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Drilling Troubles….Need Help

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Author Topic: Drilling Troubles….Need Help  (Read 546 times)
OaksPlugs
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« on: April 13, 2012, 02:10:06 pm »

I'm having some trouble drilling through stone slab. I succefully bored out holes in pieces of 1/2 thick jade, obsidian, and a white agate.

I used a Dewalt 1'' diamond drill bit in a Ryobi 1/4hp 10'' drill press set to 900rpm with little trouble. During the drilling process I had cold water poured on the bit.

However, when I went to drill a second hole in the agate, the bit only entered the material about 1/8'' and would go no further. I attempted to use the same bit with the obsidian and had similar results.

I am aware that the Agate is especially hard and am under the impression I've distroyed the bit. My concusion is that I should have used oil to lubricate and cool rather then water, and that the dewalt bit was an inappropiate choice for the material and that I might need to invest in better tools to continue.

I've worked with wood for a long time now but this is my first attempt in stone so I really don't know what I should do in this situation or what I specificly did wrong.  I was hoping some of you could help me out and give some advice on what would help with drilling large holes into hard material. Any hints or tips would be greatly appreciated.

David Oakley


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ScarlettoSara
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« Reply #1 on: April 13, 2012, 02:23:33 pm »

Nice Plugs... I know they have to be a certain thickness which makes drilling even harder I assume.
Hope someone knows the answer cause I would like to know too.
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OaksPlugs
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« Reply #2 on: April 13, 2012, 02:39:11 pm »

I'm going to be using the plugs for large gauge ear jewellery (for stretched earlobes). I've been making them out of wood for a a while but can't seem to get it right with stone. You guys could check out my stuff at http://www.oaksplugs.com/ if your curious. I'll attach an image if the shape I require the end product of these stone plugs to be.


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christopherl1234
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« Reply #3 on: April 13, 2012, 03:24:28 pm »

Checked out your site....nice work!
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lithicbeads
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« Reply #4 on: April 13, 2012, 03:29:42 pm »

 Hi , Your bits probably just wore out. What you need is a water swivel drill which fits your drill press and has core drills that are hollow ,  made  specifically to use with the water swivel attachment. When you use the water swivel a stream of water runs through the bit cooling it and washing away the swark (grindings). You need to alternate drilling and lifting the bit to further assure that adequate washing and cooling is happening at the point of contact . Engage the stone softly, always and gently increase pressure. With soft stones you must wash away the swarf after only a few seconds of drilling  and with harder stones it's not a lot longer. If the drill seems to be catching , sudden increase in pressure , lift it  quickly as it is easy to strip  the diamond through mechanical pressure  as well as lack of cooling at the cutting surface.To be honest core drills have limited utility . they wear quickly and are expensive. I only use them in applications where they are a must. For what you are apparently doing I would mark and saw out blanks and  cut them round by hand.A bit of a learning curve admittedly but it is ultimately much cheaper and faster
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« Reply #5 on: April 13, 2012, 04:09:30 pm »

Those wooden plugs are so beautiful they could be made into cabs too:)
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pete
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« Reply #6 on: April 13, 2012, 05:01:42 pm »

I prefer a slower speed, around 300-400rpm.
Drilling stone is a grinding action not like drilling wood which is a cutting action and with the core drill you're using diamond grinding principles apply.
As lithicbeads suggests, sawing would be cheaper and quicker. For a good finish on the stone you need to sand and polish so an extra minute at rough grinding the blank after sawing is still quicker than drilling the blank.
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lithicbeads
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« Reply #7 on: April 13, 2012, 05:08:58 pm »

Hi again, I've got a little more time so I thought i could tell you how I solved the problem for myself. The core drill is appealing but slow and overly expensive for production work so I  did research and found that centerless grinding makes similar shapes ( often very sophisticated shapes such as valve stems ) in metal and are probably adaptable to lapidary use but are extremely expensive, think fancy car , and are three phase power. A better choice for me was a Maxant automatic cabber which essentially has two modes , the preform or girdle shape and the dome . By stopping the machine before the dome cut began I could make a preform that was sized perfectly. This machine has two stations so it is easy to alternate changing the dops. It is a three motor machine . a half horse turns the grinding wheels while a small fractional horsepower motor turns each dopstick and rotates the stone into the wheel as well. for accuracy I dop with super glue or epoxy and heat the completed preform and dops in an electric fry pan to release the preforms from the dop. Very much an outside job due to the fumes. The only trick to the whole thing is to grind any sharp edges off of the preform ,  if a sharp edge addresses a hard  the wheel it is easy to strip diamond from  it when in automatic mode. Frank
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OaksPlugs
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« Reply #8 on: April 16, 2012, 01:44:44 pm »

Awsome! Thanks a bunch for the tips. I've been looking around at different stone trim saw's but can't quite figure out what features would be most beneficial for what I'm doing. I've been looking into Covington 6" Mounted Trim Saw and Grinder  but if anyone could recommend a saw I would really appreciate. I feel I'd be limited to straight cuts rather then rounded ones because of the broad blade which could waste alot of my stock. If there is alternative saw that can cut rounded shapes out of thick stone I would much prefer that.
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« Reply #9 on: April 16, 2012, 03:09:16 pm »

Taurus makes a ring saw that works well with minimum waste and you can cut curves.
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« Reply #10 on: April 16, 2012, 04:14:55 pm »

If you are still tempted to drill plugs, I have had success with using a wooden jig "predrilled hole" clamped over the stone to guide the bit so it doesn't "walk" and is more efficient. Go SLOOOOW!
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Thanks for looking - Gerard
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OaksPlugs
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« Reply #11 on: April 17, 2012, 08:56:11 pm »

hmm That Taurus saw seems like it would be awsome for what I'm doing, but I'm not sure It could hold up to heavy use with 1/2 thick material. My main concern is that it may be designed more for tile and glass work. Has anyone here had personal experience with this saw or a similar ring saw? And as for drill bit's I am leaning more towards investing in a saw over buying bits now.
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« Reply #12 on: April 18, 2012, 06:09:29 am »

I have a Taurus3 and it is a good saw for cutting shapes from slabs 1/4" and under. I have the Mega-blade on it as the original blade blew after the 3rd time I used it. I would not recomend for 1/2 inch material. Besides 1/2 inch will not fit the throat of the saw mounted to the table. I think a diamond saw and good st of wheels is what you need. Good luck........Bob
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Bob

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mirkaba
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« Reply #13 on: April 18, 2012, 06:42:59 am »

Just had another cup of coffee and thought about it. Maybe you could set up a lathe and use diamond tools to turn precut blanks into round stone dowels, then shape, polish and cut ypor plugs to length. Maybe modify a drill press or something.... A large chuck of some sort.......Since you are starting out it bears some thought...........Bob
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Bob

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Rocksnot
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« Reply #14 on: April 18, 2012, 09:12:24 am »

I to have had issues with drilling through rocks with diamond bits.  Not just the core bits but even regular bits.  It is a very slow process and seems to like eating bits.  Gets pricey when the bit only makes it through 2 or 3 holes.  Granted the rocks are hard and I am using cheaper bits but dang!  I just need holes in the stone.
When I worked in construction we'd core through a foot of steel and concrete with 2 - 14" bits and get hundreds of holes per bit.  It is taking me the same amount ot time or longer to drill a 2 or 3 mm hole in a rock that is only .25" or less.  what a pain!

I chuckled when I saw this post because you want the core slugs (I toss those in the tumbler) and I want the hole  :)
But it seems we have the same issue with getting through the rock in the forst place.
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