Resetting z-zero after a tool change

[dauntless]

When the entire top of a block of wood is removed during the roughing pass, how do I set z-zero after changing bits for the finishing pass?

TIA, Stan

[harryball]

You will either have to leave an area untouched or choose to zero to the machine bed. Another alternative is to use a small peice of the material to zero elsewhere.

/RB

[dauntless]

Thanks RB. I left a strip on my test piece today, but may switch to zeroing on the bed. Stan

[carlosgmarroquin]

The teacher who taught me CNC in the university, could not stress more the need to zero on the table, after that you simply offset to the top of the material. It had worked for me.

[harryball]

I have a strong propensity to zero to the machine bed. However, I will zero to the top of the material for carving when I will not be cutting through.

No matter what you do though DON'T zero to the machine bed and run a file that should have been zero'd to the top of the material. Not that I've ever done that... ;-) if you do refer to "spoil board repair" threads.

/RB

[dauntless]

For the immediate future we will be carving MDF, so we have made a stepped reference piece with each layer exposed in turn. That should get us close enough for now.

I haven't given up on the bed idea, Carlos. I only have a few test cuts under my belt, so at this early juncture, it would not be any big deal to change my habits about where to plan the zero to be.

Thanks guys! Stan

[jhicks]

Stan, one option to consider might be to simply start by zeroing on the bed as reference for the roughing pass, then Mic your material and raise your bit by the material thickness and record that number, lets say a pure 3/4". Rezero there as the top of stock, machine roughing pass and change bits.
With the new bit use table as reference again to zero, raise bit to the same dimension, 3/4" for this example, and zero your second bit there.
Run file
Probably want to zero on same spot for table reference to get as close as possible.

[myxpykalix]

This is an idea i had after i saw Ed Lang and Jay Wyants Z setup.
It seems as if their Z point is the end of a piece of round steel firmly affixed to the table.

My thought was to have the round steel set into a collar that is held in place with a thumbscrew.

Then when you want to zero to material surface that you know is going to be all cut away but need to do tool changes then you can take a level or straightedge from the top of the material over to the round steel, loosen the thumbscrew and raise the steel to the height of the bottom of the straightedge and lock it.

Or Zzero to material move carriage over to round steel and raise it to bottom of bit and lock it off (keep in mind the thickness of Zzero plate).

If this is how theirs is already made then... NEVERMIND!

[chiloquinruss]

"have the round steel set into a collar that is held in place with a thumbscrew" Great idea! Thanks. Russ

[gpari]

Please use Aluminum
Your carbide will thank you.

Gabe