# finding the center while in a vise



## cg285 (Apr 11, 2018)

just occurred to me that i often see videos, or discussions, about finding the center of round stock (or i guess any shape) by using either a dial indicator or an edge finder on both sides and then splitting that. seems like a waste of time to me. why do we waste time doing that?


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## higgite (Apr 11, 2018)

As opposed to what other method?

Tom


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## benmychree (Apr 11, 2018)

I'd hazard a guess that the wasting time question is why it would be necessary to go from both sides, when doing it from one side would suffice for nearly any purpose; I agree with the observation.


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## Dave Paine (Apr 11, 2018)

I find each edge with edgefinder then hit "Center" for the particular axis.   My pieces are never precision ground so the dimension needs to be measured by some method.   I could measure the diameter, find the first edge then advance the axis to calculated half diameter measured and set "0" on the DRO.

I normally prefer for 0,0 to be the centre of my work unless I am only working from one or both ends.

There are many ways to set co-ordinates on a milling machine.   Pick a method which works for you.


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## cg285 (Apr 11, 2018)

benmychree said:


> I'd hazard a guess that the wasting time question is why it would be necessary to go from both sides, when doing it from one side would suffice for nearly any purpose; I agree with the observation.


 
exactly
from the fixed jaw


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## kd4gij (Apr 11, 2018)

cg285 said:


> just occurred to me that i often see videos, or discussions, about finding the center of round stock (or i guess any shape) by using either a dial indicator or an edge finder on both sides and then splitting that. seems like a waste of time to me. why do we waste time doing that?




Will you have to mesure the part at some point, to find center. Mic, calipers, or dro. pick one.


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## cg285 (Apr 11, 2018)

kd4gij said:


> Will you have to mesure the part at some point, to find center. Mic, calipers, or dro. pick one.



mic is quick and even unnecessary if a known dimension


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## RJSakowski (Apr 11, 2018)

I use the same method as Dave; find one edge, zero DRO, find other edge,hit /2 on the DRo.  No waste of time,very rapid and as accurate as the DRO allows.  Spindle runout doesn't enter in nor do measurements of diameters, offsets, etc.  But hey, whatever makes you happy.


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## cg285 (Apr 11, 2018)

RJSakowski said:


> I use the same method as Dave; find one edge, zeroDRO, finde other edge,hit /2 on the DRo.  No waste of time,very rapid and as accurate as the DRO allows.  Spindle runout doesn't enter in nor do measurements of diameters, offsets, etc.  But hey, whatever makes you happy.



well my method (i didn't invent it) would also be find the first edge - fixed jaw - then i'm done


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## Bill Gruby (Apr 12, 2018)

cg285 said:


> mic is quick and even unnecessary if a known dimension



 Your statement is not entirely correct. You cannot take the word of the manufacturer that the size is correct. You arrive at that yourself with a mic. I have gotten wrong sizes at times.

 "Billy G"


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## chips&more (Apr 12, 2018)

Using an edge finder, touching both sides and dividing by 2 is more accurate. Using a mic and vise jaw pressure to name a few all have uncertainties. The fewer the uncertainties you have the better your job. And IMHO, I think it’s faster to just touch two sides with an edge finder and go. A long time ago, I noticed that when I touched just one side, I was always off center a few thou when I did the hole or whatever. Then I started to do the two/both side touching. I don’t have that problem anymore…Dave


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## Groundhog (Apr 12, 2018)

I cheat. I stick the probe in and let the computer and the cnc do the work!


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## cg285 (Apr 12, 2018)

Bill Gruby said:


> Your statement is not entirely correct. You cannot take the word of the manufacturer that the size is correct. You arrive at that yourself with a mic. I have gotten wrong sizes at times.
> 
> "Billy G"


if i have a ground precision rod and i want to put in a keyway i think it is more than close enough


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## cg285 (Apr 12, 2018)

chips&more said:


> Using an edge finder, touching both sides and dividing by 2 is more accurate. Using a mic and vise jaw pressure to name a few all have uncertainties. The fewer the uncertainties you have the better your job. And IMHO, I think it’s faster to just touch two sides with an edge finder and go. A long time ago, I noticed that when I touched just one side, I was always off center a few thou when I did the hole or whatever. Then I started to do the two/both side touching. I don’t have that problem anymore…Dave



maybe but in my mind a mic is more accurate that an edge finder x2 as there is somewhat speculation in observing an edge finder -  my opinion


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## Janderso (Apr 12, 2018)

I don't have a DRO, finding the edges and eye balling and touching off is my current method which is not acceptable.  It is something I am learning to do.


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## cg285 (Apr 12, 2018)

Janderso said:


> I don't have a DRO, finding the edges and eye balling and touching off is my current method which is not acceptable.  It is something I am learning to do.



my grandfather did some mighty fine work and he never had one either


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## higgite (Apr 12, 2018)

Well, we have progressed through this thread from round stock with no specifics given to stock of a known dimension to a ground precision bar. So far. The next logical progression would be blind faith in stock that has its center marked by the manufacturer. Then we won’t even need the edge finder at all. 

