DIY HT oven brick and mortar question

[funkyjedi]

Hey all! I am about halfway through bricking out my HT oven, and I have to say, mortaring these k23's together is a nightmare. I have been using sairbond refractory mortar, and no matter what, I cant get things to stick. The bricks literally suck the water out of the mortar right before your eyes. Even dipping the bricks in water has not really helped. So, I have two questions for you guys:

1) Any ideas on other ways to mortar the refractory bricks together?

2) Any ideas as to how long this refractory mortar takes to dry? I called the company that sells it and got a pretty vague answer.


I am at a loss, and literally wasting time waiting for these things to set up. When I get several days out, I go out to check them, and the joints just pop apart. Infuriating doesn't describe the feeling. Its been weeks of this. different textures, different amounts of water, etc. I have used the manufacturer's recommendation for mix, experimented, etc. I have 4 bricks that stuck and thats it. I think I might be going crazy.

Thanks in advance.

chris

 

[timgunn]

Why are you mortaring them together?

I have built 5 or 6 HT ovens to date and gave up on mortaring them after about the third failed attempt to stick a couple of bricks together. They work fine with dry joints.

If you need to prevent movement, a very useful cheat that I have found is to pin the bricks together with welding rod.

There is an old model engineering trick for drilling flat-bottomed holes or deep straight holes with a shop-made tool known as a D-bit. Basically, the end of a tool-steel round is ground away to leave a semicircle and a little bit or relief is ground on the end. The tool is hardened and it will then drill holes.

http://www.cnccookbook.com/img/MillStuff/CNC/OneShot/P1010859.JPG

D-bits are fairly horrible to use for deep holes because the only place for the chips to go is into the space left by the semicircle and it's not a very big space at all. As a result you are continually pecking to remove the chips.

When drilling IFB though, the "chips" are dust and, with a small hole diameter, the material you are drilling has enough voids to accept the dust as fast as it is produced. For IFB, the D-bit does not even need to be hardened if it is a one-hit job. I therefore just grind a D-bit on the end of a 3' long, 3/32" diameter welding rod and use a cordless drill to drill all the way through the IFBs, leaving it in place and nipping off the extra with end-cutters. I use stainless TIG welding rods because I have them, but I see no reason why mild steel would not work just as well.

The D-bit follows an existing hole direction very well, but it really needs a starter hole, drilled with a normal twist drill, to give it a start. Obviously it is important to get the direction of the starter hole right.

 

[funkyjedi]

Oh man. You just made my week. I could actually have this thing built in a day via that method. I have hope again! Thank you SO SO SO much for this! I have been walking circles in my garage cursing the knife making bug, but things are looking up. I will do exactly as you said and pin those rascals together. Lowes has mild steel rod in the right diameter, so I will pick some of those up and get it together.

I really do appreciate the reply. Thanks again!

 

[timgunn]

It's what the forum is for.

Please let us know how you get on and post some pics when it's done.

 

[funkyjedi]

Getting closer. Will be working on electronics next.