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Greg in RI 06-09-2010 09:34 AM

Compound cuts in fire brick
Hello everyone,

I'm looking for a way to make a clean SAFE compound cut in a fire brick. I have a protractor accessory for my wet brick saw which works well to make wedge cut pieces for the dome wall but can't figure out a SAFE way to raise the brick off of the table at an angle to make a compound cut for brick pieces at the arch opening.

Has anyone made an accessory jig of some kind that can be attached to the sliding table of a wet brick saw that can SAFELY be used to make a compound cut in a fire brick? Or, maybe a process where two SAFE cuts can result in the equivalent of a compound cut. Some of the angles are looking to be pretty tricky cuts so other than a compound cut I may resort to making some free hand cuts with my grinder and a brick chisel, holding the brick in a vice to make a SAFE cut.

I know there's got to be a way but as Curly Howard used to say, "I'm trying to think but nothing is happening" :)


Greg in RI

SCChris 06-09-2010 09:39 AM

Re: Compound cuts in fire brick
Check out ""

Read the whole thread and pay attention to changes that I'd make to the tool to improve safety.


kebwi 06-09-2010 10:03 AM

Re: Compound cuts in fire brick
I consider a grinder considerably less safe than a mounted saw. In one case the blade is fixed and you and the brick are free. In the other, the blade and you are both free and the brick is fixed. I like my blade held firmly in place, just my take on it.

As for angles, I would solidly seat my bricks on scrap wedges of brick from previous cuts to achieve the necessary angles. Whenever I pushed a brick through the saw, it was (okay USUALLY) very very solidly grounded. Admittedly, the brick wasn't necessarily "clamped" to the table, but it wasn't tittering precariously on an edge or corner. It was resting, face to face, against some angled surface (a scrap wedge between the working brick and the table).

Hmmm, I also did some stupider things occasionally, but that shouldn't detract from the rationale applied to the approach described above.

SCChris 06-09-2010 10:31 AM

Re: Compound cuts in fire brick
I have to agree with you kebwi related to grinder vs brick saw and safety. I always want to make sure that it's understood that these tools are much better suited to cutting brick than having a senior moment and loosing a finger. Always error on the side of caution with tools. The tools will last longer, work better, and so will the operator.

PS I'd rather have a bottle in front of me than a frontal lobotomy and having two hands is not, in my opinion, having one to spare.

dmun 06-09-2010 02:24 PM

Re: Compound cuts in fire brick
Make sure your blade is the smooth tile cutting blade. I'd avoid the segmented blade for any close up and personal work. Make sure your table glides are as smooth as glass: any crud in there will make you push in ways you shouldn't. I second the angle grinder advice. The wet saw is a more safe alternative.

fxpose 06-09-2010 02:57 PM

Re: Compound cuts in fire brick
I made almost all my cuts, including a few compound cuts using my old Makita 10" compound miter saw with a segmented diamond blade.

I agree extra care should be taken when using an angle grinder. Both hands should always be holding the grinder no matter how you're using the grinder. Set the brick to be ground on the table, not in your hand.


Greg in RI 06-09-2010 05:02 PM

Re: Compound cuts in fire brick

Thanks everyone for the comments and suggestions. I like Chris' tool but my table is a little different. I do have some aluminum channel stock and may try something like it. I have made an indespensible tool so i'm just one step away from Chris' solution. Chris, how do you hold the bricks to the jig?

I thought about using my compound miter but I don't like all the dust and I don't want to gum up my wood saw. I did see a Chinese knock-off for $100 and you know it never hurts to have too many tools :)

The scrap wedge is a novel idea and I have done that with wood. I will give it a shot.

I think I'm going to have to experiment and see what makes the most sense for me. I like to be safe. I'm not sure I've got the nerve to work up close with a spinning blade but I will get a solid blade to supplement my segmented blade just in case I find the guts to focus.

I've got some more picture to post.

Thanks again for the help!

Greg in RI

SCChris 06-09-2010 08:05 PM

Re: Compound cuts in fire brick
Initially I thought that I would need to somehow lock the brick on the jig and in one of the photos you’ll notice a short 1 by 2 on top of the brick. On the first brick I found that the weight of the brick and the spin of the blade did most of the immobilization. You still need to hold the brick with some pressure but not a lot is needed to fix the position of the brick in the jig. As long as you let the blade do the work of cutting rather than trying to force the cut, you should be fine, but if you want you could use a clamp. I had thought that using a narrower width metal in jig would allow me to cut narrower bricks for placement, wrong... The interior face of bricks really doesn't need to get less than 2 inches, or at least that's my memory, so using 2 inch stock for stability is fine and even widening the base well beyond this isn't really a problem, just raise the blade to clear the jig. As you move up the dome, because a 10 inch blade can only make a 3.5 inches deep cut, you’ll need to cut the brick, break the waste off, then clean the brick face up. It’s up close work just pay close attention. It’s not hard and I think it's much safer than trying to use a grinder to do this, it is freehand however.

You could also use a 14 inch brick saw and make the cuts in a single swipe. I think you’d find that you save time and save blades. I think, given a bit of support, a custom cut dome could be cut and built in a day, as long as you use a 14 inch saw, a brick cutting jig. Hendo's tool a and if the mortar would allow you to move this fast.

Someone has used a converted compound miter saw and been successful at making these cuts and building a dome. Honestly, I wouldn’t know where to start with this. Electricity and water are, in my mind a very bad mix.. I wouldn’t be comfortable using a tool not meant for wet use, with water..

Take a look at Les’s build. Les has a very different method of mortaring the custom cut dome bricks in place.
Also take the time to go through Dino’s build,
I think these builds will teach you a lot. Also look at
There is a bunch of reasoning about builds here as well.


tfasz 06-10-2010 07:18 AM

Re: Compound cuts in fire brick
I started off cutting wedges in pieces of wood that I used as a base to sit bricks on to cut an angle. The wood pieces would quickly get wet, swell, bend, etc. so that they where not consistent between cuts. By the end I was using the same method Keith described - using scrap pieces of brick usually wedged underneath the brick. They would grip well both to the brick I was cutting and the table even when wet, would not change dimensions or shape, etc.

SCChris 06-10-2010 07:31 AM

Re: Compound cuts in fire brick
1 Attachment(s)
I'm sure that you could use wood wedges to set the front to back slope of the bricks being cut and I also think a yard stick, us term?, could be used to set the radius of the course.. The jig is temporary anyway so as long as you get the stability the material is not important. JCG31 put together a slope chart that defines the course angles of a 42 inch oven and I found that I was very close to his calculations during my 42" build. These slopes could easly be used to cut wedges ahead of your brick cutting. If you used this method I think you could easly and comfortably cut a group of wedges and glue or screw them to radius arms. The only item left would be the brick cutting tray extention that the pivot point of the radius arm ties to. I'm sure someone can or has done the calculations for the radius of each course.


Here it is.. I found JCG31's chart

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