Incredibly stupid newbie question

[touser]

Hi everyone, i know this is incredibly stupid but i have a small 3 axis cnc benchtop mill which uses R8 collets. How am i supposed to properly set the bit height in the collet so that it is accurate with the material top? Up until now i have just been sliding a piece of printer paper between the end mill and material and that has been accurate enough. However, i am now wanting to create a part which is going to require a tool change midway through and i have no idea how to insert the new end mill so that it is at the proper height once the surface of the material has already been machined down? Also, what is the proper way of setting the material top so i can stop using a piece of paper? I understand i have no business running a mill with so little knowledge and when i have time i plan to enroll in a machining class at community college. Until then can anyone recommend any books that go over basic concepts such as this? Thanks!

[ger21]

You jog the machine down to the top of the part, and zero the Z axis there. You're control software should allow you to do that, as well as re-zero when doing a tool change.

[pixburghenat]

I think ger21 means the surface will be gone after the first cut.

I use a surface gauge and set my tools from it whenever my parts surface is removed.

You can also use any known highth block, the vice, or the table. Block should be machined.
Set the block next to your part and measure the difference between the top of your part and the block.
Record the difference and adjust the Z offset.

Double check your math and what you type in the control.
Write everything down in case of intruptions.

Scott

[under-dog]

I used to use the touch off to a surface(usually my vise) and recalibret Z

I recently bought an electronic height gage and love it. Red light glares on when the tool makes contact so it eliminates potential discrepencies with the paper method.


I also made a riser block for it so it is dead nuts on to the "0" of the z height of the center of my 4th axis. This way when I flip mill or run a 4 axis program and need to tool change it is easy/ Just change the tool out jog over and touch down and re zero. In the case of a 2D cut part being flip milled I just calculate in the offset to the top of my part when I re-zero the Z on tool changes.

[tikka308]

touser - check out my page & video dedicated to my electric height gauge - http://www.nyccnc.com/Herbie/HERBIES..._Tutorial.html

[bones]

Hi Touser,
There is only one way I do it now. Read this.
Another Aussie Auto Tool Zero Setter

All it is basicly is a piece of PCB from your local electronics store, a piece of wire that goes to your Parallel port and the Mach screen on the thread.

Simple as. Perfect every time.

Then to do the X & Y see this Another Aussie Adventure in Laser Zero Finding

Perfect every time too.

Cheers
Rodney

[touser]

Thank you so much everyone for the help. tikka308, can i ask which height gauge you have? Searching mcmaster and ebay for height gauge returns very expensive units which look totally different than yours. I'll also have to order some copper clad pcb and give that automatic height gauge tool a shot as well!

[under-dog]

Originally Posted by touser Thank you so much everyone for the help. tikka308, can i ask which height gauge you have? Searching mcmaster and ebay for height gauge returns very expensive units which look totally different than yours. I'll also have to order some copper clad pcb and give that automatic height gauge tool a shot as well!

Tikka is where I got the idea for mine. They are from Enco. I am sure he can give you more info. I believe the video tells at the end what it is and where it is from, if I recall correctly

[tikka308]

touser - the link WAS http://www.use-enco.com/CGI/INSRIT?PMAKA=NP636-7044 but I just checked and enco no longer carries that part number. I'll have to dig out the catalogue tonight and see what the scoop is.

It was a $95 from enco though - just FYI. It's 2" high

[tikka308]

Enco just emailed me back. Link is below. Product is $89.95

http://www.use-enco.com/CGI/INSRIT?PMAKA=636-7044

[Stepper Monkey]

It may not look like much, but as a quick and dirty solution I just mounted a micro-lathe toolholder to one end of the table and fly cut the top a few thou to surface it parallel to my table.
I used a toolholder from my Taig lathe simply because 1) it already has a t-slot mount, 2) I had an extra handy, and 3) they are like 5 bucks. You could likely use any scrap chunk of aluminum or whatever that you can clamp to the table and surface though.

[bones]

I'm loving the Z zeroer. Bolt the job down, move the cutter within 20mm of so from the top of the job, sit the pcb plate ontop and click go.
It moves the head down until it touches the plate. Then it zeros the z axis, adds on the thickness of the plate and then backs off 30mm.

You could use the same system for x and y but we use a round tube camera for x and y. http://cgi.ebay.com.au/5-0-Mega-Pixe...QQcmdZViewItem

Cheers
Rodney