Drilling Machines.

Drilling Machines

Drilling Machines Probably first mechanical device developed
Principle of rotating tool to make hole One of most common and useful machines in industry Come in several types and sizes From hand-fed to computer-controlled

Drill Presses Unit 38

Objectives Identify six standard operations that may be performed on a drill press Identify four types of drill presses and their purposes Name and state the purpose of the main parts of an upright and a radial drill

Drilling Press Drilling machine Spindle Work table
Turns drill to advance into work (hand or automatically) Work table Holds workpiece rigidly in place as hole drilled Used primarily to produce holes in metal Other operations: tapping, reaming, boring, counterboring, countersinking, spot-facing

Standard Operations Drilling Countersinking
Operation of producing hole by removing metal from solid mass using twist drill Countersinking Operation of producing tapered or cone-shaped enlargement to end of hole > Countersinking (Fig. 38-1b) is the operation of producing a tapered or cone-shaped enlargement to the end of a hole. > Reaming (Fig. 38-1c) is the operation of sizing and producing a smooth, round hole from a previously drilled or bored hole with the use of a cutting tool having several cutting edges. > Boring (Fig. 38-1d) is the operation of truing and enlarging a hole by means of a single-point cutting tool, which is usually held in a boring bar. > Spot-facing (Fig. 38-1e) is the operation of smoothing and squaring the surface around a hole to provide a seat for the head of a cap screw or a nut. A boring bar, with a pilot section on the end to fit into the existing hole, is generally fitted with a double-edged cutting tool. The pilot on the bar provides rigidity for the cutting tool and keeps it concentric with the hole. For the spot-facing operation, the work being machined should be securely clamped and the machine set to approximately one-quarter of the drilling speed. > Tapping (Fig. 38-1f) is the operation of cutting internal threads in a hole with a cutting tool called a tap. Special machine or gun taps are used with a tapping attachment when this operation is performed by power in a machine. > Counterboring (Fig. 38-1g) is the operation of enlarging the top of a previously drilled hole to a given depth to provide a square shoulder for the head of a bolt or capscrew. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Standard Operations Reaming Boring
Operation of sizing and producing smooth, round hole from previously drilled or bored hole Boring Truing and enlarging hole by means of single-point cutting tool Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Standard Operations Tapping Counterboring
Cutting internal threads in hole with cutting tool called tap Counterboring Enlarging top of previously drilled hole to given depth to provide square shoulder for head of bolt or capscrew Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Standard Operations Spot Facing
Smoothing and squaring surface around hole to provide seat for head of cap screw or nut Boring bar fitted with double-edged cutting tool Pilot section on end to fit into existing hole Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Principal Types of Drilling Machines
Wide variety of drill presses Size of drill press may be designated in different ways by different companies Some state size as distance from center of spindle to column of machine Others state size by diameter of largest circular piece that can be drilled in center

Sensitive Drill Press Parts
Only hand feed mechanism Control downfeed pressure Manufactured in bench and floor model Four main parts Base, column, table and drilling head Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Radial Drilling Machine
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Drilling Machine Accessories
Unit 39

Objectives Identify and use three types of drill-holding devices
Identify and use work-holding devices for drilling Set up and clamp work properly for drilling

Versatility of the Drill Press
Greatly increased by various accessories Two categories Tool-holding devices Used to hold or drive cutting tool Work-holding devices Used to clamp or hold workpiece

Tool-Holding Devices Drill press spindle provides means of holding and driving cutting tool End may be tapered or threaded for mounting drill chuck Most common Drill chucks Drill sleeves Drill sockets

Drill Chucks Most common devices used for holding straight-shank cutting tools Most contain three jaws that move simultaneously when outer sleeve turned Hold straight shank of cutting tool securely Two common types Key Keyless

