Rounded tenons instead of dogbones for CNC mortise & tenon?

[Sawdust Santas]

Looking at Vcarve and how things were done on the 3 legged stool, etc... I am wondering why they use the "dogbone" method for the corners of mortise and through tenons and not a method similar to the Festool Domino machine where the inside radius of the mortise corners is matched by the same external radius on the tenon?

That would make basically no gap in any of those through tenon/mortise joints.

Please advise.

I am really new to looking at the CNC methods as I am trying to get a CNC in my toy & gift charity shop.  I may be missing how difficult it may be to make those rounded tenons?

Thanks, Pete

[Kevin Goodwin]

I have used my CNC machine to cut the mortise pockets to match the domino's from my festool.. I use it on the cabinet sides and stationary shelving flat surfaces and then use the festool to do the
end mortises on the shelves..Takes some messing with but once it is setup it creates a strong  joint and less time.  Goodluck!

[Ian Bennink]

Hi Pete,

There are different ways to use round bits and a CNC to cut a square pocket - but all effectively are dogbones of some sort. I hope I understand your question correctly, but basically with a 3-axis CNC it isn't possible to cut any circles perpendicular to the x-y plane, particularly since you'd need to do a reverse cut as well. It's technically possible but very inefficient time-wise and difficult to control tolerances.
So in effect you can't efficiently create a round tenon on a 3-axis CNC machine - in effect the Opendesk designs use square ones.
Alternative you follow what Kevin describes below: use the CNC to cut the pockets and a festool for the tenons.

Hope I understood your point; let me know if not. I'm not the most experienced machinist on the forum but have cut quite a few of the designs on the website.

Thanks
Ian