Mortise & Tenion Expansion/Contraction

[Retiredguy]

I am building two Church doors to replace the 156 YO originals.
The doors are Red Oak 1 3/4" thick, and each door is 30 X 96 inches, with two 5" wide styles, and four rails (3 3/4", 6", 7" and 11").
The rails are joined to the styles with mortise & Tenion joints.

My question concerns wood movement.

I assume I will be fine with the 3 3/4" rail with its 2" X  2" tenion.  But, what about the 6" and 7" rails. The 6" rail has two 1 1/2" wide by 2" deep tenions spaced 1" apart.  The 7" rail has two 2" X 2" tenions spaced 1" apart.  The 11" rail has three 2" tenions spaced 1" apart.

Will I be OK to glue and pin the three smaller rails, and glue two of the 11" tenions, and let the third Float (al la bread board end)??

As a side note.  The doors are outside doors, they face South, and have no roof over them or protection of any kind.

[fredhargis]

I would glue them all, there are no concerns with expansion on 2" tenons. Curious, how thick are those tenons?

[Retiredguy]

I would glue them all, there are no concerns with expansion on 2" tenons. Curious, how thick are those tenons?

Thank you for your input, that's what I wanted to do, but looked up the coefficient of expansion for red oak and got scared.  The tenons are 5/8" thick.

[jteneyck]

I would glue them all, there are no concerns with expansion on 2" tenons. Curious, how thick are those tenons?

You're right in that the cross grain stresses on the tenon itself will be less the narrower it is.  But the tenons are part of the rail and the whole rail expands/contracts, too.  If it expands/contracts enough it will split, whether or not the tenons are narrow or wide.  I've had trouble with both house doors I've made with 11 - 12" wide bottom rails.  The veneer on both split at the center of the rail.  On one I replaced the bottom rail, with a different construction; the other I think will be OK with just a minor repair.  The next door I build will have a bottom rail no wider than 8 or 9".  The only way around this with a wide rail would be to use breadboard construction, as the OP asked about, but I've never seen it done.  But I'm not well versed in all the ideas that have been tried on entry doors, so maybe it has been.  

Retiredguy
[quote pid='7649210' dateline='1532738345']

Thank you for your input, that's what I wanted to do, but looked up the coefficient of expansion for red oak and got scared.  The tenons are 5/8" thick.
[/quote]

5/8" is a good choice IMO.

John

[rwe2156]

Yes, I would definitely make the tenon longer, at least 3 1/2".

IMO the best approach is glue & pin the tenon closest to edge so the edge stays flush with bottom of stiles. Draw bore the other two (glue pins but no glue on tenons and ample slotted holes, of course).

What was the original door made of?

Red Oak has issues with water absorption especially through endgrain (it will wick it like a celery stick!).

I would use epoxy glue on everything & seal the end grain on the stiles with epoxy followed by several coats of oil based paint or sealer.

[Retiredguy]

Yes, I would definitely make the tenon longer, at least 3 1/2".

IMO the best approach is glue  & pin the tenon closest to edge so the edge stays flush with bottom of stiles.  Draw bore the other two (glue pins but no glue on tenons and ample slotted holes, of course).

What was the original door made of?

Red Oak has issues with water absorption especially through endgrain (it will wick it like a celery stick!).  

I would use epoxy glue on everything & seal the end grain on the stiles with epoxy followed by several coats of oil based paint or sealer.

The original doors were clear pine/fir.  I could only find clear fir in construction sizes, no 8/4 clear lumber anywhere.  Since red oak is also native to this area (NE Kansas) the original builders could have used it for the doors. The people who are in charge of restoring the church thought that was a good reason to use it.

Longer tenons would always be better, but I couldn't figure a way to make them, other than drill and chisel, which for me, produces a really rough mortise.  Two inch deep mortises made with a router are nice and smooth, and make a really nice gluing surface.  With a 2" long tenon, 5/8" thick, and a 1/2" oak dowel through everything, is this a recipe for disaster??

I have all (32) mortises done, and theoretically, could go back and deepen them, but then I would have to scrap all the rail blanks, since they would then be too short.

Your comment about exposed end grain was a good one, do you see any problem for the end grain surrounding the tenons?  Its not exposed, but only butted up against the style?

Thank you for taking the time to think about this problem, and your thoughtful input.

[jteneyck]

You can buy end mills that will allow you to go about as deep as you want for the mortises.  I use center drilling, 2 or 3 fluted HSS end mills.  You can buy them at very reasonable prices on Amazon, McMaster Carr, ets.  And you can get 5/8" cutting diameter with a 1/2" shank, too, though the selection is more limited.  But you could buy a 1/2" diameter one and use a template and guide collet on your router, too.  

As I mentioned before, a 2" tenon won't have enough meat behind the pin to provide the strength you are hoping for.  You want at least 2" of tenon past the pin, which means your tenon needs to be at least 3-1/2" long.   

Or just stick with 2-1/2 to 3" long tenons, no pins, and glue all of them into their mortises.  Thousands of doors are made every day with three 1/2" or 5/8" diameter dowels about 8" long glued in the bottom rail.  No pins.  One of our members who hasn't been around for a several months doesn't even glue in the dowels; they are just driven in dry to keep the rails from racking; the only glue is on the cope/stick between the stiles and rails.  The point is, you have choices.  

Isn't walnut local to you?  If so, that would make a much more durable door.  If you're committed to RO you will want to seal every exposed piece of end grain really well (True for any door, but especially one made of RO.).  I would use epoxy as already mentioned.  Don't worry about the end grain on the tenons.  If liquid water gets in there you have bigger problems.  

