# Double-ended edge finders



## Bolster (Mar 8, 2011)

I have a couple double-ended edge finders. I must be doing something wrong, they're difficult to extract from the collet after use. So take my 1/2 edgefinder (a Starrett). I put it in the 1/2 collet with the .200 end of the edge finder down, use it, then upon removal, the .500 end hangs in the collet, stretching the spring, and I have to jimmy and prod it (or take the collet out and press it through) to get it loose. 

Solution? Other than rebuying single-ended edge finders?


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## Ned Ludd (Mar 8, 2011)

Just a thought, try not pushing the edge-finder so far into the collet, or am I missing something important?
Ned


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## BillTodd (Mar 8, 2011)

Sounds like its a bit tight in the collet Might be worth checking the edge finder is actually 0.5" and not 13mm. What sort of collet? Is it worth making a special one just for the edge finder or perhaps buying a 13mm instead of 1/2"? 

Either way, try not to stretch the spring 

Bill


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## BillC (Mar 8, 2011)

I've had the same problem so usually end up removing the collet and pushing the edge finder out. I've acquired a couple of single ended ones to hurry things along a bit.

BillC


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## Bolster (Mar 8, 2011)

BillTodd  said:
			
		

> Sounds like its a bit tight in the collet Might be worth checking the edge finder is actually 0.5" and not 13mm. What sort of collet? Is it worth making a special one just for the edge finder or perhaps buying a 13mm instead of 1/2"?



R-8 collet, with 1/2 (same problem with 3/8) finders. So the finder should just be slipping out? "Not Happening." 

And spring stretch is the inevitable result. 

Re putting it in not as far: You still have to put the finder in past the "other" end, so even if you're just barely getting the finder in place with minimum purchase from the collet, you still have the problem. 

If the problem is widespread, makes me wonder why double ended finders are even produced?!?

But try to find a single ended 1/2 diameter finder with a pointed end for finding hole centers...


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## BillC (Mar 8, 2011)

You know that you can use a chuck since edge finders don't really need to be running super centered....

BillC


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## Ned Ludd (Mar 8, 2011)

A-Ha, I took it that the edge-finder was catching on the rear of the collet, not just in the collet. OOPS.
Ned


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## Bernd (Mar 8, 2011)

Have you tried a piece of 1/2" brass. If it doesn't fit or fit's as tight as your edge finder, the collect must have been squeezed down to something smaller than 1/2" springing the collect to a smaller size.

Have you checked the dia. of the edge finder to maker sure it's .500" dia.?

Just some other ideas.

Bernd


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## Bolster (Mar 8, 2011)

The 1/2 and 3/8 finders fit like any bit would fit, a very gentle, slightly snug fit, but given that the "hind end" is held on with a spring, removing my two-ended finders turns them into "slinkys." The rear end doesn't want to come out; easier for the spring to expand than for the finder to slip out. 

I just thought there was some old machinist's trick y'all knew I didn't, like putting graphite on the finder before insertion, or keeping it bone dry, or whatnot.


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## mklotz (Mar 8, 2011)

Try this...

GENTLY insert the blade of a screwdriver in the collet slot and expand the collet SLIGHTLY so the edge finder drops out. Spreading the collet too far will affect its accuracy. You just want to open it enough that it releases its grip on the edge finder.


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## Bolster (Mar 8, 2011)

AHA! That makes sense! I should have thought of that myself...


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## Bolster (Mar 8, 2011)

Just tried the "Marv Maneuver" and it works like a charm. 

As the finder sticks, just put a medium-large screwdriver blade in one of the visible slots of the collet, give a fraction of an ounce of twist (takes almost no pressure), and the finder falls into your hand. Sliiiiick. Where's that applaud button...


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## picclock (Mar 9, 2011)

Just a thought - use a 13-12mm collet as this will give extra play.

My starret pointy end does that sometimes. Often use it in a good chuck I have.

Best Regards

picclock


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## Allthumbz (Mar 20, 2011)

mklotz  said:
			
		

> Try this...
> 
> GENTLY insert the blade of a screwdriver in the collet slot and expand the collet SLIGHTLY so the edge finder drops out. Spreading the collet too far will affect its accuracy. You just want to open it enough that it releases its grip on the edge finder.



Great idea- a gentle twist and it's out, with no harm to either collet or finder.

Nelson


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## thayer (Mar 20, 2011)

hi all, I am relatively new to the concept of shaping metal, having made only a couple of Elmer's wobblers. One basic thing that has puzzled me is how the hole center end of the finder actually works. Can someone point me to an explanation or better still, a video, of the process? 

