# Explain My Theory With Me??



## speedre9 (Nov 2, 2014)

I was looking at my machine the other day and wondered if, I had the table surface at the correct height. I have a "z" travel of a max 3.00", also that is the space between the gantry and the table. When the spindle motor is in its clamp the spindle nose, without the cutter, is below the gantry arm making it theoretically capable of cutting into the table. Should this dimension be changed? Should or, would it be coupled with where the touch plate is involved in the tool length/height settings which I do not thoroughly understand at this point? Does any of that make sense, or am I over compensating/complicating things for a general lack of logical thinking?
Comments please.


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## JimDawson (Nov 2, 2014)

speedre9 said:


> I was looking at my machine the other day and wondered if, I had the table surface at the correct height. I have a "z" travel of a max 3.00", also that is the space between the gantry and the table. When the spindle motor is in its clamp the spindle nose, without the cutter, is below the gantry arm making it theoretically capable of cutting into the table. Should this dimension be changed? Should or, would it be coupled with where the touch plate is involved in the tool length/height settings which I do not thoroughly understand at this point? Does any of that make sense, or am I over compensating/complicating things for a general lack of logical thinking?
> Comments please.




I assume your machine is a CNC router.  It is normal for the cutter to be able to penetrate the table in most cases.  You could raise the mounting plate so that the tool bit would only penetrate the table a maximum of 1/16 or so at full Z travel.  This may give you more Z clearance.  Normally there would be no reason to cut into the table other than to machine it flat.

You would normally set your Z zero at top of the work, and penetrate (- Z) only to the depth in the G-code.


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## speedre9 (Nov 4, 2014)

O.K. So I'm over thinking it, but. The touch plate use still evades me. I can build one o.k. but it's its use? If using the top surface as "zero" why use a touch plate at all? Does it have to be constantly resized to match the stock thickness every time or what? If I put down the plate, at table height plus the thickness of the plate itself, isn't that then "zero" in Mach 3? I clearly do not get this thing, I've never seen anybody really demonstrate its use clearly. Much fog concerning this thing?????


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## Boswell (Nov 4, 2014)

speedre9 said:


> O.K. So I'm over thinking it, but. The touch plate use still evades me. I can build one o.k. but it's its use? If using the top surface as "zero" why use a touch plate at all? Does it have to be constantly resized to match the stock thickness every time or what? If I put down the plate, at table height plus the thickness of the plate itself, isn't that then "zero" in Mach 3? I clearly do not get this thing, I've never seen anybody really demonstrate its use clearly. Much fog concerning this thing?????



A touch plate just makes it quicker and easier to set the Z to Zero when the tip of the tool is exactly at the top of the work piece. You would typically set your touch plate on top of the work piece once it is clamped down. This move the tool until it touches the touch plate (this is often automated) then you go to the Mach3 screen to set offsets. Be sure the thickness of your touch plate is entered into mach 3 and then set the Zero with the touch plate button and now when you move the tool to Z=Zero then it should be just touching the work piece. This allows for G-Code programs to be written so that any negative Z value is "into" the part and Positive Z values are above the part. I am sure there are many ways to do this. I am only describing my (self learned) process.


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## JimDawson (Nov 4, 2014)

+1 what Boswell said.


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