Core drill bits for hard materials

Here are our diamond core drill bits for granite, hard porcelain and polymer concrete.
These long lasting barrels can used with your standard drill.
Although they are a little slower than electroplated hole saws, the pros prefer them for their long life.
See instructions for use at bottom of this page (also supplied with core bit).

  • Available 6mm to 180mm diameter
  • All drill bits have an internal length of 50mm
  • Longer lasting - ideal for regular users

Suitable for coring:

  • Granite, including bench tops
  • Hard porcelain, including tiles
  • Very hard pavers when installing pool fencing
  • Polymer concrete
  • Electrical and communications cable jointing pits
  • If used on regular concrete, will wear faster

(For a less expensive option, see the seperate page on "Electroplated (HDEM) core bits" page here. 
As a comparison, a skilled operator can get up to 40 holes 10mm deep with the HDEM.
They should be able to get 150 holes out of the CGS, although they will core slower.)

Up to 29mm, the barrels are fitted with a 12mm hex shank for use with a chuck type drill (adaptors to SDS Plus available at extra charge).
32mm and bigger have a 1/2" BSP female thread, and come with a 12mm hex shank adaptor, a pilot drill bit and a wedge key. For use with a chuck type drill (adaptors to SDS Plus available at extra charge).
Drill bits with diameters up to 12mm inclusive are all solid points so they do not have a hollow core to them.

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Part Number Size  Price (each, incl GST)
CGS6-65 6mm $44
CGS8-65 8mm  $45
CGS10-65 10mm $50
CGS12-65 12mm $55
CGS16-65 16mm $65
CGS19-65 19mm $69
CGS22-65 22mm $80
CGS25-65 25mm  $80
CGS29-65 29mm  $90
CGS32-65 32mm $95
CGS35-65 35mm  $105
CGS38-65 38mm $115
CGS48-65 48mm $140
CGS51-65 51mm $145
CGS54-65 54mm $150
CGS57-65 57mm $165
CGS60-65 60mm $175
CGS64-65 64mm $185
CGS70-65 70mm $199
CGS75-65 75mm NLA - see UDT for alternatives
CGS90-65 90mm $275
CGS95-65 95mm $285
CGS115-65 115mm $290
CGS117-65 117mm $295
CGS165-65 165mm $345
CGS180-65 180mm $395
Suction Ring Set 38mm & 75mm 
Water containment for wet drilling.
Push the ring down on a flat, smooth horizontal surface and fill with water.
$20 incl GST each - ex stock
Dymaxion diamond hole enlarger - 35mm diameter. 
Suitable for most building materials including porcelain and stone. 
Will also grind irregular shapes and rebates.
Used to enlarge an existing hole. 10mm hex shank, 25mm diamond coating.
Attach to drill and slowly rotate in anti clockwise direction, using firm pressure. 
HDEE35 $99 incl GST


Use appropriate personal safety equipment - safety glasses, hearing protection etc

If using an electric drill, ensure you use an RCD to prevent electrocution.
A battery drill is much safer with water than an electric one, and does generally have slower speeds..

DO NOT use on hammer (percussion) mode.

Even though a pilot drill is included, a simple template or guide will assist your drilling.

Use water to keep the diamonds cool. Or quench drill bit in water. An over heated barrel will cut slower.
Tip: Cut a sponge to roughly fit inside the barrel, and make sure it gets wet when the barrel is cooled in water.
This will provide cooling as the barrel spins. This works best on smaller diameters.

Use only medium drilling pressure. The smaller the diameter, the less pressure is needed (otherwise you will damage the drill bit).
Drilling is usually slow with these hard materials.

Start drilling slowly and gradually increase the speed, to the recommended speed as indicated below.

Withdraw bit regularly to allow cooling, allow water inside the hole and to clear debris.

Drill with slow speed, medium pressure and lots of water.

You are not drilling a hole, you are grinding it. So it will take longer than using an SDS percussion type drill bit.

See our drill chart below as a guide for drill speeds.

Core bit diameter 12mm 25mm 50mm  75mm  90mm 
Fibreglass  1200rpm  700rpm  350rpm  250rpm  175rpm
Glass & china  800rpm  500rpm  250rpm 160rpm  125rpm
Pottery tile & marble 600rpm  450rpm   225rpm  130rpm  100rpm
Porcelain tile  500rpm 375rpm   180rpm  125rpm 90rpm 
Granite  400rpm  300rpm  150rpm  100rpm  75rpm

Tips for drilling polymer concrete (used in electrical, data and plumbing pits):

  • Pre drill pilot hole or use a template
  • Cool the diamond segments by regularly quenching in water
  • Avoid excessive drilling pressure
  • Wash down the barrel after use to stop slurry building up (dried slurry will slow coring on future holes)

Silica dust - when workers drill, polish, saw, cut, crush, drill, polish, saw or grind products that contain silica, particles are created, which are one-hundredth of the size of a grain of sand. These can get  stuck deep in the lungs. 
Ensure precautions to limit exposure to dust are in place.
See the WA government's info on silica dust here.

Please see our "Contact Us" page (here) for Australia wide shipping information.

Prices correct as of 1/10/23 but subject to change.

Disclaimer: all the information on this website is provided in good faith and believed to be reliable and accurate at this time. However, the information is provided on the basis that the reader will be solely responsible for assessing the information and its veracity and usefulness. UDT shall in no way be liable, in negligence or howsoever, for any loss sustained or incurred by anyone relying on the information, even if such information is or turns out to be wrong, incomplete, out-of-date or misleading.

Dymaxion HDEM6 Sutton Bunnings

United Diamond Tools

U9, 84 Barberry Way
Bibra Lake
Western Australia 6163

Telephone: (08) 9434 6878