finding the center of a cr?

[Adam Selene]

i have a 5.5" centering ring with a hole for a 54mm motor tube. i need to draw a line accross the diameter so i can drill holes for the 2 29mm motoer tubes i'm going to add.
any suggestions?

 

[wwattles]

Trace around it on a piece of paper. Cut out the paper. Fold it in half. Lay folded paper on ring. Draw the line.

Crude, but effective!

WW

 

[Adam Selene]

Duh!

thanks, that's simple enough.

 

[Samuron]

Put a carpenter's square on the disk, and put the point of the right triangle against the outer edge. Make a mark where the two legs of the square cross the edges, and draw a line connecting the two; that line is the diameter.

Turn the square a ways, and do it again; where the lines you drew intersect is the center.

 

[Adam Selene]

that's more the kind of thing i was thinking of.
of course there is nothing to draw on at the center, there'a 54mm dia hole there.

the paper circle idea seams to have worked just fine.

Thanks! i just love the way you get help so fast here!

 

[Stymye]

I use a compass and just mark from 4 sides.

 

[Rocketmaniac]

Originally posted by stymye
I use a compass and just mark from 4 sides.

I have used this method. The biggest problem is it doesn't work when the center is removed..... He had already cut the 54mm motor tube hole......

 

[jflis]

The folded paper idea was the best and most elegant. Actually, he wasn't so much looking for the center (as it was removed) as he was looking for a "center line"

 

[Stymye]

ahhhh,!

 

[Adam Selene]

right! it would have been much easier on a solid circle, having the hole complicated things.
but tracing the wood on a piece of paper with an exacto knife worked great!

 

[edwardw]

I use a circle center finder - a plastic tool that you draw three lines with and you get the center. It cost about $4 at a woodworking store. You could just tape with 3" wide masking tape to cover the 54mm hole. Here is a picture of my center finder on a 75mm forward closure

 

[Rocketmaniac]

Originally posted by edwardw
I use a circle center finder - a plastic tool that you draw three lines with and you get the center. It cost about $4 at a woodworking store.

I like that tool. I need to find me one of those.

 

[Stymye]

A combination square set . I use one for aligning things on larger rockets will also have a center finder.
these sets can be found cheap, like harbour freight.