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  • Electric edge finder or Wiggler

    Ever since I began machining about 13 years ago I have used an electric edge finder. It fits in the mill chuck and has a red light that lights up when it contacts the edge of anything metallic. This has worked fine for me, but I am beginning to question it's accuracy. I find that when using it to find center of small parts, it can be out as much as 0.010 to 013". I have never used a mechanical Wiggler, but I'm beginning to question if I should buy one. I haven't used a mechanical wiggler before. I do have DRO's on my milling machine.---Opinions please.---Brian
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

  • #2
    Depends on if you're talking the wiggler (Starrett 828 or similar) or an edge finder (Starrett 827 or similar). I only use the wiggler to find a scribed line or the like and mostly use the center finder for clean edges and clean holes. I like the Hermann Schmidt edge finders, they have a larger than normal lapped interface that's particularly sensitive. You'd have to find one on eBay as they're not made any more. Make sure you run the edge finder at an appropriate speed, I recall Starrett suggesting 1000-1200 rpm.

    You could check your accuracy in center finding by boring a hole (to be in line with the spindle), randomizing and finding center and seeing how close by dro (easiest) or running the boring tool back in. With a decent size hole I find that and edge finder is pretty good (<.001 off) after about 3 rounds of splitting the differences between X & Y edges.

    Edge finders are really sensitive to burrs, if you can't clean the edge use a toolmaker's chair to transfer the edge for finding.

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    • #3
      Doesn't Suburban Tool own Herman Schmidt? Didn't they keep and continue to make some of the product line?
      No, i think that was Taft-Piece.
      Last edited by reggie_obe; 03-02-2022, 01:19 PM.

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      • #4
        I don't have an electronic edge finder. I have a wiggler, but have never used it for anything. I have a couple of mechanical edge finders and use them all the time. One is china-made and a little rough but it works ok. The other is a Fowler 1/4" body, which is outstanding.

        When I'm off picking up an edge it's almost always because I've forgotten to deburr the edge and end up measuring the location of the burr and not the side of the part. If I miss the center of a part is mostly because (1) I've mis-measured the part or messed up (2) the math or (3) the move to the center. I've gotten into the habit of putting a scale on the part after the centering move to eliminate the dreaded "one-full-turn" error, especially with critical or large parts.

        If I do my part, these simple tools are plenty accurate.
        Errors of 0.010" - 0.013" are - for me - indications that I'm not paying attention and it's time to either wake up or quit for the day.

        SE MI, USA

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        • #5
          I have tried all the different edge finders over the years. I have found that a quality mechanical center and edge finder will repeat to less than .0005 every time. No batteries, it's always ready to go.

          The pointed end can be used to pick up holes that are too small for the straight end. You can either put it partway in the hole and go side to side with it spinning, or you can gently lower it all the way with the spindle off, and feel for any mismatch of the 2 main diameters with a fingernail.

          https://www.ebay.com/itm/36370242312...UAAOSw5d9fY4-i


          https://www.ebay.com/itm/28467031627...em4247ac4ef1:g :T4IAAOSwiMhiGV~x
          Last edited by Toolguy; 03-02-2022, 01:35 PM.
          Kansas City area

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          • #6
            Toolguy, have you used the pointed end in that full insert manner for picking up on a center punch mark as well?

            Obviously one wants to lower the spindle to touch the end fully with some care to avoid any undue pressure. Or would leaving the collet a touch loose serve as an overrun relief? Oooo.... I like that idea. My collets grip lightly but with nice support just with a finger grip. I'm going to try this. More in a bit......

            Brian, for your situation is there any way to set your finder up and check that it's not bent? Or maybe the collet or holder you are using has some runout? I assume you don't use it with the mill running. So if the collet or end mill holder is out a little it could read different depending on how it is turned? Could it be something as silly as the contact surface is getting coated with something that forms an insulator and it needs a few thou worth of pressure to cut through that film? Just tossing out some thoughts which might jog something in your own mind.....
            Last edited by BCRider; 03-02-2022, 02:17 PM.
            Chilliwack BC, Canada

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            • #7
              I may be wrong here (That's not uncommon). I think we all pick up the center of a bar by bringing the edge finder up to pick up one side, and when it does, set the DRO at 0 and then bring the edge finder in from the other side until it touches, and ask the DRO for half of whatever it reads for travel. Then back the table up by that amount and that is the center. I always color my parts with machinists dye, then scribe the centerline with a scriber just to make sure I don't screw up. And quite often, the "center" given by the electric edge finder and DRO are out by that .010 to .013" from the scribed line. I seldom ever try to pick up a punch mark because my electric edge finder doesn't have the capacity to do that. The second link given by Toolguy seems to show a combined center and edge finder for $16 from Ebay.
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

              Comment


              • #8
                I found this video helpful:
                https://www.bing.com/videos/search?q...6FORM%3DVDVVXX
                It was made by Suburban Tool, a company known for making quality products, some of the products that I wish I could afford.
                I have always used mechanical edge finders, but was interested in electronic and center-scope models.
                After watching this video, I'm going to just keep using the mechanical edge finders that I have.

