This is more of a discussion point than hard question. Now days with all these wonderful power tools, people talk about 1/1000th” tolerance in woodworking and the need for tight fit. However, I’d bet that Henry VIII sat in a nice chair and those mortices were probably chopped. Looking at the walls of a chopped mortice, I don’t see surfaces such as those cut by a router but those joints in Henry’s chair were good enough for a king.
At what point does tightness of fit really matter?
Gary
Replies
Gary,
Tightness does matter. If a joint doesn't have at least a moderate amount of wood to wood contact then the joint strength is entirely dependent on the strength of the thicker glue line that fills the gaps. With most of the common woodworking glues the joint's strength is reduced significantly if there are large gaps. Also, any play in a joint creates internal wear that only makes the fit worse, and the joint weaker, as time goes on.
The difference between a properly snug mortise and tenon and one that is getting too loose is only around .005 inch. You don't need to actually measure to a few thousandths, but the final trimming and fitting will only be removing that much as you test your fits. If your cutting method creates mortises and tenons that are widely varying in size, or with sides that are out of parallel, you will have to spend a lot more time fitting the joints.
When making joints by hand there are a lot of tricks of the trade, developed over the years that help considerably to create accurate joinery without actually doing precise measurements, but the accuracy is there in the best made pieces.
John White, Yestermorrow School
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