For many years I have had a somewhat skewed idea of just how valuable inaccurate combination squares are. I readily admit that I learned the hard way just how bad these things can be, and during my very frustrating learning process, I wasted a lot of wood and a ton of time.
Watch it on Youtube: https://youtu.be/dBlPoVUB_nY
My biggest problem was simply "assuming" that every combination square was true and accurate. Sadly, most of the cheap ones are NOT, you might get lucky and end up with one that is accurate, but probably if you paid $20 or so dollars or less, or maybe even more if it came with attachments ... it is not accurate, but go ahead and check it your self to see ... hopefully, you will get better results with yours than I did with mine.
Using an inaccurate combination square as a measuring tool is probably the only thing you can do with it that would be reliable.
In the example below, I am using the end of the ruler, or the hole that I drilled through the ruler (some rulers on combination squares are pre-drilled with small holes) specifically for marking with an awl or pencil. I like the whole idea as it gives a very accurate way of holding a pencil tip.
Another way of using your less-than-accurate combination square is as a precise, and adjustable "stop" for your miter gauge. I you need to make some precise cuts, and maybe even adjust and test as you go, you can easily loosen the adjusting screw on the ruler and move it back and forth as needed to make alternate cuts.
I don't use this method often, but once in a while I need to set my saw blades at a specific height and my crappy combination square is fine for this.
Warning ... do NOT bump your carbide-tipped blade with the steel portion of your combination square as even a small bump can chip a tooth, the body of most cheaper combination squares are cast aluminum which does not pose a high hazard of doing the same thing, but regardless, best to go gentle with this just the same.
I use this method OFTEN with my combination squares, a quick way of finding a center on leg ends, or for marking "reveals" for aprons on table legs.
And speaking of table legs, when you need to center a tabletop, on a set of legs you have constructed, your combination square is an easy tool to help make sure all sides are equal.
Here are places to NEVER USE AN INACCURATE Combination Square
1) When setting the vertical axis of your wood jointer
2) Never use it to check the blade angle for a true 90 degrees, OR use it to check the fence on a miter saw for being 90 degrees to the blade.
3) Never trust a crappy combination blade to set the vertical angle of our table saw blade.
If you have a combination square you can't trust and are looking for a better quality version, this square made by US manufacturer PEC, is guaranteed to be accurate, you can read more about it in the links below.
Woodworkweb Affiliate Link for PEC 12" Combination Square, have a look at it - HERE
Woodworkweb Affiliate Link for Machinist Square 4" x 3" have a look at it - HERE
I ALWAYS recommend that every woodworker has at least ONE fixed steel square, often called Machinist Squares, these squares are always accurate no matter the conditions, wet or dry, hot or cold they are always accurate, I like something around 6" but also have a 9" but regardless of length, these a valuable woodworking tools.
See ALL FIXED Steel Squares - HERE
Copyright Colin Knecht