Mortice and Tenon for table apron

What is the general rule for fitting the height of the tenon on a table apron? Since this is a cross grain situation how much room is usually left at the top and bottom of the tenon to account for expansion and contraction?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I've never heard anyone suggesting it needs to be considered. Since most aprons are 3 or 4 inches and the tenon is something less than that, the amount of expansion shouldn't be a problem.
Additionally, some folks offset the tenon from the the top creating a bigger shoulder on the upper portion to leave some strength in the upper portion of the leg vs having a mortise all the way up near the top.
I've never had a table break and I typically try to keep keep them pretty tight. I'd also like to hear if someone has learned or heard differently.
BW
foster239 wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Agreed. Starting with a ballpark worst-case scenario of 1/4" per foot seasonal movement... that's a 1/16" inch summer expansion on a 3" tennon *if* you assemble the table in the bone-dry dead of winter.
Good luck even assembling (dry fit and disassemble) that M&T joint (assuming at least a 1" depth) with less than 1/16" of top and bottom wiggle.
-Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
foster239 wrote:

expansion and glue only the top third. The size of the gap depends on the wood and its expansion rate. Tendons of 4 inches or less probably don't need to account for the expansion.
Alternately, divide the tendon into multiple smaller ones with matching mortises.
Jess.S
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Nice, now I understand why people do those multiple tenons and great advice on the glue up.
Jesse R Strawbridge wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.