To drill a hole in Opal is not as simple as it sounds. We find many people buy Opal or Gemstones and try to drill a hole in it and don’t succeed. This can be very frustrating if the following procedure is not followed.
Here is a home made version made out in the opal fields Winton Queensland for drilling holes in boulder opals.
Its a dremel drill set up on a hand press shaft so it can be levered up or down. On the base he has set up adjustable drill shank to hold the bottom drill. This is a great idea as if anyone has tried to drill hole it is hard to get the holes to match up.
As if you try and drill all the way though the opal will chip at the end so this system is easy to make at home and to drill holes both ends of the opal and thy will match perfectly.
Diamond tip drills are suitable for drilling small quantities of Opals. These drill bits have been tipped with diamonds of different grades and shapes can be round, arrow pointed, long shape or hollow point. 120 grit is suitable for drilling holes.
These drill bits can be attached to any standard home drill or dremel drill but if the drill speed is set on high speed the diamonds will burn off in a matter of seconds. This happens frequently as there is incredible heat when a diamond drill bit touches the stone and it needs constant water on the stone when you drill. The drill must be on slow speed.
Standard home drill attachments that hold a drill are suitable but you will need a block to hold the Opal stable for drilling.
Drill a hole only half way through the stone. To start the hole tilt the drill and slowly with no force go to vertical if the drill is hand held. Keep removing the drill bit from the hole to clean out excess material and this allows water to wash out the hole and keep the drill from over heating. Do not use pressure to drill the hole.
Then turn the stone and drilled in from the other side so that the join is in the middle of the Opal. This is not easy to get exact but if you just drill all way through the Opal the drill will protrude on the other side and it will chip off edges and you will get an unsatisfactory finish.
Some commercial clamps are available that can turn the stone over 180 degrees
Wooden clamps can be made but it is important that you can turn the stone over and drill in exact hole so it is a clean join
Some cutters glue the Opal to bench so it is solid and then drill the hole
If your drill doesn’t have slow speed control keep the depth of drill so it is only slightly touching the stone
Slow speed slow work is best and plenty of water
Have a tube or hose connected to tap so water flow is constant
Set drill to slowest speed 7,000 to 10,000 rpm, this is slowest setting on dremel drills
Many large cutting factories have sonic drilling machines and these cut a hole by using a high frequency vibration. This is good for large commercial operators but are expensive and the cheap versions that we have seen do not give a satisfactory finish.
Standard diamond tip wheels can be purchased that are 3-4 inches wide and these are curved so semi shaped beads are formed. Most are 100 to 140 grit.
To start shape the opal, mainly boulder opal or ironstone opal with colour bars to a rectangular shape are best. This long rectangular shape fits against the diamond tip curved wheel by another attachment that can be spinning or manually turned. The result will be uniform beads with two blocks on each end that can be sliced off with a saw blade.
Many cutters do get disappointed when making beads as rough is usually good to start but, most of the colour disappears when making beads so make sure you use Rough Opal that has colour veins running through them as they normally produce a good finished bead.
This bead cutting machine will make the boulder opal beads perfectly round. First the cuter has to cut the opal into a rectangular shape to make the bead. If you have ever tried to cut an opal into a round shape you will realize how difficult this is.
Matrix opal is also suitable for making beads
Black Opal is rarely used to make beads due to cost of Opal Rough
Rubber tips are also useful when making holes or polishing undulating surfaces on Opals.
Diamond impregnated rubber tips are ideal for finishing off edges after the hole is drilled or any undulating surface.
If you don’t have any rubber tips you can set up 1-2 inch diameter sandpaper on flexible rubber disk and use contact adhesive glue so sandpapers can be changed easily when worn.
No water is required.
You must have air suction to take air away and wear a mask whenever polishing with no water.
Vacuum cleaners can be used but it must have a strong suction and most household vacuums are not strong enough to take dust particles away from your face and mouth.
For the final polish you can use a lap and polishing power made into paste with concave and convex heads. They are good for difficult to get at spots especially on undulating Boulder Opal.
Opal books are also helpful in giving practical advice for Opal cutting and polishing. Example ‘Opal & How to work it’ by Frank Barnet.
I’m sure that you will agree that after you try and make some beads yourself you will appreciate why good quality Opal Beads are so expensive.
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