Getting a hole in the center.

Rio_Grande · Apr 22, 2013

I am trying to build a water wheel planter. To do so I need to build a wheel with sides on it running on a shaft. I have a air tank that will work diameter wise but it doesn't have nipples on the ends. It is convex in shape and welded on the edge. If it were flat I could get close with a square, but with the edges I am at a loss. It is too big to go in a lathe. Any help is appriciated.

6011Artist · Apr 22, 2013

Get or build a big compass, big enough to reach 1/2 way across the end of your tank. Put the point on the outer edge and draw an arc in the center of the end. Without changing the setting on the compass, do this from 4 or more positions around the tank end. Now you can determine the center by all the different arcs you drew. Might not be perfect but close enough for farm equipment.

Another way would be to use a ruler and measure the distance all the way across, find 1/2 way and draw a short line. Do this again from the other direction. Where the lines cross will be somewhere pretty close to the center point of the tank. Again, not perfect but close enough.

SPYDERLK · Apr 22, 2013

Lay it down on some wooden V blocks. Measure vertically from surface at v notch up to 1/2 across tank and mark. Turn tank and repeat etc. This should give you a very small circle of marks. Choose the middle of that.
larry

jwmorris · Apr 22, 2013

If its a convex shape, and it's on a level section of ground, seems like you could find center with a square.

Sort of like this OL, if the O was one convex end of the tank the L shaped square would only be able to touch the center.

Rio_Grande · Apr 23, 2013

Thanks! It is amazing I couldn't figure this out myself. I can get it now!

creekbend · Apr 23, 2013

Just a thought? Have you considered utilizing a Chalk Line? Put the chalk line on at least four end points. The middle will be where the intersecting lines meet. Best wishes.