanks for that illustration, tlfamm. Yeah... not exactly what is asked for I have a contents index for the Village Press books. I see Metalworking Book Three lists "An Automatic Punch" under shop improvements. I wonder if anyone could provide a general description of the one presented there?

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              • #8
                This link has some good images of mechanims.

                http://en.wikipedia.org/wiki/Automatic_center_punch

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                • #9
                  Harbor freight sells them cheap buy one and take it apart build one with good materials. http://www.harborfreight.com/catalog...q=center+punch

                  It is probably a China copy of the Starett.

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                  • #10
                    Originally posted by gundog View Post
                    Harbor freight sells them cheap buy one and take it apart build one with good materials. http://www.harborfreight.com/catalog...q=center+punch

                    It is probably a China copy of the Starett.
                    Actually it's a dead ringer of a Craftsman auto center punch!

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                    • #11
                      Buy one from Harbor Freight and learn how it is made. Make a copy, put the original in your car in case you ever need to break out a window.

                      http://www.youtube.com/watch?v=LLaUrJYvQG8
                      Last edited by dp; 09-15-2014, 01:26 PM.

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                      • #12
                        Here are drawings showing the internal components of auto center punches:

                        http://www.micro-machine-shop.com/Li...nter_punch.pdf

                        (slow to load)
                        http://www.micro-machine-shop.com/Ge...8_Assembly.pdf
                        Last edited by tlfamm; 09-22-2014, 11:33 PM.

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                        • #13
                          With the current enco sale, a friend reminded me that I also need an automatic center punch. But when I read reviews of the models from General, the were pretty mixed, with lots of complaints. Those are all made in India, and apparently quality tanked when they made the move. Too bad they didn't drop the price accordingly, from the lofty $20-$30. There were even some complaints about Starrett.

                          Guess I'm going to try one of the harbor frieght units for $2.99, and maybe rebuild as necessary.

                          Any other recent experiences with ACP's?

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                          • #14
                            Originally posted by Glug View Post
                            .....

                            Guess I'm going to try one of the harbor frieght units for $2.99, and maybe rebuild as necessary.

                            Any other recent experiences with ACP's?
                            I have a couple of the Harbor Freight ones, and they work just fine.
                            Lynn (Huntsville, AL)

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                            • #15
                              Originally posted by lynnl View Post
                              I have a couple of the Harbor Freight ones, and they work just fine.
                              I have a couple of cheapies, and they're both crap.

                              Making one would be an interesting exercise, but I think you would need to count on including some hardened and either ground or lapped internal parts if you want it work reliably and last a reasonable time.

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