                Comment


                • #9
                  A 3/8" shank, 0.200" tip edgefinder from Fisher Machine bought from KBC (~$20cdn) is all I've used for many years with great results. CMM verified half thou or better performance in the cnc's and around a thou or better in manuals if I do my part. Starrett, and Mitutoyo ones are great too, but I've settled on the fisher, as they're just as good IMO, and about $5 cheaper. I don't like the imports, and it's one of those tools that for the minor difference in price, you're getting way more value just buying a quality brand. Fisher is made in USA, and the owner used to be a regular poster over on PM, but I think he's retired now and the 2nd gen is running things. The imports just don't feel, or jump as smooth, which translates to reduced repeatability and accuracy. $10 import vs $20 quality is $10 well spent IMO. I have a bunch of different sizes and styles, but the standard 3/8"/0.2 is my go to.

                  https://www.kbctools.ca/itemdetail/1-811-107

                  I prefer this style to the "wigglers" by many orders of magnitude. YMMV. I don't think it's even been out of my box in long time. Some guys in the shop still use them though. Personal preference.

                  We had an electronic one at work, and it's complete junk, with about the accuracy and repeatability you state, ~0.002-0.01". It's the style with the ball on the end, and a red light in it. I'm sure there are probably some good ones out there, and a few guys that love them, but I don't. I just went out to try and find it, but I think it disappeared. We had a mass exodus a few years back and a bunch of tooling grew legs around that time.....I wish I knew who it was, so I could write them a thank you note .

                  As said above, run them about 1000rpm give or take a few hundred. I'd try and describe the best way to use one if you've never, but Don Bailey can do it much better than I can type it.

                  Comment


                  • #10
                    Originally posted by brian Rupnow View Post
                    I may be wrong here (That's not uncommon). I think we all pick up the center of a bar by bringing the edge finder up to pick up one side, and when it does, set the DRO at 0 and then bring the edge finder in from the other side until it touches, and ask the DRO for half of whatever it reads for travel. Then back the table up by that amount and that is the center. I always color my parts with machinists dye, then scribe the centerline with a scriber just to make sure I don't screw up. And quite often, the "center" given by the electric edge finder and DRO are out by that .010 to .013" from the scribed line. I seldom ever try to pick up a punch mark because my electric edge finder doesn't have the capacity to do that. The second link given by Toolguy seems to show a combined center and edge finder for $16 from Ebay.
                    Not having a DRO on either of my mills, I need to acknowledge the presence of backlash. If I found centers with this technique I'd be off by the amount of backlash in the particular axis in which I'm moving. To not have to think about this I need to go to the desired point by making a move in the same direction that I use to find the edge.

                    Once I find the edge I move in half the diameter of the edge finder (typically the diameter is 0.200", so a 0.100" move), which puts me directly over the edge. Then a move of half the width of the part puts me at the center. Both moves are in the same direction used when I found the edge. No backlash compensation since I haven't moved backwards. If I do everything correctly I'm at the center (or however far I want to be) within 0.001" every time.
                    Last edited by DrMike; 03-02-2022, 02:57 PM.
                    SE MI, USA

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                    • #11
                      Brian, try picking up the edge of something, set zero, and then turn the spindle 180° and pick up the same spot again to compare the readings. Might be that it's not concentric to the spindle. I used one at a job that was like that. We used it to measure 3D features and were just looking for relative measurements from one point to another but if we had tried to use it the way you are (picking up center) we would have seen similar errors.
                      George
                      Traverse City, MI

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                      • #12
                        At work I in the model shop we have an electronic light up edge finder.
                        It seems to depend on the runout of the collet or chuck that it is held in
                        and adds that runout to the ball diameter, no not accurate enough for me.

                        I always use a .200" kick out edge finder. Runout does not effect it.

                        Inch size "top hat" edge finders are still made by Fisher machine
                        and Shars carries them.

                        If I need to pick up an edge deep in something,
                        I use a long dowel rod. Like 3/8" by 6" long.
                        Ink up the dowel where you are going to touch the
                        part, and run the spindle, bump on the part until
                        the ink gets rubbed off ALL THE WAY AROUND
                        then you know you took out the orbit.
                        Subtract half the diameter and done.

                        -Doozer
                        DZER

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                        • #13
                          I bought a Vertex electronic one several years back, which gets used about once a year. It has a 20mm diameter which means an R8 collet. I must admit, I have never tested its concentricity on either mill, it would be easy with a lever type indicator just touching the ball so moving the pointer would be less force than springing the ball out of place. There are plenty of Chinese ones which look exactly like the Vertex, but cost 1/4 what I paid for mine.
                          Last edited by old mart; 03-02-2022, 03:54 PM.

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                          • #14
                            Have any of you used an "audible" edge finder? One of my co-workers likes them. I's an ordinary edge finder with a flat ground on the tip. I have a blown-up edge finder to reassemble, and I might grind such a flat on it to try it out.

                            https://www.amazon.com/Brown-Sharpe-.../dp/B0006J3DOU

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                            • #15
                              One of the guys we had in here years ago had one, but it was a crappy import version and while the click was a fun novelty, it didn't make up for the cheapness of the tool. I've always thought about grinding a small flat one of my good ones, but I guess I've just never got around to it. Every once in a while I have to pick up an edge that I'm blind to, but a mirror and go go gadget arms usually saves the day.

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