Starrett 827B double end edge center finder Use?

[EmilioG]

I've looked at various sites and threads and can't seem to find a definitive answer. I've even written to Starrett.
No word yet. How does one use the pointed end of the 827b double end edge center finder, the pointed center finder end?
Do you touch it against a surface first to get it spinning center or do you use your fingers to feel it so no edges are out?
Thanks

 

[KMoffett]

Not sure there is a "definitive" answer. Description starts at ~26:20 http://techtv.mit.edu/videos/142-machine-shop-1

Ken

 

[JimDawson]

It's maybe just me, but I use the pointy end only for finding the center of small holes. I use my fingers to feel for an edge sticking out, and only with the spindle turned off.

 

[chuckorlando]

I have not done so, but was taught to do as Jim explains

 

[Andre]

It's for centering over small holes or punch marks. I use the pointy end all the time on my Mitutoyo edgefinder.

 

[Tony Wells]

That's about how I use mine, but I use the back of my thumbnail rubbing just at the joint between the body and the end piece. Seems to bring the runout down to near zero. I can't see any wobble anyway. I pick up scribed lines, crossed lines without a punch mark, and small punch marks as well as small holes.

 

[frbutts]

use the same as straight end but instead of moving 1/2 of the dia. do the math with the dials and figure center.

 

[george wilson]

I have used mine to locate center punch holes by holding a mike horizontal and measuring across the intersection of the center finder's body. I do this measuring at 90º to each other. I adjust the table till I get .500" in both directions with the mike.

I hope I explained this clearly. By measuring at 2 points across the center finder,I make sure I'm finding out where the offset is on the conical tip.

I've read other descriptions of how to use the conical tip,but this is how I use mine. Some use it to get centered up on key way slots. I use my Blake coaxial indicator for that.

 

[chuckorlando]

How would you know how far down the taper you are to do the math using the correct radius? Seems it would change rapidly with very little height change

use the same as straight end but instead of moving 1/2 of the dia. do the math with the dials and figure center.

 

[Tony Wells]

Doesn't matter, Chuck, as long as you do not change the -Z- axis position. Zero your DRO or indicator on the first found edge and then whatever the distance is to the other side, half it. the "actual" diameter of the point where you are touching off is compensated for already.