Help: Need to drill hole in 1 inch slate pieces

[mannyrock]

 
Dear Guys,
 
   I am an experienced carpenter and do lots of remodeling work.  I am building a set of walls across a large slate walkway (8ft by 16ft) that connects a free standing brick garage and a brick house.  I am also building a roof over it.
 
  I have a large hammer drill, and am very experienced at drilliing holes in concrete and brickwork.
 
  But I have a problem here I have never confronted.  The walkway is tiled with very large pieces of 1 inch thick slate, which is very soft.  Underneath it, there may just be thin set on top of fill.    When I build the framing for the walls, I will need to bolt the bottom plates of the walls down onto the slate.  If it were concrete, I would just drill 3/4 inch holes in it, drop in the metal lag bolt shields, and use half inch lag bolts to bolt the walls in place.
 
   But I understand that slate is very very soft, and will disintegrate if you use a large masonary bit and a hammer drill.
 
   I need some advice please from someone you has actually drilled round holes into soft slate blocks of tile.  I don't necessarily have to but huge bolts down into it, as I am just anchoring the bottom of the wall.  Half inch or 5/8ths inch bolts would probably do fine.
 
  But, how do I drill these holes?    Maybe a brand new 5/8ths masonry bit, keeping it wet all of the time, and drilling on a regular drill setting (not hammer) really really slowly?
 
   Or, maybe I buy a really expensive titanium high speed metal bit, and keeping it totally wet, drill at a really slow speed?  (I only have to drill about 8 holes, and don't care if I ruin the bit.)
 
  Thanks for all advice.
 
Mannyrock
 
   

[Old Syko]

Use a diamond hole saw in a standard 1/2" drill.  A 1" cup in standard length will run you 20 to $25 at Home Depot, Lowes, or your local tool supply.  Deeper cups are of course more money.  You should already have an arbor.  They make short work of tile, stone, slate and just about anything else you can find.

[52bagman]

You can also use the smaller masonry bits used for tapcons, 1/4" to start and work your way up to larger bits. Be gentle.

[Old Syko]

You can also use the smaller masonry bits used for tapcons, 1/4" to start and work your way up to larger bits. Be gentle.

Slate tends to shatter like glass if you try to use carbide masonry bits.  Even to use a hole saw you need to use a diamond guide bit. 

[superd]

  a hammer drill or hole saw will bust it up. our large local tile supply houses carry a bit that looks very much like a hole saw without the center guide bit. that in a conventional drill and water will do the trick, but do not try to go fast

[Old Syko]

  a hammer drill or hole saw will bust it up. our large local tile supply houses carry a bit that looks very much like a hole saw without the center guide bit. that in a conventional drill and water will do the trick, but do not try to go fast

The cutter your're describing is to be used only in a core drill.  Without a way to hold the drill in place as with a core drill they are useless as their is no way to keep it from walking.  This is why you use a diamond center bit with a hole saw and a hand drill.  Hole saw cups and core drill cutters are basically the same tool.

[mannyrock]

 
Guys,
 
   Thanks for all of the great advice.  Syko sounds like he's done this alot.
 
   Skyo, I apologize but I am lost.  You have mentioned alot of separate bits and rigs.
 
   Would it be possible for you to  list, in simple terms, exactly what I need to buy, piece by piece, so that I could hand the list to someone at an  appropriate store and get them all?

   I currently own a 3/8s battery powered drill, and a 1/2 inch hammer drill.  I don't own any type of circular hole saw, though all of the ones I have used in the past were for cutting holes in wood.
 
  Thanks again.
 
Manny

[Old Syko]

Mannyrock if you only need to drill a handful of holes I'd use a hand drill with a diamond hole saw.  You'll need an arbor compatible to the brand of hole saw you choose.  The same hole saw you use to cut wood works fine as long as you get a diamond cup to match it.  I use mostly Greenlee but places like Home Depot and Lowes have items that do the same thing and some are interchangeable with other brands.  As an example Home Depot's Rigid brand has a hole saw arbor, diamond cup and 1/4" diamond guide bit available that will do the job.  These 3 items along with your drill (not a hammer drill) and a water hose to keep things wet will work. 


If you have a bunch of holes to cut you may want to rent a core drill and cutter of appropriate size for a half or full day to do the job.  [size=78%]Not trying to be a jerk but a core drill is basically a drill press that uses  air pressure to form a [/size][size=78%]vacuum to hold the drill in place while you drill.  It also has an attachment to which you attach a hose to supply water to allow you to cut.  Not a cheap machine to purchase, but if you have a lot of stone or concrete to drill you can't do without it no matter if you purchase or rent.[/size][size=78%]  [/size]

     

[mannyrock]

 
   Syko,
 
     Thanks so very much.   I only have about 8 holes to drill.  I will go to Lowe's and buy it all of the things you have listed.
 
    Last issue.  I will need to sink lag screws down into these holes, to hold down the bottom plate of the wall.  There is no danger that the wall will be pulled upward against the screws, as the sides of the wall will be bolted against the brick walls that are being enclosed, and a large amount of weight from the double rafters and roof will be sitting on top of the wall.
 
    The main purpose of the bolts into the bottom plate is to keep the wall from sliding back or forth.
 
    Normally, with concrete, I would just put lag guards in the holes and screw the lag screws into them.  But, in this instance, the slate is only one inch thick, and there is only thinset and loose fill underneath.
 
    Should I put anchor cement plus lag shields in the holes before I screw down the bottom plate?

    Should I just put in lage shields alone?
 
    Should I forget about shields, fill the holes to the top with anchor cement, and then screw the screws down into it to hold the plate?
 
  Thanks for all advice.
 
Mannyrock

[Old Syko]

1" slate above loose fill isn't going to support the weight you're talking about without breaking up in a short amount of time.  I'd suggest you take up the slate and pour a footer.  If you live in an area that requires you comply to proper building codes you could be getting yourself into something you don't want to get into.  Drilling holes in slate is one thing but structural design and building codes are something of a different animal and code varies depending on location.

[superd]

  BTW Syko I have used the bit I spoke of when used in hand drill it will not walk and it was made for cutting tile not to be used in a core drill

[mannyrock]

 
 
Syko,
 
    Thanks for the warning about the weight on the slate. 
 
    In order to take care of this issue, I have bolted a six by six post to the brick wall on each end of the space where the wall will go.  The posts are each held into the walls with six 1/2 lag bolts.  The wall will run between them.
 
   On TOP of the posts, I am placing a beam, made of three 2x8s bolted together upright, to form the "top plate" of the wall.  In effect, this is an 8 ft long header, and it is capable of supporting more than 1,000 pounds.
 
   The rafters of the roof (which will only be six foot long spans of 2x6) will sit perdendicularly across the top of the beam, and will each be notched to sit flat on the beam.
 
   So, the only weight that will be on the slate itself will be the bottom plate, and the weight of the upright studs, which themselves will be firmly attached at the top to the underside of the beam.  The sheathing for the two sides of the wall will be 3/4 inch T-111.
 
   I know that there is no gurantee about the slate, but the amount of weight on it will be prettly low, especially when the lumber dries out, and will be spread evenly upon it by the bottom plate.
 
   Thanks again, Manny