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A small magnetic arbor press pin chuck

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  • A small magnetic arbor press pin chuck

    I’ve been involved with a project in the last several months that extensively use small (2-3mm diameter, 6-12 mm long) slotted spring pins (McMaster-Carr’s term, you may know them by other names). I’ve come to like designing with slotted spring pins and greatly appreciate their features. Assembling and disassembling parts with these pins is another matter however, and even though I have the nubbed and starter pins made for these little beasts I often find myself needing another couple of hands, and preferably smaller, stronger and more nimble hands than the meaty, arthritic sandwich clamps that I’m blessed with.

    I have been looking hard at the magnetic arbor press pin chuck from Matthews Engineering, but have some issues with it. It’s expensive for what it does, it uses a key-less chuck which takes up a lot of space in the throat of a small arbor press, and the 3/8” capacity is overkill for my needs. The idea is sound, however, and so I went at making a similar item that would suit my purposes better.

    Near me in SE MI there is a tool emporium (Kitts Industrial Tools) that features a multitude of products from the Far East that don’t meet Harbor Freight’s high quality standards. If you can get over the intense smell of cosmolene grease smeared over everything, there are always amazing use-once-and-toss deals to be had. So, I donned a KN95 and ventured in - and soon exited with a 1/4” keyed drill chuck (complete with a very thin coating of genuine Chinese surface rust - it was the best one that moved freely all through its range), a 3/8”-24 x 1” hex head bolt-like thing and a package of ten ½” round x 3/16” deep magnets – total cost: $7.50.

    Firing up Fusion 360, I came up with this 3D printed carrier to hold these simple components:

    Click image for larger version

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    The hex bolt sits in the slightly oversized center recess and is threaded in to the back of the drill chuck. It is free to move vertically in the carrier. The head has been faced off to contact the ram squarely. Three magnets are oriented around the bolt head, but not quite contacting it, and are slightly (0.5 mm) above the bolt head. If anyone cares, the wall thickness is 3 mm. The magnets are glued into the carrier and hold the assembly against the end of the ram, which has been previously machined square to its axis. The magnets don’t quite cover the entire end of the ram, but there is enough in contact to keep the assembly in place when using the tool.

    When pressing, the chuck lifts about 0.5 mm and the bolt head contacts the ram. The hex bolt is threaded as far as it can be into the drill chuck body, providing a stop to the pins. Small-diameter pins can be tightened short of the end of the bolt so they slip instead of bend when they encounter excessive resistance. The plastic carrier and magnets do not ever see any force, they only keep the chuck from falling off the end of the ram.

    After consuming 84 cents of PLA plastic and exercising the 3D printer for an hour or so, here it is completed and at work. Yeah, I know that is one seriously small arbor press, but I can't deal with that issue for $8.34.


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    And how does it work? WAY better than I had hoped!! It stays firmly in place but isn’t hard at all to reposition or remove. Best of all, using it to install or remove spring pins is far easier than without it, the ultimate test of any tool. I am pleased, especially considering the magnitude of my investment. I could cut 3 or 4 mm off the length of the bolt, freeing up more space under the chuck... but for now I'm just going to use it.

    One unintended but appreciated bonus feature is that the three-lobed plastic carrier is plenty strong enough to use to snug up the punch pins in the jaws, eliminating the need to use the key in the chuck.

    Now what to do with the 7 magnets I have left over?
    SE MI, USA

  • #2
    Hey Mike- just built a press and the spindle is .500 bore with set screw. This IS a great idea ! Thanks for posting .....love the magnets.

    Click image for larger version

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    • #3
      Thanks.
      I really like that press. Nicely done!
      SE MI, USA

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      • #4
        Looks neat.

        But let me get this straight.

        You insert a pin tool in the chuck that is the same diameter (or larger?) as the spring pins you want to install and use it to insert the spring pins which are hand held.

        Is that how it works?

        And do your tool pins have a plain, flat end or some kind of feature, like a center nub, to center them on the spring pins?
        Paul A.
        SE Texas

        And if you look REAL close at an analog signal,
        You will find that it has discrete steps.

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        • #5
          The pin tools that go into the chuck look like shorter versions of the punches used to deal with them in the conventional way. The idea here is to eliminate holding a punch, the roll pin and the part while tapping it in (or out) with a hammer. The drill chuck holds the punch, the arbor press provides the force.

          The punches can be plain-ended or have a small nub to go into the center hole and help guide the roll pin, both of these can be either larger in diameter than the pin (to install) or slightly smaller (to remove). Often the pin is held in needle-nosed pliers when installing, to get fat fingers out of the way.

          The punch can also have a shallow axial hole that helps align the pin when starting to install. If the hole is sized correctly it’s an easy press fit for the pin and eliminates the need for needle-nosed pliers or skinny fingers.
          Last edited by DrMike; 03-05-2022, 05:30 PM.
          SE MI, USA

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          • #6
            Nice job DrMike going to try to make one out of aluminum don't have a 3D printer maybe some day ill get one

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            • #7
              Now that's putting your thinking cap on. Well done DrMike.

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              • #8
                very cool! I have an old and beat Jacobs drill chuck on a straight shank arbor that fits in the hole in my arbor press ram. Haven't needed it yet, but the idea is the same.

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                • #9
                  Nice work DrMike,I’ve used Drill Chuck for a few years on my Greenerd&Big Dake with Socket Adapter.Those Arbor Presses are really handy. Click image for larger version

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