Today, we turned to making a new tool to help us slice angled ends to a certain number of our rafters that needs to fit up against diagonal hip or valley beams in the roof.
We took an old portable electric circular saw and cut away the original blade shroud to allow a much larger diameter blade to be fitted. To this reduced metal plate, we mounted a sheet of plywood that is bigger than the new blade (300mm diameter) and then put a half a box over the upper section of the exposed blade to protect us from the spinning teeth!!
We then put on a double hinge near the bottom of the saw machine and mounted a thick 18mm plywood base which will serve as the sled to run across the surface of the rafter, with an arm sticking out so that it can be fixed down to achieve the desired angle we need when slicing the bevels. We can now get any angles from a minimum of 22 degrees and go all the way up to an impractical angle of about 85 degrees! We only need to get to 60 degrees for our maximum angle!
The second part of the machine is a template to fit onto a rafter which will provide the support and guide for the sawing unit. We wanted to have the template to flip around from doing a left handed cutting to a right handed cuts without having to unscrew and refit various parts. The design calls for a parallelogram aligned set of bracing arms (to hug the edges of the rafters) and the second set to provide the guide for the saw unit itself.
But it proved to be very difficult to get everything exactly measured and aligned. We tried several different methods and measuring schemes to position the mounting screws but we couldn’t get it working.
So tomorrow, we will have a rethink and come up with a much simpler design and just work with the main premise of just needing a straight guide for the saw unit, set for the required angle and also parallel to the end and then clamp or screw it to each rafter in turn. Perhaps have a second one made to do the flipped around cuts. We will see what comes out with a night of sub-conscious thinking!