Chucks Hold straight-shank drills Mounted on drill press spindle
Taper Threads Held in spindle by self-holding taper in larger machines Four types of drill chucks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Types of Drill Chucks Key-type Keyless Precision keyless Most common
Three jaws move simultaneously when outer sleeve turned Tighten with key Keyless Chuck loosened or tightened by hand without key Precision keyless Holds smaller drills accurately Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Types of Drill Chucks Jacobs impact keyless chuck
Hold small or large drills accurately using Rubber-Flex collets Gripped or released quickly and easily by means of built-in impact device in chuck Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Drill Sleeves and Sockets
Used to adapt cutting tool shank to machine spindle if taper on tool is smaller than tapered hole in spindle Drill Socket Used when hole in spindle of drill press to small for taper shank of drill Used also as extension sockets Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Drill Drift Used to remove tapered-shank drills or accessories from drill press spindle Always place rounded edge up so this edge will bear against round slot in spindle Use hammer to tap drill drift and loosen tapered drill shank Use board or piece of masonite to protect table

Work-Holding Devices Angle vise Drill vise
Angular adjustment on base to allow operator to drill holes at an angle without tilting table Drill vise Used to hold round, square or odd-shaped rectangular, pieces Bolt vise to table for stability Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Work-Holding Devices Contour vise V-blocks Step blocks
Has special movable jaws that automatically adjust to shape of odd-shaped workpiece V-blocks Made of cast iron or hardened steel Used in pairs to support round work for drilling Step blocks Used to provide support for outer end of strap clamps Various sizes and steps

Work-Holding Devices Angle plate Drill jigs
L-shaped piece of cast iron or hardened steel machined to accurate 90º May be bolted or clamped to table Variety of sizes Drill jigs Used in production for drilling holes in large number of identical parts Eliminate need for laying out a hole location

Work-Holding Devices Clamps or straps
Used to fasten work to drill table or an angle plate for drilling Various sizes Usually supported at end by step block and bolted to table by T-bolt that fits into table T-slot Modifications are double- finger and gooseneck clamps Finger clamp U-clamp Straight clamp Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Clamping Stresses Don’t want stresses to cause springing or distortion of workpiece Clamping pressures should be applied to work, not step block Step block should be slightly higher than work Bolt close to work Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Clamping Hints Always place bolt close to workpiece
Have packing block slightly higher than work surface being clamped Insert piece of paper between machine table the workpiece to prevent shifting Place metal shim between clamp and workpiece Use sub-base or liner under rough casting Shim parts that do not lie flat to prevent rocking

Twist Drills Unit 40

Objectives Identify the parts of a twist drill
Identify four systems of drill sizes and know where each is used Grind the proper angles and clearances on a twist drill

Twist Drills End-cutting tools
Used to produce holes in most types of materials Two helical grooves, or flutes, are cut lengthwise around body of drill Provide cutting edges and space for cuttings to escape during drilling process

Twist Drill Parts Most made of high-speed steel Carbide-tipped drills
Replaced carbon-steel drills for two reasons Can be operated at double the cutting speed Cutting edge lasts longer Stamped with letters H.S or H.S.S. Carbide-tipped drills Speeds for production have increased up to 300% over high-speed drills

Three Main Parts of a Drill
Point Three Main Parts of a Drill Body Shank A drill (Fig. 40-1 on p. 312) may be divided into three main parts: shank, body, and point. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Shank Straight-shank drills Tapered-shank drills Held in drill chuck
Up to ½ in. in diameter Tapered-shank drills Fit into internal taper of drill press spindle Tang provided on end to prevent drill from slipping Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Body Portion of drill between shank and point
Consists of number of parts for cutting Flutes Two or more helical grooves cut around body of drill Form cutting edges, admit cutting fluid, allow chips to escape hole Body Clearance Undercut portion of body between margin and flutes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Body, cont. Margin Web Narrow, raised section on body of drill
Next to flutes and extends entire length of flutes Provides full size to drill body and cutting edges Web Thin partition in center of drill, extends full length of flutes Forms chisel edge at cutting end of drill Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Drill Point Characteristics
The use of various point angles and lip clearances, in conjunction with thinning of the drill web, will allow: Control size, quality and straightness of drilled hole Control size, shape and formation of chip Control chip flow up flutes

Increase strength of drill's cutting edges
Reduce rate of wear at cutting edges Reduce amount of drilling pressure required Control amount of burr produced Reduce amount of heat generated Permit use of various speeds and feeds for more efficient drilling

