Types Of Bits Research Articles

Fundamentals of Bit Selection and Use

Choosing an appropriate bit can be a confusing process for horse enthusiasts. This 6-page illustrated fact sheet describes the various types of bits and how to select the best bit for horse and rider. Written by Edward L. Johnson and Kylee J. Duberstein. Published by the UF Department of Animal Sciences, January 2010.

An approach for Intranet Data Security

In this paper, combined the encrypting and compressing processes to consider the choices of which types of bits are most effective in the selective encryption sense when they are changed. So, instead of encrypting the whole file bit by bit, changed only these highly sensitive bits. Moreover, by combining the compression and encryption tasks and reducing the total encryption work required, it will helps to achieve a savings in system complexity. Selective encryption is the technique of encrypting some parts of a compressed data file while leaving others unencrypted. Selective encryption is not a new idea. It has been proposed in several applications, especially in the commercial multimedia industry. Hover, selective encryption of lossless compressed text files has not been explored, and that is the focus of this paper.

A note on bit types at Hasanlu, Iran

Hasanlu Tepe is a large mounded site in the Solduz Valley of western Azerbaijan dating from Islamic to Neolithic times. One of its main occupation levels belonged to the Iron II period (Fig. 1). This settlement was sacked and burned around 800/780 BC, preserving a large quantity of objects of daily living in the collapsed buildings (Dyson and Voigt 1989). One building (BB II) is thought to have been a temple (Dyson and Voigt 2003). Two others (BB IVE and BBV) appear, from the presence of urine stains and horse skeletons, to have been in use as stables at the time of the destruction, converted from an earlier function. They, as well as other areas, contained horse gear as well as skeletons of horses (de Schauensee and Dyson 1983; de Schauensee 1988: 47–9; 1989). Two types of bits for horses were found. Comparisons between them, combined with associated material, suggest that they had distinct, non-overlapping functions.

Effects of different bits and bridles on frequency of induced swallowing in cantering horses

AbstractIt has been suggested that the presence of a bit reflexly increases salivation but, at the same time, interferes with the horse's ability to swallow. The objective of this study was to compare swallowing frequency in 12 horses exercising at canter while wearing a head collar, a bitless bridle, a jointed snaffle bit and a Myler correctional-ported barrel bit. Laryngeal movements were recorded videoendoscopically as the horses cantered (8 m s−1) on a high speed treadmill, with the use of side reins to flex the poll. Swallowing was stimulated artificially by infusion of sterile water at a constant rate of 5 ml min−1through a cannula in the endoscope's biopsy port. The results showed large differences in swallowing frequency between horses. Swallowing frequency was lower for the Myler snaffle than for the other conditions (P<0.05). It is concluded that the presence of a bit does not preclude swallowing during exercise at canter with the poll in a flexed position, but certain types of bits may be associated with a reduction in swallowing frequency.

Radiographic study of bit position within the horse's oral cavity

AbstractThe objective was to describe and compare the positions of different types of bits within the horse's oral cavity. Eight horses were fitted with a bridle and six bits [jointed snaffle ( JS), Boucher, KK Ultra, Myler snaffle (MylerS), Myler ported barrel (MylerPB), Myler correctional-ported barrel (MylerCPB)]. Lateral radiographs and custom software were used to measure the position and orientation of the bits relative to the horse's palate and second premolar teeth without rein tension and with 25±5 N bilateral rein tension. The results showed differences in the position of the bits within the horse's oral cavity and in their movements in response to rein tension. Without rein tension, single-jointed bits were further from the premolar teeth ( JS 32.2±10.6 mm; Boucher 33.9±10.8 mm) than the Myler bits (MylerS 20.2±9.7 mm; MylerPB 12.8±6.7 mm; MylerCPB 14.6±4.3 mm). Single-jointed bits moved closer to the premolars when tension was applied to the reins (JS 20.8±6.3 mm; Boucher 19.7±6.8 mm). The cannons of the Boucher were more elevated than those of the other bits. The cannon angulation decreased significantly from 38.7±13.7 deg. to 21.6±6.9 deg. for JS and from 43.1±10.1 deg. to 27.8±10.1 deg. for the Boucher when tension was applied to the reins. The Myler bits showed minimal change in position in response to the application of rein tension.

