Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. PowerPoint to accompany Krar Gill Smid Technology of Machine Tools 6 th Edition Reaming Unit 43

43-2 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

43-3 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

43-4 Reamer Main Parts Shank –Straight or tapered and used to drive reamer –Hand reamers have square on end to accommodate tap wrench Angle of Chamfer –Part of reamer that actually does cutting –Ground on end of each tooth –Clearance behind each chamfered cutting edge

43-5 Body Several straight or helical grooves or flutes and lands (portion between flutes) Body clearance angle: clearance behind margin that reduces friction while reamer cutting Rake angle: angle formed by face of tooth when line drawn from point on front marginal edge through center of reamer –No angle on face: said to have radial land

43-6 Reamer Parts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Three main parts 1.Shank 2.Body 3.Angle of chamfer

43-7 Hand Reamers Finishing tools Holes bored to 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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

43-8 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

43-9 Rose Reamer Straight or tapered shanks with straight or helical flutes Teeth on end have 45º chamfer backed off to produce cutting edge Cut on end angle only Usually made.003 to.005 in under normal size Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

43-10 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.

43-11 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.

43-12 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.

43-13 Advantages of Shell Reamers 1.Economical for larger holes 2.Various head sizes can be easily interchanged on one arbor 3.When reamer becomes worn, it may be thrown sway and driving arbor used with other reamers

43-14 More Reamers Adjustable 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.

43-15 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.

43-16 Reamer Care 1.Never turn reamer backward; ruin edges 2.Always store reamers in separate containers to prevent cutting edges from being nicked 3.Never roll or drop reamers on metal surfaces 4.When not in use, reamer should be oiled 5.Fine, free-cutting grinding wheel should be used for resharpening reamers

43-17 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.

43-18 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

43-19 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

43-20 Reaming Hints 1.Examine reamer and remove all burrs from cutting edges with hone 2.Cutting fluid should be used in reaming operation to improve hole finish and prolong life of reamer 3.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 6.Use roughing reamer first and then finishing reamer to obtain hole accuracy and good surface finish 7.Never turn reamer backwards 8.Never attempt to start reamer on uneven surface 9.Select reamer with incremental cut to avoid chatter 10.Always use stub center in drill press spindle to keep reamer aligned

43-22 Reaming a Straight Hole Two types of reamers –Hand reamers Square on one end Used to remove no more than.005 in. from hole –Machine reamers Straight shanks held and driven by drill chuck Tapered shanks fit directly into drill press spindle Generally used to remove from.015 in. to.030 in. of metal from hole depending on hole diameter

43-23 Hand Reaming a Straight Hole Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

43-24 Procedure for Hand Reaming a Straight Hole 1.Mount work on parallels in vise and clamp it securely to table 2.Drill hole to proper size, leaving allowance for hand reamer to be used 3.Do not move location of work or table; remove drill and mount stub center in drill chuck 4.Start end of reamer in drilled hole

Fasten tap wrench on reamer 6.Engage stub center in center hole on end of reamer 7.With downfeed lever, apply slight pressure while turning reamer clockwise by hand 8.Apply cutting fluid and ream hole 9.When removing reamer, turn it clockwise, never counterclockwise

43-26 Machine Reaming a Straight Hole 1.Mount work on parallels in vise and fasten securely to table 2.Select proper-size drill for reaming allowance required and drill hole 3.Mount proper reamer in drill press 4.Adjust spindle speed to suit reamer and work material

Start drill press and carefully lower spindle until chamfer on reamer starts to cut 6.Apply cutting fluid and feed reamer by applying enough pressure to keep reamer cutting 7.Remove reamer from hole by raising downfeed handle 8.Shut off machine and remove burr from edge of hole

43-28 Reaming a Tapered Hole 1.Mount work on parallels in vise or on drill table and fasten securely 2.Align hole center under drill point 3.Drill hole.015 in. smaller than smallest diameter of tapered hole 4.Obtain drill 1/64 in. smaller than size of finished hole measured at diameter

Drill hole.060 in. less than depth of large hole (C in following diagram) 6.Mount roughing tapered reamer in drill spindle 7.Adjust spindle speed to ½ speed used to ream straight hole 8.Rough-ream hole to about.005 in. undersize while applying cutting fluid 9.Mount finish reamer, apply cutting fluid, and finish-ream hole to size

43-30 Reaming a Tapered Hole Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.