Conventional Point (118º)
Most commonly used drill point Gives satisfactory results for most general-purpose drilling Lip clearance of 8º to 12º for best results Too much weakens cutting edge and causes drill to chip Too little results in use of heavy drilling pressure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Long Angle Point (60º to 90º)
Used on low helix drills for drilling of nonferrous metals, soft cast irons, plastics, fibers, and wood Lip clearance generally from 12º to 15º Flat may be ground on face of lips to prevent drill from drawing itself into the soft material Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Flat Angle Point (135º to 150º)
Used to drill hard and tough materials Lip clearance on flat angle point drills only 6º to 8º to provide as much support as possible for cutting edges Shorter cutting edge tends to reduce friction and heat during drilling Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Four Systems of Drill Sizes
Fractional Range from 1/64 to 4 in. (steps of 1/64th ) Number Range from #1 (.228 in.) to #97 (.0059 in.) Letter Range from A to Z (A = .234 in., Z = .413 in.) Millimeter (Metric) Miniature (0.04 to 0.09 mm, steps of 0.01 mm) Straight-shank standard (0.5 to 20 mm) Taper-shank (8 up to 80 mm)

Types of Drills Wide variety manufactured to suit specific drilling operations and materials Design of drills vary Number and width of flutes Amount of helix or rake angle of flutes Shape of land or margin Shape of flute: straight or helical Whether helix is right-hand or left-hand

Twist Drills Manufactured from three main materials
Carbon-steel drills Used in hobby shops not for machine shop work Cutting edges wear down quickly High-speed steel drills Used in machine shop work Cutting edges withstand more heat and wear Cemented-carbide drills Operated at high speeds, withstand higher heat, and can drill hard materials

General-Purpose Drill
Has two Helical flutes Designed to perform well on wide variety of materials, equipment and job conditions Can be made to suit different conditions and materials by varying point angle, speeds and feeds Straight-shank drills called general-purpose jobbers length drills Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Oil Hole Drills Have one or two oil holes running from shank to cutting point Compressed air, oil, or cutting fluid can be forced through when deep holes being drilled Used on turret lathes and screw machines Cutting fluid cools drill's cutting edges and flushes chips out of hole Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Step Drills Used to drill and countersink or drill and counterbore different sizes of holes in one operation May have two or more diameters ground Each size or step separated by square or angular shoulder Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Saw-Type Hole Cutter Cylindrical-diameter cutter with twist drill in center to provide guide for cutting teeth on hole cutter Made in various diameters Used for drilling holes in thin materials Little burr produced Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Drilling Facts and Problems
Excessive speed Excessive clearance Excessive feed Insufficient clearance Cutting lips with unequal angles Cutting lips with unequal in length Loading and galling Examples of each on following slides

Excessive speed will cause wear at outer corners of drill
Excessive speed will cause wear at outer corners of drill. This permits fewer regrinds of drill due to amount of stock to be removed in reconditioning. Discoloration is warning sign of excess speed. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Excessive clearance results in lack of support behind cutting edge with quick dulling and poor tool life. Despite initial free cutting action. Clearance angle behind cutting lip for general purposes is 8º to 12º. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Excessive feed sets up abnormal end thrust, which causes breakdown of chisel point and cutting lips. Failure induced by this cause will be broken or split drill. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Insufficient clearance causes the drill to rub behind the cutting edge
Insufficient clearance causes the drill to rub behind the cutting edge. It will make the drill work hard, generate heat, and increase end thrust. This results in poor holes and drill breakage. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The web is the tapered central portion of the body that joins the lands.

Cutting lips with unequal angles will cause one cutting edge to work harder than the other. This causes torsion strain, bellmouth holes, rapid dulling, and poor tool life. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cutting lips unequal in length cause chisel point to be off center axis and will drill holes oversize by approximately twice the amount of eccentricity. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Loading and galling is caused by poor chip removal with insufficient dissipation of heat so that material anneals itself to the cutting edge and flute. This condition frequently results from using wrong drills for the job or inadequate cutting fluid application. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Characteristics of a Properly Ground Drill
Length of both cutting lips equal Angle of both cutting lips be the same Lips should be free from nicks or wear No sign of wear on margin Note: Resharpen drill if it does not meet all of these requirements.

