Top Hammer Drilling Method
Drilling with top percussion, also known as "Top Hammer", or "Drifter" method(s),
is very common in several areas of the drilling industry. Benching, and pre-shear drilling during mine construction uses this method, as does road building, pipeline construction, tunnelling, and rock removal where explosives are used to break up the rock formations. Civil construction employs this method using hollow anchor bars for support and temporary tiebacks. The top hammer uses a striker bar or shank adapter which is used to rotate the steel, as well as "hammer" it into the rock via hydraulic percussion from above.
Typically, Drill Steel comes in three popular threads, T-38, T-45, and T-51. As drills become larger, and the top hammer increases in power, larger steel is starting to appear in the market to accommodate the changes. The bigger sizes being commonly used are T-60, as well as EL-68. The steel comes in two common types; Extension type rods which are Male/Male (M/M) and require a coupler; and Speed type rods which are Male/Female (M/F) rods that thread together like conventional Drill Steel does.
Bit sizes are relative to both drill steel, and the application being performed. Commonly used Top Hammer Bit sizes are between 2.5” and 6”, although not necessarily relative to each size of Drill Steel listed above.
There are three commonly used bit types, Convex, for softer formations where an aggressive bit can be used for faster penetration; Drop Center, for medium to hard formations where penetration and flushing is important; and Flat Face, which is predominantly used in harder rock. In addition to the standard flushing ports the bits come with, Venturi flushing holes can be added to further expedite the cutting upward, in a quicker fashion.
Pinnacle Drilling Products are suppliers of the following typical drill steel configurations but can source other lengths or thread types if required.
- T-38 x 12' or 14' in M/F or M/M variations, round
- T-45 x 12' or 14' in M/F or M/M variations, round
- T-51 x 12' or 14' in M/F or M/M variations, round
Please contact us for other sizes and configurations