Mechanistic Model for Spade Drills for Wood Drilling Operations, Part 1: Model Development

The purpose of this work is to present an investigation of the force system generated during spade drill-bit drilling processes that is a prerequisite for the design of spade-drills with improved performance. The technical literature offers no references to this type of bit and process; hence an approach based on the well-established mechanistic force prediction methods will be used. The force and torque prediction models are based on a complete analytical model of a generalized spade bit that takes into account the cutting action of all the characteristic cutting edges of the spade bit, namely of its chisel edge, tip and major cutting edges. In conjunction with the model an efficient model calibration method is also introduced and experimentally verified.

The Effect of Bit Geometry on Rock Cutting Efficiency

Abstract This article presents an analysis of the performance of various types of bits during rock cutting. Six types of bits, including conical (point attack) and drag bits, were tested at depths of cut ranging from 3 to 18 mm. Three force components—cutting, normal, and lateral—were measured for each experiment. The cut surface of the rock was photographed and analyzed for depth of cut and damage to the rock surface (i.e., chipping or crushing) at the conclusion of the test. The cut surface was also casted to measure rock yield, and the effect of bit geometry in regard to bit rock interaction was analyzed. The study indicated that bit geometry is the most significant parameter affecting both bit wear and cutting action. For a typical angle of attack, approximately 45°, some bits had only the bit body contacting the cutting surface, resulting in excessive bit wear, higher normal force to cutting force ratio, more crushing and less chipping of the cutting surface, and less bit penetration into the rock. T...

Dull bit grading and rock strength analysis key to bit selection: S. Tiwari, Oil & Gas Journal, 92(49), 1994, pp 45–51

The selection of a suitable bit appears simple and straightforward if one merely reads bit comparison tables; however, in the field, bit selection is considerably more difficult. Many times bit selection is more of an abstract and intuitional decision based on experience rather than an analytical decision based on facts. The following bit selection procedure has five parts: determine the rock compressive strength; identify the type of bit on the basis of rock compressive strength; accurately grade and analyze the previously run dull bit; clearly identify the causes of bit wear and suggest possible improvements in operating practices and bit type; and determine the features on the next bit based on formation characteristics and wear pattern of previous bit. This diagnostic approach of bit selection imparts the desired weight to each factor: formation strength, formation properties, bit limitations, and operating practices. All the practical limitations of field operations have been kept in mind in designing these procedures. A flexible (large and diverse) inventory of bits near the drill site will facilitate the effective implementation of this bit selection procedure.

Status of Polycrystalline-Diamond-Compact Bits: Part I Development(includes associated papers 19032 and 19900 )

