Domino sizing for interior passage doors?

[woodferret]

Just as a brief, doors are to be 1-3/8 inches thick, split french doors across a 32-in opening.  No glass, just painted MDF panels.

Doing research, I keep seeing the suggestion to use a pair of 14x170 dominos for rail-stiles.  However, I'm guessing this was based more on thicker doors as I would have assumed a 12mm domino would suffice and fit the 1/3 rule better.

Advice?  12mm would probably be fine regardless given each door is half the usual weight, but I'll likely be building a full 32 later so I'd like to clear this up.  Thanks.

 

[ChuckM]

I'd do double tenons...at least for practice, if not for strength.

 

[JimD]

I would make custom 14mm thick tenons to fit the width of the rails.  There have been tests of mortise and tenon joints using thicker tenons than result from the 1/3 rule and they found going up as high as 1/2 the wood thickness was stronger.  14mm would be well under 1/2 but a little more than 1/3.  Seems about right to me.

If you have a planner, it takes little time to make your own tenons.  The planner is my key tool to get the thickness right.  Width and rough thickness are cut on the table saw, then thickness to final size in the planner, then round over the edges on the table saw.  I make up extra and store it in 3 foot lengths. 

You could use several premade tenons and could also use 12mm ones.  The premade ones are beech so it is pretty strong and should be plenty strong for interior doors.  I made some with dowel joints once and they were strong enough. 

 

[flair woodworks]

I would use two or three 12 mm dominos per joint, depending on the width of the rail.

 

[Cheese]

From Festool UK

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[Cheese]

From another Festool catalog on the DF 500 & DF 700.

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[woodferret]

Thanks all for the input.