Conditions That Indicate Drill Be Examined and Reground
Color and shape of chips change More drilling pressure required Drill turns blue because of excessive heat Top of hole out of round Poor finish produced in hole Drill chatters when it contacts metal Drill squeals and may jam in hole Excessive burr left around drilled hole

Factors Causing Premature Dulling of Drill
Drill speed may be too high for hardness of material being cut Feed may be too heavy and overload cutting lips Feed may be too light and cause lips to scrape rather than cut May be hard spots or scale on work surface

More Factors Work or drill may not be supported properly, resulting in springing and chatter Drill point may be incorrect for material being drilled Finish on lips may be poor

Procedure to Grind a Drill
Wear approved safety glasses Check grinding wheel and dress it to sharpen and/or straighten wheel face Adjust grinder tool rest so it is within in. of wheel face Examine drill point and margins for wear

Hold drill near point with one hand, other hand hold shank of drill slightly lower than point
Move drill so it is approximately 59º to face of grinding wheel Hold lip or cutting edge of drill parallel to grinder toolrest Bring lip of drill against grinding wheel and slowly lower drill shank

Check angle of drill point and length of lips with drill point gage
Remove drill from wheel without moving position of body or hands, rotate drill one-half turn, and grind the other cutting edge Check angle of drill point and length of lips with drill point gage Repeat operations 6-10 until cutting edges are sharp and lands are free from wear nicks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cutting Speeds and Feeds
Unit 41

Objectives Calculate the revolutions per minute (r/min) for inch and metric size drills Select the feed to be used for various operations Calculate the revolutions per minute for the reaming operation

Cutting Speeds and Feeds
Two important factors Diameter and material of cutting tool Type of material being cut Speed of twist drill referred to as cutting speed, surface speed or peripheral speed Distance point on circumference of drill will travel in 1 min

Recommended Cutting Speeds
For every job, choose the drill speed that will result in the best production rates! Portion of Table 41.1 from text Drill Size Cutting Speeds in Feet per Min or Meters per Min in mm ft/min 12 m/min 60 ft/min 18 m/min … 1/ 1/ 3/ Steel Casting Tool Steel

Economical Drilling Speed Variables
Most important! Type and hardness of material Diameter and material of drill Depth of hole Type and condition of drill press Efficiency of cutting fluid employed Accuracy and quality of hole required Rigidity of work setup

Revolutions per Minute
Compute correct number of r/min of drill press spindle for given size drill Type of material to be drilled Recommended cutting speed of material Type of material from which drill is made

Formula (Inch) where CS = recommended cutting speed in feet per minute for the material being drilled D = diameter of drill being used Revolution per minute = number of revolutions of the drill necessary to attain proper cutting speed for metal being machined.

Simplified Formula Since not all machines can be set to exact calculated speed, pi (µ) divided into 12 to simplify formula Example: Calculate r/min required to drill a ½ in hole in cast iron (CS 80) with a high-speed steel drill.

Feed Distance drill advances into work for each revolution
May be expressed in decimals, fractions of an inch, or millimeters Three factors govern rate of feed Diameter of drill Material of workpiece Condition of drilling machine

Drill Feeds General –purpose Work Drill Size Feed per Revolution
Table 41.2 Drill feeds Drill Size Feed per Revolution in. mm in mm 1⁄8 and smaller 3 and smaller to to 0.05 1⁄8 to ¼ to to to 0.1 ¼ to ½ to to to 0.18 ½ to to to to 0.38 1 to 1 ½ to to to 0.63

Drill Feeds General rule: feed rate increases as drill size increases
Too coarse – chip cutting edges Too light – chattering noise, dulls cutting edge Hard steels or alloys use slower feed Softer metals drilled with faster feed Blue steel chips indicate too much heat at cutting edge Dull cutting edge or too high speed

Cutting Fluids Provide both cooling and lubrication
Properties of an effective liquid in dissipating heat Able to absorb heat rapidly Have good resistance to evaporation Have high thermal conductivity Oil: good lubricant, poor coolant Water: best coolant, no lubricating value (promotes rust)

Drilling Holes Unit 42

Objectives Measure the size of inch and metric drills
Drill the correct size center holes in workpieces Drill small and large holes to an accurate location

Drill Press Safety Do not operate before understanding mechanism and how to stop Always were approved safety glasses Never attempt to hold work by hand Keep your head back from revolving parts As drill begins to break through work, ease up on drill pressure

