Hard Coral
 

I am trying to drill through hard corals and neither concrete bit or high speed steel will touch it.....anyone drill really hard coral

Diamond drill bit?

https://www.homedepot.ca/en/home/p.5...000529505.html

A concrete bit will drill through it if you have it on have it on the hammer setting. If you don't want to risk cracking it you would want to use a diamond bit as stated above. What type of coral are you drilling and what size is the hole?

used diamond bit, masonry bit wouldn't touch it, thanks for the replies

You're drilling coral or rock?

drilling very hard coral, some of it is softer!

Like Tyfigher said, concrete/masonry bits will work but they need to be used in a hammer drill on the 'hammer drill setting'. The size/brand/quality/condition of the bit and drill makes a difference too. They are however pretty rough/violent and wouldn't be my first choice.

There are bits for drilling through tile as well as diamond coring bits which have already been mentioned.

There are bits for drilling through tile as well as diamond coring bits which have already been mentioned.

This is what I've used

Try using a diamond grit tile coring bit, they go as small as 1/4” basically the same bit for drilling bulkheads in our tanks except tiny diameter-wise. Should do the trick just remember to flush the hole with water to keep the core clear and the bit cool.

Edit: methodology of drilling is important. Lubricating the “cut” as well as keeping the drill bit cool. High speed, low feed or low speed high feed. Feed rate = amount of pressure you apply during the cut. If you have tried this already then I guess check geology websites that may have some insights we don’t have.. I’ve seen core samples that have been taken from granite that use a diamond cobalt coring bit and they use a lot of drilling fluid. Try Rapid-Tap, you can get it from Acklands-Grainger

Try using a diamond drill
LOL