# Finding top edge



## Maplehead (Nov 29, 2021)

Hi All
Other than bringing the end mill down and using the feeler gauge method, is there a way to find the top edge using a wiggler to make an accurate discovery as possible, or with some other tool?


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## Aukai (Nov 29, 2021)

On You tube I saw a thin sheet of paper used.


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## DAT510 (Nov 29, 2021)

There are also gages like this from Shars








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						Precision Magnetic Z Axis Zero Setter 2" Height x 0.001"
					

<!-- <ul><li>Graduation: .001"</li><li>Accuracy and repeatability: .0004"</li><li>Square: 2.05"</li><li>Height Holding: 2"</li><li>Power: 6.5lbs</li></ul>  -->




					www.shars.com


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## JimDawson (Nov 29, 2021)

I use paper or just bring the tool down until it just touches.


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## Chewy (Nov 29, 2021)

A sharpy mark or light coat of dykem.  Turn the mill by hand until the mark just disappears. back up a couple of tenths and move over and try again. A little practice and you can get to where you just wipe off the sharpy. You should be within a few tenths of the top. If you are actually milling the top, go for a very thin scratch line and you should be around a thousand or so, about what you get with the paper method. 
You still have to debur and mic the piece when you get close to finish size.


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## Ken226 (Nov 29, 2021)

I use one of these for most things.





For round stock,  I touch off the edge with an edge finder,  then move Y the radius of the part plus the radius of the edge finder to find center.  Then  use sheet of cigarette paper for the Z height.


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## RJSakowski (Nov 29, 2021)

It depends upon your desired accuracy and the equipment you have.  I use Tormach's TTS system on both my Tormach CNC mill and my RF30 clone.  The tools are loaded into ER20 holders and I can predetermine offsets off the machine.  I use a tenths reading digital dial indicator for locating the surface and for zeroing a digital height gage.  The tool offsets are then measured with the height gage and recorded in the tool offset table on the CNC mill or as appropriate subdatum points on the RF30 clone DRO.

For a more expedient approach, I will bring a tool down to just touch the surface as indicated by a light scratch.  This will get me to within a thou.  I have used the feeler gage and the paper method too and they are usually with a few thou or better.  For less critical ops like drilling, i will just etball the tip of the tool.  Drilling depth callouts traditionally are done to the shoulder of the drill and the distance from the shoulder to the tip can vary depending upon the width of the web and angle pf the cutting edge so there can be a fair amount of variation anyway.  

For a project that I did some fifteen years ago, before the CNC mill, I made a sensitive version of the Z axis zero setter using a relay contact.  The contact was set up outside the work zone and I could zero each new tool using the incremental setting on the DRO.  This was useful as the original surface of the part was modified with previous machining steps which prevented zeroing on the part.  I used the relay contact because I was using tools with diameters as small as .005" and over shoot by a small amount would have destroyed the tool on a standard tool setter.


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## Illinoyance (Nov 29, 2021)

With the mill spindle stopped move the part in X or Y while bringing the quill down.  When you see a scratch on the part you are there.


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## Weldingrod1 (Nov 29, 2021)

For a quick and dirty, just lower the quill by hand until the mill is touching the top.of the part. Lock the quill and call that "close to zero" ;-)

Sent from my SM-G892A using Tapatalk


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## MrWhoopee (Nov 30, 2021)

Weldingrod1 said:


> For a quick and dirty, just lower the quill by hand until the mill is touching the top.of the part. Lock the quill and call that "close to zero" ;-)


This is what I do. Don't forget to zero the knee.


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## homebrewed (Nov 30, 2021)

I've been thinking about making something like this.  It also could be used as an edge finder, perhaps handy if you don't want to remove your cutter.   You'd want the work surface and cutter to be free of swarf so you're finding the actual work surface.

The circuit is pretty old-school, but the IC still is available -- Jameco has them for $.49 apiece.  Any quad opamp that works with a 9V supply and has low offset should work.  By "low offset" I mean 2 millivolts or less.  Many modern opamps go down into the microvolt range so that requirement is not particularly demanding by current standards.  However, the circuit does depend on the "long" leg of the circuit formed by the path from the cutter, through the spindle and down to the body, to be at least 2 ohms.  Going with a better opamp may be necessary if the path for a particular machine is less than that.

The device uses super-magnets attached to spade connectors so you can experiment with different locations on your machine to see what works best.


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## frankly2 (Nov 30, 2021)

I’ve been using ZigZag papers for the last 55 years, bring tool down and touch, if paper can be pulled out without cutting that’s about 1 thou ! Hasen’t failed me all these years, he he he !


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## aliva (Nov 30, 2021)

Illinoyance said:


> With the mill spindle stopped move the part in X or Y while bringing the quill down.  When you see a scratch on the part you are there.


Same process you would use on the lathe to "touch off"


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## compact8 (Dec 1, 2021)

The Z axis movement of my hobby mill ( EMCO FB2 ) is too erratic for the scratching or paper methods to be used. When the Z-axis wheel is turned, the head comes down in a rather jerky manner. Unlike the X and Y axes for which I can change the position smoothly in steps of 0.005 mm ( resolution of the DRO ), the Z-axis position jumps in steps every now and then, sometimes by as much as 0.05 mm. Then I found the Z-axis tool setter mentioned in the replies above and it has become one of my most-used measurement device ever since.