Always remove burrs from drilled hole with file or deburring tool
Never leave chuck key in drill chuck Never attempt to grab work that may have caught in drill Stop machine first Always keep floor around drill press clean and free of tools, chips, and oil

Drilling Hints Treat cutting tools with care
Always examine condition of drill point before use – do not use dull tools Make sure drill point angle correct for type of material to be drilled Set correct revolutions per minute for size of drill and workpiece material

Set up work so drill will not cut into machine as it breaks through workpiece
Work should always be clamped securely End of workpiece farthest from hole should be placed on left-hand side of table so it will not swing toward operator Always clean tapered drill shank, sleeve, and machine spindle before inserting drill Use shortest drill length possible and/or hold it short in chuck

Good practice to start each hole with center drill
Provides guide for drill to follow Thin workpieces should be clamped to hardwood block for drilling Chips from each flute should be same shape; if blue during drilling, check drill point condition Drill squeak usually indicates dull drill When increased pressure must be applied during drilling, reason usually dull drill or chip caught in hole between drill and work

Measuring Size of a Drill
Good practice to always check drill for size before drilling Check for size Drill gage Micrometer Most accurate Check measurement across margin of drill

Lathe Center Holes Use a combination drill and countersink
Commonly called center drill Must be drilled to correct size and depth Too shallow or deep, poor support for work Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Spotting Hole Location With a Center Drill
Chisel end on drill wider than center-punch mark on work Spot center-punch mark with center drill Small point on center drill will accurately follow center-punch mark and provide guide for larger drill Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Spotting Hole Location With a Center Drill
Mount small-size center drill in drill chuck Mount work in vise Do not clamp Set drill speed to 1500 r/min Bring point of center drill into center-punch mark and allow work to center itself with drill point Continue drill until one-third of tapered section of center drill has entered work Spot all holes to be drilled

Drilling Work Held in a Vise
Spot hole location with center drill Mount correct-size drill in drill chuck Set drill press to proper speed for size of drill and type of material to be drilled Fasten clamp or stop on left side of table Mount work on parallels in drill vise and tighten it securely

Start drill press spindle and begin to drill
With vise against table stop, locate spotted hole under center of drill Start drill press spindle and begin to drill Holes up to 12 in. – hold vise against table Holes over 12 in. – Clamp vise to table Drill until full drill point into work With drill revolving, deep drill point in work and tighten clamp holding vise Raise drill occasionally and apply cutting fluid during drilling Ease up on drilling pressure as drill starts to break through workpiece

Drilling to an Accurate Layout
Clean and coat surface with layout dye Locate position of hole from two machined edges of workpiece and scribe lines Lightly prick-punch where two lines intersect Check accuracy of punch mark Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Scribe circle to indicate diameter of hole
Scribe test circle .060 in. smaller than hole Punch four witness marks on circles up to .750 in. in diameter and eight witness marks on larger circles Deepen center of hole location with center punch to provide larger indentation for drill to follow Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Center drill work to just beyond depth of drill point
Mount proper size drill in machine and drill hole to depth equal to one-half to two-thirds drill diameter Examine drill indentation; should be concentric with inner proof circle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Start drill in spotted and grooved hole
If spotting off center, cut shallow V-grooves with cape or diamond-point chisel on side toward which drill must be moved Start drill in spotted and grooved hole Drill will be drawn toward direction of grooves Continue cutting grooves into spotted hole until drill point drawn to center Continue to drill hole to desired depth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Drilling Large Holes Drills increase in size; thickness of web also increases to give drill strength Thicker web, thicker point of drill Thick web not follow center-punch mark easily Two methods to overcome poor cutting action of thick web on large drills Web is thinned Lead, or pilot, hole is drilled

Using Pilot Hole with Large Holes
Drill pilot hole diameter which is slightly larger than thickness of web Care must be taken to drill pilot hole on center Pilot hole then followed with larger drill Problems when pilot hole too large Cause chattering Drill hole out-of-round Spoil top (mouth) of hole

Procedure for Drilling Large Holes with Pilot Hole
Check print and select proper drill Measure thickness of web at point Select pilot drill with diameter slightly larger than web thickness Mount workpiece on table Adjust height and position of table so drill chuck can be removed and larger drill placed in spindle after pilot hole drilled and lock table

