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[nwbeachrocker]

Hello,
I'm looking to drill some holes in agate and other rock.  I have seen some examples of cabs on this site with some clean holes, nice beveled edge and all.  I recall seeing a few that Gergis had done.  Any recommendations on the best type/brand/source for drill bits for this?  I've been using some cheap harbor freight diamond coated bits, but would like to invest in something decent.  Cheers

[lithicbeads]

Any sintered bit works well if well lubricated and a light touch is used.

[peruano]

The person who said any sintered bit knows his stuff, so there's your answer.  I believe my bits always come from lasco, and while I have broken my share of stones in the drilling process, its a matter of a light touch, patience, a new bit when appropriate, and practice.  I use a Dremel drill press attachment but many small lapidary drills will work as well.  There is a tapered bit that can be used to flare the hole superficially,.   And of course don't allow that stone to slip in the process.  I nest mine on a layer of thick cardboard that when soaked with water does allow the stone to nestle securely, and provides a bit of gap so I don't drill through to the bottom of the container holding the water coolant.  Drill away with confidence, but practice on some slabs before you do your best and final produced cab. 

[gemfeller]

Maybe I'm behind the times but all my diamond bits from Lasco are plated.  I don't think they supply sintered bits unless it's something new.

Several companies offer sintered tools including Badger, Mountain Mist, Kingsley North, Diamond Pacific, Gesswein, etc.  I'm not sure how cost-effective they are compared to the cheap Chinese plated bits.  If you're careful and aren't doing production work you can make quite a few holes with the disposable cheap ones.

[nwbeachrocker]

Great info, thanks.  Are we talking about solid shank or core drills here?

[gemfeller]

My reply concerned solid bits,  except for Badger (both).  Just Google "sintered diamond core drill bits" and you'll get lots of hits.