Thanks,

Thayer


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## mklotz (Mar 20, 2011)

There's (at least) two ways I use the cone end...

Using a wooden stick get the cone to run true. Then the cone tip indicates the true rotation axis of the machine. Align it to your marked out location.

With the edge finder NOT rotating (i.e., machine off), insert the cone in hole to be centered. Adjust hole location until there is no offset of the cone from the edge finder body. I check the latter with my high precision fingernail but, if you're fanatical, you can put a mike across the line where the cone joins the body and keep adjusting until it reads the edge finder body diameter all the way round. For holes too large for the cone, I've made adaptors that work pretty well.


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## thayer (Mar 20, 2011)

Okay, that is making more sense then. I had thought that it was used dynamically, like an edge finder.

Thanks,

Thayer


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## rklopp (Mar 20, 2011)

By center hole end, I assume you mean the conical end. That is for finding the center of large round stock laid on its side, not for finding center holes. Say you want to mill a key slot or drill a cross hole in a shaft too large for the cylindrical end of the center finder to reach. To center the mill spindle over the center of the shaft, use the conical edge finder. With the spindle turning at around 1000 RPM, approach one side of the shaft at a Z height such that the middle of the edgefinder cone touches the shaft surface. This will be at something like 30 degrees north latitude on the shaft, so to speak. When the cone "kicks" off to the side, zero the Z axis and whichever other axis is perpendicular to the shaft axis. Get clear of the shaft, move to the other side, get back to Z=0, then re-approach the shaft from the opposite direction. Note the reading on the other axis when the cone kicks. The center of the shaft will be exactly half the reading on this axis. In essence, you have taken the average of the position readings on two sides of the shaft. You can see why it is critical that both sides be touched at the same Z height.


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## thayer (Mar 21, 2011)

rklopp,

Thanks for that additional input. I can easily see that operation in my mind.

Thayer


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## shred (Mar 21, 2011)

You can also use the cone-end when running to find center of little holes the other end won't fit in (easiest with a DRO)

Put the point approximately in the center of the hole. Drive it over in X until it finds the edge. Zero DRO. Drive it the other way in X until it finds the other edge. Divide X by 2 and go to the new X zero (dividing by two 'splits the difference' between the zero and the other side). Repeat for Y.

Go around again in X and Y for even more precision.

Marv's way also works pretty well for this (unless you want to do obscure things like finding center of thin slots) as well as for finding center punch spots.


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## ruralearl (Mar 21, 2011)

Hello, Thank you rklop & shred, learned something, never heard except the marv fingernail maneuver. Regards, Earl


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## Bolster (Mar 25, 2011)

rklopp  said:
			
		

> ...approach one side of the shaft at a Z height such that the middle of the edgefinder cone touches the shaft surface. This will be at something like 30 degrees north latitude on the shaft, so to speak. When the cone "kicks" off to the side, zero the Z axis and whichever other axis is perpendicular to the shaft axis. Get clear of the shaft, move to the other side, get back to Z=0, then re-approach the shaft from the opposite direction. Note the reading on the other axis when the cone kicks. The center of the shaft will be exactly half the reading on this axis...



This is assuming DRO, correct? I assume that a humble manual user such as myself must factor in backlash...?


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## mklotz (Mar 25, 2011)

I just mike the diameter of the shaft, touch off with the edgefinder, and then move (in the same direction) half the diameter plus half the edgefinder cylinder diameter. The cone isn't used and backlash isn't a concern.


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## Bolster (Mar 25, 2011)

OK. That would be using a standard edgefinder at the 3 o clock position on the cylinder I assume. Should work well for smaller cylinders where you can get an edgefinder into the 3 oclock position.


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## mklotz (Mar 25, 2011)

Bolster  said:
			
		

> OK. That would be using a standard edgefinder at the 3 o clock position on the cylinder I assume. Should work well for smaller cylinders where you can get an edgefinder into the 3 oclock position.



The "other kind" of double-ended edge finder has the standard 0.2" diameter probe on one end and a 0.5" diameter probe on the other end. Since the body is 0.5" diameter, one can't get the 0.2" end to touch a large diameter workpiece but the 0.5" probe works just fine. Visualize it and you'll see what I mean.


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## Allthumbz (Apr 4, 2011)

One thing that I find annoying is getting the edgefinder back together when the spring pops off. Someone tolf me to use thread to guide the spring through the center, but thread isn't strong enough. Anyone have any other tips?

Thanks,


Nelson
***************.com


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