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Author Topic: Drilling holes in stone freehand with plated bits and a 18,000 RPM Foredom  (Read 1185 times)

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Redrummd

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I took time to write this as a response to a question about drilling cabs for mountings, so I thought I should post it here and get it "stickied".  It is the lowest cost method for drilling stone and also the fastest way but it does require mastering the technique.  I do not recommend using a drill press.  It costs too much, takes too much time and gives most a worse result (blow outs) than learning to drill by hand from both sides of the stone.

I use an 18,000 rpm Foredom that is reversible and with a variable speed foot pedal.  For most stone I run it at about 1/3 to 1/2 speed.

The basic set up is a shoplight, a small plastic container for water; a 6 inch long 3/4 by 3/4 inch piece of hardwood; a kitchen counter size towel; and 1mm, 2mm and 3mm diamond plated drill bits.  I fold the towel in half, put the water right behind the towel and the hardwood block about an inch in front of the water container. As I am left handed,  I put the shoplight in position to light from the right side for the drilling spot on the hardwood used for backing of the cab.

I hold the piece I am drilling in my right hand at an angle that puts the spot I expect the bit to come through on the hardwood.  I start the drill spot on both sides of the cab and drill from both sides, starting with a 1mm bit.  I did the piece in water about once a minute and flip it over each time.  I drill slightly down from the point where I expect to be the top of the hole as it takes time to learn how to drill freehand and straight and it is better to have both sides meet just a bit low than a bit high. 

After doing this a few dozen times I got to the point I could drill from both sides of a piece about 1/2 inch thick and hit in the middle with just the 1mm bits.

Once you have a 1mm+ hole, open it up with the 2mm and if needed, the 3mm if you want a bigger hole.

I then use a 4mm round ball bit to clean up the edges of the drilled hole.  I drill the pieces after sanding to 600 grit as occasionally you will slip and the 1mm bit will leave a pretty good tail that usually will be fairly quickly removed by going back to the 600 grit wheel.

I RECOMMEND DOING THE FIRST FEW DOZEN HOLES IN A SOFTER STONE!  A good hard agate can take up to 30 minutes to drill through a 1/4 inch thick piece!

Buy the cheap plated bits on Amazon.com and use a aluminum oxide dressing stick to clean the bits and to see if they are still drilling.  If you see black mud the bit is toast.  Some of the cheap bits die in seconds and others will drill many holes as quality control in China is not so good!  Reverse the direction of the Foredom every few minutes of drilling if you have a good bit and it will last longer.

You use a very slight circular motion and a few pounds of pressure on the bits.  The circular motion is needed or the few diamonds on the tip will create a circle pattern and simply stop removing material - another reason to pass on the drill press.  When using a 1mm bit the top of the hole will be about 1.5 to 1.7 mm across due to the circular motion.  You can also go in a back and forth linear (or up and down) line to get the same effect which is better if you need a 2mm + hole size and drilling goes faster too.


I should note that the 1mm bits occasionally break very unexpectedly and will scare the ----- out of you.  I have occasionally required a bandaid after I also ran the broken bit into me too.

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Redrummd

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Re: Drilling holes in stone freehand with plated bits and a 18,000 RPM Foredom
« Reply #1 on: November 16, 2016, 07:10:15 PM »

Part two - Space left in case I want to add more information or photos later.

montanajohn

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Thank you for your replies.  I was hoping there was a faster way, or an automatic way so I could find something less boring to do while it drills.  Some of these "to big to set" agate cabs sure look nice hanging in my windows but 30 minutes of drilling time is a big price to pay
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