Center Finder Question

[hwingo]

I have a Brown & Sharp double ended "edge/center finder". One end is the conventional edge finder while the other is a conical-pointed "center finder". I would prefer that we limit answers to "How To Correctly Use" the pointed end.

I have a metal plate consisting of a series of unevenly spaced and positioned holes (~.200 dia). I desire to "map and record" these holes using my DRO while utilizing the pointed center finder. Though I believe I have, in a round-about manner, accurately found center of each hole and their X,Y positions relative to all other holes, I would like to know how the center finder is to be "officially" (properly) used to locate center of a hole.

Thanks,
Harold

[38_Cal]

Is the pointy end of your center finder larger or smaller than the holes you need to plot? If it's smaller, or the same size, I would turn a plug to a snug slip fit to the holes with a small 60* hole in the opposite end to allow you to engage the point. Center up the point in the plug and get your coordinates.

David

[hwingo]

Hi David,

The pointed end comes to a very sharp point and the hole-size, as mentioned, is .200” dia. From the sharp point, the body of the center finder has diverging walls (cone shaped). The large end of the cone stops short (~ 1/16”) of passing through the .200” dia hole thus the cone comes to rest in the hole leaving 1/16” of cone remaining.

I used the center finder (probably incorrectly) by placing the center finder in my mill’s quill and slowly lowering the quill into “eye-ball” position while attempting to get the center finder as close to center as possible. At that point I lowered my quill until the center finder engaged the hole. When the center finder engaged the hole under a slight amount of pressure, the center finder, as designed, slipped a bit to the back and side producing an obvious ledge between the body of the instrument and the conical portion that’s designed to “slip”. Carefully, I moved the X and Y axis until I could no longer see a ledge nor feel a ledge when using my finger nail. Feeling no ledge between the body and head of the center finder I called it “good”, zeroed the X,Y axis of the DRO and moved to the next hole and repeated that process just described. Once “center” was located in the second hole I documented the DRO’s reading of the X,Y distance/position from the previous hole and moved on to the next hole, etc., until the plate was mapped.

I was wondering if I should have had the quill turning when attempting to map the plate? If so, how fast? I also was wondering that if using power to find center, would I be running a risk of either messing up the hole or scaring the surface of my center finder?

Harold

[tdmidget]

Use it just like an edge finder. Bring it over the hole and lower Z until the point is in the hole . Lock Z so it stays the same throughout the process. Move it in X until it kicks out on both sides. Split the difference and that is your X center Do the same in Y. I usually do it again to double check.

[38_Cal]

For what you are doing, I would leave the motor off on the mill. Since the cone engages the holes as you described, I would say you're doing it right. Using the edge finder end, the motor should be running. My dos centavos worth!

David

[hwingo]

Thanks for the replies. Much appreciated.

Harold

[Carld]

Harold, I don't use that pointed end because I have not found a way to make it work with confidence. If the hole is not a straight hole that is not threaded I have found it next to impossible to use. Trying it in a threaded hole is useless.

I either use a plug in the hole and indicate around the plug or use an indicator inside the hole.

I too would like someone that really knows how it's used to explain it, not someone that is just guessing.

I could possibly get an answer on the PM site but I don't go there any more and would never post there under any condition.

[Mcgyver]

leave the machine off. bury the point in the hole (or centre pop mark or whatever) and centre it by feeling when the cylinders line. you can do the same with edge finder end and you'll surprise yourself that you'll get it to within a thou or two - you don't need the machine running to use either end..

Feel should be good to a thou, however you're picking up the top edge of the hole - dings or burrs will put it off. If you need more accuracy than this make an accurate fitting plug and indicate it as .200 is to small to indicate directly.

[tdmidget]

So Carl , you are saying that everyone who has replied is guessing? You say that you use an indicator in threaded holes but you want to demean others?

[Toolguy]

Edge Finder Point

I have used edge finders every day for a lot of years. In that time I've had a lot of time to experiment and see what works and what doesn't (for me anyway). I use the pointed end 2 ways. One way is to find hole locations as hwingo is asking about. With the spindle off, I run the pointed end into the hole with the quill until it seats. This is assuming the hole is in a flat surface, deburred, and smaller than the large end of the point. Then line up the sides of the edge finder until they match accurately. You can get very close by running a fingernail over the joint or you can use a mike to tell when you're at zero mismatch. The other way I use the pointed end is to have the spindle running (I like 900 to 1200 RPM for either end) and lower the quill to the quill stop for a repeatable depth. When the end kicks over, you're there, just like on the straight end. This way is useful for finding center on cylinders too big to use the straight end or the mouth of tapered holes, or the top edge of a piece at an angle in the vise. In machining, everyone has their own favorite ways of doing things. This is simply my 2 cents.

[Carld]

No tdmidget I don't use an indicator in a threaded hole, I thread a plug in and indicate around the plug.

Show me where I said I use an indicator in a threaded hole.

This is my first sentence in the post:

"Harold, I don't use that pointed end because I have not found a way to make it work with confidence. If the hole is not a straight hole that is not threaded I have found it next to impossible to use. Trying it in a threaded hole is useless."

Please read my post before you make fun of what I say. You will also note that my post #7 has not been edited so it is verbatim as I first posted it.

Thanks, I accept your apology.

Yes, using the pointed end the ways here described are just guess work but if it can be off a few thousandths it will work. If you need it .001" or less use an indicator.

[tdmidget]

So obviously you did not try the method I suggested. Now for all you stick it in the hole and feel guys, lets make it a 2 inch hole. You have a 1/2 inch diameter centerfinder.

[Harvey Melvin Richards]

So obviously you did not try the method I suggested. Now for all you stick it in the hole and feel guys, lets make it a 2 inch hole. You have a 1/2 inch diameter centerfinder.

I use the stick it in the hole and feel method. I have a high enough IQ to realize this won't work on a hole larger than the angular tip.

For larger holes I'll sweep it with an indicator, use an indicol & indicator, or use my Blake.

[Mcgyver]

So obviously you did not try the method I suggested. Now for all you stick it in the hole and feel guys, lets make it a 2 inch hole. You have a 1/2 inch diameter centerfinder.

do the x/y thing against the inside of the hole with the edge finded or it a lot of them make a plug with a centre hole/spot or if it needs to be accurate indicate it. Is this a trick question, the op had .200 holes