Angle Jig for HR Saw

[cbailey]

I made a jig to help make compound angle cuts easily on a brick saw, specifically the HR model. I've seen several jigs made out of two pieces of wood joined by a piano hinge (it an be opened like a book) and placed on the saw platform to make the cuts. I didn't like it for two reasons. 1. the jig was to thick. It raised the brick more than an inch above the platform. I would have to release the saw into it's chop saw position. That could require two cuts to complete the brick' and potentially be less stable. That concerned me. It takes two cuts that should be accomplished with one. Twice the work. 2. I wanted the jig to be waterproof.

My humble solution was to buy 2 two thin plastic cutting boards from Walmart. They were $0.99 a piece. For a backstop, and adjustable horizontal feature, I attached a short 3/4 inch length of aluminum angle using an 8/32 bolt on one side of the board (the pivot point) and secured it on the other end with a small c clamp from Harbor Freight. I marked the cutting boards at 4.5 inches, or the width of a fire brick, and at 6 inches where I positioned the bolts for the vertical angle. I used 1/4-20 bolts with a standard nut on the bottom, and a wing nut on the top. It works out well for very fine height adjustments.

These work well if you are trying to reduce the vertical gap as you go up in the courses (the inverted "V") and reduce the amount of mortar needed in the vertical space at the back of the brick. As you get up in the higher courses, the horizontal angle decreases to zero, while the vertical angle increases quickly. These jigs help to make the cuts on sequential brick uniform. However, you may still need to trim bricks with an angle grinder. The dome just doesn't seem to cooperate!

Best of luck.

[Oceanrover]

Thank you cbailey! I've been looking at various designs and really like your use of the plastic cutting boards vs. wood or steel. Thanks for sharing this method for compound angle cuts.

[cbailey]

Hello Oceanrover. I’m glad you found it useful. It worked exremely well for me. I hope it does for you as well.

Cory

[7caesers]

Cbailey thanks for the cutting board tip. I used it with much success cutting my voussoirs for my inner arch. I do have a question about cutting the dome bricks. How many steps did it take you to cut two identical bricks out of one, like Chipster? Or what method did you use with your cutting board setup?

Thanks

[cbailey]

During construction of the first few courses, when I was only worrying about the width/amount of mortar on the outside of the dome, I could get two bricks out of one with three cuts. The first cut separated the brick in half and created the proper taper on one side the two brick. The next two cuts were made to the square side of the brick to match the taper created during the first cut. It gets more complicated as you go up in courses as you try to minimize the inverted "V"s by cutting a bevel when cutting the taper. After several attempts at minimizing the number of cuts I found the results not to be accurate enough. I ended up simply cutting the brick in half, and then cutting the taper and bevel on each side of the brick. 2 bricks requiring 5 cuts.

As many have pointed out, only cut a couple of bricks at a time and check how they align. Theoretically you can determine the dimensions of every brick in the dome. In reality, our cuts are simply not that accurate. Some mistakes are user error. Some equipment limitation. A couple millimeters off here or there can make a big difference in just a few bricks.

In the attached photos you can see where the bar at the bottom of the jig sets the taper. The bolts are used to cant the cutting board to set the bevel. I used 5/16th x 20 bolts, because that's what I had laying around. There are 20 threads per inch, so each full turn of the bolt will move the jig up or down 1/20th of an inch. You can make very fine adjustments.

One other tip I received that help tremendously was when you start a new chain. Mortar a single brick in place the day before so it is a solid anchor as you start the chain.

I hope that helps,

Cory

[Marchal]

Is there an elegant way to "fix" those little misalignments?