[TowerTalk] Concrete drill bit?

[K7LXC at aol.com]

Howdy, TowerTalkians --
 
    I've added anchor bolts to existing concrete bases  many times and 
historically have rented a roto-hammer and bit. It wasn't a  concrete drill bit 
but it was sort of a concrete coring bit. But instead of  being hollow, 
there was an inverted dome in the middle just above the cutting  blade. 
Apparently what the dome did was to pulverize the concrete as you drilled  down. It 
would cut thru rebar with no problem and was perfect for the job. 
 
    Now I have to do the same thing and nobody around  here (the PNW) has 
even heard of the bit - including the Hilti  distributor. Can someone tell me 
what this bit was? It makes the job so easy.  Since we couldn't find the 
aforementioned bit, we spent a lot of money on  different bits and drills 
before we gave up and had a professional concrete  coring company stop by. He 
used a hollow concrete coring bit and just broke off  the stuff in the hole. 
Worked FB but I'd still like to know what I'm missing as  far as the bit I've 
used before. Tnx.
 
Cheers,
Steve    K7LXC