Cutting a partial hole in a board question


I have a brick wall, about a 1/2 foot high, that used to surround a playset that got burned down. The brick wall had 2x10 boards on the top of the wall that created a ledge.
There's metal bolts in the brick to hold the board down. In the current burnt boards, the person that built it put a "sink", for lack of better terminology where each bolt was located. IOW, a round hole was cut in the board at each bolt location that went about 1 inch deep. I guess this was done with a hole saw.
Let's say the holes were 2 inches in diameter, cut 1 inch deep, then the next inch drilled creating a hole the bolt can slip thru. When I tighten the bolt, the bolt will rest at the bottom of the 2 inch hole cut I made.
If I cut a circle in the board and cut 1 inch down, how do I get that piece out of the board? Do I use a chisle? Or do hole saws permit me to create a "sink" that won't go thru the entire board?
Thanks for any advice you can provide.
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More than likely the former was done w/ a spade bit, but a Forstner would provide a "cleaner" hole. A holesaw is a possibility, but at least third down the list of choices.
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wrote:

They sell 2" spade bits? Never seen one that big. Back when I did summer labor building outdoor stuff, the auger they used for the threaded rod holes had a wing thing at the proper depth to make the countersink. Didn't think much about it at the time- probably a trade specialty item, rather than big-box.
aem sends...
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Some drills have an adjustable stop, which you set for the depth you want the bit to go. If you drill half way through a board with a hole saw, you can usually just pop the slug out with a screwdriver

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I'm betting that the hole that holds the head of the bolt below surface level is *not* 2". Most builders of these sets use spade bits - cheaper than Forstners and adequate for the task - and most bolt heads probably don't exceed 1". Determine the bolt that you will use and carry it over to the bits and choose one that is just slightly bigger than the bolt head. If you are using a washer under the bolt head (a good idea if the chosen bolt is hex head as opposed to carriage) the bit will have to be big enough for the washer size. Be sure you drill the large hole first to a depth slightly deeper than the bolt head (+ washer, if used). Then, drill the bolt hole through. Go slowly, and when you see the tip of the spade bit just barely poking through pull the drill out and insert the tip through this little hole and finish the hole. This will prevent tear-out or splintering as the bit exits the wood. Oh yes, use galvanized hardware which is rust resistance. Good luck on your project.
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The hole you are talking about is a 'countersunk hole' so the bolt head won't stick out above the lumber surface. Drill the countersink first then finish with the 'bolt size' bit.
The common tool used is a spade bit, just a flat chunk of meteal sharped to cut with a point in the middle and a rod up to go in the drill. The most common brand is "Speedbore" Just ask for that at the store. I don't know how big they make them but I know I have a 1 1/4" and think I have a 1 1/2". Unlikely that you would need one anywhere near 2". What is needed is one big enough to clear any washer you use plus make sure that a socket for those bolts will fit down in there.
Harry K
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