Drilling insulated firebrick

jwmelvin

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I'm working on some forge projects and I'd like to drill some insulated firebrick. It is very soft, porous material made primary of silica and alumina (see info here). Thus it is abrasive but cracks very easily. I do not need much precision on the holes, but it will be a large number of high aspect-ratio holes. Say about 100 holes, 1/8" diameter, 2.5" deep.

I'm guessing that a masonry bit is the best approach, and that clearing dust out will be key. I will not be doing this on my mill, I'll use a drill press and will have a shop vac running. I was wondering about using some sort of spade bit, even a shop-made one, just because the material is so soft. Any thoughts on best approach? With so many holes, I really want to avoid cracking the brick on my 87th hole or so. I will do some experiments but figure it's worth asking your collective wisdom.
 
This kind of brick is just too friable for this kind of work. It sounds like you are trying to make a ribbon burner. Maybe just try a few experiments the more standard way?
 
Yes, making a ribbon burner. I will try casting one too but some people have reported success drilling so I figured it was worth a shot if I could optimize my approach.
 
Because of the small diameter,m a carbide twist drill might be a better choice. If using a masonry bit, I would dress the cutting edges. The masonry bits that I have used have all had blunt edges out of the package and tended to bull their way through rather than cutting.
 
This brick is really soft. Any drill will cut this stuff. You don't need an impact or hammer drill like you would for regular brick. I would experiment with several kinds or bits and see what gives the cleanest hole. You could even make a bit like a D type bit by just sharpening a rod. You could toughen the brick after shaping it by coating it with ITC 100.
Robert
 
I've used these type with good success on the softer ceramic and brick materials. They tend to be sharper than the standard masonry style of bit, so less pressure needed.

-frank


292873
 
Thank you all, I will report back after I get a chance to try a few things.
 
I replaced the soft firebrick in my small Paragon furnace a while ago, and it was very quick and easy. Used a diy t-shaped bit (cut down from a spade bit) so the heating element could be retained in the wall without staples same as the original was. Definitely use a shop vac or you will be sorry. Finished job as good as original with no cracking. Try this company for inexpensive soft firebrick. It's first rate. http://refwest.com/z-239straight9x45x252300fifb.aspx
 
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