Can someone tell me how to make accurate 45 % cuts that actually fit
together nicely? I was building an deck and have some herringbone and
mitered joints that were an devil to do , using number 2 grade spruce.
I love making sawdust.


From What I have read:

It has to do with the force from the blade, how it cuts the kerf, and how
the wood is supported (or secured from movement.)

The force of the motor is way more than you can hold with your hand the
wood against movement. A 90 degree crosscut usually has a lot of support
by the geometry of the cut which prevents wood movement. However a 45
degree cut as a lot a force working to shift the wood due to the blade.
Vector math, resultant forces, and all that.

Step 1, therefore is to check and double check that the wood is secured
in such a way as to prevent the wood from movement during the cut. Stop
blocks do work well in this case.

Several very well written articles in Shopsmith magazine over the years
on this subject. And I believe in the results of the jigs I have built
from Shopsmith to overcome this 45 degree gap problem.