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Author Topic: Drilling small holes in stone with a standard drill press  (Read 1863 times)

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cobbledstones

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Drilling small holes in stone with a standard drill press
« on: June 30, 2016, 09:00:52 PM »

This is intended to be an introduction into stone drilling for the purpose of bead making.  Larger core drilling with sintered bits and a water swivel is not covered, but is discussed here.  For an introduction into ultrasonic drilling check here.  Also, what follows is just a collection of my experiences from drilling holed in rock. If you have any tips or comments, I would love to see them in this thread.


Part 1: Hardware

Bits come is a variety of configurations and sizes. Some examples are shown in the picture below.  If all other factors are equal, the speed of drilling is influenced by the grit on the bit, the speed of the slowest moving grinding surface, and the total amount of material that must be removed.  Most bits below 3mm in diameter will be solid core bits (far right). These remove the entire core through grinding action and have a very slow moving grinding surface at their center.  What this means is that they tend to drill slowly unless you have a drill press with a high RPM setting.  If you are new to drilling, and only have a standard drill press, avoid this type for now.  They are better suited for foredom or dremmel tools. Standard core drills (left) are available from 3mm diameter and larger.  The cheapest bits have a rim of plated diamonds that is about 1mm thick.  Core bits drill much faster than their solid core cousins.  If you want to give stone drilling a try, pick up a pack of these.  They cost less than a buck a piece on ebay direct from China.   Thin walled core bits (center) drill even faster because they only have to remove a tiny bit of stone material.  They cost more, and require a lighter touch that comes with experience.


Just remember that drill bits are consumable goods.  Even with good care, all bits of this type have a short lifespan.  I buy them in 100 packs.  Yes, I buy the cheapest bits possible on Ebay direct from China.  I have tried more expensive, and don’t see the savings.  I get about 1-2” of hole depth per bit.  Your mileage may vary. 

The drill press is a versatile and inexpensive tool.  Any bench top or larger unit can suffice for stone drilling applications.  What you want to look for is a unit that has some kind of RPM control.  The easier it is to change the RPM the better.  Seriously, get friendly with those belts of you have them.  Then check the unit for runout. You want the drill bit to turn with no wobble whatsoever.  Cheaper units tend to have more runout. Avoid these units if at all possible.  A quick bit change is a nice bonus feature if you find it.  I use an old craftsman benchtop unit that I bought from a garage sale.

The biggest thing to learn about the drill press is that it can apply a huge amount of downward force.  If you are new to stone drilling, take a bathroom scale and place it below the chuck (no bit in the chuck).   Then, apply varying degrees of pressure to the scale.  Learn what it feels like to apply 10lbs, 20lbs, 50lbs, 100lbs.  It is amazingly easy to reach the 100lb mark because of the mechanical advantage in the press.  Learn what a light touch actually feels like.  The easiest way to prematurely burn up a drill bit is to apply too much pressure. 

All drilling operations will take place underwater in a flat bottomed vessel.  The purpose is 2 fold: to control dust, and to help remove heat generated from the drilling operation.  A flat bottomed container is best because it makes the full contact with the table of the press and won’t flex when you start to apply pressure to the bit.  This allows greater control and precision.  The container doesn’t need to be very deep, just enough to cover the stone in question by ½” or so. 
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cobbledstones

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Re: Drilling small holes in stone with a standard drill press
« Reply #1 on: June 30, 2016, 09:05:13 PM »

Part 2 Stone Preparation

Ok, we have a drill, and we have some drill bits, let’s talk about stone.  The rough shape of most stones is not conducive to the drill press.  Remember, we are applying a downward force on an object sitting on a flat surface.  Any tilting or wobbling of the stone during drilling can lead to the bit catching and breaking or the stone cracking, or a plain old ugly hole.  This means that the cleanest holes will be drilled in material that sits flat on the table.  You can get a flat rock in 2 ways, either cut the rock so it’s flat, or add something to the bottom of the rock to make it flat.  Sand free tile grout is particularly effective for this application.  Rio Grande sells a moldable plastic for this purpose, but I never bothered to try it.  For most stones of lapidary quality, I just cut thick slabs or cubes.



They are the easiest to work with little hassle.  For small or valuable material where I want to preserve every gram, I encase the stone in tile grout and let set overnight.  Ice cube trays work well as molds for small stones.

If you are using slabs, remember to remove the little nib leftover from the saw’s operation so that the slab lays flat. Note the grind marks on the upper edge of this slab where I removed the protruding portion

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cobbledstones

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Re: Drilling small holes in stone with a standard drill press
« Reply #2 on: June 30, 2016, 09:28:03 PM »

part 3: drilling action, use personal protective gear when drilling...ear plugs, safety glasses etc.

Now is the time to talk about heat.  Heat is the enemy.  Heat destroys the cladding that holds diamonds onto the drill bit.  Heat will destroy the cladding faster than the stone wears out the diamonds.  If enough heat is generated, the stone can crack or the bit can expand and get lodged in the partially drilled hole.  Everything you do in the drilling operation is to slow the buildup of heat and help remove waste heat from stone and bit.  The cooler everything is kept the longer your bits will last and the faster the drilling progress

Some things to keep in mind: more RPM=more heat, more pressure=more heat, deeper hole=slower heat removal
In general, use the coldest water your fingers can stand in your water pan.  If you are drilling a heat sensitive material, put it in the freezer overnight to get a head start on the heat (no I am not kidding)


The tips above are only stopgap measures to help with initial heat buildup.  The real heat control is in the RPMs, the applied pressure and the cleanout rhythm. 

