MACHINERY'S REFERENCE SERIES EACH NUMBER IS ONE UNIT IN A COMPLETE LIBRARY OF MACHINE DESIGN AND SHOP PRACTICE REVISED AND REPUBLISHED FROM MACHINERY NUMBER 25 DEEP HOLE DRILLING SECOND EDITION CONTENTS Introduction Principles of Deep Hole Drilling, by LESTER G. FRENCH and C. GOODRICH Deep Hole Drilling in Gun Construction, by J. SCHEELE Construction of Deep Hole Drills, by FRANK B.

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2 E 294 DRILLING Deep hole drilling - Gun drilling E F G J D ROT - ENG ROT - ENG ROT - ENG DRILLING Deep hole drilling - Gun drilling Gun drills Solid carbide heads 428.9 and 428.2 l2=Overall length with or without driver Dc=Drill diameter l21=Addition for regrinding lm=Depth of hole l26=Minimum chip evacuation distance lc=Length of drive dm=Driver diameter. Screen is the instruction manual for every single project featured in “I Can Do That.” It’s a living document; as we introduce new techniques or ideas, we’ll update this manual and load it to the web site for you to retrieve. Eventually, we think you’ll outgrow this manual as your skills improve. I bet you will want a table saw someday.

KLEIN HANS, OTTO ECKELT, and E. NORTON Deep-hole Dril l ing MACHINERY MAGAZINE - AUGUST S, 1926 BY F.W.B Deep-Hole Dril l MACHINERY MAGAZINE - MARCH 10, 1927 BY F.C.M Reprinted by Lindsay Publications lnc - all rights reserved 2 3 4 S 6 7 8 9 0 - 2001 - ISBN 1-SS918-2S8-X 1Introduction The difficulties to be overcome in producing deep drilled holes can be classified in three groups.

In the first place the drill has a great tendency to 'run out' thus producing a hole that is neither straight, nor uniform in diameter; in the second place great difficulties are encountered in trying to remove the chips in a satisfactory manner, and in the third place the heating of the cutting tool is difficult to prevent. Comparison between Action of Cutting Tool when Drill and when Work revolves. The principle involved in common drill presses where the drill is given a rotary motion simultaneously with the forward motion for feeding is the one least adapted to produce a straight and true hole. Better results are obtained by giving only a rotary motion to the drill, and feeding the work toward it. It has been found, however, that for drilling deep holes the reversal of this, that is, imparting a rotary motion to the work, and the feed motion to the drill will answer the purpose still better. It seems as if there could be no material difference between the two latter methods. An analysis of the conditions involved will show, however, that there is a decided difference in the action of the drill.

If the drill rotates, and the work is fed forward as shown to the left in Fig. 1, the drill, when deviating from its true course, will 2be caused to increase its deviation still more, by the wedge action of the part B, which tends to move in the direction BA when the work is fed forward. In the case of the work rotating and the drill being fed forward, as shown to the right in Fig. 1, the point of the drill when not running true will be carried around by the work in a circle with the radius a, thus tending to bend the drill in various directions. The drill is by this action forced back into the course of 'least resistance,' as it is evident that the bending action, being exerted on the drill in all directions, will tend to carry the point back to the axis of the work where no bending action will appear. The chips, as is well known, are carried off by forcing a fluid into the hole, which upon its return carries with it the chips.

This fluid being oil will serve the double purpose of carrying away the chips and lubricating the cutting tool, keeping it at a normal temperature. In the following chapters, we shall deal with the practice of deep hole drilling as met with in a number of prominent American shops, presenting at the same time a collection of useful data covering different classes of work. The relation between ordinary drilling and deep hole drilling, dealing with first and fundamental principles, is treated in Chapter I, followed by a detailed account of the practice of deep hole drilling at the Pratt & Whitney Works, Hartford, Conn. In Chapter Il the boring of large guns, according to the practice employed at the Watervliet Arsenal, is described. Chapter III is devoted to illustrating and describing various constructions of deep hole drills of merit, together with hints regarding their making, thereby completing the treatise. 3CHAPTER I Principles of Deep Hole Drilling The process of drilling deep holes in metal is a familiar one in many shops, particularly where firearms are manufactured, or heavy ordnance is constructed.