Tom


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## cg285 (Apr 12, 2018)

higgite said:


> Well, we have progressed through this thread from round stock with no specifics given to stock of a known dimension to a ground precision bar. So far. The next logical progression would be blind faith in stock that has its center marked by the manufacturer. Then we won’t even need the edge finder at all.
> 
> Tom


but you will somehow have to get that "marked center" squared up. time for a new thread


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## Bill Gruby (Apr 12, 2018)

cg285 said:


> if i have a ground precision rod and i want to put in a keyway i think it is more than close enough



 This is really tough to answer when new variables are added after we answer. LOL

 "Billy G"


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## cg285 (Apr 12, 2018)

Bill Gruby said:


> This is really tough to answer when new variables are added after we answer. LOL
> 
> "Billy G"


haha
you win


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## Bill Gruby (Apr 12, 2018)

That's odd, I don't remember trying to win anything. LOL

 "Billy G"


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## Janderso (Apr 12, 2018)

The old videos of assembly lines of machinests standing over their lathes and mills producing one part after the other shows a time in our country when we probably had over a million very talented fellows. They could reproduce the same part over and over again with amazing efficiency.
No safety glasses, no DRO's, using basic measuring devices, incredible.


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## Robert LaLonde (Apr 12, 2018)

Groundhog said:


> I cheat. I stick the probe in and let the computer and the cnc do the work!



Yep, and if your probe or spindle isn't perfect you can probe, zero, rotate 180, probe again, and divide by 2.  I think I recall somebody said they had a Bridgeport that did exactly that automatically.  If your feature is not the zero point of your work offset you then move to 0,0 and set the work offset value of the center of the feature.  

You know, I need to put ports on all my machines for my probe, and put a connector on the cable... right now its hardwired into a machine that has a bad axis motor.  LOL.


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## RJSakowski (Apr 12, 2018)

Tormach has a program in PathPilot that will probe pockets or bosses at the touch of a button and set the center point.

You are correct in that spindle and/or probe runout can affect the center point setting.  The probes that I have seen have adjustments for centering the probe.  There is still some possible spindle runout to contend with but if care is used to orient the probe  in the spindle exactly the same, runout shooulden't be an issue.

Spindle runout is why I use an edge finder.  Its  design is such that runout doesn't enter into the determination.  Prior the the jump, the edge finder is centered exactly on the spindle axis.  Used with care I find that I am consistently repeatable to .0001".  In fact, I usually repeat the process two or three times to verify that my trip point is the same to .0001".

My method is to come to an edge rather quickly to get a rough idea as to where the edge is, back off and approach the edge at about .0002"/sec. (my Tormach has a jog feature that moves .0001" with each jog).  The reason for going so slow is that it allows the edge finder to find true center.  If if is off center and hits the edge it can jump prematurely or if moving fast enough, overshoot the edge giving a false location for the edge.  Moving slow gives the edge finder a chance to settle in.

I use a similar process for the mill drill but manually advance my feed while watching the DRO.  I will advnce to increas/decrease the reading by .0002" (minimum resolution) and check the edge finder.  The actual jump point will be between the last observed centered condition and the first observed jump condition.  With some care and practice, rhis is repeatable to .0002".

To speed up the process, once I have hit the work edge, I  back off and use my thumb nail or a pencil tip to nudge the edge finder to center again so the number of jogs to find the edge takes two or three seconds.


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## Groundhog (Apr 12, 2018)

I use MachStdMill - an add-on program to Mach3 that has a bunch of probing and touch off routines. It seems to handle most any geometry, and find centers, corners, angles, velleys and islands, etc. After it probes it will set set zero for all (or selected) axis,  set work offsets, etc. 
I have my probe in a dedicated R8 holder and dialed in to a "home" mark on the the spindle. While not perfect it is acceptable for most things I do. I have it wired using miniature a RCA plug and socket (like a headphone jack). I don't have another machine to use it on but at least I can unplug it and get it out of the way!


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## Robert LaLonde (Apr 12, 2018)

For Mach Users the Blue Screen set has some probing functions coded in, and for more advanced probing Probe-It is a reasonably priced probing plug-in for finding centers, perimeters, etc.  

If you don't care for the Blue Screen Set Klaus has a nice Mach Screen editor you can use to look at the features of a screen set and then create your own.  

I am still learning the capabilities of my Tormach/PathPilot system.


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## dlane (Apr 12, 2018)

I’ll throw this out there, 
How about finding center of a hole in the vise clamped part ?.


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## Groundhog (Apr 12, 2018)

If you are looking for a good screen set for Mach3 look at MachStdMill by Calypso Ventures. It hasn't changed in a few years but it really adds a lot to the functionality of my mill. There is a lot to it so it takes a while to learn.

http://calypsoventures.com/


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## Dave Paine (Apr 12, 2018)

dlane said:


> I’ll throw this out there,
> How about finding center of a hole in the vise clamped part ?.



