plywood thickness

Forrest Chapman · Post by **Forrest Chapman** » Mon, Sep 03 2007, 12:35PM

Rick,

I almost always do 50% tenons. Most machines have a few different bits to choose from to do the dado whatever size it may be.

Mike,

I think you mean 99% thickness. Yes you can do this and I have in times where I wanted full shear strength.

Robert,

I should just clarify that the machine looks at the the top surface of the material and machines down from there however it is referencing from Z0. So if it thinks that the material is 1\" but it is 1.02\" then the tenon actualy will be slightly less than 50% thickness of material. If the material is .96\" then the tenon will be more than 50% thickness. No matter what the variation it will machine the dado to fit the tenon.

Robert Glenn · Post by **Robert Glenn** » Mon, Sep 03 2007, 1:16PM

OK Forrest now I'm confused again.

You wrote

\"No matter what the variation (in material thickness I'm assuming you mean) it will machine the dado to fit the tenon.\"

If the thickness of the tenon varies with material thickness then how does the CNC know to compensate for that variation when cutting the slot for the tenon?

And if ecab used \"tenon thickness\" and refered to Z=0 when cutting the thickness then wouldn't this problem go away?

Rob

Forrest Chapman · Post by **Forrest Chapman** » Mon, Sep 03 2007, 1:58PM

Robert,

Lets say for instance your material is \"set\" at 1\" with a 50% tenon. The tenon will machine down to Z .5\" and the tenon will be 1/2\" thick. The dado will be machined at .5\" plus your clearances. If the material is thicker or thinner then you will have a small issue with alignment in some areas but, the fit will be consistant. The router will machine down from what it thinks is the top surface of the material ie. (Z 1\" down to Z .5\"). All of this is referenced from Z0.

Ps. Now I'm confused.

Michael Yeargain · Post by **Michael Yeargain** » Mon, Sep 03 2007, 6:05PM

Forrest Chapman wrote:I think you mean 99% thickness.

Thanks for clarifying.

Dennis Englert · Post by **Dennis Englert** » Wed, Sep 05 2007, 7:59AM

Blind dado....is typically a half tenon that's stopped on either end. The thickness of the tenon is designated in a setting in eCabinets and is based on a percentage of the thickness of material. So if the percentage is set to 50%, then the tenon will be 3/8\" (.375) for 3/4\" thick material. If the percentage is set to 100%, then it would be a stopped dado, but the full thickness of the material. It does not make a surface cut on the tenon to ensure that it is 100% of the material. After all it is 100%. If, as someone asked, it is set to 1% then tenon would be 1% of 3/4\" or .0075 (a pretty thin tenon, to say the least).

The accuracy of the blind dado actually comes from the defined surface of the material. If the material is defined as 3/4\" thick, then the surface of the material is established as Z0. For those that are using CNC's, this number is reflected in the ZSHIFT value. The final depth for a 50% thickness blind dado would be Z-.375. While the thickness of the material may vary, the machine always cuts (in this case) 3/8\" down from the Z0 (surface of the material as established by the material thickness in eCabinets). Therefore, as long as the operator has accurate daylight values and has accounted for the wasteboard (handling sheet) accurately, the then thickness will be consistant from sheet-to-sheet, or job-to-job.

Forrest Chapman · Post by **Forrest Chapman** » Wed, Sep 05 2007, 8:21AM

Dennis,

I like your version better.

Forrest

Thermwood / eCabinet Systems

plywood thickness

Re:

Blind Dado