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Since the adoption of hollow spindles for lathes and other machine tools, the methods for machining the bores of guns have been employed in machine tool shops for drilling these spindles; and through this and other means the principles of the operation have become better understood. It is not an easy matter, however, even with the best appliances, to drill or bore a, deep hole smooth and round, of exactly the required diameter from end to end, and perfectly straight. While many mechanics are familiar in a general way with the methods and tools for doing this work, specific information upon the subject will be appreciated by those who have not had actual experience in deep hole drilling. It is well known that a long, or deep, hole-that is, one long in proportion to its diameter is best roughed out and finished by using a tool on the end of a long bar which enters the work from one end.

This is true, whether drilling into solid metal, or boring and reaming a hole that has already been drilled or bored out. A boring bar which extends through the piece, and on which is either a stationary or a traveling head, is not satisfactory for very long work, owing to the spring and deflection of the bar, which is made worse by the fact that the bar must be enough smaller than the bore to allow room for the cutter head. While a long hole may sometimes be finished satisfactorily by means of such a boring bar, by packing the cutter head with wooden blocks which just fill the part of the bore that has been machined, and so support the bar, the method is fundamentally incorrect for long work. The best methods for machining deep holes are nothing more nor less than an adaptation of what has been found successful in ordinary drilling and boring in the engine lathe or chucking machine. We will therefore first discuss certain types of chucking tools and drills, and show their relationship to tools that may be used for deep hole drilling.

The Flat Drill 4To start with first principles, consider the ordinary flat drill. It is useful for rough work or in drilling hard metals, because it can be easily made and tempered; but it has too much of an inclination for drilling holes that are neither round nor straight, and whose diameter seems to bear no relation to the diameter of the drill. When a flat -drill runs into a blow hole or strikes a hard spot, it is deflected, as in Fig. 2, the only resistance to this deflection being the narrow edges of the drill. Under such conditions the hole will be out of round, and crooked. Add to this natural tendency of a flat drill to run out the fact that such drills are often carelessly made, and one understands why they have a reputation for poor work.

Thus, if the point is not in line with the axis of the drill, and if the lips are of unequal length, or do not make equal angles with the axis, the hole will be larger than the drill diameter. This is illustrated in Fig. 3, where one lip is longer than the other, and the point does not lie in the central axis of the drill.

The tendency of the drill is to rotate about its point, and thus the axis will move in a small circle about this point, causing the hole to be of larger diameter than the drill. It is obvious that to improve the action of a flat drill, it should be so guided as to prevent its wabbling and to compel it to move forward in a straight line. This is partially accomplished with the flat chucking drill, which is a near relative of the ordinary flat drill, differing from it in that it is generally more carefully made and is adapted for use in the engine lathe. 4 is an illustration of a chucking drill at work on a piece in the lathe, and to make the comparison fair it is shown with one lip longer than the other, as was the flat drill in Fig. The work is held in the lathe chuck and turns with the spindle. A rest steadies the drill at a point near the work, and in starting the hole, the drill is held firmly against the rest by means of a monkey wrench. It will be noted that while a poorly ground chucking drill will make a large hole, just as does the drill in Fig.

3, if properly started it will not wabble, and it 5will drill the hole where it is wanted and approximately in line with the lathe centers. To attain these results, however, the drill must be started right. If it is found to wabble when left free, it must be started over again, before the full size of the hole has been attained, by crowding it into the work and toward the operator at the same time, causing only one edge of the drill to do the cutting. This edge will then true up the hole, and in proceeding with the drilling the trued hole will guide the drill. The latter will thus be continuously supported near the cutting edges by the cylindrical surface of the hole, and the drill will tend to advance in the direction in which it was started. After the hole is drilled, it is usually brought to size by a flat reamer, like Fig. For reasons that will be explained, the flat drill is not an accurate tool, even when well made and used in the lathe, and the flat reamer is not as reliable as one with more blades.

