Touch plate with small bits?

[Mimbler]

I'm about to start an inlay project that uses very small dia bits (.4 and .6 mm). My touch plate is convenient, but I don't know if you can use it with such tiny bits. Any experience out there on this topic?
thanks, Mike

[4DThinker]

I had a student use the touch plate with a tapered 1/16" ball nose bit and it worked fine. .0625" is still much larger than your .4mm and .6mm bits though.

[Mimbler]

I had a student use the touch plate with a tapered 1/16" ball nose bit and it worked fine. .0625" is still much larger than your .4mm and .6mm bits though.

I know, and they are kind of pricey! Still that is a good data point, thanks 4D!
Mike

[joethegasman]

I have some small orifice gauging bits down to about #68 or so what ever that measures out to, that i would be willing to subject to sacrifice to see if it can withstand the touchplate if you would like me to try it.

just let me know.
JTGM

[Mimbler]

I have some small orifice gauging bits down to about #68 or so what ever that measures out to, that i would be willing to subject to sacrifice to see if it can withstand the touchplate if you would like me to try it.

just let me know.
JTGM

#68 is .031 inches dia which is one of the sizes I'll be using. If you would be willing to test it, that would indeed be helpful Joe, thanks Mike

[joethegasman]

And the results are in!

Once I knocked the corners off the hex handle of the gauging drill so it would chuck into the bosch colt router's chuck, I ran the touch plate app and it worked flawlessly.

the 1" length bit didn't even flex in the slightest. just for kicks i put a caliper on the bit as well and it measured .027 in. it may be a bit smaller than what you are running but good for this test.

I hope this helps,

JTGM

[Mimbler]

Thanks Joe,
that is very helpful! Nothing like real experience to answer a question. Thanks again for taking the time to run the experiment! I'll be willing to try the bits now,

Mike

And the results are in!

Once I knocked the corners off the hex handle of the gauging drill so it would chuck into the bosch colt router's chuck, I ran the touch plate app and it worked flawlessly.

the 1" length bit didn't even flex in the slightest. just for kicks i put a caliper on the bit as well and it measured .027 in. it may be a bit smaller than what you are running but good for this test.

I hope this helps,

JTGM

[Rando]

I do some PCB and acrylic drilling with bits down to 0.026" (26 mils, 0.66mm) and haven't had any problems with them. That said, let's face it: Aluminum always has an insulating oxide layer at it's contact with air. For the probe to work, since it's a pretty small current (just measured at 0.5mA), it does have to mechanically break through that to make electrical connection. While that force might be small, the exact amount of force is going to be the amount of torque from that micro-step (assuming they're using them, and of course they must be) through the drive mechanics, "softened" by upward flex in the router plate. So, it's not a lot, likely in the 10s of milligrams of force. But, that is non-zero. There's probably some bit size, or even just some tiny level of microscopic examination that would reveal some "change" in the bit tip.

The vendor I get most of my small bits from (PreciseBits) optionally provides a depth-ring; I have them set all mine at the default of 0.8", or 20.32mm. While they are very accurate, the are not set to with 0.000000001 mm, so there's always some questioning. But, that's far more an issue with end mills and such. With drill bits, it's always only a vertical up-and-down (peck or otherwise), so as long as the safe height is multiples of the difference, it won't be a problem during the run.

But, that then leaves the homing action, in which that zeroed bit might be a tiny amount inside the material. Wood, not so much a problem with 0.02mm ding. But in Aluminum, that 0.02mm very well could affect that tiny bit. One way to deal with that is that after you've established 0-0-0, have the CNC drill a nice hold there, so when you put those tiny bits in, it doesn't become such a potentially breaking issue.

Hope that helps or at least adds to the thinking.

Thom

[Mimbler]

Thanks Thom,
My bits have the ring at .8 as well. I suppose I could snug the collet down with no bit in it, then raise it .8 and rezero and install the bit. I'll try it with the bits installed based on responses I've gotten, and if I have problems use the rezero trick.
Mike

I do some PCB and acrylic drilling with bits down to 0.026" (26 mils, 0.66mm) and haven't had any problems with them. That said, let's face it: Aluminum always has an insulating oxide layer at it's contact with air. For the probe to work, since it's a pretty small current (just measured at 0.5mA), it does have to mechanically break through that to make electrical connection. While that force might be small, the exact amount of force is going to be the amount of torque from that micro-step (assuming they're using them, and of course they must be) through the drive mechanics, "softened" by upward flex in the router plate. So, it's not a lot, likely in the 10s of milligrams of force. But, that is non-zero. There's probably some bit size, or even just some tiny level of microscopic examination that would reveal some "change" in the bit tip.

The vendor I get most of my small bits from (PreciseBits) optionally provides a depth-ring; I have them set all mine at the default of 0.8", or 20.32mm. While they are very accurate, the are not set to with 0.000000001 mm, so there's always some questioning. But, that's far more an issue with end mills and such. With drill bits, it's always only a vertical up-and-down (peck or otherwise), so as long as the safe height is multiples of the difference, it won't be a problem during the run.

But, that then leaves the homing action, in which that zeroed bit might be a tiny amount inside the material. Wood, not so much a problem with 0.02mm ding. But in Aluminum, that 0.02mm very well could affect that tiny bit. One way to deal with that is that after you've established 0-0-0, have the CNC drill a nice hold there, so when you put those tiny bits in, it doesn't become such a potentially breaking issue.

Hope that helps or at least adds to the thinking.

Thom

[Mimbler]

Just to give feedback for future people's reference, I gathered up my courage and tried the touchplate with my .024 in dia router bit. Joe's research helped steel my resolve. It turned out to be a non event. Worked great, gave me an accurate zero, and appeared to be very gentle to the bit,
Mike