jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 12, 2018 6:25:42 GMT -5
I hope you followed the above TheRock. There may be a sweet medium of torque and speed. My 0-30,000 RPM Dremel failed so I have been using a 0-10,000 RPM Dremel. I need to purchase another 0-30,000 Dremel and try the higher speeds. Maybe. 10,000 RPM and cheap drill bits do not necessarily work so well together. I noticed some off-balance or more precisely some out-of-roundness in the cheap drill bits causing serious glass breaking vibration. One may have to purchase more expensive balanced bits for drilling glass at speeds higher than 10,000. 5000 to 7000 may be a more optimum speed for cheap bits.
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Post by fernwood on Oct 12, 2018 6:29:51 GMT -5
I use a diamond bit with the ball type end. Yes, it appears to carve the hole. There was no chipping of the glass, but it took a while to do.
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Post by grumpybill on Oct 12, 2018 7:04:23 GMT -5
I don't have a drill press. Should probably buy one.
I've gotten my fastest results by using a ball bit to make a divot, then drilling with a tapered/needle bit.
Tried an overpriced 1/8" Dremel brand core bit. The core got plugged on the 3rd hole, so I've set it aside until I figure out how to clean it out.
Tried 1mm bits in a Foredom handpiece thinking the lower speed would make the bits last longer. Hard to get them centered in the chuck. Broke 2 of them on the first hole and went back to the Dremel.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 12, 2018 7:56:39 GMT -5
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,630
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Post by NRG on Oct 12, 2018 10:12:54 GMT -5
You can get finer grit too for finishing surface on carvings.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 12, 2018 10:30:41 GMT -5
Found some larger 4mm bits with aggressive 50 grit diamonds fitted with a slot for removing core. Pretty sure these are going to make some quicky holes. Big holes for some funky designs, no problem. 10 for $8.54
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Post by TheRock on Oct 12, 2018 22:27:32 GMT -5
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 13, 2018 3:49:32 GMT -5
Interesting, Mr. Clayton's site says to limit 1mm to 2.5mm drill speeds to 2000 RPM. Oops, I broke that warning. Been spinning similar bits up to 10,000 RPM using the Dremel. 2000 RPM would slow drilling rate substantially. Wearing better googles from here on. Maybe the EBAY sellers mention this safety limit too. Note that he does not mention the diamond grit size on his small drill listing. They appear to be 100 to 200 grit size. Going to continue stalking the coarser grit suppliers. Some of these cheap bits have some really poorly shaped tips. As if the tip had been cut sloppy. Note what he says about "pinched end drill bit blanks". Talk about a good reason to break your material while drilling: "" Quality Comparisons: When purchasing small drills from other suppliers look at the end of the drill that is not diamond plated. If it is square and polished then that was probably the way it was prepared on the other end before the diamond plating was applied, which is the proper way to prepare a drill blank. If the end of the drill was pinched cut, then the end of the drill does not look square and polished. It will have a raised chisel shape end on the drill. If the drill has the raised chisel shaped end on it then the diamond was probably applied over the same chiseled end on the other side. Pinched cut ends dramatically reduce the life of the drill. Our drills are never plated over pinched cut ends. Cautions: Maximum Speed Rating: 2000rpm. Always wear safety goggles. Always wear an appropriate mask so you do not breath in particulates and harmful vapors. Always wear hand and body protection. Failure to adhere to these cautions may result in serious injury or death."" And right off of an EBAY seller listing is pinch cut drills with a chiseled end with will both vibrate and wear the diamonds prematurely at the chisel tip and stop drilling. In particular, the 5th drill bit from the right side:
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 13, 2018 4:13:36 GMT -5
Lets blow this photo up. Most cheap diamond bits do NOT look this well shaped and coated on the end where it counts. And don't trust you e-packets from China to look like this when you receive them:
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 13, 2018 4:33:58 GMT -5
This is a spent 3mm bit at 25X magnification using micro on little Olympus camera. Nice flat end on blank. Looks to be 100 to 150 grit. The brazing is a bit lopsided, evident at the top section of the bit on photo #2. No idea when the bit was purchased or from whom. But a fairly high quality bit judging the nice square tipped blank.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 13, 2018 4:54:32 GMT -5
And for what it is worth a X10 micro of 1.2mm, 1.5mm and 2mm bits. Looking good with nice flush ends. The brazing covers the diamonds a bit but should wear away quickly to unleash the diamonds. These look to be 50 to 80 grit. Easier to tell after some of the brazed coating is worn back. Photo below to compare 40 grit and 300 grit.