The general principle, however, of first starting with a true hole, and then having the drill body designed to follow in its path and so guide the cutting edges, is the fundamental principle of deep hole drilling. 6 shows how a flat drill may be adapted for deep hole drilling. The drill from which the illustration was made was employed for drilling a four-inch hole through steel rolls seven feet long. Instead of depending upon the narrow edges of the drill proper to guide and support the cutting edges, the cutting edges are formed on a blade inserted in a cylindrical cast-iron head, the outside diameter of which is turned to a sliding fit in the hole that is being bored. The cutting edges are grooved to break up the chips, enabling the latter to pass out through the passage E, on each side of the head. The grooves are laid out so that those in one blade come opposite to the lands in the other blade. In the illustration, A is the cutter, B one of the screws holding the cutter to the head C, and the head is attached to the bar by the shank D.

The Twist Drill The modern twist drill accomplishes all that is attained by the arrangement in Fig. 6, and in addition can be ground without seriously affecting the rake, and will free itself from chips more readily, owing 7to its spiral flutes. The lands of a twist drill present a large cylindrical surface to bear against the sides of the hole and take the side thrust. If the drill is also guided by a hardened bushing, at the point where it enters the metal, as in the case of jig work, the drill will have very little chance to deflect, and the hole will be accurately located and will be quite true and straight. The twist drill in a modified form is also employed for deep hole drilling. The hollow drill introduced by the Morse Twist Drill Co., New Bedford, Mass., is adapted for this purpose, and in Fig.

7 is shown the arrangement recommended by this company for feeding this drill into the work. The drill has a hole lengthwise through the shank, connecting with the grooves in the drill, as indicated. The shank can be threaded and fitted to a metal tube which acts as a boring bar and through which the chips and oil may pass from the point of the drill.

Oil is conveyed to the point on the outside of the tube, as shown in Fig. In using the hollow drill, the hole is first started by means of a short drill of the size of the hole desired, and drilled to a depth equal to the length of the hollow drill to be employed.

The body of the hollow drill acts as a stuffing, compelling the oil to follow the oil grooves provided, and the chips to flow out through the flutes and the hollow shank. The methods of supporting and driving the work, and of feeding the drill, are clearly shown in Fig. Drills of this type are regularly manufactured in sizes up to three inches in diameter, and it is stated that the best results are obtained, when drilling tool steel, by revolving the drill at a cutting speed of 20 feet per minute, with a feed of 0.0025 inch per revolution, while machine steel will admit of a cutting speed of 40 feet per minute and a feed of 0.0035 inch per revolution.

Number of Cutting Edges Desirable 8 When drilling a hole out of solid stock, some type of drill having two lips or cutting edges is usually the most feasible, and probably nothing will be devised that on the whole surpasses the twist drill for such work. As is well known, the ordinary twist drill is always provided with two flutes, but twist drills having three or more flutes have been devised, made and tried.

The advantages gained by adding to the number of cutting edges have, however, not been great enough to justify the increased cost of manufacture. When added to this comes the weakness caused by the increased number of grooves, and the complicated operation of correctly grinding such drills, it is clear why drills having two flutes only have been and should be adopted. An end mill, like that in Fig. 11, can be used for drilling, if it has a 'center cut,' and it will presently be explained how a tool with a single cutting edge may be advantageously employed, particularly for deep hole drilling.

The familiar D-drill is of this type, and also its modification as used by the Pratt & Whitney Co. In drilling gun barrels. When it comes to truing up or enlarging a hole previously drilled or bored, the two-lip drill is not suitable in any of its forms. For boring a true hole nothing can surpass a single-pointed boring tool, the ideal condition for finishing a hole being when the cutting point is a real diamond, or a rotating wheel of abrasive material. It is obvious that when a hard or soft spot is encountered, in boring with a tool having a single cutting edge, only that particular place is affected by the spring of the tool. With a double cutter, as shown in Fig. 9, first sketch, any deflection due to irregularities, such as at a or b, will cause the tool to spring and the cutting edge on the opposite side to introduce similar irregularities in the opposite side of the 9hole.