Place center drill in drill chuck, set proper spindle speed, accurately drill center hole
Using proper-size pilot drill, drill pilot hole Shut off machine, leaving pilot drill in hole Clamp work securely to table Raise drill spindle, remove drill and chuck Clean taper shank of drill and spindle hole Mount large drill in spindle Set spindle speed, feed and drill hole to required depth

Drilling Round Work in V-Block
Select V-block to suit diameter of work Mount work in V-block and rotate it until center-punch mark is in center of work Check distance from both sides equal Tighten U-clamp securely or hold work in vise Spot hole location with center drill Mount proper drill size and set speed Dill hole (do not hit V-block or vise when drill breaks through work)

Reaming Unit 43

Objectives Identify and state the purpose of hand reamers and machine reamers Explain the advantages of carbide-tipped reamers Calculate the reaming allowance required for each reamer Ream a hole by hand in a drill press Machine ream a hole

Reamers Rotary cutting tool with several straight or helical cutting edges along body Used to accurately size and finish hole previously formed by drilling Two classifications Hand Machine

Reamer Parts Three main parts Shank Body Angle of chamfer

Hand Reamers Finishing tools Holes bored to .003-.005 in.
Square on shank for wrench Teeth on end tapered so can enter hole easily Never turn backwards Taper hand reamers Remove frequently to clean A square on the shank end allows a wrench to be used for turning the reamer into the hole. The teeth on the end of the reamer are tapered slightly for a distance equal to the reamer diameter so that it can enter the hole to be reamed. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Machine Reamers Used in any machine tool for both roughing and finishing hole Called chucking reamers for holding method Wide variety of types and styles Rose reamers Fluted reamers Carbide-tipped reamers

Fluted Reamers Have more teeth than rose reamers for comparable diameter Lands relieved for entire length Fluted reamers cut along side as well as at chamfer on end Considered finishing tools and used to bring hole to size Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Carbide-tipped Reamers
Similar to rose or fluted reamers, except carbide tips been brazed to cutting edges Resist abrasion and maintain sharp cutting edges even in high temperatures Outlast high-speed steel reamers Can run at higher speeds and still maintain their size Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Shell Reamers Reamer heads mounted on driving arbor
Shank of driving arbor may be straight or tapered Two slots in end of reamer fit into lugs on driving arbor Sometimes locking screw in arbor Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

More Reamers Adjustable reamers Emergency reamers
Have inserted blades that can be adjusted approximately at .015 in over or under nominal reamer size Adjusting nuts on either end Emergency reamers Drills whose corners have been slightly rounded and honed if reamer of particular size not available Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Another Reamer Expansion reamers Amount expanded limited
Body slotted and tapered, threaded plug fitted into end Turning this plug will allow 1 in. reamer to expand up to .005 in. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Reamer Care Never turn reamer backward; ruin edges
Always store reamers in separate containers to prevent cutting edges from being nicked Never roll or drop reamers on metal surfaces When not in use, reamer should be oiled Fine, free-cutting grinding wheel should be used for resharpening reamers

Reaming Allowances Amount of material left in hole for reaming operation depends on number of factors Type of machining operation prior to reaming Hole punched, rough-drilled, bored General rules for amount of material to leave in hole for machine reaming Holes up to .500 in. diameter, allow .015 in. Holes over .500 in. diameter, allow .030 in.

Reaming Speeds Factors for determining most efficient speed
Type of material being reamed Rigidity of setup Tolerance and finish required in hole Generally reaming speed 1/2 to 2/3 speed used for drilling same material High speed – used when setup rigid Lower speed – used when setup less rigid Coolants improve surface finish and allow speed

Reaming Feeds Feed used for reaming usually two to three times greater than that used for drilling Rate varies with material reamed Generally .001 to .004 in. per flute per rev Feed too low: glazing, excessive reamer wear, chatter Feed too fast: reduce hole accuracy, poor surface finish Exception: tapered holes need light feed

Reaming Hints Examine reamer and remove all burrs from cutting edges with hone Cutting fluid should be used in reaming operation to improve hole finish and prolong life of reamer Helical-fluted reamers should always be used when long holes and those with keyways or oil grooves are reamed

