Finding Beam Center


For a motor mount (quadcopter) I need to drill holes more or less exactly in the center line of a carbon beam to avoid twist. However the beams are varying slightly in thickness as the are roll-wrapped. With hand tools I’d use a simple self centering doweling jig, but with the shapeoko3 I’m scratching my head :slight_smile:

It might sound easy to you but:
How do find the centerline of such a beam with the shapeoko3?

Hints and clever hacks would be much appreciated!

Br Michael

Hmmm… might be easier to make a jig with the shapeoko and then use the hand tools to finish. Are you drilling the center of the ends of the rod, or center along the edges?

How I would do it

  1. Clamp the beam as close to parallel with the Y axis as you can manage
  2. Jog the Z axis so that the bit is at the same level as the beam, and the Y axis to where you want to place your hole
  3. Jog X so that the bit is as close as possible to the beam, similar to how you would jog the Z axis to the top or bottom of your workpiece normally
  4. Record the X axis value
  5. Jog Z axis up to clear the beam
  6. Repeat steps 2-5 on the other side
  7. The average of those two numbers is the X coordinate of the center.
1 Like

Hi John,

Thanks for your reply.

The beams are 15x15x360mm and wall thickness is approx 1mm. The holes and cutouts need to be on different faces of the beam. In CAD I’m using the centerline on the faces.
I’m using the end of the beam as y zero, but the x zero is tricky to get zeroed to the centerline.

In the mealtime I thought about attaching the jig to the endmill, set zero anywhere, clamp one side, move y, clamp again. However I thought there might be an easier way.

Hi Joel,

Thanks for your reply.
Do I get you right that you would “touch” both sides and take the center between the readings?

Br Michael