Drill Materials The two most common types are 1. HSS drill - Low cost 2. Carbide- tipped drills - high production and in CNC machines Other types are Solid Carbide drill, TiN coated drills, carbide coated masonry drills, parabolic drills, split point. Types of drills Twist drill: most common drill Step drill: produces holes of two or more different diameters Core drill: used to make an existing hole bigger. Tool Holding devices The different methods used for holding drill in a drill spindle are By directly fitting in the spindle hole.
By using drill sleeve By using drill socket By using drill chuck. Drilling operations Operations that can be performed in a drillin g machine are Drilling Reaming Boring Counter boring Countersinking Tapping. Reamers :Multi tooth cutting tool Accurate way of sizing and finishing the preexisting hole. Accuracy of 0. Boring tool is held in the boring bar which has the shank. Types of cutters Countersinks :Special angled cone shaped enlargement at the end of the hole Cutting edges at the end of conical surface.
Cone angles of 60, 82, 90, , , Counter Bore Tool:Special cutters uses a pilot to guide the cutting action. Accommodates the heads of bolts. Types of cutters Combined Countersinks and central drill :Special drilling tool to start the hole accurately. At the end it makes countersinks in the work piece.
Gun drill :Machining of lengthy holes with less feed rates. For cutting internal thread Multi cutting edge tool. Tapping is performed either by hand or by machine. Minor dia of the thread is drilled and then tapping is done. Precautions for Drilling machine Lubrication is important to remove heat and friction. Machines should be cleaned after use Chips should be removed using brush.
T-slots, grooves, spindles sleeves, belts, pulley should be cleaned. Machines should be lightly oiled to prevent from rusting.
Safety Precautions Do not support the work piece by hand use work holding device. Use brush to clean the chip No adjustments while the machine is operating Ensure for the cutting tools running straight before starting the operation.
Never place tools on the drilling table Avoid loose clothing and protect the eyes. Ease the feed if drill breaks inside the work piece. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Carousel Next. What is Scribd? Explore Ebooks. Bestsellers Editors' Picks All Ebooks. Explore Audiobooks. Bestsellers Editors' Picks All audiobooks.
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Uploaded by Shrvan Hirde. Document Information click to expand document information Description: detailed info on drilling its types and processes. Did you find this document useful? Tungsten-alloy disks are sealed in the bar to counteract vibration and chatter during boring. The control systems can be computer-based, allowing for automation and increased consistency.
Because boring is meant to decrease the product tolerances on pre-existing holes, several design considerations apply. First, large length-to-bore-diameters are not preferred due to cutting tool deflection. Next, through holes are preferred over blind holes holes that do not traverse the thickness of the work piece. Interrupted internal working surfaces - where the cutting tool and surface have discontinuous contact - are preferably avoided.
The boring bar is the protruding arm of the machine that holds cutting tool s , and must be very rigid. Because of the factors just mentioned, deep-hole drilling and deep-hole boring are inherently challenging areas of practice that demand special tooling and techniques. Nevertheless, technologies have been developed that produce deep holes with impressive accuracy. In most cases they involve multiple cutting points, diametrically opposed, whose deflection forces cancel each other out.
They also usually involve delivery of cutting fluid pumped under pressure through the tool to orifices near the cutting edges. Gun drilling and cannon boring are classic examples. First developed to make the barrels of firearms and artillery, these machining techniques find wide use today for manufacturing in many industries.
Various fixed cycles for boring are available in CNC controls. These are preprogrammed subroutines that move the tool through successive passes of cut, retract, advance, cut again, retract again, return to the initial position, and so on.
These are called using G-codes such as G76, G85, G86, G87, G88, G89; and also by other less common codes specific to particular control builders or machine tool builders. Lathe boring is a cutting operation that uses a single-point cutting tool or a boring head to produce conical or cylindrical surfaces by enlarging an existing opening in a workpiece.
For nontapered holes, the cutting tool moves parallel to the axis of rotation. For tapered holes, the cutting tool moves at an angle to the axis of rotation. Geometries ranging from simple to extremely complex in a variety of diameters can be produced using boring applications. Boring is one of the most basic lathe operations next to turning and drilling.
Lathe boring usually requires that the workpiece be held in the chuck and rotated. As the workpiece is rotated, a boring bar with an insert attached to the tip of the bar is fed into an existing hole. When the cutting tool engages the workpiece, a chip is formed.
Depending on the type of tool used, the material, and the feed rate, the chip may be continuous or segmented. The surface produced is called a bore. The geometry produced by lathe boring is usually of two types: straight holes and tapered holes. Several diameters can also be added to each shape hole if required. To produce a taper, the tool may be fed at an angle to the axis of rotation or both feed and axial motions may be concurrent. Straight holes and counterbores are produced by moving the tool parallel to the axis of workpiece rotation.
The four most commonly used workholding devices are the three-jaw chuck, the four-jaw chuck, the collet, and the faceplate. The three-jaw chuck is used to hold round or hex workpieces because the work is automatically centered. On these chucks the runout faces limitations; on late-model CNCs, it can be quite low if all conditions are excellent, but traditionally it is usually at least. The four-jaw chuck is used either to hold irregular shapes or to hold round or hex to extremely low runout with time spent indicating and clamping each piece , in both cases because of its independent action on each jaw.
The face plate is also used for irregular shapes. Collets combine self-centering chucking with low runout, but they involve higher costs. In deep holes with tolerances this tight, the limiting factor is just as often the geometric constraint as the size constraint. In other words, it may be easy to hold the diameter within. Grinding, honing, and lapping are the recourse for when the limits of boring repeatability and accuracy have been met.
Surface finish roughness in boring may range from 8 to microinches, with a typical range between 32 and microinches. Sometimes a part may require higher accuracy of form and size than can be provided by boring.
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