# Thread: How to find this center?

1. ## How to find this center?

Ok let me describe my problem. On another thread somebody posted a pic of a damper for the stepper motors which I decided I would try to make since I was having some resonance problems. I milled a 2x5x1 steel parallel and faced one long side. Next I zeroed in the block, on the y and z this was no problem, but on the x since I didn't mill the ends of this block , I just eyed it , figured it wouldn't be a problem because it really didn't matter as long as I was close. I milled out the two center holes first(these go all the way thru), then the controller pc froze up before I could start the next op which was the 9 hole pockets circle pattern, I got the part zeroed back in as close as I could(was off by .020 but figured after I milled the 9 hole pattern I would go back and re mill the center holes as they needed to be enlarged anyway), I finished the 9 holes and had to leave , put the machine on hold and over nite the power went out. Now I need to find the center of the 9 hole pattern. Any ideas on how I can do that? Heres a pic http://www.cnczone.com/forums/attach...1&d=1200072366
Damper.jpg

2. As you can see in the pic it's kinda hard to find the center because the holes are not directly across from each other. And yes I wish I would have faced off the ends so I could have correctly zeroed in the x and I wouldn't have had this problem(kicking myself in the head as i type) but its a little late and because the machine is a cnc Sherline took 8 hrs to mill out the 9 hole patterns I don't want to remill them if i don't have to.

3. Pick up the centers of three evenly spaced holes. These give you the corners of an equilateral triangle. Now use a bit of trigonometry to calculate where the center of this traingle is, that is the center of your part.

4. Figures I would figure out right after I posted this. Actually the hole that is to the right of the center of the pattern is pretty close to the center line of the whole piece(off by .0008). So I,ll just pick up from that hole bring my mill over from that and re bore the centers. Thanx guys for the quick replies.

5. Here is a VB program that I've written that will do the calculations. Just enter XY of three points.