Drilling a hole through Amethyst?

[rivett608]

Not quite machining metal... but a drilling problem. How would you drill a .025" hole thru about a 5/16" piece of amethyst. Also would inside surface of the hole be smooth so it didn't look ugly when you see it through the front of the stone... Thanks

 

[eKretz]

Could you try a PCB or CBN type tool? Drill or endmill maybe in that small of a size? Or maybe someone makes something that has that carbide grit and you could just abrade thru? Never tried that, just thought I'd offer some suggestions and help brainstorm it a little. Post again when you find something that works.

 

[Evan]

Amethyst is quartz with a mhos hardness of seven. Easiest way to drill that is with a laser. Failing that fine diamond grit, stiff wire and a lot of patience.

 

[richardny]

I saw them use bamboo sticks and diamod compound in a die shop, the diamond being pushed into the bamboo and being held there

just as a matter of principle

i doubt you can make an .025 bamboo stick and put it in a drill press, but maybe brass could be used to make a dull end diamond lap/drill

just brainstorming as well

 

[DanR]

You can buy drill bits with diamonds set into the otherwise blunt, fluteless tip. They grind a fairly smooth hole through just about anything. You may have to use a decent coolant to keep heat from fracturing your stone.

I think they are even available through Dremel, but if not a lapidary supply store should have them. If you are not in a large town you may have to mail order them.

 

[Evan]

You won't need to worry about heat fracturing the amethyst. The coefficient of linear expansion of quartz is very small.

 

[toolmakerjim]

use a disintergrating drill.
try www.technodiamant.com
its a coated diamond and usually has a through hole for coolant to flush the chip.
feed is .001" per rev...jim

 

[ralphe]

You might try a diamond drill. One source is www.lopacki.com.

 

[MitsTech]

I believe Amethyst are conductive, an EDM drill would do it but it would most likely not leave the surface quality you are talking about.

 

[Neil]

Ask a jewler maybe? Lapidiary supply catalog?

 

[Evan]

I doubt amethyst is conductive. It does owe it's color to traces of iron but there isn't much of it. Being quartz it is peizoelectric.

 

[Greglea45]

Diamond drill, you can use it in a flex shaft or a small stationary drill press or mill, low speed, drill it while it is under water in a pan or bowl. come back and touch up the the hole with a diamond cone,ball or tapered burr. Rio Grande in N.M. has everything you will need.

 

[cartertools]

Just as another data point, diamond drill is what you want. If they (Rio Grande or other lapidary supply) have the Crystalite "Triple Ripple" drill in that size, use it as it tends to drill a little better. Get a couple of drills as they can be burned out by the novice.

Work with the stone immersed in a wather bath or with copious water flowing over, and peck frequently to get out the "swarf" (mud). Glue a sacrificial stone or have plaster on the back of the hole if it's a through hole to eliminate chipping or drill from both ends.

You can do it with a wire and SC grit too but it's slow...
To polish, use some copper wire and SC grit or diamond.

 

[fen2art]

The diamond drills mentioned above will work much faster than SC. If you can find a core drill that small your cutting will go much faster just stop periodically to break out the core to improve coolant flow.(Assuming through tool coolant) Use a small pump (like little giant coolant pump) to keep a constant flow of h2o/coolant. I have used plate glass and beeswax/resin to support the exit to reduce blowout with reasonable success. This also helps maintain positioning for the time it will take to drill through. Polish as cartertools suggests. If you can't get the diamond tooling, brass tubing with diamond paste and lots of patience will get you there.

 

[toolmakerjim]

when i suggested the disintergrating drill. which is a diamond core drill, i was basing the advice on 3 years of drilling optical glass and crystals.
if Rivett looks at the website i suggested he will find diamond core drills as small as .023"~.028 up.
the most efficent way to use them is to mount the stone on a dpo using rosin heat the rosin to appros 170 to 200 deg too hot and it may fracture the stone.
DO NOT COOL THE STONE it will fracture just let it cool naturally.
the disintergrating core drill works best using through coolant to flush the swarf.
IIRC the spindle speed was 7000 RPM and i know the feed was .001" per rev.

 

[Evan]

Amethyst is unlikely to crack with thermal shock because of the low CLE. There is another reason to avoid heating though as it will bleach it heated too much. It also shouldn't be left in direct sun for the same reason. If it does become bleached the color can be restored by placing in a nuclear reactor for a few minutes.