finding center

A friend, who died of cancer about a year ago, was working in his shop one day while I looked on. He was drilling a hole in a piece of 2" square tube to make into a trailer hitch. He had a little tool or device that he used to find the center, side to side, to drill the hole into which the retaining pin would be inserted and secure the hitch. Does this "thing" sound familiar to anyone? I'd like to find it for my own use.

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Edge finder?


Reply to
Grant Erwin

They're easy to make.

Imagine a bar with two pins set into it. Pin-to-pin separation is greater than the width of the material in question. Imagine a hole to accept a transfer punch drilled in the bar midway between the two pins.

Drop over material, twist until both pins contact the sides of the material, and the hole will be centered on the material. Insert transfer punch in hole and make center mark.

I made one with the added feature of adjustable pin spacing and it's useful for non-precision jobs.

I have no idea what it's official name is. I just call mine a "centering gizmo".

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things

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Marvin W. Klotz

Reply to
David Billington

There are any number of such devices.

Take a short flat of CRS, 4" long. Drill a hole through both ends, attach a spacer to each hole, so it stands proud.

Find the exact center of the flat, both in width and length, between spacers, and drill a 1/16" hole.

Now, whenever you place the flat over a straight object, with a spacer on either side, that center hole is in the center of the straight object. No matter how diagnally the tool is.


Rule #35 "That which does not kill you, has made a huge tactical error"

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Proctologically Violated©®

Perfect. Thanks a lot for the guidance.

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Marv sez: "> I have no idea what it's official name is. I just call mine a "centering

It is a takeoff on a 3-pin device called "The Preacher" that clock makers have been using for a long time. (From one of W.R. Smith's books on the subject.) In the preacher there are three pins closely spaced to go among the pinion holes in a clock plate. One of the pins was conical shaped to fit the range of pinion holes in any particular clock. The other two pins were sharp pointed. The clock maker would use the preacher to locate exact center of worn bearing or pinion holes. The conical pin was inserted in the worn hole and 2 centers were punched with the other 2 pins. Then the clockmaker goes about the job of drilling out the old hole and pressing in new material in the form of a stock, or custom made bushing. After dressing the bushing to the clock plate, the preacher is brought up to fit in the 2 previously center punched holes. Then the conical pin is punched with great assurance it will be located in the same place as the original hole.

Bob Swinney

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Robert Swinney

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