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Post by fernwood on Oct 13, 2018 5:26:23 GMT -5
I have used bits like that with the spent tips for another purpose. Since the rest of the bit is still in good shape, have been using the edge to shape cabs. Works well. Also lets me think I am getting full use of the bits.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 13, 2018 6:34:33 GMT -5
I have used bits like that with the spent tips for another purpose. Since the rest of the bit is still in good shape, have been using the edge to shape cabs. Works well. Also lets me think I am getting full use of the bits. Funny how you barely use 5% of the diamonds on those bits. Get you money's worth with your trick. There are so many interesting diamond wheels being introduced to the market. Just in the 6 years I have been a member here a vast amount of new shapes have been introduced. The prices have dropped a lot too. This trend should continue.
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Post by fernwood on Oct 13, 2018 6:54:28 GMT -5
Yuppers. I am all about getting the most I can for the $$$. I am using some Dremel diamond wheels for trimming small slabs. Working great so far. My Dremel is getting a work out. Much easier than using files and doing by hand.
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Post by grumpybill on Oct 13, 2018 7:00:16 GMT -5
jamesp I have some 1.5mm straight bits coming across the ocean from THK. I'll let you know what I think of them when they get here. I bought a set of tapered/needle bits from eBay seller "diamondtools30" a while back. They were worthless. Diamonds came off as soon as they touched the stone.
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Post by grumpybill on Oct 13, 2018 7:14:18 GMT -5
Mr. Clayton's site says to limit 1mm to 2.5mm drill speeds to 2000 RPM. Oops, I broke that warning. Been spinning similar bits up to 10,000 RPM using the Dremel. 2000 RPM would slow drilling rate substantially. The speed isn't variable on my ancient ~30,000RPM Craftsman-branded Dremel, so I was hoping the slower speed of a Foredom would help the bits last longer even if it took longer to drill the hole. But...as I mentioned above, a real pain in the behind getting 1mm bits centered in the key-type chuck. I have some 1.5mm bits with a 3mm shank that I'll try at the lower speed when/if it stops raining. (Mrs. Grumpy doesn't like the noise/mess indoors.)
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,178
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Post by jamesp on Oct 13, 2018 7:40:30 GMT -5
Mr. Clayton's site says to limit 1mm to 2.5mm drill speeds to 2000 RPM. Oops, I broke that warning. Been spinning similar bits up to 10,000 RPM using the Dremel. 2000 RPM would slow drilling rate substantially. The speed isn't variable on my ancient ~30,000RPM Craftsman-branded Dremel, so I was hoping the slower speed of a Foredom would help the bits last longer even if it took longer to drill the hole. But...as I mentioned above, a real pain in the behind getting 1mm bits centered in the key-type chuck. I have some 1.5mm bits with a 3mm shank that I'll try at the lower speed when/if it stops raining. (Mrs. Grumpy doesn't like the noise/mess indoors.) I was totally surprised by that conservative 2000 RPM rating. Sounds like the foredom is perfect. The bit construction apparently plays a big role in the longevity and cutting quality. I'll post any brands that seem of best quality. Best to purchase small quantities to test and share with other users when buying oversea diamond tools. All grinding is out with the dogs at this household too.
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Post by grumpybill on Oct 22, 2018 18:58:29 GMT -5
jamesp I have some 1.5mm straight bits coming across the ocean from THK. I'll let you know what I think of them when they get here. The bits from THK got here today. The grit looks a lot courser than on the ones The Rock Shed sells. I'll give them a test spin tomorrow and report back.
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panamark
fully equipped rock polisher
Member since September 2012
Posts: 1,343
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Post by panamark on Oct 22, 2018 22:39:03 GMT -5
following this thread with interest James. I have spent a LOT of time drilling cabs and beads of stone. The THK bits are the best I have found so far, at least in the 1.5 to 3 mm size. One suggest is that I have found using a drill press HUGELY improved the speed AND the quality of the hole. Just like any drill press beats hand held for about any material. I drill in water using a small metal tray of water with a preformed piece of wood that roughly holds the cab just slightly submerged. If I want to get even better I can glue the cab in the wood with a slow-water-solvent glue. The wood allows me to better hold the bead/stone and consistently hit the hole perfectly as I use the tap-tap-tap drilling technique.* One thing I am doing more and more with some success is to keep the water just to the surface of the rock and fill the hole that is forming with a slurry of silicon carbide grit. This can really increase the drilling speed. The ancients use this slurry with bamboo drill bits to pretty good effect.
Anyway, as always it is a joy to watch you think and tinker!
* =still working on a practical underwater stone micro-vice. No good solutions yet. And I have used modelling clay to hold the piece in place, but with limited success.
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