I was taught a new way to use an edgefinder today. What are your thoughts?

Morning everyone! Please keep the conversation focused on the merits of the ideas and make sure we don’t drift into what could be misinterpreted as personal or ad hominem attacks on such a trivial life matter.

I think somebody said that at the end of the day, if the part is good, then there you go what’s the big deal?

I’d like to hear from members which method is faster, more repeatable, etc., without hearing that the other side is wrong - because they may be achieving the same accuracy but with more aggravation, more effort, more rpm, more hand wheel work , more math , etc.


Sent from my iPhone using Tapatalk
 
Holescreek nailed it. Backlash would be your enemy attempting to return. I have a dro and really don’t worry about backlash except for these exact reasons.
 
How I was taught by a tool and die maker, is what is 9t8z28 tried first, except that he taught me to zero the DRO after the first attempt, and then repeat, always 2 tries. If they don't agree, you have to repeat until you get the same measurement. He demonstrated to me getting to withing one tenth reliably, many times in a row, with a very sloppy lead screw (just before he rebuilt the nut).

with my offshore edge detectors, I am getting within 2 tenths every time, wo it is what I do...
 
I find the edge just as Dabbler suggests. Zeroing the dro after the first touch off with edge finder and checking until I get repeatable readings. Good discussion by members
 
Cigarette rolling paper works for me, I have an edge finders but the papers are quicker. :cool:
 
Pre DRO I learned the move in slow to the kick. set the dial to half the Dia. of the edge finder then repeat to check work. It's funny but I make a habbit of doing things analog (or mechanical) then check my work with the DRO and feel so proud of myself when I hit it within a thou. or 2
 
I don't like to leave the cylinder rubbing on the work for long, figuring that will cause wear in and on the edge finder. I go in once fairly quickly, then once slower, backing out immediately after seeing the number. On something more fussy I go more slowly, and had most of RJ's excellent and eloquent post figured out, but use it rarely when I am trying really hard to get it right.
 
I would suggest that anyone concerned about of their edge finding method run an R &R test.

Repeatability: make multiple approaches to the edge and note the position with a tenths reading DRO, dial indicator, or test indicator.

Accuracy: find the opposite edges of a reference block, noting the difference in position with a tenths reading DRO. Measure the reference block with a known good micrometer and compare. This test would be more difficult without a DRO as position would depend on the accuracy of the lead screw, the ability to accurately read the dial to a tenth of a thousandth, and would have to take backlash in the lead screw into account.

I ran an R & R study this morning using my mill. I mounted a 1-2-3 block on the table and swept the 3" face to verify that is was parallel to the y axis within .0005" I zeroed the DRO in both y and z to ensure that I could return to those settings. I then ran the edge finder to the left side of the block and zeroed the x axis. I was able to return to the exact same reading on multiple approaches. Readability to .0002" (the resolution of the DRO) confirmed.

Next, I lifted the edge finder to clear the block and approached the opposite side. I approached multiple times, again verifying repeatability. My reading was 2.4998". Subtracting the .5" edge finder tip diameter., the distance across the block was 1.9998". Finally, I measured the the 1-2-3 block at the contact point at 2.0000" with two different micrometers. This amounted to a difference of .0002" or .0001" per side. The Accuracy confirmed.

In my experience, several considerations are in order when using an edge finder. The edge finder contact surface and the surface of the edge being found should be clean and smooth. An oil or coolant coating will will create a film which will create drag on the edge finder tip and cause a premature jump. I use a contact length of about 1/8" rather than exposing the entire tip surface. When center finding using opposite edges, I make sure to use the same contact length. I use around 700 - 800 rpm for spindle speed. I also use a very light coat of oil between the tip and the shank of the edge finder. I apply a droplet of oil to one surface and wipe it off, removing most of the oil. I find the this gives more consistent jumps. Erratic movement of the tip is a good indicator of the need for lubrication. I set the preload on the spring at about 2 lbs. n My edge finder of choice (I have two full sets of them) is a 1/2" one that I bought from Enco or Travers maybe thirty five years ago. I prefer the 1/2" to the .200"; I think that it gives a crisper jump. The larger radius means that less drag force will be required to make the jump.
 
I don't like to leave the cylinder rubbing on the work for long, figuring that will cause wear in and on the edge finder. I go in once fairly quickly, then once slower, backing out immediately after seeing the number. On something more fussy I go more slowly, and had most of RJ's excellent and eloquent post figured out, but use it rarely when I am trying really hard to get it right.
The one fault that I have with the edge finder is the mark that it makes on softer materials. There is the possibility of creating a slight indentation on materials like plastic and I will also try to back off as quickly as I can. As far as wear of the tip goes, I can't measure any after 35 years of use.
 
Back
Top