Well, for people who know all the angles, it's just a matter of
degree. 

*ducking and running away!*

	-----------------------------------------From: "Chuck Taylor" 
To: "gtgrouch@r...", "Curt Seeliger"
Cc: "Darrell", "oldtools@g..."
Sent: Thursday December 1 2022 5:21:44PM
Subject: Re: [oldtools] knockdown shelf project continues to entertain
me

 Oh dear indeed. In suggesting the use of slopes instead of degrees, I
deliberately left out the gory details because it isn't necessary to
deal with gory details in order to make furniture. Yes, I did use
trigonometry to calculate the degree equivalents in order to
illustrate that the results are essentially the same, but it's much
simpler not to deal with degrees at all. You don't suppose that
18th-century galoots used degrees in marking out their furniture, do
you? It is much easier to set your adjustable bevel gauge using slopes
rather than degrees, and much more repeatable. 

 Another practical use of slopes is in evaluating bevel angles of
chisels and plane irons. If the width of the bevel is twice the
thickness of the blade/iron, then you have a 30-degree bevel. If it's
more than 2:1, then you have a shallower angle. If it's less, then you
have a steeper angle.

 For the curious, I used an HP48 calculator emulator on my smartphone
(set to calculate in degrees) to make that table, and I did indeed use
the arctangent function.

 Cheers,
 Chuck Taylor
 north of Seattle USA