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## homebrewed (Dec 2, 2021)

You also can buy an electronic touch detector -- like this from Shars.  It costs more than their Z setter, but it should be relatively easy to make one.  Not necessary to make it exactly (say) 2 inches high -- make one and measure its height, from there you're good.  A transistor in there would make the device even more sensitive and (hopefully) more accurate.

I have one a bit like the Shars version mentioned here but the top plate is aluminum (I clearly didn't read the product description very well).  I don't use it much because I don't think it will hold up, too soft and flexible.  But it should be possible to replace the top plate with something harder.  Or maybe just put a hardened gage block on top of it.  The latter approach depends on having no junk underneath the gage block, as well as a very smooth top surface on the touch detector itself.

The viability of these options really depends on your particular needs.  Getting below .001" accuracy likely is going to be more challenging to your wallet.


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## homebrewed (Dec 22, 2021)

I designed a PCB to implement the touch sensor I mentioned earlier in this thread, but I added the option of using a 4-terminal sensing connection that isn't sensitive to the resistance of the connector wires.  It's called a Kelvin connection, see here.  I emailed the original designer, Rick Sparber, and he is OK with me making my PCB design open source, so I will do that once I have made sure the board works.  BTW, he has since come out with a couple more versions, both quite different from the one I laid out.  They also use a 4-wire sensing method, so I didn't really break any new ground there .

Here's a photo of my board.  It's hard to judge the scale of a board when you're laying it out, so a photo of the real thing is helpful.  The resistors/capacitors are 603's, about the smallest I want to use for hand-soldering.  It should fit just fine in an Altoids-sized box.


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## Mitch Alsup (Dec 23, 2021)

Along with the touch-and scratch method, the paper method, there is also the sharpie-and-run-it-backwards method.

None of these is closer than 1 and a ½ thou.


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## rock_breaker (Dec 29, 2021)

I have a battery powered edge finder that seem to work well on the top. It does take some jiggling to eliminate free play (backlash). Keith on Facebook's Vintage Machinery even measures the thickness of the paper and incorporates that in his calculations. He has a DRO.
Have a good day
Ray


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## homebrewed (Apr 9, 2022)

homebrewed said:


> I designed a PCB to implement the touch sensor I mentioned earlier in this thread, but I added the option of using a 4-terminal sensing connection that isn't sensitive to the resistance of the connector wires.  It's called a Kelvin connection, see here.  I emailed the original designer, Rick Sparber, and he is OK with me making my PCB design open source, so I will do that once I have made sure the board works.  BTW, he has since come out with a couple more versions, both quite different from the one I laid out.  They also use a 4-wire sensing method, so I didn't really break any new ground there .
> 
> Here's a photo of my board.  It's hard to judge the scale of a board when you're laying it out, so a photo of the real thing is helpful.  The resistors/capacitors are 603's, about the smallest I want to use for hand-soldering.  It should fit just fine in an Altoids-sized box.
> 
> View attachment 389490



I finally got around to building up my touch sensor board and testing it.  It works pretty good -- the indicator switches from a no-touch to a touchdown condition without any measureable change in my Z axis DRO.  I'm not crazy about the bi-color LED I got though, because the green LED is pretty dim compared to the red.  I should have paid more attention to the light output specs for the two colors, but that's a minor quibble.

To make the force/sense electrical connections I modified a pair of miniiature battery-charger clips.  The original connector wires are used as the force lines.  To make the sense contacts I drilled a hole in one of the clip jaws and installed a nylon screw+nut I had modified by drilling/threading a hole down the center, then running a brass screw into the hole.  The head makes contact to the cutter or work (through the vise), and the sense wire is connected to the other end of the screw with a spade and nut.  Like this:




I learned from the original designer that it's best to have a separate contact for the sense line, rather than just soldering the sense wire to the clip.  So that's why I used the modified nylon screws.  I placed the mounting hole so that the nut, which is on the inside, is prevented from turning by the bent end of the clip.

I do need to clean up the wiring setup for this -- I used four separate wires and they really get in the way.  I think I will get some 4-conductor wire to tame that problem.  Or maybe use some spiral cable-management stuff.....I have some (somewhere).


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## compact8 (Jun 9, 2022)

I tried today using my 30+ year old and cheap multimeter as a touch sensor for my Emco FB2 bench mill and much to my surprise, the precision is VERY good !

With one probe touching the table and the other touching the arbor, the resistance measured is 1.1 ohm when the tool is not in contact with the workpiece. This value varies a lot depending on the angular position of the spindle. It can go up to something close to 10 ohms but it never went below 1 ohm. As soon as the tool comes into contact with the workpiece, the reading would drop sharply to zero.