RPMs.  The numbers below come from my personal experience.  If you are burning up bits quickly, try a lower RPM setting or a lighter touch or both
1mm-->9000 RPM
2mm-->4500 RPM
3mm-->3000 RPM
4mm-->2250 RPM
10mm-->900 RPM
Don’t worry if you don’t have the exact setting, just try to get close.  Remember the bigger the diameter, the slower the RPM.

Pressure…Remember the bathroom scale? Try to use less than 20lbs, lighter is better.  Let the bit do the work.

Cleanout rhythm…you will get a feel for this.  I watch the swirl of dust that appears during the drilling action and listen to the noise that I hear to tell me when to raise the bit so that it can cool in the cold water bath.
First contact

Starting to dig in

Good cutting action

 
Time to lift the bit and have it cool


This whole process should take only a few seconds.  Let the bit spin in open water for a few seconds then reengage and repeat. If the ‘smoke’ coming out of the hole turns black, stop the operation and check the bit.  It is likely that the cladding is starting to fail or has failed.  Swap bits and continue.  You don’t want large chunks of cladding coming off in the hole as they are nearly impossible to get out and the piece will be ruined.

Use your ears as well as your eyes during the drilling process.  You should hear a distinctive grinding sound.  Increase the pressure and the pitch changes.  Learn the noise your system makes when the drilling is good.

still to come, drilling deep
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mirkaba

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Re: Drilling small holes in stone with a standard drill press
« Reply #3 on: July 01, 2016, 09:54:30 AM »

Nice presentation. I have always shied away from drilling but when needs be have gotten it done with the cheap plated Chinese bits. I have an order for lots of ear rings (cringe) and have ordered some 1.4 mm triple ripple bits. Looking forward to see how fast I destroy them. :)
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lithicbeads

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Re: Drilling small holes in stone with a standard drill press
« Reply #4 on: July 01, 2016, 11:46:43 AM »

Very nice , thank you.
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johnjsgems

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Re: Drilling small holes in stone with a standard drill press
« Reply #5 on: July 01, 2016, 12:18:10 PM »

Excellent tutorial.  If you want to do the really small jewelry bits you need a chuck that closes to zero.  I used to sell bench top "mini drill presses" that were around $100. Kingsley had same ones.  They had a small chuck and worked well.  Very precise and quiet.  Much better than Dremel.  I also used to run into a tool guy at shows that sold Dremel accessories (might have "fallen off truck").  He sold the keyless chuck for Dremel along with a stem that I think was a part of the flex shaft connector.  The two parts together made a great adapter to chuck up in a standard drill press for the tiny wire drills.  Wish I would have bought more when I could.   
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cobbledstones

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Re: Drilling small holes in stone with a standard drill press
« Reply #6 on: July 01, 2016, 02:30:20 PM »

Nice presentation. I have always shied away from drilling but when needs be have gotten it done with the cheap plated Chinese bits. I have an order for lots of ear rings (cringe) and have ordered some 1.4 mm triple ripple bits. Looking forward to see how fast I destroy them. :)

good luck with your order, if you are only drilling through thin slabs, a hole can be achieved in short order.  Report back on the triple ripple bits it you get the chance.   I haven't had the chance to try them.
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kenefick

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Re: Drilling small holes in stone with a standard drill press
« Reply #7 on: July 01, 2016, 03:11:49 PM »

I'm not a "production driller", but do drill quite a few for pendants and earrings.  The triple ripple bits do seem to last longer (more holes per bit) than the cheaper Chinese types.  I have had a problem with blow out.  Can't seem to let up enough when nearing completion.  I think I have found a way around the blow out.  I start the hole on one side, and about halfway, stop and use set of cheapo calipers to mark the opposite side, then drill to meet the first side hole.  So far, so good.
I also put a piece of 1x4 in the container so that when I do drill through, the drill goes into the wood and not the bottom of the container.
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southerly

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Re: Drilling small holes in stone with a standard drill press
« Reply #8 on: July 03, 2016, 12:56:13 AM »

Nice tutorial, thank you. Always looking for ways to improve my lapidary.
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hummingbirdstones

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Re: Drilling small holes in stone with a standard drill press
« Reply #9 on: July 03, 2016, 06:19:44 AM »

Very nice tutorial, thank you.  One tip for keeping the water cool is to put a couple of ice cubes in the water. 
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Robin

johnjsgems

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Re: Drilling small holes in stone with a standard drill press
« Reply #10 on: July 05, 2016, 10:55:14 AM »

On Jim Barzee's video tutorial on drilling he uses dop wax to stick the stone to a piece of wood.  He marks the depth of stone on the drill so he knows when to slow down.  The dopping and slow finish is supposed to prevent blow out.  I used to sell his videos and they are pretty well done.  Sold under "Mar-Zee Lapidary Tutorial DVD's" and found in Rock & Gem Magazine R&G Shopper ads.  And no, I am not selling them, making any money off them, etc.  Jim is a friend from many years of doing gem shows around the country.
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