To drill sea glass successfully takes practice, patience, use of the right equipment and most important, good technique. It is easy to ruin a prize piece and spoil the finish or in extreme cases reduce it to fragments. Drilling sea glass is not for everyone so here at ‘Imogen’s Beach’ we have a wide range of ready drilled sea glass in our web store , we also offer a drilling service where we drill and return your sea glass to you.

Drill types

Diamond burrs are used in a rotary tool (Dr*mel clone) to drill sea glass. The best type of burr to choose is a flat faced burr of the required diameter. You may also see advertised diamond coated twist drills these are less effective than flat faced burrs and the fluting tends to weaken them and make the susceptible to being bent. Drilling should be done wet to cool and lubricate the burr, this prevents the diamonds and coating burning off due to friction. The water also acts to remove the glass dust which would otherwise slow down the cutting process.


Drill Sizes

We mostly use 2 mm burrs for pendants and charms and 4 mm for thongs, however if you wish to use jump rings through thicker pieces of glass you may need to use a larger hole to accommodate the curvature of the ring. In the case of smaller (thinner items) such as earring drops we use 1 mm burrs.

If you can obtain them it is best to choose the heavier 3 mm shank burrs rather than the thin straight shank burrs.  Wider shanks are easier to grip and center in the collet, also you don’t have to change collets when you change drill size.


Drilling Pressure

If you have a good burr drill bit with sharp diamonds then a light pressure when drilling is all that is required.  In order to get a feel for the pressure applied it is generally better to hold the work-piece in one hand and the drill in the other – bench type drills are unlikely to permit enough control over the pressure to achieve consistently satisfactory results and are likely to result in broken drills and splintering of the glass.


Drill Speed

You will find plenty of advice on the ‘interwebs’ saying drill glass slowly, this is excellent advice if you are drilling a 100 mm hole in a pane of glass with a core drill but is almost always mistakenly applied to all glass drilling. This advice is just plain wrong when applied to small diameter drills. Small drill bits have a significantly lower linear cutting speed than large core drills. When using small drills it is therefore necessary to increase the rotational speed to achieve an equivalent linear cutting speed.


A 100 mm diamond core drill rotating at 300 rpm  would have a linear speed of approximately 1 meter per Second, whereas a small 2 mm  drill  would need to be running at 15,000 rpm to achieve the same linear cutting speed.


Starting to Drill

Diamond burr drills generally have a flat end to them and if you were to apply them perpendicular to the glass they would skeeter off course and not drill in the required position. To start the drilling process it is best to angle the drill to the work-piece so that the corner of the burr bites into the glass and establishes the cut, then with the drill still running and in contact with the glass smoothly change the angle of the drill until it is perpendicular to the work-piece


Drilling Action

As the diamonds remove glass from the hole the glass dust created mixes with the water and makes a thick paste like slurry. This slurry can form a seal between the shaft of the drill and the walls of the drilled hole that effectively prevents fresh water from reaching the cutting face of the bit. The slurry and lack of cooling water can cause the drill bit to heat up excessively and this can significantly reduce the life of the drill. Using a short pumping motion with the drill (i.e applying pressure then pulling back a small amount and repeating ) will prevent the slurry building up and allow clean water to cool and lubricate the cutting face.


Avoid Blow-Out

Blow-out is where a jagged cone shape of glass splinters out from the back of the work-piece as the drill exits the reverse side of the glass. There are a number of techniques that can be used to minimise this unsightly problem:

  • When the drill gets close to exiting the back of the work-piece you should reduce the pressure applied to minimise the chance of blow-out.
  • Drill mostly through the glass then flip the work-piece over, line the drill up with the hole and drill through until the two holes meet – don’t forget to also use the technique described in ‘starting to drill’ for the second hole.
  • Use a small pilot drill (e.g. 1 mm) to drill through the glass then use a finishing drill (e.g. 2 mm) to widen the hole, again drill from both front and back when widening the hole.


Fixing mistakes

Glass is brittle by nature and no matter how careful you are at drilling some holes are just going to be raggedy. To clean up a less than perfect hole you can use a cone shape diamond burr to chamfer the edges of the hole, this has the added advantage that it helps prevent jump-rings from chipping the corner of the hole. If you have blown-out a large chip you can try blending it in by lightly grinding with the side of the diamond burr.


More on Drill Bits

Most diamond burr drills are made by applying a coating of diamond dust to the ends of a steel rod and electroplating over the top to fix the diamonds in place. Diamond burrs used for drilling will have a coating that extends up the shaft but it is actually only the diamonds on the flat end that have any effect when drilling.

Sometimes the coating is poor and you may get the odd burr that doesn’t have sufficient diamonds on the end to drill effectively – these drill bits generally have to be discarded.

If the electroplating is too thick and the diamonds on the end are buried within the metal of the electroplating the drill may not cut very effectively at first but as the metal wears away and the diamond is revealed their cutting ability will improve.

If you find that a drill is not cutting properly and leaving grayish or black marks on the glass then this is usually an indication that the electroplating has worn away and the steel base metal is exposed – time to discard the drill as it is worn out

Safety Warning!

Using water near mains electrical equipment is extremely dangerous!
I personally use an electrical RCD socket to add a level of protection to this operation – however this does not guarantee safety and should not be relied on to prevent shock.

Tie hair back when using rotating equipment

Always wear safety glasses when drilling glass

NB The article is provided for general information purposes only, it is not a substitute for independent professional advice. It is the responsibility of the individual to determine any risk to themselves or others and seek expert safety advice where required.

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