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[How do I?] Possible to find center on out of round?

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EmilioG

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#1
Is it possible to find the center of a hole that is out of round? I used a hole saw to cut a 2” hole in aluminum plate. Took it off the mill and it won’t indicate 360 after putting it back in the vise. Possible to just you x and y? To get close so that I can bore it?
 

BaronJ

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#2
Just average the readings from max/min at 90 degrees to each other.
A bit like centering a four jaw chuck.
 

mmcmdl

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#3
Sure . Just indicate it like it was round .
 

ttabbal

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#4
My first thought, which might be off so I hope someone will let me know, would be to use an edge finder to pick up the inside edge of the hole. Then zero the DRO, pick up the opposite side (X or Y movement only), and take 1/2 that for the center on that axis. Zero there, then do the other axis.

Then you can use a boring head to even it out.
 

EmilioG

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#5
I’m worried about the boring bar chipping.
I’ll just start over with a good hole and not move the part. Thanks
 

mmcmdl

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#6
Why would the boring bar chip ? :confused 3:
 

BaronJ

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#7
Hi Emilio,

The boring head, is I assume is what you mean by boring bar. If you set it up properly it will make the hole perfectly round, and if so desired move the hole to where you want it.
 

Cadillac

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#8
I’m worried about the boring bar chipping.
I’ll just start over with a good hole and not move the part. Thanks

When using a boring bar or endmill to clean up a out of round situation or even moving the hole over 5,10 thou, half a hole or what have you it will cut the hole without any influence of the existing hole. Light down feed and let the cutter work. Use the biggest endmill or bar for the hole to help with deflection. You want a solid setup so your tool doesn't walk or wobble the part. If everything is rigid their should be no chipping just cutting.
 

EmilioG

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#9
Thanks. I’ll just start a new hole. I’ve done it many times before but never after moving the part off the vise.
 
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