Replies

1. 
   eddiefromAustralia | Aug 29, 2003 11:44pm | #1

   BG,

   If 1 3/4" wide, OK to leave as a single tenon

   If 4 1/2" wide, I'd make a castellated or double tenon - when trained, the max width of a tenon was told to me to be approx 45mm / 1 3/4" due to shrinkage/cross grain movement.  If you glue a castellated tenon, only glue one tenon, cut the mortice for the other one a little long (not deep) to allow for cross grain movement.

   Cheers,

   eddie

1. 
   BG | Aug 30, 2003 12:47am | #2

   Eddie,

   I don't know what 'Castellated' is....but I did cross my legs just in case..:-)

   Seriously, these tenons will be seen (arts and crafts style) on the front side.  If I make them a double with a space in the middle won't that look funny?...maybe I am misunderstanding. thanks 

1. 
   eddiefromAustralia | Aug 30, 2003 02:01am | #3

   HI BG,

   Castellated is the term used to describe something that looks like the top of a medieval castle - little square sections.

   I missed the 'through' part of your question.

   I suppose if you wanted to you could cut a tenon 4" wide by 1/2" thick, but to me that's too skinny a thickness for the width of the tenon.  Due to the width, I wouldn't expect glue to hold a/c cross grain movement, so I'd still glue but drawbore the middle of the tenon, and limit the movement at both ends to approx 0.5mm, rather than pin/glue one end and leave it to float, giving approx 1mm movement at both ends

   Is that in keeping with Arts and Crafts style?? I don't know as I've only ever seen a few pictures of the same.  They've dumbed down certain parts of the technical training and our discussion on furniture styles now took approx 4 hours in total.

   Cheers,

   eddie

1. 
   yotonyb | Aug 31, 2003 04:19am | #4

   At the dimensions you're proposing, movement should be nominal, but there are a couple of accomodations you can make to keep the fit comfortable.

   I've seen a number of arts & crafts originals with some sort of stress fracture from a "too-tight" through tenon.  A typical failure is a long split with the grain on a side panel that has a horizontal through mortise.  Imagine a bookcase where the top or bottom are joined to the sides with a through mortise and tenon.  As the wide side panels contract around the tenon, you're virtually guaranted a split at the end of the mortise.

   Also, it's easy to blow-out the end grain at the top of a leg or post with a tenon that's too tight.  I've seen this happen frequently to new woodworkers unfamiliar with the properties of wood as they try to fit a tight tenon.

   I've also seen it happen to me.  More than once.  Some people just don't learn!

   As much as I like to see a tight mortise and through tenon -- tight from top to bottom -- I now leave about 1mm (1/32" to 1/16") difference in the height of my tenon compared to my mortise.  It makes it easier to fit and allows for some expansion and contraction.  And I'm not disturbed by that gap on any completed piece.

   I'll apply glue to the full width of a tenon up to about 4".  Wider tenons get glue only on the middle half to two-thirds to allow for expansion.

   Also, I pin virtually all of my joints unless I'm building a true reproduction that doesn't utilize pinned tenons.  The pinned joint adds another level of mechanical strength.  The dowel pin also add a measure of stress.  Too tight, too close to the edge can also fracture with the expansion of the dowel or contraction of the post or rail.

   Hope this helps!

   tony b.

1. 
   BG | Aug 31, 2003 06:02am | #5

   Tony,

   This does help, thanks.  I noticed you said you'll glue the entire m&t up to 4" and also pin. As I was thinking about this it occured to me this was similar to a breadboard edge..and maybe I should glue around a pin in the center only...they are so big it might be adequate....or two pins and enlarge the whole in the tennon for expansion ....am I going overboard ?..what do you think?

   If A&C did not pin, what did they do?

2. 
   yotonyb | Aug 31, 2003 07:57am | #6

   Since the pin is exposed and adds a decorative element to the piece, it follows that placement of your dowel pin should should be appropriate and proportionate to the design.  One is probably adequate, and two would be acceptable on a 4" tenon.  Do the layout and actually draw the dowel pins on your rail or leg and decide whether or not it's visually appealing...that's the real test.

   Based on the dimensions you listed before, I think you can glue the entire tenon without too much risk of hindering movement.

   While the dowel pin adds mechanical strength and a decorative touch to the joinery, it's not always necessary.  Plenty of arts & crafts furniture, and contemporary furniture, with mortise and tenon construction rely purely on the glue bond in conjunction with the tight/firm fit of the joint.

   tony b

3. 
   BG | Aug 31, 2003 12:54pm | #7

   Tony,

   Again, thanks.  I got all the parts fitted last night and did an initial sanding with 100 grit.  It looks pretty good...from an appropriate distance..it would look great in the middle of a football field. I am concerned about the splitting of the legs at the top ...it would not take much to split this QS white oak.

   Next is the draw...I've got a piece of figured white oak for the front...gonna do half blinds...very gently with a sharp chisel..

   thanks