Finding exact centre of wooden wheel

[Dengue]

I have to replace the broken wheels on a toy, and would like to know if there is a technique to determine the exact centre of a wooden wheel about 30mm diameter?

I seem to recall reading something ages ago, but cannot remember the details. :(

regards,
Jill

[mic-d]

If you draw two chords, say about a quarter of a circle apart, then find the midpoint of each and run a line perpendicular to each chord, they will meet in the centre. A chord is just a line intersecting the circle.

Cheers
Michael

[watson]

That's it..three become more accurate......a la Scrapheap Challenge last night.

[Skew ChiDAMN!!]

A couple more alternatives:


1. Measure the diameter of the wheel, get a compass, set it to half the diameter (ie. the radius) and then, with the point right on the edge of the wheel, scribe an arc.

Move the compass around by about 90° and scribe again. The intersection should be the middle. (But just for double-checking, I always do scribe one or two more.) Even if you've set the compass out by a mm or so, it becomes obvious where the centre is.


2. If you're doing a few of 'em, it can be quicker to make a jig. (Compasses canbe fiddly things) This is basically just an L-shaped piece of wood - at 90° of course - with a ruler glued on top so that one edge runs along the 45° angle.

Just fit the wheel in the L, scribe a line. turn the wheel 90° and scribe another. Et voila, the intersection is the centre.

Being a turner, I use the last method all the time when mounting my blanks. :)

[mic-d]

A couple more alternatives:



2. If you're doing a few of 'em, it can be quicker to make a jig. (Compasses canbe fiddly things) This is basically just an L-shaped piece of wood - at 90° of course - with a ruler glued on top so that one edge runs along the 45° angle.

Just fit the wheel in the L, scribe a line. turn the wheel 90° and scribe another. Et voila, the intersection is the centre.Being a turner, I use the last method all the time when mounting my blanks. :)

number 2 reminded me of a way to do it with a combination square and a framing square or a small flat square. Clamp the combo square on its 45º edge so it bisects the framing square Et Voila again:)

Cheers
Michael

[Rocker]

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=6538&highlight=centre-finding

Rocker

[Dengue]

Thanks for the excellent suggestions. I like the idea of a jig, esp the one shown by Rocker; though for one off jobs, the combination square and the framing square was a great idea

I found it also in "101 Shop Tips for Woodworkers" ( Tip #1) issued by Time Life.

regards,
Jill

[jchappo]

$6 from Carbatec (http://www.carbatec.com.au/measurement/centre-finders/carba-tec-centre-finder) :)

[keju]

I had wondered why nobody said : go by a centerfinder before now....

I've just recently disovered one in Ken's shed and hijacked it! :)

Juvy