This is one objection to the two-lip drill for accurate work. With three points the tool is somewhat better supported when a high place is encountered, as shown in the second sketch, Fig. 9, and when a cutting point strikes a low place the other two edges are not moved away from their position so much as if they were opposite the first edge.

Hence a tool with three edges should prove better than one with two, and one with four, being better supported, would seem better on this account than one with three, but has the disadvantage of opposite cutters. Five edges ought to give still better results.

Titanium drillingDrilling is a process that uses a to cut a hole of circular in solid materials. The drill bit is usually a rotary, often multi-point.

The bit is against the work-piece and rotated at rates from hundreds to thousands of. This forces the cutting edge against the work-piece, cutting off from the hole as it is drilled.In 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 or within the hole (, DTH). Drills used for horizontal drilling are called.In rare cases, specially-shaped bits are used to cut holes of non-circular cross-section; a cross-section is possible. Contents.Process Drilled holes are characterized by their sharp edge on the entrance side and the presence of on the exit side (unless they have been removed). Also, the inside of the hole usually has helical feed marks.Drilling may affect the mechanical properties of the workpiece by creating low around the hole opening and a very thin layer of highly and disturbed material on the newly formed surface.

This causes the workpiece to become more susceptible to and at the stressed surface.A finish operation may be done to avoid these detrimental conditions.For drill bits, any chips are removed via the flutes. Chips may form long spirals or small flakes, depending on the material, and process parameters. The type of chips formed can be an indicator of the of the material, with long chips suggesting good material machinability.When possible drilled holes should be located perpendicular to the workpiece surface. This minimizes the drill bit's tendency to 'walk', that is, to be from the intended center-line of the bore, causing the hole to be misplaced.

The higher the length-to-diameter ratio of the drill bit, the greater the tendency to walk. The tendency to walk is also preempted in various other ways, which include:. Establishing a centering mark or feature before drilling, such as by:., or a mark into the workpiece. (i.e., center drilling)., which is machining a certain area on a casting or forging to establish an accurately located face on an otherwise rough surface. Constraining the position of the drill bit using a withproduced by drilling may range from 32 to 500 microinches. Finish cuts will generate surfaces near 32 microinches, and roughing will be near 500 microinches.is commonly used to cool the drill bit, increase tool life, increase, increase the surface finish, and aid in ejecting chips. Application of these fluids is usually done by flooding the workpiece with coolant and lubricant or by applying a spray mist.In deciding which drill(s) to use it is important to consider the task at hand and evaluate which drill would best accomplish the task.

There are a variety of drill styles that each serve a different purpose. The subland drill is capable of drilling more than one diameter. The spade drill is used to drill larger hole sizes. The indexable drill is useful in managing chips. Spot drilling.

Blast hole several meters long, drilled in graniteDeep hole drilling is defined as drilling a hole of depth greater than ten times the diameter of the hole. These types of holes require special equipment to maintain the straightness and tolerances. Other considerations are roundness and surface finish.Deep hole drilling is generally achievable with a few tooling methods, usually or BTA drilling. These are differentiated due to the coolant entry method (internal or external) and chip removal method (internal or external). Using methods such as a rotating tool and counter-rotating workpiece are common techniques to achieve required straightness tolerances.

Secondary tooling methods include trepanning, skiving and burnishing, pull boring, or bottle boring. Finally, a new kind of drilling technology is available to face this issue: vibration drilling. This technology breaks up the chips by a small controlled axial vibration of the drill. The small chips are easily removed by the flutes of the drill.A high tech monitoring system is used to control, and acoustic emission.

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Vibration is considered a major defect in deep hole drilling which can often cause the drill to break. A special coolant is usually used to aid in this type of drilling.Gun drilling. Main article:Gun drilling was originally developed to drill out gun barrels and is used commonly for drilling smaller diameter deep holes.