John

[Retiredguy]

You can buy end mills that will allow you to go about as deep as you want for the mortises.  I use center drilling, 2 or 3 fluted HSS end mills.  You can buy them at very reasonable prices on Amazon, McMaster Carr, ets.  And you can get 5/8" cutting diameter with a 1/2" shank, too, though the selection is more limited.  But you could buy a 1/2" diameter one and use a template and guide collet on your router, too.  

As I mentioned before, a 2" tenon won't have enough meat behind the pin to provide the strength you are hoping for.  You want at least 2" of tenon past the pin, which means your tenon needs to be at least 3-1/2" long.   

Or just stick with 2-1/2 to 3" long tenons, no pins, and glue all of them into their mortises.  Thousands of doors are made every day with three 1/2" or 5/8" diameter dowels about 8" long glued in the bottom rail.  No pins.  One of our members who hasn't been around for a several months doesn't even glue in the dowels; they are just driven in dry to keep the rails from racking; the only glue is on the cope/stick between the stiles and rails.  The point is, you have choices.  

Isn't walnut local to you?  If so, that would make a much more durable door.  If you're committed to RO you will want to seal every exposed piece of end grain really well (True for any door, but especially one made of RO.).  I would use epoxy as already mentioned.  Don't worry about the end grain on the tenons.  If liquid water gets in there you have bigger problems.  

John

Thanks for the info, John.

As much as I wanted to convince myself that 2" tenons were sufficient, I finally had to agree that they weren't.
I took your advice and bought an end mil, so I could do 3 1/2" long mortises. The new end mil is 1/2" in diameter, four flute, and 6" long. It fits my router and the jig I used to make the 2" deep mortises, and is just long enough to make the 3 1/2" deep mortises.

I'm having a problem trying to make the 2" mortises deeper.  I made the original router jig with a center line that lines up with the center of the original mortise, this allows me to put the jig back over the original mortise pretty accurately. 
Every mortise that I have tried to deepen with the new cutter has "caught", severely jerked the router, dug into the side of the mortise, and scared the pee out of me.

 Have any idea what I may be doing wrong?

[handi]

I am building two Church doors to replace the 156 YO originals.
The doors are Red Oak 1 3/4" thick, and each door is 30 X 96 inches, with two 5" wide styles, and four rails (3 3/4", 6", 7" and 11").
The rails are joined to the styles with mortise & Tenion joints.

My question concerns wood movement.

I assume I will be fine with the 3 3/4" rail with its 2" X  2" tenion.  But, what about the 6" and 7" rails. The 6" rail has two 1 1/2" wide by 2" deep tenions spaced 1" apart.  The 7" rail has two 2" X 2" tenions spaced 1" apart.  The 11" rail has three 2" tenions spaced 1" apart.

Will I be OK to glue and pin the three smaller rails, and glue two of the 11" tenions, and let the third Float (al la bread board end)??

As a side note.  The doors are outside doors, they face South, and have no roof over them or protection of any kind.

On wider rails, it is not unusual to see the one long tenon split into two shorter ones with a gap in between. Expansion and contraction across the grain is a percentage of the width, so narrower tenons will move less. 

But remember that to a large extent, these “rules” were developed when glues were made from animal hide and finishes were also primitive. In a modern joint that uses epoxy or other waterproof glue, buried underneath a high tech finish, VERY little moisture will be exchanged inside the mortise.

[jteneyck]

I am building two Church doors to replace the 156 YO originals.
The doors are Red Oak 1 3/4" thick, and each door is 30 X 96 inches, with two 5" wide styles, and four rails (3 3/4", 6", 7" and 11").
The rails are joined to the styles with mortise & Tenion joints.

My question concerns wood movement.

I assume I will be fine with the 3 3/4" rail with its 2" X  2" tenion.  But, what about the 6" and 7" rails. The 6" rail has two 1 1/2" wide by 2" deep tenions spaced 1" apart.  The 7" rail has two 2" X 2" tenions spaced 1" apart.  The 11" rail has three 2" tenions spaced 1" apart.

Will I be OK to glue and pin the three smaller rails, and glue two of the 11" tenions, and let the third Float (al la bread board end)??

As a side note.  The doors are outside doors, they face South, and have no roof over them or protection of any kind.

Red oak is a poor choice for outside use.  Most exterior oak doors use white oak.  I'm not a huge fan of white oak either, because of it's high seasonal movement, but it's far more durable than red oak.  Better choices would be mahogany, Douglas fir, walnut, etc.  If you do use red oak, maintenance of the finish is going to be critical for it to look good long term.  A 2K poly would be about the best finish choice.    

I would make the tenons longer.  2-1/2" would be about the minimum and the longer the better.  If you can't make longer tenons you might want to consider dowels instead.  I don't see much benefit in pinning a 2" long tenon; there isn't enough wood on the outboard side to prevent it from pulling out behind the dowel and if you believe glue is what holds a joint together (as I do) then there's no point anyway.  But if you wanted to make thru tenons you could pin them and forget the glue altogether, as was done in yesteryear.  

I would use just two tenons on the 11" rail, 3-1/2 - 4" wide with a 2 inch space between them.  And long.  In any case, I'd glue them all.  

What are you doing with the panels?  One piece panels are likely to crack if the church is heated.  Two piece, back to back panels that can move independently, have a much better chance of behaving over the long haul.  

Good luck.  

John