Shars Z-axis indicator

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Swede

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A while back, I picked one of these up to help determine pesky z-axis settings for spindles without fixed tooling. Here's what it looks like:



In use, it's a nifty tool. You touch your tool tip to the button, slowly move the Z, and when the indicator is zero'd, your tool is exactly 2.000" above the base of the gauge. It works fine.

Time for a long-shot question... the spring in this thing is HEAVY. I'd like to use it for some extremely sharp and somewhat fragile 1/8" carbide engraving cutters, and I am almost positive it'd both damage the cutter tip, and score the gauge. I'd like to take it apart and cut a turn or three off the return spring. Has anyone done this?

Lacking such a gauge, the best way I've found for setting Z is to use a round pin gauge. Let's say you have a 0.500" pin gauge - jog the spindle down until you cannot roll the gauge pin under the tool. Incrementally jog up as needed while gently trying to roll the pin gauge under the tool. When the pin gauge rolls free, I generally jog back down 0.001", and set Z = 0.500. This works well.

But I'd still like to use this gauge on the small & fine cutters. Has anyone got any other fast, easy, and accurate methods of setting Z?
 

steamer

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You can always use the old smoking paper trick. Get some rolling paper, and a 1-2-3 block in the vise.

Stick the paper down with a small dab of oil to the 1-2-3 block....now bring the tool down until it JUST grabs and spins the paper....your .0008-.001" of an inch away...I use the Zig Zag brand ....one package will last about a life time....

Dave
 

Swede

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Thanks Ray and Dave. My CNC machine does not have handles. I have to use the jog system, which means manually approaching any fixed surface is not a comfortable thing. I don't have any sort of touch probe.

Ray, I like that concept in your device. I need something that allows a bit of overshoot. What sort of accuracy do you feel like you are getting with it? Do you feel confident that it is less than 0.001"? When engraving with these tiny bits at 40,000 RPM, a thousandth in Z can be big!

These are the cutters I am using. This guy sells a lot of them on eBay, and they come from China. I am thrilled with them... I'm used to carbide engraver bits costing several dollars each, and they break so easily. This guy is selling them for a buck & change each.

http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=130397979736
 

ironman

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Swede, mine is not that precision of repeatable accuracy. Closer to .003 and/or .005.
I have thought about using a better spring or eliminating that spring and switch altogether and using a micro momentary switch on top. I am working on one that is only .68 inches tall in its acetal case. FYI, ENCO sells one that is 1 inch tallbut no meter.

Ray
 

Lakc

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This may sound like a really stupid question coming from a guy with no real cnc experiance, but I trust you will go easy on me. :)

Why cant you jog down a toolheight above a 1-2-3 block and then insert the cutter, and tighten the collet holding the tool against the block?
 

Swede

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TY Ray. In my experiments with good micro-switches, they tend to repeat to about 0.0006", and they allow a bit of overshoot. I'll bet they'd work fine.

The good thing about a dial gauge is that you don't have to find the zero point, you can extrapolate off the dial, like 1.000" +/- 0.012 or whatever. Then, enter the Z value. Saves a bit of time.

Maverick - That tool is incredible! Beautifully done and compact to boot. I like it and might need to copy it. TY.

Lakc - Setting the Z is often done outside of a tool change. If you're making 6 identical components with the same ball end mill, all you might need to do is add new stock, find the Z, and click start, so a device really needs to be able to Z-set with the tool fixed.

One of these days, I am going to figure out a tooling system with fixed Z for the tiny spindles I use and use a proper tool table in the software. Thanks for all the suggestions, they are good ones.
 

Swede

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Well, I decided to go for it and take it apart. As usual, I messed it up a tiny bit, but managed to sole the problem.

Here's how it comes apart on the long shot that anyone might want to replace this ridiculous spring. And it also allows one to calibrate the internal 2.000" test position.

First, remove completely the large screw in FRONT OF the disk.

On the sides of the block behind the indicator are three TINY screws. These hold the indicator in place. Loosen all three just a few turns. Next, take a small punch and press down (GENTLY) into the hole at the top where the large screw used to live. Then, carefully pull the indicator out. Once the indicator is free, the disk/piston can be removed at the top. At the bottom of the piston is a punch device that is secured by a nut, and it is this punch device (which screws in or out) that sets the internal 2.000" standard.

Once the indicator is out, it's pretty self-explanatory. I reset the internal standard, cleaned and lubed, then replaced the spring with one much gentler. Works well now, but I'd still like one similar to Mavericks, or a microswitch job similar to ironman's, that interfaces with the CNC automatically.
 

maverick

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Swede,
If your interested, I can post some pictures of the individual parts. It was made without a drawing,
Just copied from a catalog pic and the insides dreamed up.

Regards,
Mike
 

Swede

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If it's not too much trouble, I'd be interested, and I'm sure others would be too, thanks. It looks to be beautifully made.
 

maverick

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Here are the components of my tool setting gauge.






The DI is held in place with a socket head set screw and a brass saddle, too much screw pressure
will bind the plunger. A thin aluminum back replaced the original lug on the DI for clearance.



This shows the bore, plunger and conical spring. The spherical contact point on the DI bears
against the angle on the plunger. I forget the angle, but the DI reads .005 for about .03 plunger travel.



The body is ground to 1.000 height and the DI is set to zero with the plunger pushed flush with the top
of the body. Exept for the zero, the DI graduations are not used.

 

Swede

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Beautifully done, thanks for sharing it. It's obvious you take great pride in tool-making. :bow:
 

SmoggyTurnip

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Maverik that is a great looking tool. I have a few questions if you don't mind.

1) What (if anything) stops the plunger from turning?
2) What is the purpose of the little ledge shown on the left half of the pluger?
3) What is the purpose of the shallow slot seen on the right hand side of the plunger?



 

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