How to create Tendons?

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GrandpaB
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How to create Tendons?

Post by GrandpaB »

I need to create 1' long Tendons in a number of 2x4's that have been jointed and planned to the same dimensions. After cleaning up the 2x4" I will measure the boards' width and depth. I would like to use these dimensions to create the tendons. Each tendon is to be 2.5" x 0.5" and 1.0" long. I want to route the same thickness from each side of the board leaving 0.5" in the middle. Then I want to route the same thickness from each edge of the board leaving 2.5" in the middle. The next batch of tendons will probably have different widths and depths. How can I use the measured widths and depths as system variables to create the toolpaths for these projects? Once this problem is solved I'll want to use that knowledge to create matching mortises.
Thanks for your assistance.

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adze_cnc
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Re: How to create Tendons?

Post by adze_cnc »

You want tendons? Try turkey thighs. They same to have the greatest concentration of tendons I know. Rabbits too…

For this project to create tenons you’ll have to create the vectors for the lengths and widths manually (VCarve is not parametric).

The depths could be set using docment variables (see https://docs.vectric.com/docs/V9.0/VCar ... ables.html)

You could also use “t/3” as a depth in your (probably pocket) toolpath. T is a built in variable for material thickness.* For a 1.5 inch piece of material t/3 will give you the 0.5 inch depth of each pocket and leave 0.5” left over.

I wonder if someone has written a mortise and tenon gadget?

*Note: you can also use z as a substitute for t but I don’t think that’s as intuitive.

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TReischl
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Re: How to create Tendons?

Post by TReischl »

Tenons are best done vertically. Trying to do them flat on the table is iffy at best. For a good fitting tenon the tolerances are very small. The minor differences in thicknesses between boards becomes very apparent when trying to cut tenons with the board flat on the table.

One thing you could do is make them a very small amount too big and then do a fit up.
"If you see a good fight, get in it." Dr. Vernon Johns

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JoeBlow
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Re: How to create Tendons?

Post by JoeBlow »

Being this will be a 2 sided job, I would.....

Set up a jig on the spoilboard for consistent part placement.
Set Z to spoilboard.
Run Pocket Toolpath1 for the face cut on Side A followed by Pocket Toolpath2 for (1) edge cut on Side A.
Flip board and run Pocket Toolpath1 for the face cut on Side B followed by Pocket Toolpath2 for the 2nd edge cut on Side B.
The two edge cuts is where tenon drift to the right or left could occur resulting in an ill fitting tenon as it would be difficult to have a very precise X point set for origin, assuming the 2x4 is aligned to the Y axis lengthwise. Running one edge cut on Side A and then one edge cut on Side B will greatly improve centering your tenon. Milling in this fashion will yield fairly uniform tenons with any dimensional irregularities getting pushed to the outside where final sanding takes care of it.

As for the mortise, follow TReischi's advice and up-fit until you have a desirable fitment. Should only take a couple runs to get those numbers dialed in. Keep in mind you will not get square cornered mortises off the cnc so you will be rounding over your tenon edges according to your choice of bit used for the mortise.
Patrick

The hurrier I go, the behinder I get

Charlie_l
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Re: How to create Tendons?

Post by Charlie_l »

I’d do similar to Joe but would design the two sides having Z zeroed on the same side. So side A may be cut with z set to the spoil board. Side B would have Z set to the top of the board.
Charlie
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