Drilling through concrete like refractory

[Whiskeymike]

I need to drill several 1/8” holes in refractory that sets in a very similar manner to Portland based concrete. The refractory block is 4”x8”x3”. Aggregate is very fine.

My plan is to use drill press with 1/8” masonry bit with a shop vac running. If the bit gets warm, I’ll start spraying water on it.

I have a hammer drill but I’m thinking the hammer action is likely to do more damage on such a small piece Thoughts?

I also saw Bosch masonry bits for impacts. Anyone tried an impact driver for this type of thing?

Any other advice on avoiding cracks?

 

[lukedwag]

I would use water from the start. Ideally you would use a diamond bit. https://troxellusa.com/cart.php?suggest=97b97dce-c65f-4250-8887-8c1c20fdbe27

 

[LXCam]

I’d suggest a diamond bit and water as well.

 

[Whiskeymike]

Thanks guys. They look hard to come by. I’ll check my local suppliers and see if they have something in stock.

 

[tim9lives]

Personally....I find hammer drills do a much better job at drilling in any masonry. Hardly ever worried about overheating with hammer drills. The cheap harbor freight sds works great and comes with a decent set of masonry bits. I’ve had two. First one died after going under flood waters after Katrina.
I bought a second one and have used it often since 2005. Really one of their better power tools in my opinion.
That said....even a DEWALT or Ridgid cordless with the hammer clutch does better than a regular masonry bit in a drill press in my opinion

 

[egdede]

Do not use a hammer bit on refractory. Some newer 'vibratory' systems might be ok (like on my Bsch SDS plus).

I just bought a bit like this at Lowes:

https://www.lowes.com/pd/Kobalt-Porcelain-Diamond-Drill-Bit/3534322

This link says unavailable on the web. The one I bought was Bosch, can't find on their website. It kicked ***. Leaned it at 45 degrees to start, and slowly stand it up. It drilled right through the ceramic tile like butter.

 

[LS6 Tommy]

Just out of curiosity, why do you need to drill through refractory?

Tommy

 

[Whiskeymike]

Just out of curiosity, why do you need to drill through refractory?

Tommy

Making a ribbon burner from Kastolite 30 for a naturally aspirated forge and underestimated the number of holes I needed for the fuel/air mixture I’m running. I’ve started making another plenum, but I’m hoping to experiment with more holes to reduce back pressure so I can dial in the final count.

 

[LS6 Tommy]

That sounds like a really neat project!

Tommy

 

[rlitman]

Do not use a hammer bit on refractory. Some newer 'vibratory' systems might be ok (like on my Bsch SDS plus)...

Wait, what? SDS hits much harder than any hammer drill out there.

I do agree that hammering will likely cause damage. As for the bit, the problem with ordinary carbide tipped masonry bits, whether standard hammer drill, or SDS style, is that the tip geometry is all wrong for non-hammer drilling.

Hammer bits have a negative rake angle on the tip. They just drag along on the surface until you start hammering with them, so in a drill press, they heat up more than they drill.

I'd suggest a carbide tipped "multi-material" bit like these Irwin bits, or the Bosch Daredevil bits, or this DeWalt option.

All of these carbide tipped bits that claim to also cut metal have a zero rake angle. Basically, the cutting edge is perpendicular to the surface, so it has a chance at lifting chips and cutting without a hammer action, unlike hammer bits.

 

[Varty Yo]

IT will be a light-mid weight castable you are drilling into. Use a small hammer drill and start drilling on the exposed side as it will tend to spawl when exiting. 100% masonry bit. Start slow on the trigger to get the hole started then sink it in. Im a refractory bricklayer for over 20 years. If it is a light weight castable (you can scratch some away with your finger) then a reg drill bit will work. Dont worry about adding water while drilling.

 

[velocipede]

Have a Harbor Freight nearby?
https://www.harborfreight.com/diamond-rotary-bit-set-4-pc-69664.html

 

[James-W]

I don't think a drill press is going to work very well. I have tried to drill concrete with a regular drill and I have to say, a hammer drill works a whole lot better.

 

[Whiskeymike]

Yep, I have HF. Problem with the diamond bits I’ve see are too short. Refractory is just shy of 4” thick. Masonry bits are working ok so. One snapped after about 20 holes, but I gotta keep them cooler. It seems higher speed is best

 

[dfiler2]

Just out of curiosity, are you using a hammer drill or the drill press?