Simple Center Finder




About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

Superthunder bolt did a good Instructable titled Carpenter's Center Finder. He relied on careful measuring and drilling for critical dimensions. What follows automates the process of locating the necessary holes and makes accuracy inevitable.

1 x 2 hardwood
Dowel rod
Masking tape

Drill press and drills
Wooden base piece for drilling

Step 1: Mark Center

I made an "X" to mark the center of a piece of 1 x 2 inch oak. I marked the intersection of lines from opposite corners.

Step 2: Drill a Pivot Hole

I drilled a hole through the 1 x 2 at its center and let the drill go almost through a base piece of plywood. I hoped this hole would grip the pencil firmly, but the bit I had was a tiny amount large. So, the pencil was loose in the holes. I wrapped a layer of masking tape around the pencil to remove the slack. Make a line down the middle of the 1 x 2 that goes through the center of the hole just drilled.

I used the pencil as an axis for the 1 x 2 and set the pencil off an inch and a half or so. I clamped the base piece to the drill press table. Use the drill press to drill a hole to match the dowel you will be using on the line that runs the length of the 1 x 2. I had a 5/16 inch dowel.

Step 3: A Second Hole Near the End of the 1 X 2

Swing the 1 x 2 half of a turn and drill a second hole. The pencil used as an axis will guarantee that the distance of both holes from the center hole for the pencil is identical.

Step 4: Add Dowels

I cut two pieces of dowel identical in length and glued them in the holes.

Marks on the oak are from dirt on the workbench and are marks I made for another project before I changed my mind.

Step 5: Mark the Center of the Work Piece

Place the centering guide over a piece of wood or something else with parallel sides. The tip of the pencil lead needs to come though the oak piece just a little. Press the dowels firmly against the sides of the workpiece and slide so a mark is left as in the photo in the Introduction.

This is a no weld version. Originally, I see 1/8 inch strap iron and 1/4 inch rod. The center hold was drilled for the size of a finish nail, and then made conical with a countersink bit. The hole for the finish nail is about right for a pencil lead. I welded the 1/4 inch steel rod into holes drilled in the strap iron.



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    12 Discussions

    Phil Brc jedi

    Reply 3 years ago

    Thanks for your comment. In the version Superthunder bolt made, he made the space between the two pins much longer. You could make several of different sizes to cover all needs


    3 years ago

    This I clearly a nice and simple copy of the commercial dowel aids, that work completely in the same way!

    3 replies
    Phil BEmilioSchwarz

    Reply 3 years ago

    Thank you. My main purpose was to show how the main part can be drilled precisely without measuring by using a pivot at the center.

    EmilioSchwarzPhil B

    Reply 3 years ago

    Hi, I used the attached apparatus, for only 17 €.

    Very handy to do all the joining with dowels and for drill holes to match.

    dowel aid.jpg
    Bill WW

    3 years ago

    Nice, Phil. Using the center hole as pivot point to precisely locate the other two holes is an excellent tip. Brilliant.

    I made centerline finder/marker using a parallel ruler concept, with a hole drilled at centers of the Plexiglas links. Yes, a lot more work than yours, and no more accurate. But with mine you can lock the wing nuts and then slide it along a board as you mark the center line.

    Always good to see your Instructables.

    Merry Christmas,


    1 reply
    Phil BBill WW

    Reply 3 years ago

    Merry Christmas, Bill. It is good to hear from you. Your parallel ruler would do a fine job. "Brilliant" is probably too complimentary. I have done several things by anchoring a base piece to a drill press table and creating a pivot point, including an arc slot for making a miter gauge on a table saw improvised from a circular saw. (Naturally, I used a grinder to remove material between the holes. But, the pivot point as a drill guide nicely defined the needed arc and yielded results that made it look like I knew what I was doing.)

    Phil BCraftAndu

    Reply 3 years ago

    Thank you for looking. Give credit to Superthunder bolt and his original version which I simply modified.