Holescreek, would you mind going into detail on how to use this method? Not everyone has a DRO, wiggler, or the electronic devices used for centering. Most everyone has a DTI. This would be a good teaching moment for some of us to learn.
Can I do that inside someone else's thread?
I guess a mod could split it later.
Picking up an edge.
1) Get the ball of the indicator under the spindle centerline by moving the joints (mine are only tight enough to hold position after adjustment) and tilting the indicator side to side.
2) you know it's on center when the ball appears to stay in position wen you rotate the spindle by hand.
3) turn the spindle by hand so the indicator body is parallel to the edge you want to indicate.
4) adjust the hand wheels so the ball is centered over the edge by eye.
5) pull the indicator back a little bit and lower the Z axis so the ball can touch the edge.
6) without twisting or turning the indicator push it up to the edge so the ball makes contact and the indicator needle moves .01~".015" (my Interrapid has .06" travel)
7) rotate the spindle CW and CCW to find the high point on the edge and set the indicator dial to a reference number of your choosing. You may need to adjust the indicator swivel to the high point contact is made when the front of the ball touches instead of the side of the ball.
8) raise the spindle then rotate the spindle 180 degrees over top of the edge you just touched.
9) place a ground object (I use an old gauge block) against the edge you're checking and bring the spindle down so the ball can make contact with the gauge block.
10) adjust your axis hand wheel based on the reading you get on the indicator dial wen the ball touches the block as you rotate it back and forth.
11) Continue alternating the two positions (0-180) until the reading on the indicator dial is exactly the same.
It's way harder to type instructions than to actually do it. If you see it done (might take a minute?) you just say wow! You can also use a similar technique to measure radii and offset boring bars to an exact size. All you need to know is the distance from the known edge.
I do prefer to use an edge finder in conjunction with a DRO for most milling work but if I'm doing something important, or inspecting a part, the indicator is as close as I can get to a CMM in my home shop.
I found some old photos in my PB account that might help:
