BS 328-2:1972

What is BS 328-2 - Combined drills and countersinks about?  

BS 328-2 is the second part of the BS 328 multi-series that discusses drills and reamers. 

BS 328-2 gives designations and dimensions for the following types of centre drills. 

• Type A, combined drills and countersinks (centre drills) for centre holes without protecting chamfers 
• Type B, combined drills and countersinks (centre drills) for centre holes with protecting chamfers 
• Type R, combined drills and countersinks (centre drills) for centre holes with radius form 

Who is BS 328-2 - Combined drills and countersinks for? 

BS 328-2 on drills and reamers is useful for: 

• Designers of drill bits 
• Drill bit manufacturers 
• Quality control personnel 

Why should you use BS 328-2 - Combined drills and countersinks?  

When screws are screwed into holes drilled by normal drills their head tends to stick out on the surface of the material. To resolve this issue countersinks and combined drills are used, as the holes drilled by them allow the screw head to stick inside the material and prevent the slight protrusion of the screw head. 

BS 328-2 provides dimensions and tolerances for the afore-mentioned combined drills and countersinks. These dimensions enable you to produce combined drills and countersinks that drill holes specific to the commonly used screws in the industry.  

Overall, these dimensions of BS 328-2 help you in the production and quality control phases of these drill bits and thereby enhance their build quality