Shopsmith Forums

Taking Guesswork out of 45° Cuts

I watched a video of someone using a Framing Square to set his miter gauge at 45 degrees. He had to line up one of the numbers (8”) on the body with 8” on the tongue. He pointed out that it took a lot of adjusting back and forth to get it right. Then there was the problem of getting it locked there while he adjusted his miter gauge. What if his square wasn’t square? They do get out of square.

Your table should be set square and parallel to the saw blade. If it isn’t this won’t work. A geometry rule states that if A is parallel to B which is parallel to C then C is parallel to A. Remember that from the past century?

Begin by verifying that your table saw insert is parallel to the miter slot. Lots of ways to do this but the most precise is with calipers. Once you have verified that use a Speed Square to set the angle. A speed square will always be square. BTW a plastic speed square from Harbor Freight a few years ago was not square.

I do this the same way except that I use a larger speed square and the miter track. This eliminates any variability that might be introduced by the table insert. I have a pair of speed squares that I store with my more sensitive measuring devises.

I also have a couple pieces of aluminum that were milled to be perfectly square. I often use one of these in the same manner but with the intention of setting to 90 degrees rather than 45 degrees with the blade as the reference surface.

Then use the speed square to validate the sides of the main table. If you do all of this successfully you can be confident that those miscues are human error rather than poor setup. It is amazing what can be confirmed/validated by inference.

Oh, I also check my rip fence for "parallel to blade" using that aluminum block (which could just as well be a piece of wood).

Drafting triangles are typically very accurate.