Bevel angles

[Rob Matarazzo]

Recently, I have been building a project by following some published plans. One step called for cutting a 38 degree bevel into two pieces of wood, along the edges. (Each piece is initially 3/4” x 2” x 36”). The two pieces are then joined along the beveled edges.

I set my table saw for 38 degrees and cut the bevels, with each piece running through with the 2” face against the saw table. The resultant angle is of course the complementary angle, i.e., 52 degrees.

This made me wonder about what angle was really intended by the instructions, as the drawing was not very clear on it. After mulling it over for a couple of days, I decided that 52 degrees had to be correct. The reason being that two 38-degree bevels laid face-to-face would yield a combined angle of 74 degrees. The combined angle clearly needed to be more than 90 degrees for this application.

So getting to my real question: Is there some unwritten standard or convention that is implied when a bevel angle is specified? Is it the stated angle, or it’s complement?

[Wayne Lomman]

Drawings must show the actual angle of the finished component. The complementary angle may need to be considered when manufacturing the component but that is your choice as manufacturer.

A list of instructions is a different kettle of fish. There you are depending on someone else's interpretation of the drawing and your understanding of their language. Working directly from the drawing is much more reliable. Cheers

[Jeff Heath]

When using power tools, the complementary angle is often the only one available for use in a safe setup. Table saws have a tilting range from 0-45°, obviously, so you sometimes either have to stand the part on edge against the fence (not always safe) or use the complement.

As Wayne stated, the design drawings tell all. Different in every case.

[johnny means]

I would never assume that instructions are correct. Always do your own layout. More often than not the designer/draftsman has never actually fabricated anything.

[Rob Matarazzo]

Thanks all. The instructions did not really represent the angle in an unambiguous way, so I was a bit puzzled for awhile.