WorldWide Drilling Resource

Feed Rate and Bit Pressure by Scott Cosby This month’s article will focus on two important drilling variables - feed rate and bit pressure - whether it’s water well, geothermal, or geotechnical drilling. The basic function of drilling is to advance the hole from the surface to a deter- mined depth, and perform other required activities (well placement, foundation tests, etc.). Every drilling professional should have a firm grasp of the importance of feed rate and bit pressure vari- ables. Feed Rate: This is the rate the bit is advanced into soil or rock material. It can be expressed in inches per minute, inches per bit revolution, or the number of bit revolutions per inch of advance. You can visually time the movement because the feed rate is easily seen by the downward motion of the rig’s piston rods within the hydraulic cylinders. Bit Pressure: This is the weight or pressure applied to a bit during drilling operations and is expressed as the number of pounds or tons of weight applied. A gauge is used to monitor the bit pressure. Most drill rigs will have a bit pressure gauge instal led some- where near the primary drill rig controls. I have not seen a written determination for the proper use of feed rate and bit pres- sure. The drill bit itself should be consid- ered in terms of feed rate and bit pressure, so know the limitations of your drill bit. Another consideration is the soil or rock materials being drilled. In soft materi- als, increasing the feed rate and bit pres- sure may cause the bit to become clogged, where the bit is actually forced into the material and not cutting through it. Sound judgment of the material is also needed from the person drilling. Drill rig technology allows the operator to “dial” a specific feed rate and bit pres- sure during drilling, but a firm knowledge of these two essential drilling variables, along with sound judgment of the soil and/or rock materials being drilled will ensure success in any type of drilling operation. Watching the gauge and making sound material judgment calls are the final keys for the drill operator. Scott Scott Cosby may be contacted via e-mail to michele@ worldwidedrillingresource.com Typical drill rig controls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orldWide Drilling Resource ® JANUARY 2016 On January 13, 1957, the company Wham-O manufactured this fun product using newly-invented Phillips Petroleum polymer plastic. Hint: It will throw you for a loop! Can you guess what it is? Find out on page 32!