Small Bits (1/8 or smaller) versus Touchplate

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sharkcutup
Posts: 408
Joined: Tue Mar 08, 2016 5:23 pm

Small Bits (1/8 or smaller) versus Touchplate

Post by sharkcutup »

Hello Everyone,

I no longer use the touch plate for setting Z-Zero Axis or running Virtual Z-Zero Throughout --- dang thing keeps breaking my small bits! Heck, some of them have never even tasted wood yet - Brand spanking NEW bits!!! There are more times that the bit does not sense the touch plate thereby continuing to plunge and breaking the BITS so I use paper between bit and project material from now on!

Sharkcutup
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Rando
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Location: Boise, ID
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Re: Small Bits (1/8 or smaller) versus Touchplate

Post by Rando »

Sharkcutup,

I hear ya! I started using a 1.5" square piece of nice, soft sheet aluminum, 0.020" thick as my touch-off plate. There's a control panel preference setting for the thickness. The added bonus (for me) is that the 0.020" error introduced by the Z-height system in a cut, is automagically cancelled. In wood, it's difficult to tell, but when you're trying to make a slot 0.100" deep in a plate of aluminum, and it keeps coming out 0.120", things gotta change. As you know, most of my work is metal, so I don't have to have a wire most of the time: the contact is through the material, vise and bed. When I do work with non-conductive materials, I just use a test lead from the bed to the thin plate, like using one of the vise hold-down bolts. Sometimes bits do leave small divots in it, with no breaks using that plate yet (fingers crossed, knock on wood, all of those).

Though, I will say it's pretty extreme that it would break a 1/8" bit; my bit breaks, when the do happen, tend to be in the under 0.050" sizes, mostly drills bits, too. Hopefully there's not something else going on. I guess if it was doing that to me, I'd keep a length of wire handy, and test the bit-to-touchplate connection each time. Yeah, it says touch the plate to the bit, but if it's not making contact until it breaks the bit, then contact really isn't good, and lifting that plate off to test against the bit might be "changing" something in how it takes it's measurement.

I know we've talked about static control before. One of the things I found was I had to reverse the polarity of the touch sensing circuit in order to get it to work properly. (I just hacked a short headphone extension cable to swap tip and ring+sleeve) IIRC, the plate was at a positive potential, with the spindle at ground in the original. The connection being made via the safety ground of the router/spindle. Unfortunately, if the plate is electrically touching the bed (and the bed is hard-tied to the safety ground), that could mean it can't sense the contact. While I was first figuring out the static drain-wire thing, that was the only time it aggressively broke an 1/8 bit like you're saying, when I fully expected it to work properly. That issue is why I ended up going with the high-value resistor to drain the static, so it didn't interfere with the touchplate sensing circuit. Hopefully that isn't what you're seeing, but daaaaang. Bits is spendy! IIRC, you can check if this is a problem by putting a piece of paper under the touchplate to ensure it's not contacting anything metal, and then testing that.

Hmmm...puzzling. Hope it clears up, sir.

Regards,

Thom
=====================================================
ThomR.com Creative tools and photographic art
A proud member of the Pacific Northwest CNC Club (now on Facebook)

sharkcutup
Posts: 408
Joined: Tue Mar 08, 2016 5:23 pm

Re: Small Bits (1/8 or smaller) versus Touchplate

Post by sharkcutup »

I know we've talked about static control before. One of the things I found was I had to reverse the polarity of the touch sensing circuit in order to get it to work properly. (I just hacked a short headphone extension cable to swap tip and ring+sleeve) IIRC, the plate was at a positive potential, with the spindle at ground in the original. The connection being made via the safety ground of the router/spindle. Unfortunately, if the plate is electrically touching the bed (and the bed is hard-tied to the safety ground), that could mean it can't sense the contact. While I was first figuring out the static drain-wire thing, that was the only time it aggressively broke an 1/8 bit like you're saying, when I fully expected it to work properly. That issue is why I ended up going with the high-value resistor to drain the static, so it didn't interfere with the touchplate sensing circuit. Hopefully that isn't what you're seeing, but daaaaang. Bits is spendy! IIRC, you can check if this is a problem by putting a piece of paper under the touchplate to ensure it's not contacting anything metal, and then testing that.
Nope this is not what I am seeing cause I have 3/4" MDF spoil board on table underneath my project board then the touch plate. Oh and just so that you know I move the touch plate to the bit each time to make sure connection is responding --- I have noticed that it acts as though the small magnet contact to spindle is not that great, small contact area, miniscule saw dust particles, etc... between magnet and spindle.

Will continue to use paper between bit and project board for setting z-zero until I resolve the issue with the touch plate.

And yes in addition to the new bits not even tasting wood they are SPENDY as you have said!!!

Sharkcutup
V-Carve Pro Tips, Gadget Tips & Videos
YouTube Channel - Sharkcutup CNC
V-Carve Pro 11.554

Rando
Posts: 757
Joined: Tue Jan 06, 2015 3:24 pm
Location: Boise, ID
Contact:

Re: Small Bits (1/8 or smaller) versus Touchplate

Post by Rando »

Cool, thanks for ruling those out. Yeah, more than once that magnet fell off to great panic for me. That might very well have been part of my original desire to have it use the bed, vise, etc., and not the touch plate.

Seems like a good reason to cut the magnet and change it to an alligator clip if it turns out its the culprit ;-)

I suppose it might be just possible that if you were putting the magnet on the BODY of the spindle there might be a weak connection to the actual rotating part. But, to be an issue, that would require like ceramic bearings or something to keep them insulated. To me, that wire never seemed long enough that I thought the body was the right place for it, so I'm guessing you're attaching it down below to the collet nut or the rotating part, or even directly to the bit.

There's no chance the magnet is being applied to a piece of anodized aluminum, or black-oxide coated steel, is there? The collet nut that came with my spindle (one of those generic 3hp water cooled ones out of China) is black-oxide coated on the flats, which is an insulator. I suppose it's conceivable that might get in the way too.

Perrrrplexing.

In any event, sounds like Paper it is!

Regards,

Thom
=====================================================
ThomR.com Creative tools and photographic art
A proud member of the Pacific Northwest CNC Club (now on Facebook)

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