Straight-fluted reamers generally used when extreme accuracy required
Use roughing reamer first and then finishing reamer to obtain hole accuracy and good surface finish Never turn reamer backwards Never attempt to start reamer on uneven surface Select reamer with incremental cut to avoid chatter Always use stub center in drill press spindle to keep reamer aligned

Hand Reaming a Straight Hole

Procedure for Hand Reaming a Straight Hole
Mount work on parallels in vise and clamp it securely to table Drill hole to proper size, leaving allowance for hand reamer to be used Do not move location of work or table; remove drill and mount stub center in drill chuck Start end of reamer in drilled hole

Fasten tap wrench on reamer
Engage stub center in center hole on end of reamer With downfeed lever, apply slight pressure while turning reamer clockwise by hand Apply cutting fluid and ream hole When removing reamer, turn it clockwise, never counterclockwise

Machine Reaming a Straight Hole
Mount work on parallels in vise and fasten securely to table Select proper-size drill for reaming allowance required and drill hole Mount proper reamer in drill press Adjust spindle speed to suit reamer and work material

Start drill press and carefully lower spindle until chamfer on reamer starts to cut
Apply cutting fluid and feed reamer by applying enough pressure to keep reamer cutting Remove reamer from hole by raising downfeed handle Shut off machine and remove burr from edge of hole

Drill Press Operations
Unit 44

Objectives Counterbore and countersink holes
Select and use the proper tap to thread a hole in a drill press Use three methods to transfer hole locations

Counterboring Operation of enlarging end of hole that has been drilled previously Depth slightly greater than head of bolt, cap screw or pin it is to accommodate Supplied in variety of styles Each have pilot in end to keep tool in line with hole Some interchangeable pilots to suit variety of holes

Procedure to Counterbore a Hole
Set up and fasten work securely Drill proper size of hole in workpiece to suit body of pin or screw Mount correct size of counterbore in drill press Set drill press speed to approximately one-quarter that used for drilling Bring counterbore close to work to see that the pilot turns freely in drilled hole Start machine, apply cutting fluid and counterbore

Countersinking Process of enlarging top end of hole to shape of cone to accommodate conical-shaped heads of fasteners Head will be flush with or below surface Countersinks available with various included angles 60º, 82º, 90º, 100º, 110º, and 120º

Countersinking 82º countersink used to enlarge top of hole so it will accommodate a flat-head machine screw Holes to be threaded countersunk slightly larger than tap diameter Speed is approximately 1/4th of drilling speed Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Procedure to Countersink a Hole for a Machine Screw
Mount an 82º countersink in drill chuck Adjust spindle speed to about ½ that used for drilling Place workpiece on drill table With spindle stopped, lower countersink into hole Clamp work if necessary

If several holes to do, set depth stop
Raise countersink slightly, start machine, and feed countersink by hand until proper depth is reached. Diameter checked by placing inverted screw in countersunk hole If several holes to do, set depth stop Countersink all holes to depth set on gage

Tapping Performed by hand or under power with tapping attachment
Done immediately after drilling operation Hand taps In sets containing taper, plug, bottoming tap Machine taps Designed to withstand torque required to thread hole and clear chips

Set of Hand Taps Taper Plug Bottoming

Types of Machine Taps Gun Stub-flute Spiral-flute

Fluteless Tap Actually a forming tool used to produce internal threads in ductile material Copper, brass, aluminum, and leaded steels Fluteless tap Lobes of the tap Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Procedure to Tap a Hole by Hand in a Drill Press
Mount work on parallels with center-punch mark on work in line with spindle and clamp work securely to drill press table Adjust drill press table height so drill may be removed after hole has been drilled without moving table or work Center drill hole location

Drill hole to correct tap drill size for tap to be used
Mount stub center in drill chuck Or remove drill chuck and mount special center in drill press spindle Fasten suitable tap wrench on end of tap Place tap in drilled hole, lower drill press spindle until center fits into center hole in tap shank Turn tap wrench clockwise to start tap Continue to tap hole, applying light pressure

Tapping Attachment Mounted in a drill press spindle to rotate tap by power Built-in friction clutch that drives tap clockwise when drill press spindle fed downward Reversing mechanism to back tap out of hole Two- , three-fluted machine or gun taps used for power Ability to clear chips Tapping speed ranges from 60 – 100 r/min

Drilling Machines.

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Drilling Machines.

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About project

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