Have a stone countertop. The opening for the lav sink is already cut out. The lav sink
is an undermount which requires 4 – 3/8″ dia 1/2″ deep holes for female threaded
metal plugs which will be epoxied into the holes. The threaded plugs will then
support the clips which in turn will support the sink under the top.
I do not want to use a hammer drill for fear of damaging the stone. Because of the
weight of the countertop these holes will have to drilled with a hand drill.
The stone is very hard – not marble like – more like granite. My Google searches lead
me to think that I need a diamond drill bit using water as a lubricant.
I have to get this sink operational within the next 2 days or so.
Any help would be appreciated.
Chuck
Replies
Chuck: You are right about a diamond drill. The stone is probably 30mm thick, so it is a non-trivial problem! Also, you are drilling a hole w/ a blind bottom. Carbide just won't cut it! (Pun intended.) Are these holes in the underside of the stone? That will be even more fun. Considering the cost to replace it when (Not if) it breaks using a hammer drill leads you to a diamond bit. These drills are core bits - cutting a ring around a core that remains behind - just like a hole saw for wood. The core will snap off very easily. I drill such sized holes in stone all the time. You must be very careful not to tilt the bit out of the perpendicular plane while drilling or it will bind up and ruin the bit. Also, you really need water fed through the center of the bit to cool it - especially if you have to drill upside down. You can buy the bits from Sommer & Maca on the web. Cost about $30 each. If you spring for the special chuck that center feeds water, it's another $90, roughly. These things are designed for use in a drill press, but given the guts and necessity, they can be handled in a large electric half inch chuck drill. It gores without saying - use a GFCI. You have to run it at about 1000 RPM for near optimum cutting. You have to apply gentle pressure in pulses lasting a few seconds at a time to cut then allow the water to clear out the swarf, otherwise you clog the "Pores" in the bit and it won't cut. Press too hard and you destroy the plated diamond coating that does the cutting. It is a stretch to hope you can get the bits/etc in a day. Don't know where you live, but S&M only has about 4 sites where they stock the items. Also might check out CR Lawrence, also on the web. They sell core bits, too. Also Hard Rock Tool. Any good full service stone fabricating tool supply house should have what you need. Not cheap, by any stretch. Oh, yes, how to break off the core: Use a narrow screwdriver that will be a force fit into the kerf. Just gently tap it in, and it will crack off the core fairly close to the bottom. If it leves a stump, sacrifice a small steel chisel to chip it out - doesn't take much to take it off. Also, plan on drilling a bit deeper to allow for a short stump in the bottom of the hole. If I can help more, let me know.
Don Reinhard
Don,
Thanks a lot for your very informative reply. These holes will be on the underside of the stone, but the top is not yet installed on a cabinet so all I have to do is flip it over. Think I'll rig an open top table with a shallow plastic mortar tub beneath to catch most of the water.
Also thinking of using a variable speed plunge router, but have to check the different rpm settings first.
It's amazing to think I could get such a detailed reply within 2 hours of asking the question.
Thanks again,
Chuck
Woodbury, CT
"Also thinking of using a variable speed plunge router,"
Chuck,
I don't think you want to go that route.They spin WAY too fast. Diamond tipped hole saw at like 100RPM with a good water bath is the way to go. If your not in a rush AND it's a one shot deal, HF sells some cheap diamond hole saws. Won't last too long, but @ $10 a pop, they do the job.
Jon
roger that
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Hi,
I've had to do similar work were the bit needs lubrication. I made a little rim out of plumbers putty around the hole and filled it with water. You can go as deep as you want or as high rimmed I should say. Makes a messy job managable. Has the benefit of always being flooded and if you use enough water will last the job. Cleans up easy of course too.
Good luck,
Warren
Thanks for an excellent tip.
And thanks to all who replied. I really appreciate it.
Chuck
Woodbury, CT
Just had three ceramic and two stainless sinks installed on the job last week by the guys who supplied the granite counters. They tossed the anchors and clips that came with the sinks and used silicone .Their work is garanteed and looks great .
..........Rik...........
"Just had three ceramic and two stainless sinks installed on the job last week by the guys who supplied the granite counters. They tossed the anchors and clips that came with the sinks and used silicone .Their work is guaranteed and looks great ."
Mine was installed the same way, the flanges on the right and left ends of the sink met up with the edges of the cabinets, Silicone has held the rest. I was uncomfortable with it to start but seems to have held the test of time. I had to hand it over to the countertop guys, they assured it would be just fine, I argued but they won me over. So far they are right......
I don't do stone slabs......
Ever try to pull the diff cover off your truck, after you take the bolts out the only thing holding it on is the silicone, still takes a whack from the hammer and splitter.
Chuck, two days is a problem if you have to mailorder a bit.
Is there a Harbor Freight anywhere in your area?
Believe it or not, they sell little diamond core bits that work great. For 4 holes you can do it for about $5.
I bought every diamond bit they had in the catalog & spent about $30 with the postage. You won't drill 100 holes with them, but they do work.
And you will also get 50 pounds of catalogs after your order.
http://order.harborfreight.com/EasyAsk/harborfreight/results.jsp?ts=Sun%20Jun%2013%2012:05:34%20PDT%202004
Joe H
Edited 6/13/2004 3:05 pm ET by JoeH
Chuck,
forget about the cheezy clips that come with the sink, they will never fail to let you down. get ahold of a granite fabricatiors supply near you. ( keystone , stone boss, check the web for a locaiton near you ), pick up an epoxy that they recomend for this application and also get a " sink setter " it is a brace that goes on the cabinet before installaiton, it has some thumb screws that will allow you to screw it up to support the sink.
now set the sink setter ( they are about $20, cheaper than the diamond core bit ), put in the sink on it and set the counter on top, check for fit. when you have it how you like it draw a line around the bottom edge of the sink. remove , flip the counter upside down, apply a thin bead of the epoxy to the sink flange ( staying away from the edge that will show ), set the sink within the line you drew and wait for the whole mess to cure, then complete installation.
you can leave the sink setter installed to provide additional support ( i do ) but keystone insists that the epoxy will hold for life, i am a belt and suspender type guy so ...... you get the idea.
i suppose you could even leave out the epoxy and just use the sink setter and caulk, your choice.
james
Chuck
I've had success with a standard carbide drill bit and a hand drill at very low speed WITHOUT the hammer. Just sorta grinds its way in. I usually touch up the carbide with a diamond hone to get a V edge on the carbide.
However, I second the epoxy route. One thing to check if you drill for the plugs — is the granite top thick enough to support the hole?