I saw this in some video so not my idea, but works well for my needs.

I use edge finder.   Set this somewhere in the middle.   Find e.g. farthest Y, set DRO to 0, find closest Y, hit "Center" on DRO.   Move Y to 0, then set edge finder to left on X axis, set DRO to 0, then find right on X axis and hit "Center" on DRO, then move X to 0.


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## cg285 (Apr 12, 2018)

dlane said:


> I’ll throw this out there,
> How about finding center of a hole in the vise clamped part ?.



 i usually just tram it with an indicator. what do you do?


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## cg285 (Apr 12, 2018)

dlane said:


> I’ll throw this out there,
> How about finding center of a hole in the vise clamped part ?.



maybe there is something hidden in the "vise clamped part"


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## jmarkwolf (Apr 12, 2018)

I'll admit, times that I don't need great accuracy, I'll chuck up a drill bit or gauge pin of the same size as the hole, and carefully adjust the table X & Y until I can lower the bit into the hole (not turning), then hit 0,0. Quick and easy.
If I need the accuracy, I'll sweep the hole with an indicator.


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## dlane (Apr 12, 2018)

That’s kinda what I’ve been doing the dowel method


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## projectnut (Apr 12, 2018)

Bill Gruby said:


> Your statement is not entirely correct. You cannot take the word of the manufacturer that the size is correct. You arrive at that yourself with a mic. I have gotten wrong sizes at times.
> 
> "Billy G"



I would agree.  In the last 10 years I can't count the number of pieces of stock I've purchased that have been slightly under or over sized.  There was a time when a 1/2" piece of 6061 or 4140 round stock was .500".  More recently it can be as little as .498" or as much as .503".  

I was making some collet bushings for a Black Diamond drill Grinder last week.  I picked a piece of round stock labeled 5/8".  The base OD was supposed to be .562 so I set the cross slide to cut a depth of .0315".  As an old habit I measured the finished diameter "just to be sure".  I was a bit surprised when the micrometer read .565".  I cleaned the micrometer and the stock a couple times,  remeasured, and got the same results.  I then went back to the original stock to find it was actually .628" rather than .625".

Every once in a while I still get caught thinking 1/2" = .500".  That may be mathematically true, but in the real world it isn't necessarily so.  Many times close enough is good enough.  The only way to be sure is to buy stock that comes with certifications.  If you've ever bought stock that has to be certified as to alloy content and dimensions you know it's considerably more expensive than off the shelf stock.  I've found it more cost effective and less frustrating to just "measure twice and cut once".


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## RJSakowski (Apr 12, 2018)

dlane said:


> I’ll throw this out there,
> How about finding center of a hole in the vise clamped part ?.


Is the hole vertical or horizontal?  How big a hole?


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## RJSakowski (Apr 12, 2018)

Vertical: If the hole s large enough, I use the edge finder.  A smaller hole I would mount a test indicator in the spindle and sweep the hole. A still smaller hole, I would use my spindle mounted microscope to find the edges as I would for the larger hole and edge finder.

When I find the center of a hole, I will pick a y position close to the center by eyeball and find the edges in the x direction and set my x center zero.  Then I move to x = 0 and find the edges in the y direction and set my y center zero.  If I am really being picky, I'll redo the x zero but usually I'm dead on. 

If I am not concerned with dead nuts accuracy, I'll lower a pin or tapered pin into the hole, adjusting x and y position until I get a good fit.  Sometimes, I loosen the vise slightly so the work is free to move.  I then lower a close fitting or tapered pin into the hole which will position the work parallel to the jaws.  I then move the position perpendicular to the jaws until the work just touches the fixed jaw tightening the vise at the same time,

Horizontal: If it is a hole size that I have a pin gage for and is deep enough for a stable mount of the pin, I'll insert the pon and find the outermost positions of the pin.  If I can't use a pin, I would mount a test indicator and move until I see a deflection of the indicator to establish one sid.  Then do the same for the opposite side.  Average the positions for the center line.


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## hman (Apr 16, 2018)

RJSakowski said:


> If I am not concerned with dead nuts accuracy, I'll lower a pin or tapered pin into the hole, adjusting x and y position until I get a good fit.  Sometimes, I loosen the vise slightly so the work is free to move.  I then lower a close fitting or tapered pin into the hole which will position the work parallel to the jaws.  I then move the position perpendicular to the jaws until the work just touches the fixed jaw tightening the vise at the same time,


For a close approximation, I've been known to use the pointed end of a center finder.  Lower the cone into the hole, then feel both sides while adjusting X.  Then feel both front and back while adjusting Y.  I've read that it's quite easy to detect differences of less than a thousandth by touch.  Both the shank of the edge finder and the full diameter portion of the pointed section are sharply defined, so misalignment is pretty easy to feel.


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