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  • Edge finder differences?

    Ok the edge finders below are .2 and .5 diameter. Whats the difference?
    Is the same RPM used for both (surface feet per min)?
    At the same SFPM would they both "pop off" the same amount? The only
    advantage I can see is the smaller one will fit into tighter spaces. Or are they like right hand vs left hand screw drivers???

    http://www.physics.wisc.edu/faciliti...images/edgefin
    ders.gif

  • #2
    Originally posted by ahidley
    Ok the edge finders below are .2 and .5 diameter. Whats the difference?
    .5 - .2 = .3

    http://www.physics.wisc.edu/faciliti...images/edgefin
    ders.gif
    But seriously:

    Can't make the link work.
    I like using these dodgy edge finders, makes me feel like I know what I'm doing.
    Mike

    My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."

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    • #3
      It's strictly a personal preference. I have both sizes and use the same rpm for both, somewhere around 1000rpm's I dont fuss about it though. I prefer the smaller one because it is easier to subtract/add .1 than .25

      fixed your picture

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      • #4
        I've only ever used the .200 ones and hey're the best thing since bridgeports.

        I will offer this to anyone looking to pick one up though: I have one made by Starrett and one 'economy' grade one. The Starrett is appreciably easier to use and more accurate. Not even a contest, the cheapie chinese one is just unusable.

        I've used other guys finders as well and my results are typical with every one I've tried.

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        • #5
          I'll echo the great superiority of a Starrett edge finder over the cheap ones.
          ----------
          Try to make a living, not a killing. -- Utah Phillips
          Don't believe everything you know. -- Bumper sticker
          Everybody is ignorant, only on different subjects. -- Will Rogers
          There are lots of people who mistake their imagination for their memory. - Josh Billings
          Law of Logical Argument - Anything is possible if you don't know what you are talking about.
          Don't own anything you have to feed or paint. - Hood River Blackie

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          • #6
            +1 on the Starret. : We have 3 at school that are black on the "kick off"
            part and they don't kick nearly as far when it goes. Also the black vs shiny
            part is much harder to see in the poor illumination on several of the mills.
            I don't know what "brand" they are, maybe the "cheep" brand. :-)
            ...lew...

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            • #7
              I have Starrett for serious work. It will repeat to .0002. I have a chink .500 that I have used in a special situation. When locating the centerline of a round part on a rotary table, pick up one side. With the .500 you don't have to worry about the radius of the part getting in the way. Make this first side "0". Now pick up the other side. Half of the distance is your centerline. The error in the cheap one will be canceled out by picking up both sides. It has worked for me in critical aerospace parts. The secret is that the error is the same on both sides. If you have a part 8" in diameter you cannot get on it with a .200" finder with a .500" shank.

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              • #8
                I have one each of Starrett and Brown & Sharp and both are excellent. I bought a cheap import as a test and after I tried it I threw it away, it was worthless.

                I use the .5", .375" and the .2" for different jobs. When I'm using a 1/2" collet for everything I use the .5" shank with the .2" or .5" depending on clearances. If I am using the 3/8" collet I use the .375" edge finder. If I'm using a drill chuck and the tolerance is loose I use the edge finder in the drill chuck.

                It's all relative to the tolerance and what your doing.
                Last edited by Carld; 02-10-2011, 09:22 PM.
                It's only ink and paper

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                • #9
                  The old-timer who taught me to use an edgefinder 'splained that the 1/2 inch tip was intended for use with a 4 TPI leadscrew. Zero the micrometric collar at the edgefinder "kick", get the edgefinder out of the way, and count the first leadscrew turn as zero.

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                  • #10
                    The 1/2 inch will pick up around steps or ledges where the offset of the .200 tip would be a hindrance. It will also be usable on certain size rounds where again the offset of the .200 tip would be interfered with.

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                    • #11
                      Originally posted by Carld
                      I have one each of Starrett and Brown & Sharp and both are excellent. I bought a cheap import as a test and after I tried it I threw it away, it was worthless.
                      Exactly same experience.

                      The good edge finders are centerless ground (i.e., they're round), and the interface between the two sections is lapped, so the snap when you hit the edge is crisp and distinct.
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                      • #12
                        The Starretts are nice, but the real trick edgefinder is the Hermann Schmidt edgefinder. Same .200 tip but a lapped interface that's .500 round for more kickout. Unfortunately they stopped making them for stock (they might make 'em on request, I can't remember).

                        Recently Fisher Machine offered a "Super Jump" edgefinder made in the same way and so I bought one for comparison - very close readings and much the same performance.

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                        • #13
                          Yeah I've seen a Herman Schmidt. Used to work with a guy who had one. It was good for .0002" just like the Starrett.

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                          • #14
                            Originally posted by Carld
                            . I bought a cheap import as a test and after I tried it I threw it away, it was worthless.
                            That's funny...I just bought my first edge finder from CDCO (junk) and thought I must be missing something. I thought they were supposed to snap....this one does nothing. I generally just use a piece of tissue paper and the when my end mill tears the paper, I'm at the edge. I'll try and find a proper B&S or Starrett and see what happens.

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                            • #15
                              I have ones from Starrett I bought new and they are excellent. I also have a Hermann-Schmidt (they no longer make them) because I heard so many people sing its praises... no discernable difference between the HS and the Starrett. If you want inexpensive but still US made try the ones from Fisher Machine which are also excellent.

                              I did some tests a few months ago to figure out which, if any, was better or more accurate. Here is the thread. Basically one can get to within a tenth (0.0001") with all of them. What I DID notice was that the biggest difference is practice. As I was doing the tests I got better at it.

                              If you want to go nuts get a "chair gage". Moore Precision Tools sells them for around $5,000 new!

                              -DU-

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