Tongue and Groove Defined in Machining Detail

When we setup the Tongue and Groove, and value we use in the “Tongue Thickness” it will make the Groove position move further away from the edge, below is a detailed breakdown to what is happening and why it was set that way.

1) With the tongue the same size as the groove (ie 0mm undersized thickness).

G+B=D

G=T

B=A

this can make the fit a little tight (that is why the default undersize is 1mm).

2) With the tongue reduced in thickness (by X) and the groove the same as in (1) above.

G+B=D

G-X=T1

B+X=A1

3) With the tongue reduced in thickness (by X) and the groove also moved inwards by X.

G+B1=D+X

G-X=T1

B1=A1

The objective is that the Bottom faces (green) line up.

Theoretically, both (2) and (3) can succeed depending on the position of the tongue within the groove.

i.e. In (2) the blue faces touch and in (3) the orange faces touch.

But, we are dealing with board that is not always the thickness it is advertised to be (eg 16mm board is usually at least 16.1mm).

Therefore, depending on the z-zero (‘Top or Bottom of Plate’ in EnRoute terms) when on the flatbed, the thickness of the Tongue (T1) or the gap A1 could be larger than anticipated.

With ‘Top of plate’, T1 will larger by the extra thickness of the material.

With ‘Bottom of plate’ A1 will larger by the extra thickness of the material.

Either case will make (3) the only viable option.

Example:

Settings:

board thickness (D) = 16mm;

groove width (G) = 9mm;

tongue thickness reduced by 2mm;

then A1=D-9+2=9mm;

and T1=D-A1=7mm.

Reality 1:

board thickness = 16.2mm;

‘Top of Plate’ in use;

CabMaster still calculates A1=9mm;

‘actual’ A1=9mm;

‘actual’ T1=16.2-9=7.2mm.

So, using (2) above the green faces will not line up because D>G+B .

But, using (3) above (with the orange faces touching) the green faces will line up (as A1 will always equal B1).

Reality 2:

board thickness = 16.2mm;

‘Bottom of Plate’ in use;

CabMaster still calculates A1=9mm;

‘actual’ A1 =16.2-7=9.2mm;

‘actual’ T1=7mm.

So, using (2) above the green faces will not line up because D>G+B .

But, using (3) above (with a gap of [‘actual’ A1]-A1 between the orange faces) the green faces will line up (as long as the thickness reduction X >= the difference between the actual and specified material thickness, otherwise the tongue is too big; i.e. X>=[‘actual’ A1]-A1).

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