The depth-to-diameter ratio can be even greater than 300:1. The key feature of gun drilling is that the bits are self-centering; this is what allows for such deep accurate holes. The bits use a rotary motion similar to a twist drill; however, the bits are designed with bearing pads that slide along the surface of the hole keeping the drill bit on center. Gun drilling is usually done at high speeds and low feed rates.Trepanning Trepanning is commonly used for creating larger diameter holes (up to 915 mm (36.0 in)) where a standard drill bit is not feasible or economical. Trepanning removes the desired diameter by cutting out a solid disk similar to the workings of a. Trepanning is performed on flat products such as sheet metal, granite , plates, or structural members like.

Trepanning can also be useful to make for inserting, such as.Microdrilling Microdrilling refers to the drilling of holes less than 0.5 mm (0.020 in). Drilling of holes at this small diameter presents greater problems since coolant fed drills cannot be used and high spindle speeds are required. High spindle speeds that exceed 10,000 RPM also require the use of balanced tool holders.Vibration drilling. Vibration drilling of an aluminum-CFRP multi-material stack with MITIS technologyThe first studies into vibration drilling began in the 1950s (Pr. Poduraev, Moscow Bauman University). The main principle consists in generating axial vibrations or oscillations in addition to the feed movement of the drill so that the chips break up and are then easily removed from the cutting zone.There are two main technologies of vibration drilling: self-maintained vibration systems and forced vibration systems.

Most vibration drilling technologies are still at a research stage. In the case of self-maintained vibration drilling, the of the tool is used in order to make it naturally vibrate while cutting; vibrations are self-maintained by a mass-spring system included in the tool holder.

Other works use a piezoelectric system to generate and control the vibrations. These systems allow high vibration frequencies (up to 2 kHz) for small magnitude (about a few micrometers); they are particularly suitable for drilling small holes.

Finally, vibrations can be generated by mechanical systems: the frequency is given by the combination of the rotation speed and the number of oscillation per rotation (a few oscillations per rotation), with magnitude about 0.1 mm.This last technology is a fully industrial one (example: SineHoling® technology of MITIS). Vibration drilling is a preferred solution in situations like deep hole drilling, multi-material stack drilling (aeronautics) and dry drilling (without lubrication). Generally, it provides improved reliability and greater control of the drilling operation.Circle interpolating. The orbital drilling principleCircle interpolating, also known as orbital drilling, is a process for creating holes using machine cutters.Orbital drilling is based on rotating a around its own axis and simultaneously about a centre axis which is off-set from the axis of the cutting tool. The cutting tool can then be moved simultaneously in an axial direction to drill or machine a hole – and/or combined with an arbitrary sidewards motion to machine an opening or cavity.By adjusting the offset, a cutting tool of a specific diameter can be used to drill holes of different diameters as illustrated. This implies that the cutting tool inventory can be substantially reduced.The term orbital drilling comes from that the cutting tool “orbits” around the hole center. The mechanically forced, dynamic offset in orbital drilling has several advantages compared to conventional drilling that drastically increases the hole precision.

The lower thrust force results in a hole when drilling in metals. When drilling in the problem with is eliminated.

Material Drilling in metal. High-speed steel twist bit drilling into aluminium with methylated spirits lubricantUnder normal usage, swarf is carried up and away from the tip of the drill bit by the fluting of the drill bit. The cutting edges produce more chips which continue the movement of the chips outwards from the hole.

This is successful until the chips pack too tightly, either because of deeper than normal holes or insufficient backing off (removing the drill slightly or totally from the hole while drilling). Is sometimes used to ease this problem and to prolong the tool's life by cooling and lubricating the tip and chip flow. Coolant may be introduced via holes through the drill shank, which is common when using a gun drill. When cutting in particular, cutting fluid helps ensure a smooth and accurate hole while preventing the metal from grabbing the drill bit in the process of drilling the hole.

When cutting brass, and other soft metals that can grab the drill bit and causes 'chatter', a face of approx. 1-2 millimeters can be ground on the cutting edge to create an obtuse angle of 91 to 93 degrees. This prevents 'chatter' during which the drill tears rather than cuts the metal. However, with that shape of bit cutting edge, the drill is pushing the metal away, rather than grabbing the metal. This creates high friction and very hot swarf.