Distinguished Author Series articles are general, descriptiverepresentations that summarize the state of the art in an area of technology bydescribing recent developments for readers who are not specialists in thetopics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and presentspecific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleumengineering. Summary. Polycrystalline-diamond-compact (PDC)bits have become anestablished new generation of oilfield bits particularly for drillingsoft-to-medium-hard, nonabrasive formations. The development of these bits isstill at an exciting stage. The state of the art in PDC cutters and bits isdiscussed and illustrated by a rich source of fairly recent literature. A lookinto the future is attempted in light of the bits'potential. Introduction In the past, roller-cone bits dominated rotary drilling and diamond bitscoring and turbodrilling. The manufacturers of bits made either roller bits ordiamond bits. During the 1980's, this picture changed markedly because of thesuccess of the PDC bit and more recently the collapse of oil prices. PDC bitshave taken an important share of the drilling. coring and motor-andturbodrilling, market, and are now produced by both diamond-bit androller-cone-bit manufacturers as a new generation of bits. The trend among themanufacturers is clearly toward fewer, more integrated companies that sell allthree types of bits in addition to other tools for downhole use. This paper focuses on PDC bit development through the 1980's and highlightsthe state of the art in the PDC cutters and bits. PDC Cutters Most characteristics of the PDC bit stem from those of the PDC cutter, whichhas been in use in the oil field for roughly 10 years. The development of PDCcutters lies mainly in the hands of cutter manufacturers. The originator ofthese cutters has maintained a leading, role but competing companies haveplayed a stimulating role in bringing, about a steady improvement in thequality and variety of the cutters. Cutters and bits currently are manufacturedby separate companies but a trend is apparent that bit manufacturers areexploring the idea of integration. The strength of the bit manufacturers isthat they can get firsthand, rapid feedback on cutter performance in the field, whereas cutter manufacturers must rely on their clients' responses-i.e., thebit manufacturers. In addition. for cutter manufacturers the oilfield is onlyone of many application of diamond technology, albeit an interesting one. This section provides some understanding, of the status of today's cutter, as developed for oilfield use. Nomenclature. A selective number of terms are used to identify PDC bits."PDC" refers to the cutter (Fig. 1a) that is mounted in PDC bits and isdiscussed here. Such generic terms as "shear bits" and "polycrystallinediamond" (PCD) are not limited to the specific diamond compact with atungsten-carbide substrate identified in Fig. 1a. The term "Stratapax bit"isdying out; it referred to the trade name used by the originator of the diamondcompact. A new product, the thermally stable polycrystalline (TSP) diamond, is asynthetic diamond, not a diamond compact, and therefore more related to diamondbits than to PDC bits. A TSP diamond (Fig. 2) is used to replace crystallinenatural diamonds in diamond bits, TSP diamonds will be discussed briefly forthe sake of completeness. Characteristics. A characteristic of the PDC cutter is the thin(=0.5-mm[=-0.02-in.]) PCD layer on top of a thicker (=-3-mm [-=0.12-in.])tungsten-carbide substrate (see Fig. 1a). This characteristic is of paramountimportance in the PDC bit: the cutter is self-sharpening because the tungstencarbide wears at least an order of magnitude faster than diamond and hence theweight on bit (WOB) is carried by the diamond layers. This explains why PDCbits can drill so rapidly at light bit loads, a feature exploited by many ofthe applications to be highlighted in "Status ofPolycrystalline-Diamond-Compact Bits: Part 2-Application" (scheduled for theJuly 1988 Journal of Petroleum Technology). The cutter-set at a negative rake of 0.26 rad [15 degrees] (Figs. 1b and1d)-acts initially as an extremely sharp cutter. The cutter wears with time anda thin flat develops on the diamond, which is why the bit load needs to begradually increased to maintain penetration. This is sometimes overlooked whenPDC bits are being tested in the laboratory: test results for a brand-new bitmay not be representative of an average bit run under conditions prevailingdownhole. The advent of the PDC cutter has in fact given rise to what is probably thefirst self-sharpening drag bit. Such a bit suffers from less chip holddown thandoes a roller-cone bit and much less than a diamond bit. This feature isanother reason for its rapid drilling characteristic downhole in the absence ofballing phenomena.

New Type of Bit from Iran

New Type of Bit from Iran

CHILDREN'S ACTIVITY AND TELEVISION COMPREHENSIBILITY

Children's attention to television, measured by visual attention and by self-reports, varied in this study depending on the comprehensibility of the content. Children's visual attention was lower when they viewed Sesame Street, Greek, and backwards language bits than with randomly edited or normal bits, but their visual attention did not discriminate between random and normal bits. However, self-reports of effort to comprehend showed that the oldest children found the random bits harder to understand than the normal bits. Because the older children's visual attention was equivalent for two types of bits that they reported were different in difficulty, the results suggest that comprehensibility may be of limited value in explaining older children's active television viewing, but also that studies explicitly tying together visual attention, effort, perceptions of a wide variety of program characteristics, and comprehension are in order.

A fluoroscopic study of the position and action of different bits in the horse's mouth

Fluoroscopy was used to visualize the position and movements of different types of bits within the horse's oral cavity. The jointed eggbutt snaffle normally lay between the tongue and palate with the joint hanging down toward the incisor teeth. By arching and elevating the tongue the horse was able to raise the mouthpiece between the cheekteeth. The jointed mouthpiece was suspended in a more horizontal position when keepers were used with a cheek snaffle to fix the position of the bit rings relative to the cheekpieces of the bridle. In addition, the mobility of the bit within the oral cavity was reduced by using keepers. Similarly less intra-oral movement was observed in bits with an unjointed mouthpiece. The Dr. Bristol bit, which has two joints connected by an angled plate, could be attached to the bridle in two ways so that the plate lay either parallel to the tongue and palate or perpendicular to them. This would be expected to have a marked effect on the severity of action of the bit. The high tongue port of the Hannoverian pelham pressed against the palate when the reins were used, causing considerable discomfort.

