Drilling Process
– Drilling is a cutting process where a drill bit is spun to cut a hole in solid materials.
– The drill bit is usually a rotary cutting tool, often multi-point.
– The cutting edge of the bit is pressed against the work-piece and rotated at high speeds.
– Chips (swarf) are cut off from the hole as it is drilled.
– Rock drilling involves hammering a drill bit into the hole with repeated short movements.
Hole Characteristics
– Drilled holes have a sharp edge on the entrance side and burrs on the exit side.
– The inside of the hole usually has helical feed marks.
– Drilling can affect the mechanical properties of the workpiece, making it more susceptible to corrosion and crack propagation.
– Different types of chips are formed during drilling, indicating the machinability of the material.
– The position of the drill bit should be carefully controlled to avoid walking and misplaced holes.
Surface Finish and Cutting Fluid
– Surface finish produced by drilling can range from 32 to 500 microinches.
– Cutting fluid is commonly used to cool the drill bit, increase tool life, and aid in chip removal.
– The application of cutting fluids can be done by flooding the workpiece or applying a spray mist.
– The choice of drill depends on the task at hand, with different drill styles serving different purposes.
– Subland drills, spade drills, and indexable drills are examples of drill styles with specific uses.
Spot Drilling
– Spot drilling is used to drill a hole that acts as a guide for the final drilling process.
– The hole is only drilled partway into the workpiece.
– Spot drilling is often done using center and spotting drill bits.
– It helps in accurately positioning the final hole.
– Spot drilling is an important step in achieving precise drilling results.
Deep Hole Drilling
– Deep hole drilling refers to drilling holes with a depth greater than ten times the diameter.
– Special equipment is required to maintain straightness, tolerances, roundness, and surface finish.
– Gun drilling and BTA drilling are common methods for deep hole drilling.
– Trepanning, skiving and burnishing, pull boring, and vibration drilling are other techniques used.
– Vibration drilling uses axial vibrations to break up chips and prevent drill breakage. Source: https://en.wikipedia.org/wiki/Drilling
This article needs additional citations for verification. (June 2008) |
Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the work-piece, cutting off chips (swarf) from the hole as it is drilled.
In rock drilling, the hole is usually not made through a circular cutting motion, though the bit is usually rotated. Instead, the hole is usually made by hammering a drill bit into the hole with quickly repeated short movements. The hammering action can be performed from outside the hole (top-hammer drill) or within the hole (down-the-hole drill, DTH). Drills used for horizontal drilling are called drifter drills.
In rare cases, specially-shaped bits are used to cut holes of non-circular cross-section; a square cross-section is possible.
The difference between drilling and boring is: the purpose of drilling is to obtain the depth of the hole, while the purpose of boring is to obtain an accurate radial hole based on the existing void.
