Why are "156" burs so very important => 10 photos. Essay #2, of 2 POSTS.

  The main problem is that the Carbide steel is quite soft as compared with the HSS burs. What happens is that the bur makes contact with a hard metal, the claws get easily damaged & ruined.

This 45degree angle cutting bur is great for cutting bearings.

How far down into the bezel should the HSS bur go? The 'Rule' is that the bur should not go deeper than the tip of the teeth.

In this photo you can now see two shapes of the burs...45 & the 90 degree angles.

 This is a photo of slightly worn teeth on a 156C bur.

                              (These are the teeth on a HSS BUR)

  (These are my favourite photos, that I personally took.)

 You can see each individual tooth of the bur starting to cut a bearing. WOW, eh!

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 You can now see just how low the rotating bur should go. 'The tip of the teeth' IS THE RULE FOR DECIDING THE DEPTH INTO THE BEZEL WALL. 

  The rotating bur mustn't go any lower than shown here!!!

 

  (My diagram drawings are not perfect, but 'the thoughts' are there.)

 You can easily see where the HSS bur teeth are about to cut into the pre-notched claw.