Fitting a Brace question.

[Jim_Rogers]

This morning I received an email asking about the correct way to fit up a brace to make it sit/seat correctly.

Here is the question:
Having a heck of a time to fit braces.  Measurements are all checking out. Mortises are clean.  Tenons seem to be all good but it is tough to get them to fit and they don't seem to fit as tight as I would like.
Is there a methodology to fit braces? 

And answer:
The most important part of fitting a brace if all measurements are accurate is the bearing end.
This end of the tenon must seat correctly against the bearing end of the mortise.

 

You need to check the bearing end of the mortise with a combination square and verify that it is inline with the hypotenuse point.

Like this:

 

Next you check that the end of the mortise is inline with the surface cut, like this:

 

and is truly 90°. if the bottom of the mortise is not then it will hold the brace out and not seat correctly.
Next you need to check the slope of the bearing end on the tenon.
This is done by holding a framing square along the side of the brace and a speed triangle against the framing square and the bearing end.
like this:

 

if the bearing end is not truly 45° from the edge of the brace it can hold the brace out and not align the hypotenuse with the measuring spot.


If the shoulder of the brace is not truly at 45° to the body of the brace it too can hold things out a bit.
check like this:

 

Part of fit up is understanding where the improvement needs to be done to make it better and not trimming off in the wrong spot and making it worst.
Careful inspection is needed to determine the correct spot to improve.
Good question.
Hope this helps.

Jim Rogers

[Andries]

Thanks for taking this "public" Jim.
Details like this take all of us past the theory to the best methods and practises.
Well done.