Higher Pump Pressures Can Reduce Drilling Costs

Deep-well drilling costs can be reduced substantially by using higher mud pump pressures. This has been demonstrated during the drilling of 1267 m (4166 ft) of 12 1/4-in. and 8 1/2-in. hole with a land rig, using pump pressures approaching 35 MPa (5000 psi) over a period of six weeks. Drilling costs were reduced by 25 percent (approximately $134,000) in the test well as a result of the higher pressures. The tests used drilling bits which combined mechanical and jet action, viz., extended-nozzle bits and a diamond bit designed to withstand the increased mud velocities. Both types of bits gave significantly improved performance when used at the higher pressure. Further tests were made with standard downhole turbines driving conventional bits. Improved performance was achieved at the higher pressure, provided the correct bit was selected for the formation encountered. In these cases the increase in penetration rate was due to the higher mechanical power developed by the turbine rather than increased jet action at the bit. Of the four turbine runs, two were found to be more economic than rotary runs made in similar formations in the reference well. The high-pressure mud pumps and other conventional equipment used in the tests performed well at the 35 MPa (5000 psi) pump pressure. Two standard triplex mud pumps were provided with fluid ends of an Exxon Production Research design and manufactured in Germany under Shell supervision. No failures occurred during six months of operation and in general, the equipment performed with the same downtime at the high pressure as the conventional equipment used in the reference well at the usual operating pressure (21 MPa (3000 psi)).

Further Notes on Wooden Pumps

AbstractThe following is an addendum to the writer's article on wooden pumps which was published in Vol. 7 of Folk Life. It is based on information which was supplied by Vincent, Raymond and John Grace, sons of the late Mr Raymond Grace of the Coombe, Dublin, after the original article had been written.The Grace brothers worked at the trade with their father. They confirmed that larch logs were used for the pipes and not elm as stated in error on page 107 of the original article. They claimed larch was used because it was particularly straight and it was easily bored with the type of bit that was used. In addition, it did not split and it withstood immersion in water very well.

Selecting the Proper Rotary Rock Bit

Introduction On Aug. 10, 1909, Howard R. Hughes patented the first rotary rock bit, which he called a "boring drill." The drill resembled two pipe reamers set on journal bearings attached to a drillpipe sub. This invention enabled rock formations to be drilled and was the starting point for 62 years of rock-bit development. This development history is traced in Fig. 1. It is not our purpose here to discuss these changes, nor to detail the basic designs of rock bits. The major bit manufacturers provide, for the asking, very good manuals on this subject. It is our purpose to provide the engineer who plans casing and drilling programs with the plans casing and drilling programs with the information he needs to take advantage of the most modern bit technology. Casing programs that force the use of obsolete bit types, and drilling programs that do not run the new bits properly are programs that do not run the new bits properly are more costly than they need be. Optimization of drilling is coming into its own after 10 years of intensive development. Often, however, the optimization procedures are handicapped by preset casing programs that force the use of off-size or obsolete bits. How good is modern bit technology? If you are drilling a "standard" hole size, the answer is "great." We are drilling footages and hours on single bits that would have been unbelievable just 2 years ago. Many of the new design features, which were experimental in the early 1960's, have been made generally available in the last 4 years. As shown in Fig. 1, it is estimated that improvements in rock bit development have been 30 percent greater in the last 4 years than in the 50 previous years. In fact, some optimum drilling programs planned just last year for ultradeep wells have become obsolete before the wells have been completed because of the introduction of new types of bits that were not generally available when the wells were originally planned. planned. Roller-Rock-Bit Classification Complete rock-bit nomenclature can be found in most bit catalogs and, therefore, will not be introduced here. However, several terms should be described for the following discussion. Rock bits are usually classified according to tooth material and height, cone offset, and journal angle. The teeth may be hard-faced, case-hardened, or inserts of tungsten carbide. The cone offset, sometimes called "skew," is a measure of how far the center line of a cone misses the center of the bit. Journal angle is the angle the center line of the bearing journal makes with the bottom of the hole. A rock bit may be built with any one of four different types of bearing assemblies: nonsealed roller, sealed roller, sealed journal, and "super" journal, with the price increasing in the order listed. A rock-bit classification guide based on these features for the four major bit manufacturers is given in Table 1. Bits on the same fine in the chart are designed to withstand roughly the same operating conditions. JPT P. 1359

