[Spaventa]

Thought that title would thin the herd!

If you know about making stuff like Jewellery or ornaments or whatever from crystals or stones, I need advise about drilling a fairly large hole in a fairly large piece of Hematite.

The Hematite is a 45mm diameter ball. The purpose is to make it into a gear knob for my car.


The hole will be 12mm in diameter and 25mm deep.
I found this drill bit which I plan to use in a pillar drill at slow speed with continuous liquid cooling.



I still have to work out how to clamp the thing and have no idea if it will just shatter or explode so I thought Id see if anyone here can help. Cheers

[Andyo]

use a couple of bits of leather in a stand drill vice
vice
personally id use 3 sizes of cobalt drills marking with a center punch then 1/8th 3/16th and then final size.
need slow speed stand drill.
https://www.youtube.com/watch?v=wC65HqYcPTw
IMO the video = drill too big to start and a bit fast and he is using a hand drill
needs a stand drill to control down pressure and not wobble.

[I wood]

My first thought is that an abrasive bit would be the thing to use.
Not sure what type that is you've shown though.
Industrial diamond drills are pretty cheap these days.
They are a bit slow to grind a hole but have always worked for me on things like porcelain and cast iron sinks, glass and stone.

The leather is excellent advice.

[Spaventa]

3 stages sounds like a good idea thanks Andyo

[Spaventa]

Originally Posted by I wood

My first thought is that an abrasive bit would be the thing to use.
Not sure what type that is you've shown though.
Industrial diamond drills are pretty cheap these days.
They are a bit slow to grind a hole but have always worked for me on things like porcelain and cast iron sinks, glass and stone.

The leather is excellent advice.

yes maybe an abrasive one. That one I've shown is just a very good quality tile drill, diamond type. They work well if you have continues water cooling from a squirt bottle.
after a cheap cutting disc came apart on me a 10,000 rpm, I won't use anything cheap.


Im going to hole saw a 45mm hole in some wood, cut in half and use the halves as jaws in pillar drill vice. Some leather strips to face the wooden jaws will be nice.

[gaiusmarius]

let us know how it goes

[St. Phatty]

Often what people use for clamping round materials is - wood that has a round shape machined it into it.

Also, aluminum, with a round shape machined in.

That basically describes the vises used to dis-assemble & re-assemble hunting rifles. (vises are steel, but with aluminum, wood, & sometimes lead lining.)

Be careful about the hematite powder, you do not want to breathe it ! One of the best approaches I've found to machining dust is LIGHT - so you can see the dust plumes and make sure you aren't inhaling near them.

Save your lungs for the good stuff

[Spaventa]

Originally Posted by St. Phatty

Often what people use for clamping round materials is - wood that has a round shape machined it into it.

Also, aluminum, with a round shape machined in.



That basically describes the vises used to dis-assemble & re-assemble hunting rifles. (vises are steel, but with aluminum, wood, & sometimes lead lining.)

Be careful about the hematite powder, you do not want to breathe it ! One of the best approaches I've found to machining dust is LIGHT - so you can see the dust plumes and make sure you aren't inhaling near them.

Save your lungs for the good stuff

Thats what I said basically There will be no dust cos water cooling

[Spaventa]

Bought this lot. Core type drills should put even less force through the stone. Theres 6,8,10 and 12mm so I can do it in 4 stages.

[Stond_Face]

Im an old machinist. But, the closest material i worked on was drilling glass and ceramic..

Thats a great idea with the shift knob.

I never tried, but id bet the hematite is not too hard. You see different shapes sold for not too much money. That implies that it is easy to machine and polish.

Those diamond core drills you have will work. However, they are very slow. You need to use very light pressure with diamond core drills otherwise all the diamond chips come off straight away. When younare finished drilling, you would have to break the core out of the hole. The core in a 25mm diameter would probably be about 3/4" diameter. That could be really tough to break off. And, use the core drills with flowing water to manage heat and flush the slurry away.

I never tried using core drills in stages. My intuition tells me the first hole would go OK. However, with the subsequent holes, it may be really difficult to get the larger size bit started in the previously drilled smaller hole. Id be curious to learn how that works if you try it.

That carbide tipped Bosch bit you have looks like a glass and tile bit. I would try that first.