Fire brick problem. PLEASE HELP!!

[Nic Cox]

So ,I have started building my wood fired oven in the last few days, I am at the stage where I am cutting my fire bricks to make the floor of my oven.

I am using a 9" angle grinder with a diamond cutting blade to chop up my bricks (which are 64mm thick) the blades cost about ?25 each, and so far I cut between 5-7 bricks and the blade dulls and becomes too blunt to use!!!

At first I thought it was because I was trying to cut the curved lines of the outside wall of my oven and the blade isn't designed for this, so I brought a new blade and only did straight cuts, using a masonry file to give me a curve, but I am still only getting about 5-7 bricks in and the blade becomes blunt again!!!!!

I have about 120 bricks left to cut and at this rate I am going to spend a small fortune on blades. I must be doing something wrong, and advice would be greatly appreciated!!!!

[cobblerdave]

Re: Fire brick problem. PLEASE HELP!!

G'day
Is a simple a case of the bricks being to soft to open up the new diamonds. Just cut into an old piece of concrete or rock and it will bare some new diamonds on the surface of the blade.
Regards Dave

[Tscarborough]

Re: Fire brick problem. PLEASE HELP!!

Correct. The diamonds are embedded into a matrix. To keep the blade "sharp" you have to wear away the matrix to expose the cutting points, i.e. diamonds. Some blades have a soft matrix, some have a hard matrix, but the way to "sharpen" either is cut the opposite hardness of the material the blade is designed for.

[Nic Cox]

Re: Fire brick problem. PLEASE HELP!!

Thanks guys as soon as I get back from work I will give your advice a go and see if it works.

Thank you for responding so quickly, I was thinking that I was going to have to rent a masonry chop saw, so you may have saved me some money, I will let you know how I get on.

Thanks again!!!

[Laurentius]

Re: Fire brick problem. PLEASE HELP!!

Hi Nix,

Also retrieve those other blades they still have some cut in them!

[Nic Cox]

Re: Fire brick problem. PLEASE HELP!!

Thanks guys, your advice has worked! I am still finding it really hard to cut the bricks but after a couple of passes over a normal red brick the blade does sharpen up, but not enough to cut a full fire brick.

I have finished by oven floor now, and on Monday I shall start on the dome, this brings me to my next question; on most of the sites I've researched building my oven , people seem to cut their bricks in half to build the dome, is there a reason for this or can I use full size bricks??

[Tscarborough]

Re: Fire brick problem. PLEASE HELP!!

You may need something harder than a brick. A chunk of old concrete works well.

[SableSprings]

Re: Fire brick problem. PLEASE HELP!!

I have finished by oven floor now, and on Monday I shall start on the dome, this brings me to my next question; on most of the sites I've researched building my oven , people seem to cut their bricks in half to build the dome, is there a reason for this or can I use full size bricks??

In my opinion, the three reasons most people cut the bricks in half are;

1) Cost Saving - Why buy twice as many bricks as you need to do the job? Since a dome wall half a brick thick (4 1/2" or 10-12 mm) heats relatively quickly and provides plenty of stored heat after pizza for most home baking use (chicken, bread, cookies, etc.),

2) Time Saving - The full sized bricks will take much longer (and more wood) to heat and achieve thermal stability--not so important for pizza, but very important for the chicken, bread, cookies, etc.

3) Structure Specs - The increase in oven mass is obviously significant in several ways. If you go to full bricks, the time & cost increases in the build will dig into your pocketbook more deeply. There will be a need to be more conscious about the support structure of your foundation and oven platform...since there will be at least twice as much weight involved (depending on your increased mortar use covering the larger gaps that will form outside between the full bricks of the dome... ) and with a physically larger dome you will need quite a bit more insulation and stucco/finish to cover it ($). Since you will be burning a lot more wood, you'll also need to consider building a larger storage facility for it.

...if you're interested in making an oven intended for baking large amounts of bread daily--like going commercial--then the increased heat storage mass of full bricks (and a barrel shape for ease in loading/unloading) will be an advantage. If you aim for some pizza a couple times a week or for casual home baking use like most of us, then the half brick makes for a much more efficient system (less wood, less time, more pizza/bread sooner)

[cobblerdave]

Re: Fire brick problem. PLEASE HELP!!

G'day



Break the bricks in 1/2 with the brick bulster, the rough cut bit to the outside.
Saves heaps of time and energy

Regards dave

[Nic Cox]

Re: Fire brick problem. PLEASE HELP!!

Thanks for all the help it has been very useful, I also found that spraying water on the bricks as I cut them made life so much easier!!!

My oven floor is down and my soldier row up tomorrow I start on my arch, there is a high probability that I will ask for more help before the project is finished so keep an eye out for a desperate pizza enthusiast!!!

thanks again guys!!!

[Novaslo]

Re: Fire brick problem. PLEASE HELP!!

Good luck Nick.
You have a long haul ahead and it will be totally worth every sweaty minute. I purchased a cheap wet saw- one that you can sell when you are done. But using the brick Bulster will make things easier. Lot of pounding though.

Wear eye protection!!
CYA

[tonybaker]

Re: Fire brick problem. PLEASE HELP!!

yes, the easiest way to cut bricks for the dome is to use a bolster chisel (wide blade) and a lump hammer (small sledge hammer). Put the brick on a soft but firm surface and give it a good whack all around the edge to be cut. Be sure to use safety glasses though.

I did not try to mortar the joins on the inside surface of the dome, just poked mortar in from the outside. I was conscious of the fact that I did not want mortar flaking off the inside and falling into the pizza! In the end I realised that perfection is not needed with the dome, you will tidy up the outside later with insulating material anyway.

I used perlite bricks which are easy to cut being softer, the oven heats up quickly and the heat reflects down onto two slabs of refractory material situated in the middle of the base.

We tend to use our oven most often for slow cooking tougher cuts of meat, or roasting chickens etc... It does not take much wood to get the heat up and I use old dry pallets mostly. As long as they are stamped HT you are ok to use them.

Good luck with your build and don't be too fussy!

[Nic Cox]

Re: Fire brick problem. PLEASE HELP!!

Thanks for all the advice so far it's been a massive help.

The next problem I can see Is that I will run out of heat proof mortar building my dome. the stuff i brought is very expensive and hard for me to get as the company is miles away and delivery seems to be expensive. Is there a way I can make my own mortar???

[Greenman]

Re: Fire brick problem. PLEASE HELP!!

You can make home brew mortar with Portland Cement, Hydrated Lime, Powdered Fireclay and fine sand 1:1:1:3.

It works fine, I used a little plasticiser in mine that just makes it a bit more pleasant to use.

[huskerduck]

Re: Fire brick problem. PLEASE HELP!!

You can make home brew mortar with Portland Cement, Hydrated Lime, Powdered Fireclay and fine sand 1:1:1:3.

It works fine, I used a little plasticiser in mine that just makes it a bit more pleasant to use.

Is the 1:1:1:3 by weight or container size and how long does the mix stay useable?