How hard would it be to produce a DIY auto tool height sensor? 

Maybe a macro that starts with every tool change and goes to a specific location, touches off the tool tip, and offsets itself?

Anything commercially ready now?

The Macro is simple I will code one for you if you make the hardware 

I've got an idea on the hardware.  To start, I've ordered the probe offered by DeskCNC. 

I really appreciate the offer to write the macro, but I'd truely like to understand how it's done so I can be a "super dude" like you!

I love CNC.  Don't know why.  Just do.

I can show you what I did and why.. Once I do that you are ready to make your own macro!

sounds like fun!

For that kind of touching,there's a hell a lot of ways to do the hardware with pretty impressive repeatability without the probe(that said,I do own that probe).But anyway,if you need any tips on the electronics,just scream.-Keith

Keith,

I would really like to hear your electronics tips for make a touch off probe. 

I have a real simple micro switch that I mounted at the x and y reference points.  So I reference x and y first and then reference z to reset to new tool.  Works great But I too would like a macro for this.

Dfurlano,well I don't think you can just 'tip' at the electronics because in order to tame the kind of precision you can get, you have to delve into the particulars. But so many fantastic sensors now ;thin film pressure resistors,thin as a piece of paper,run through a small(and cheap) micro or conversely a seperate a/d convertor and then micro. Something like that would have incredible precision,out put a pulse or a trigger from the micro and not cost more than $10 in parts. I worked with an $8 accelorometer that could measure tilt way past the 10 bit a/d convertor I had in the micro already! GMRs(giant magnetoresistive,which of course the word giant is relative ,it's still the size of a surface mount 8pin chip) also give the repeatability and precision necessary. Even some micro optical triangulation units are available from people like SHARP via digikey.com for very little.I could go on. It all of course assumes some knowledge of electronics but ,if you want to 'crawl' towards any of these approachs,I would be happy to coax you through it.-Keith

Here is the macro...
http://machsupport.com/forum/index.php?topic=1100.0