I have (an old skip dive) enough lightweight insulating and hard zirconia firebrick battens (around 19 inches / 500mm long) to line (I think) a fairly sizeable furnace, but the logical approach seems to be to cut a slight angle on two of the long faces, much like barrel staves (giving a trapezium cross-section, 50mm deep, 50mm wide tapering to e.g. 46-47mm on the hot side - still need to do the jommetry) - I'm unsure how to go about this! My thought is to use a diamond blade in my radial arm saw with the head in in-rip position and canted slightly and run the firebricks through, perhaps with a vertical "featherboard" to prevent them lifting from the table - does someone With A Clue think it'll be necessary to cool the blade with a flow of water? I have a lathe coolant pump spare, can swap the RAS table for something waterproof with a catch pan beneath, and the RAS motor is a fully-sealed TEFC unit. With luck the water would control the dust... Any simpler, easier way would be good. Next question: I'll have to cut through either several battens once assembled and in the shell, or one of the few larger slabs, to allow the tuyere to enter - any solutions? I can mig a short section of tube onto the outside of the shell (and plasma cut the hole in the shell!), to act as a guide, but a carbide or diamond holesaw seems the only realistic way... Any suggestions? Advice, critical laughter, and warnings received gratefully! Dave H. (the other one)
What size furnace are you after? The above figures seem to roughly indicate a 'jommetry' of 24 battens and 300mm ID at 50mm deep x 50mm base x 39mm short side. I used a wet tile saw to cut a couple hard firebricks, might be worth a day's hire/rent so as not to mess up radial arm saw. Radial arm blade speed would be far greater than a normal wet saw blade I think. PS the 39mm might need to be 37-38mm to allow for mortar, please check math for your own purposes...
I agree with Tops. Also for dust control and quality of cut. Depending upon their density, you may need to dry them out somewhat gently until you drive off most of the water. If you are going to mortar them together, wetted surfaces can be beneficial for bonding and working time. If you use mortar, be sure to allow some thickness for the joints in your sizing. It adds up over a large number of joints. How many KGs of dense fire brick will that be? As the furnaces becomes more massive, heat times can become quite long. Best, Kelly
Thanks all, very helpful! I did the jommetry and it'll be 36 of the lightweight bricks, 30 of the hard facing (ignoring mortar), so cheek angles of 5 and 6 degrees (to fit a cut down oildrum) - the tile cutters at my local hire place only have 90 and 45 degree blade positions, the man onthe phone tells me! The RAS I can set to what I like... Pretty sure it wouldn't suffer too much, it's had a hard life already! What's a typical mortar joint thickness? Other than "depends how good the fit" - is there a minimum for it to hold itself together? Re the heat capacity of the hard facing, would I be better halving the thickness to 25mm (allowing for saw kerf, 23.5 or so)? I could I guess take a first pass and end up with twice the battens! That would also leave enough for another project or two... Thanks again, Dave H. (the other one)
You can make a little fixture to hold the brick/stock at the desired angle of cut and leave the blade set at 90 degrees/vertical. Probably most dependent upon how thick you mix the mortar and whether you slide the bricks to smear/shear the joint. I'd say 1/32 to 1/16" . Experiment on a smaple piece and measure. Might be wise to build one layer, inner or outer, measure, and adjust when you cut the next layer IMO yes. I think 1" is plenty for the hot face, especially if backed by IFB. Best, Kelly
Kelly beat me to it! I was also told to make refractory mortar joins thin, not like brickwork on a building. I was thinking of a sled on the tile saw too. You'd probably want the sled to have a vertical piece that slided on fence of saw, I just drew the angled bottom.
Zirconia brick is some serious stuff. Bet that will be blinding white in operation. you’ll have to use diamond. Carbide also gets wrecked.
Agreed, I have a diamond blade I purchased from AldiLidl (they have some interesting stuff now and then! - like plasma cutters for £80 (=$100)) that'll fit the RAS nicely and the essentials for water-cooling the blade All I need now is some space to set up in... And time not being taken up with my homebrew TIG torch cooler, motorbike, car, damn it, you name it! Dave H. (the other one)