Bottom Scavenging-A Major Factor Governing Penetration Rates at Depth

Abstract A laboratory study has been made to determine what factors affect the penetration rate of roller bits, diamond bits and drag bits in rock drilling with clay/water muds. The rather simple relations that exist when pressures in and around the borehole are equal become more complicated when under down-hole conditions the penetration rate is hampered by the existence of a pressure differential between the mud at the hole bottom and the pore liquid at cutting depth. Expressions that have been derived for both the penetration rate and the magnitude of the pressure differential in permeable rock together fully account for operating, rock, mud and bit variables. In impermeable rock a similar pressure differential is caused by the bit action itself. In all cases, the pressure differential and the reduction in penetration rate increase with the effectiveness of the plastering at the bottom of the hole by mud particles. Where bits are employed whose action is largely that of crushing, however, the plastering may become even in ore effective owing to the addition of rock particles rubbed into the pores of the rock. With roller bits, a plastically behaving layer may be formed, which causes a further reduction in penetration. In the case of bits whose action is chiefly scraping, moreover, penetration may be arrested by the bit's becoming balled-up. The various adverse effects are reduced by thorough scavenging of the hole bottom. This paper shows how with jet bits the efficiency of such scavenging may be improved by suitable choice of the position of the nozzles. Introduction The reduction in a bit's penetration rate with increasing depth of hole has been the subject of many investigations. Various investigators have independently reached the conclusion that this reduction occurs not so much because the rock-breaking process becomes more difficult as it does because the lifting of the rock fragments is impaired by a fluid pressure differential holding the fragments down. When such a pressure differential can be avoided, as in air drilling and to a smaller extent in water drilling, penetration rates remain high. Although the range of applicability of these techniques is being extended, most oil wells still have to be drilled with mud. In this paper we present the results of laboratory experiments carried out to determine what factors govern the hold down effect encountered in mud drilling. In the course of this investigation, the well known importance of bottom scavenging came more and more into prominence. Not only may it reduce the magnitude of the hold-down forces, but also it appeared to be a means of preventing the accumulation of a plastic mass of cuttings and mud on the hole bottom and bit which may cause penetration to cease almost completely. So that the effects of fluid pressures may be more readily understood, the factors that govern penetration rate in the absence of these pressures will first be discussed. The effect of down-hole pressures will then be assessed for the case of permeable rock where fluid pressures are well defined, and it will be demonstrated how rock strengthening due to confining can be accounted for. Subsequently, fluid pressures in less- permeable rock will be examined; we will show that in impermeable rock it is the bit action that governs fluid-pressure distribution and hold-down. In the case of poor scavenging and/or high bit load, cutting cake manifests itself. The effect, like various others, appears to depend on the type of bit used. From the very beginning, therefore, we shall base our discussion on the three main types of bits used in rotary oil-well drilling--roller bits, diamond bits and drag bits. Since space is limited, it will be impossible to make more than a passing reference to many aspects of the problem. Moreover, certain relations that are not of primary importance to our argument will unavoidably have to be stated in a somewhat dogmatic fashion, and the experimental data on which these are based necessarily must be omitted. EQUIPMENT The drilling experiments were performed on three machines, of which one has been designed for the realistic simulation of down-hole pressure conditions. HIGH-PRESSURES MACHINE In this machine (diagramed in Fig. 1) the mud, pore and confining pressures can all be adjusted independently. The foil-covered rock sample contained in the inner pressure vessel is confined by oil that is pressurized by means of a hand pump. The pore space of the water-saturated sample is connected to an arrangement which keeps the pressure in the pore space constant regardless of the rate of filtrate flow through the sample. JPT P. 187^