What is a "CUP BUR"? => 14 photos

 The official name for this bur is a "77B". This bur is meant to do just one thing: create a spherical shape on the claw tips.

  As you can see clearly, the bur teeth are inside the 'cup'.

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 With the common bur, the teeth are on the inside to cut into the metal. But in this case, the teeth are meant to change the shape of the claw tip.

 After a few bur rotations, the tips of the claws will be reshaped into a ball as shown here in the cluster pendant.

  As with all metal shaping tools and instruments, keep these burs WELL LUBRICATED.

In this photo, you can see the teeth inside the "77B-Cup Bur".

 Here is a good example of 'rounding of the claws' before stone setting.

Get those centre claws rounded before setting. If you have a chance, you can polish the tips and round the claws before proceeding with the setting of gemstones.

 I always trim the claw tips before the stone setting commences.

 Don't let the edge of the Cup bur make contact with the soft stone. What I do is to 'rotate' the cup around the top of the claw.

 Before you set any cluster top stones, make sure that the height of the claws is uniform and is also polished. 

Then all that is remaining is to set the stones.

 What I do most of the time is to round all of the claws before stone setting.WHY? This will prevent the '77B Cup' bur from touching any soft stone, such as in an Amethyst or Emerald.

 You have an option for this ring; either you can trim the claw tips and create square tops.

 Or the next step is to use your "Cup Bur" and make all of the claw tips ROUNDED.

In this cluster pendant, all of the claws are uniform!