To test the precision, I made a shallow cut on the top of an aluminium block with the end of the mill ( 8 mm carbide ) to get a clean datum surface. Then I raised the head, connected the multimeter and very slowly lower the mill head until a sharp drop in reading occurred. Then I locked the head, painted the workpiece surface with a marker pen and did another pass. The paint was not scratched a bit. After that I lowered the head by just 0.005 mm ( or 2 tenths of a thou ) and cut again, the paint was completely removed. This proves that cutter was brought back to the original Z position with practically zero error.

I will definitely use this method a lot more in the future.


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## Janderso (Jun 9, 2022)

frankly2 said:


> I’ve been using ZigZag papers for the last 55 years, bring tool down and touch, if paper can be pulled out without cutting that’s about 1 thou ! Hasen’t failed me all these years, he he he !


I always feel awkward buying them so I bought a roll of .002” shim stock.


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## Janderso (Jun 9, 2022)

MrWhoopee said:


> This is what I do. Don't forget to zero the knee.


My quill DRO died. I started using the knee instead if the quill for depth if cut.
I kind of like it as I had issues with accuracy with the cheap quill DRO.
If I buy another one I’ll get a good one.


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## MrWhoopee (Jun 9, 2022)

Janderso said:


> I always feel awkward buying them so I bought a roll of .002” shim stock.


You should do it proudly, no one knows how to roll anymore.


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## homebrewed (Jun 9, 2022)

Janderso said:


> I always feel awkward buying them so I bought a roll of .002” shim stock.


If you order them from Amazon they will come in an unmarked envelope 

I suspect that most rolling paper purchases are for something other than tobacco....


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## Janderso (Jun 9, 2022)

MrWhoopee said:


> You should do it proudly, no one knows how to roll anymore.


Uh, I bet I could still roll one out. Kind of like riding a bike.


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## Janderso (Jun 9, 2022)

homebrewed said:


> If you order them from Amazon they will come in an unmarked envelope
> 
> I suspect that most rolling paper purchases are for something other than tobacco....


Exactly, who rolls smokes? Of course at $10 per pack maybe it’s becoming more popular.
Although, I rarely see anyone smoking anymore.


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## MrWhoopee (Jun 28, 2022)

A few years ago I was working with a friend who had a well service. Because of cost, he had switched to rolling his own with pipe tobacco, which he was constantly doing while driving and talking on the phone. I talked him into letting me roll for him, but I rolled too tight and they didn't draw freely enough. I ended up driving instead.


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## 682bear (Jun 29, 2022)

I've never smoked any '100mph Winstons',  but when I was in my late teens/ early twenties, I enjoyed smoking a pipe loaded with Borkum Riff Bourbon Whiskey...

I did learn to 'roll my own' with Prince Albert, though... I was almost fired from my job because the boss thought it was something besides tobacco.

-Bear


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## jmkasunich (Jun 29, 2022)

For touching off Z, I keep a 1/4" dowel pin next to the machine.  Put the end of the cutter (not spinning, of course) about 0.2" above the work, lay the pin on the work and gently push it under the cutter.  Now slowly raise the cutter.  The pin will slide under as you get close to 0.250" and slip right through when you are exactly there.  On a CNC or with a DRO you can set the display to 0.250" at this point.  On a manual machine crank in 0.250 on the knee to get to the surface of the part.

Don't try to bring the cutter down onto the dowel, you'll damage the flutes.  Always go up.

After doing it a couple of times you'll find this to be very fast and very accurate.


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## homebrewed (Jul 1, 2022)

jmkasunich said:


> For touching off Z, I keep a 1/4" dowel pin next to the machine.  Put the end of the cutter (not spinning, of course) about 0.2" above the work, lay the pin on the work and gently push it under the cutter.  Now slowly raise the cutter.  The pin will slide under as you get close to 0.250" and slip right through when you are exactly there.  On a CNC or with a DRO you can set the display to 0.250" at this point.  On a manual machine crank in 0.250 on the knee to get to the surface of the part.
> 
> Don't try to bring the cutter down onto the dowel, you'll damage the flutes.  Always go up.
> 
> After doing it a couple of times you'll find this to be very fast and very accurate.


I definitely need to try this!  I happen to have a bag of .250" dowel pins.  It will be interesting to see how it compares to my (much more complicated) touch detector.


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## compact8 (Jul 4, 2022)

jmkasunich said:


> For touching off Z, I keep a 1/4" dowel pin next to the machine.  Put the end of the cutter (not spinning, of course) about 0.2" above the work, lay the pin on the work and gently push it under the cutter.  Now slowly raise the cutter.  The pin will slide under as you get close to 0.250" and slip right through when you are exactly there.  On a CNC or with a DRO you can set the display to 0.250" at this point.  On a manual machine crank in 0.250 on the knee to get to the surface of the part.
> 
> Don't try to bring the cutter down onto the dowel, you'll damage the flutes.  Always go up.
> 
> After doing it a couple of times you'll find this to be very fast and very accurate.


I have heard about using metal sheets of known thickness in the same way but using dowels should be better as metal sheets may not be flat after some use so the accuracy will be affected. Furthermore, the roundness of dowels should produce a sudden movement once it's cleared like the kicking of edge finders upon contact.


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## Parlo (Jul 4, 2022)

An unusual method is to use a 90 degree head and an edgefinder.


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