Diameter of bit cutting typical tenon joints?

[Gene Davis]

What is the bit diameter typically used to cut the 3/8" mortise and tenon work in 3/4" panel stock?

I'm doing some how-to-assemble illustrations using Sketchup and want to accurately portray the geometry.

So, bit size for thru-cuts (full part cutout)?

If different, bit size for 3/8" mortise (dado)? If we've specified .010 fit clearance, does the router make a circuit cut for each mortise, the return path .010 offset?

[Donald Thomson]

I use a 1/4" two-flute down cut spiral bit for mortises and tenons. Spindle 14K RPM, feedrate 6 IPM.

I use a 1/4" two-flute compression bit for cutting parts out. Spindle 14K RPM, feedrate 6 IPM. Depending on bit and machine flex, you might have to adjust cut depth. I always make my first cuts in a climb direction, leaving a 1/32" skin. The climb cut will push the bit away from the cut line. I do a final conventional cut, full depth + .020". The conventional cut pulls the bit right to the cut line.

I cut several hundred sheets of plywood every year and this combination has served me very well. I use a bit for about 25 sheets then change bits. Veneer and plywood resins can dull a bit pretty fast.

Just make sure you get an accurate micrometer measurement of the diameter of the cutting flutes. This, along with spindle speed and feed rate, will have a BIG impact on joinery fits. The toolpath generated for mortises and tenons take into account bit diameter and the width of the mortise/tenon and generates the code necessary to clean out the material.

[Gene Davis]

Thanks for that info, but if you've the time, take a look at this pic, attached.

I am trying to arrive at a good standard for my seed builds, and what is displayed is the result of me specifying for 4" stretchers and back-edge tops in base cabinets with drawers, a lock dado joint with these settings

3/4" thickness material
3/8 depth tenon cut (50 percent of material)
3/8 depth mortise cut plus .030 fit extra depth
1/100 dado fit extra
Blind dado inset 5/8" L and R edges (or front and back if oriented such)
KD/RTA gap between tenons 3/8"
1/8" dia. pilot hole for screw (done with pattern)

I did the 3D model assuming a 1/4" diameter bit is used to cut the tenons (the thru cut) and the mortises (dados).

The tenon width of 1" is from a careful examination of part geometry using the part editor.

The mystery here is the gap between, specified as 3/8, but actually 3/4". Or measured across the flat between machined tenons, it is 1/2".

So where is the 3/8". Try it yourself, measure, and explain to me what the 3/8" setting does.

I included a screencap of the construction settings for this part, a 4" top set flush to back.

[Gene Davis]

I think it may be that eCabs code takes that KD/RTA tenon gap value input by the user, doubles it, and makes the result the gap between tenon tips. This has to be it.

Unless someone has another explanation.

[Gene Davis]

I played with the settings some more and examined results with different inputs.

What is called the LOCK DADO TENON GAP is more accurately described as TENON OFFSET FROM CENTER OF KD/RTA FASTENER. Thus, twice (2x) the value inputted is the tip-to-tip tenon gap. It is a gap thus measured no matter what diameter cutting tool creates the parts.

[Donald Thomson]

I have to admit, I haven't even played with KD/RTA joinery, so I've worn out my usefulness on this matter. Might want to reach out to Thermwwod to see what they say.

[Clint Buechlein]

Gene,

The help manual tells you what the Lock Dado Tenon Gap refers to.

-Clint-