Tom's Tips

Center Finder

I was trying to find the exact center of the root rib on an Aquila XL so I could replace the tiny 1/4" rods with a decent 1/2" carbon joiner.  Trying to get the measurement just right with just a rule, wasn't that easy.   I had a Robart center finder that has really helped me find centerlines for hinges and such.  The only problem is that it is too small for a lot of my needs.  Soooo... I made a quick and simple center marking gauge large enough to fit the thicker ribs on many of my planes. 


(2) 1/4 inch by 3/8 inch by 3 inch block (you can vary the sizes however you want)

(1)  5/8 inch by 3 inch block (the longer this block the thicker the thing you want to find the center of can be)

(2) Machine screws ( I used 8-32 stainless because that's what I have handy)

(2) Nuts 

(2) "O" rings (optional)

(1) Scribe insert (optional)


1:  Cut out the blanks and mark for the holes. 

2:  Drill the appropriate end holes in the three blocks.  I counter sunk for the screw heads, but it is not necessary.

3:  Assemble the unit (I chose to use knurled nuts and "O" rings to make it work like I wanted).

4:  This is a critical step to get the exact center.  Take and push the blocks together and scribe a line on the main block.  Flip the outer bocks the other direction and scribe again.  This gives you an "X" right in the center of the block.

5:  Drill the center hole.  I chose to use a center scribe insert, since I had several in my tool chest, but you can drill a small hole for a pin or a larger one for a pencil.





Knurled Cap Nuts and "O" rings

Scribe Centerline right and left

Scribe Insert

Using Pen or Pencil

Shown on Gemini root.