Center Funding With an Edge Finder

[CJ5Dave]

Was setting up to bore a hole bigger on a milling machine. Manual, No digital. I have a new edge finder and was trying to use it to indicate center. I bumped one edge, then the other. Edge finder is 2 tenths diameter. I moved 1/2 the travel, then 1/2 less the edge finder radius, then 1/2 the travel plus the edge finder radius, etc. None found center. What’s the math for this on a manual mill? All I can find are videos that say find the edge and punch some DRO button.

 

[ChazzC]

When finding the center the diameter of the tip doesn’t matter: just touch off both sides and move half the distance. The closest to the center you are when you touch off the better.

By “2 tenths,” I assume you mean 0.200”?

 

[CJ5Dave]

Yes 0.200. I did that. Ain’t center. Not sure why.

 

[ChazzC]

Did you do both X & Y?

 

[CJ5Dave]

Yes.

 

[ChazzC]

Instead of setting a DRO to zero, set your dial to zero. The other thing you will need to do is account for backlash (the indicated distance tge dial shows when reversing direction before the table moves): that can be the reason you’re not getting to the center - this is one reason DRO’s are popular.

 

[woodchucker]

Backlash is messing you up. With a dro backlash is eliminated for measurements.

Using dials you move one way then the other. No way to eliminate the backlash unless you move in the same direction.

 

[mmcmdl]

Amazon.com

For $15 . Edited for spending others money !

 

[ChazzC]

Dave hit it on the head: use a DTI on a universal holder.

 

[CJ5Dave]

I have seen that video. Like I said, no DRO. No video out there not with DRO. And I compensated for backlash to some extent but still way off. I will mess with it again when I finish the project I’m on.