I recently learned that what I’ve always called a Johnson Speed Square is officially called a Johnson 7 Inch Johnny Square. Draw lines along the sides of your square stock connecting the corresponding octagon cut marks that you made on the stock ends. While 27 feet is used as a rafter length in some texts to calculate run length, and while 27 appears ALMOST as a whole number in some framing square tables, that’s about it. Making use of the last bit of free space on the back of the framing square blade, Empire includes a table of recommended pilot hole diameter for wood screws of various sizes. There is no other tool available today that holds the answers to common roof framing problems than the framing square.
Measure the distance along the framing square from the place you wish to put your angle to the corner of the framing square. The speed square can basically be used as a protractor because it has degree graduations along the diagonal edge, making reading the angles fairly simple. I have an existing Window Sill that I need to determine the angle that it is, so I can Frame it. How do I use the speed square to do this, instead of hit and miss. If that one is perfect use it as a master rafted template and make copies of it. Briefly, this is how to use speed square angles for common and hip/valley roof rafters.
Good old HB had a bunch of these in stock the day I purchased it. It works well as a straight edge and has all the functions of my old square. Since I bought this a few weeks ago I’ve been struggling to understand how I was failing to get good results with it. Tonight I finally twigged.. IT’S NOT SQUARE. I miss my old square but truth is, I had allowed the old one to get a bit rusty.
To mark the seat cut you will flip the square over and place the pivot point where the seat mark meets the edge of the board. For 90 degree cuts, the rafter square fence can be left flush against the side of the wood. Then measure up from the edge of the shed floor and mark the overall height of the rafter assembly. When held in this position, the wider longer blade or body arm is pointing to my left and shows me a table of common rafter lengths per foot of tun, hip or valley rafter lengths per foot run. The traditional steel framing square was black while newer framing squares are often made of aluminum. And as the finish wore off of this tool, if I did not use it often enough it was prone to rust.
But along the hypotenuse edge lies a relatively accurate – and super fast – protractor: a way to read and mark angles. Back then the square was as powerful a tool to the skilled tradesman as a fully loaded laptop computer is to today’s structural engineer. The framing square used by carpenters is nothing more than a right triangle and when you adjust it on the side of a piece of lumber, it produces two accurate cut lines. Of the six combination squares that we tested, the best for most people is the Irwin 1794469 12-inch Combination Square (about $11).
My old Stanley (right) came with a protective coating on the blade, but that has long since worn off, and now I can’t even read the ruler. Make sure that they are snug up against the rafter edges and that the rafter is in its exact position. If the bay wall protrudes from the building line 2 feet, you can strike the bay angle line because now you know its length has to be two times the diagonal of a 12-inch square or 34 inches, (33-15/16-inches precisely).
The square of the length of the hypotenuse (a) equals the squares of the lengths of the opposite sides of a right triangle (b) and (c) – which is a mathematical way of saying that if we know any two roof slope measurement numbers we can compute the third. The rafter angle square is similarly used to make common and hip/valley rafter markings on the workpiece. The first rafter will be used as a template to aid in marking the remaining rafters.
Specifically, the offset nature of the scribe guide notches makes it difficult for a user to mark lines using the scribe guide notches in both directions without flipping the rafter angle square over. If you know the unit rise and run of the roof you are laying out, then you can determine the length of the rafter using the rafter tables stamped on the face of the square. Beg to differ, but to accurately make the side cut you should make the cut at the angle that the square lays out. Like the older version the new Johhny Square has an easy to read angle scale from 0 to 180 degrees.
In carpentry , a square or set square is a guide for establishing right angles (90° angles), usually made of metal and in the shape of a right triangle. At the end of this article at REFERENCES you’ll find more texts and articles on using a framing square and written by other experts. The Bow should always be on the upside of the rafter so when the weight of the tiles goes on it will more likely straighten the rafters out than bow them down even more.
This square has two legs, a 24 inch long by 2 inch wide leg called the blade and a 16 inch long by 1.5 inch wide leg called the tongue. The regular hip/valley rafter runs at a 45° angle to the main roof and the unit of measurement is 16.97 inches of run. The mark on the rafter corresponding to the outside wall point should be scribed along the tongue of the framing square as was the top cut on the rafter. Learning how to check for square and make an adjustment is worthwhile, and it isn’t a big deal at all ( this video explains everything). Speed Square is actually a trademarked name, but like Kleenex, it is often used as the generic name for this class of tool.
Regular steel blades will rust to the point where the markings become impossible to read. The square has a fence element configured to assist the user in positioning the square flush against the edge of a workpiece, such as a board, piece of lumber, or the like. You can use the speed square to mark an angle, such as when cutting a rafter tail, by holding the pivot point against the board. The table below, found near the end of the back of our framing square blade converts all of the common inch-fractions into decimal fractions.
This is accomplished by use of the main protractor and two specialty protractor angle guides on the inside of the tool. Protracting – To use the protractor feature, you first find the Pivot point marked in the 90° corner of the square. Although I’ve read this in books and done a couple of simple rooves I never quite got the hang of it but now that I am armed with this information things will be simpler on my next project.
As an apprentice, I thought this was a ridiculous method to use in laying out rafters-especially with instant access to a rafter table book and a tape measure. The least expensive metal-bodied square we looked at, this tool satisfies the basic requirements (zinc body, stainless-steel ruler). The square is slid up the board until the tread is placed on the mark and the process is repeated.