Tightening a collet up will cause the bit to pull in (rise).
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Yeah, I tried that some time ago. Worked (sometimes) but you had to hold the bit as you tightened collet. Just not enough hands to get it right every time. I now use a .025" feeler gauge. It’s easy to feel the drag on the metal and get it very precise every time. Not like the paper that catches and tears. Then just drop Z .025" and you’re there. Also use ohm meter and plate sometimes. Prefer feeler gauge. So much faster.
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Get your 1-2-3 block, and jog the tool to about .950, above your work surface.
then jog up until your block JUST slides through.
No deflection, or chipped carbide that way. Adjust your z -1.00 and run.
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i’ve done it and found also that it is less accurate compared to the paper method.
I did have another idea though. Would it be ok to add a switch of some kind that disables the Z motor only. I mean put it on the carriage somewhere in the wiring going directly into the motor. This way, the X and Y remain positioned perfectly, and the Z can be manually lifted, change tools, and manually reset to zero.
I sometimes disable power to all three motors to do exactly this, but sometimes it tends to slightly move in the XY plane when powering back on.
Maybe try a thin piece of plastic instead of metal or paper. Shouldn’t hurt bit and won’t tear like paper. Don’t really matter how thick. Just jog down z the thickness of whatever you use. I think I’ll give the plastic feeler gauge a try.
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Touch-plate, man! Really, really easy to install and works like a charm every time. 
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Yep. Takes one solder joint, and you’re golden. I’d personally suggest adding it to a head phone jack on the outside of the case, for ease of use. Then an alligator clip and anything metallic with a known thickness, and you’re set for touch-plate zeroing.
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It’s seriously worth it. Takes only a small fraction of the time, and the extension is perfect every time.
I picked up a ten pack also a while back, I managed to crunch my Z axis limit when I sent a command intended for Y to Z instead. Oops!
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A great trick gets it close every time (old timer trick) is the use of dowel pins. Take, say a .250 pin, then bring your cutter down to approximately .230-.240 above your part, roll the pin up against the cutter and slowly raise the cutter (I personally use .0001 jog at work) until you can just roll the pin under the cutter. Then move the pin away and lower the cutter one increment (whatever jog you are using) and check the pin. It should be stopped from rolling under. Then raise the cutter by one increment, the pin should roll under. Zero z, then change the number to .250 (or whatever you happen to be using). This is about as precise as you can get without a touch plate.
I’ve used this when I have broken cutters and had to be SURE that the z offset was correct to continue.
You can use any round object in this method, just get a good measurement (micrometer, not caliper) and use that number. I use dowel pins because they are cheap and precise.
Edit to say, I missed the 123 block post. Same exact idea.
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