Drilling Processes Drill bits

If a shallow kick off in soft formation is required (e.g. to steer the borehole away underneath platforms) a technique using jet bit deflection or badgering is employed (Fig. 3.16). A rock bit is fitted with two small and one large jet. With the bit on bottom and oriented in the desired direction the string is kept stationary and mud is pumped through the nozzles. This causes asymmetric erosion of the borehole beneath the larger jet. Once sufficient hole has been jetted, the drill bit will be rotated again and the new course followed. This process will be repeated until the planned deviation is reached. 

Warehouses are normally considered low risk occupancies unless high value or critical components are stored. Some high valve components normally overlooked in warehouses are diamond (industrial grade) studded drill bits or critical process control computer boards. In these cases the economic benefits of installing an automatic sprinkler system should be investigated. 

Sampling of vapour can be extended to any depth above the water table by analysing the exhaust air from an air-drilled well. Complications occur because of dilution effects by the air injected for drilling and by the additional fact that the drill bit disaggregates and liberates rock or matrix gas in the process of drilling the hole. 

A waste process directed to the cleanup of drilling fluids is being developed by Critical Fluid Systems Inc. (Anon., 1982). Oil-based drilling fluids (commonly termed muds) are used to lubricate and cool drill bits and to... 

As the drill bit penetrates, microfissuring occurs, plasticity processes develop, and the intrinsic properties of the shale change. 

In the process of gas extraction drilling, if the drill bit encounters with the rocks in the coal seam, the drill pipe will deviate from the expected trajectory... 

Drilling is a separating process that produces a round hole. The hole may or may not pass aU the way through the material (Figure 16-18). A drill bit is used as the cutting tool. Drill bits may be used in portable electric hand drills or in a machine called a drill press (Figure 16-19). 

Core drilling The process by which a cylindrical sample of rock and other strata is obtained through the use of a hoUow drilling bit that cuts and retains a section of the rock or other strata penetrated. 

The high deposition temperature (- 1000°C) of CVD diamond may exclude deposition on substrates such as high-speed steels for drill bits and cutting tools. These steels would lose their hardness and strength during processing and in order to coat them, a process must be developed that will keep the deposition temperature below 600°C. 

In addition, higher Tg resin systems can be harder and more brittle than lower Tg systems. This can adversely affect productivity in the printed circuit manufacturing process. In partic-nlar, the drilling process can be affected as slower drilling, reduced drill bit life or reduced stack heights can be reqnired for high-Tg materials. 

Undercut drill bits generally provide better hole quality with these materials. Other drill process variables must also be examined, and include ... 

Material Utilization. The material manufacturing costs, which correspond to 30 to 40 percent of total costs, are directly related to the sqnare inches of material processed.The material costs can include the following laminate, prepreg, copper foil, solder mask, photoresists, drill bits, chemicals, and so on. Generally, these materials are consumed relative to the panel area manufactured. 

Effects. Excessive backup penetration depth increases drill wear and the occurrence of breakage of small-diameter drill bits, adversely affects hole quality, and increases process time per load. Insufficient backup penetration depth results in incompletely drilled holes. This impiies that thickness variations of the backup material are very important, meaning that minimai variations are a much desired characteristic of the backup and need to be considered when choosing a material suitable for your application. 

Definition. The maximum hits per tool specified for any given drill size implies the number of drill strokes a drill bit is used for until its expected effective life is expired. Maximum hit count per tool is product and process specific and is affected by laminate material construction, panel thickness, drilled stack height, surface speed, and the type of entry and backup material used. Therefore, no specific number of hits per tool can be arbitrarily specified. 

Effects. The less the stack clearance distance between the drill point and the top of the stack, the shorter the drill stroke and therefore the shorter the processing time per load. Increasing the stack clearance distance allows more time between drill strokes and gives the tool table more time to settle, which may improve hole registration accuracy and prevent smaii-diameter drill bit breakage. In addition, the greater the time between drill strokes, the... 

The point of a postdrilling inspection process is that if one takes the time on a regular basis, to examine materials and drill bits after drilling, many driUing problems would be solved before they get out of hand. 

Drill bits (called tools) are critical in the drilling process. A wide variety of tools are available and your tool vendor can be very helpful with selecting feeds and speeds. Be sure to try several vendors to find the best tools for your particular process. 

The condition of the used drill bit is a key indicator of the control and capability of the drilling process and provides an indication of the condition of the drilled hole wall. A wealth of process information can be extracted from the used drill bit. Examining drills before the... 

Drill machine operators and drill bit resharpeners shonld regularly evaluate the condition of used drill bits and report the findings to the process engineers. The areas of greatest concern when evaluating the condition of used drill bits are ... 

When tracked over time, this information can help alert the engineering team of any sudden changes in the drilling process. Although the used drill bit condition information is subjective, with properly trained personnel it can serve as a key indicator of the level of hole wall quality. 

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