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Mech 200

Department of Mechanical Engineering

Machining Facility Lab ManualOctober 11, 2002

Objectives

∑ To expose students to the basic workings of a manual milling machine and manuallathe and procedures required to produce precision parts conforming to thespecifications on the drawings.

∑ The parts must be machined to the tolerances stated on the drawings without beingtest fitted to their mating parts, i.e. the brass bushing must press fit to pillow blockwithout deformation and excessive force. All parts will be assembled at the end ofthe Lab to produce a functioning “Rotor Assembly”.

∑ This exercise is intended to replicate a real world manufacturing condition in whichvarious parts are produced from many different sources and final assembly must beattained without having to fit and rework the parts. To accomplish the above,students will appreciate the relevance of producing quality drawings which conveyall the necessary details.

∑ Some tolerances required in this Machining Lab are relatively tight and will requireparticular attention to detail. Most parts can be easily machined to ±0.005” (0.2mm)on the machine tools used in the shop.

∑ The following example will give some physical size relevance to tolerances anddimensions to be used in the machining of the Rotor Assembly parts:The average human hair = 0.0025” (0.01mm) thick, average sheet of paper = 0.004”thick. Some positioning and diameter tolerances required in this Shop Lab will be±0.0005” and +0.0000” –0.0005” respectively i.e. 1/5 the thickness of the averagehuman hair.

∑ This will also give the student an appreciation of the care and time (cost) required toproduce parts with tight tolerances. Therefore in the design process tight tolerancesshould be kept to a minimum and only used where necessary.

Lab Safety

Students must be familiar with and conform to the Machining / Design Facility UsePolicy in Appendix A.

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Manual Milling Machine

Fig. 1 The milling machine used in this Lab is commonly referred to as a “Bridgeport”style Knee Mill.

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Milling Machine (Mill) Safety Procedures

∑ Only one student to operate the machine at any one time. Multiple people workingon a machine leads to confusion and inadvertent operations which can endanger theother operator. Non-operating members of the group can watch, advise the operatorand can add coolant to the work piece (part being machined) if required.

∑ Always shut-off the Mill before removing parts from the vise or measuring parts inthe vise. Immediately apply the break to stop the spindle rotation after switching offthe motor. Do not let the spindle coast to a halt. This ensures the cutter is stationarywhen the operator needs to handle or measure the workpiece.

∑ Remove the draw bar wrench immediately after use and replace it on the providedpeg. Always check to ensure the draw bar wrench is not on top of the mill prior toswitching on the motor.

∑ If the cutter will not release easily from the collet after loosening, always use a clotharound the cutter to protect your hands and fingers while removing the cutter.

∑ Do not use fingers to clear away chips. Use the air gun, but with caution andconsideration for others.

∑ If you are not sure about the set-up for machining your part ask the instructor.

Use and Care of the Milling Machine

∑ Refer to (Fig. 1) to familiarise yourself with the names and parts of the Manual KneeMill.

∑ Oil the Mill first using the hydraulic oiler on the side of the machine before use (onepump is enough).

∑ Change the speed of the Mill only while the motor is running. This is due to theinfinitely variable speed drive belt and pulley configuration (similar to that used inan infinitely variable speed snowmobile transmission.)

∑ When changing the ”back gear introduction lever” on the side of the Mill headalways ensure it is properly engaged by turning the spindle by hand first.

∑ Using the wrench, it is only necessary to tighten the draw bar 1/3 of a turn pastfinger tight.

∑ When removing cutting tools or the drill chuck from the collet, ensure they areprotected on the tip with a plastic cap. This prevents the tools and the vise frombeing damaged when they are “tapped” out, and accidentally dropped onto the mill.

∑ Always place tools on the plastic trays on the mill table. This prevents the steel tools“dinging” the precision ground Mill table. (Do not place the collet wrench on theplastic trays, return it immediately to its home peg.)

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∑ Ensure the “Way Lock Levers” are loose when moving any of the X, Y or Z axis.They can be tightened if required to prevent movement on the desired axis.

∑ The compressed air can be used to clean the Mill but do not blow into the slides ofthe machine.

∑ Coolant can be used liberally on the machine, any excess coolant deposited on thefloor must be cleaned up immediately to prevent a slipping hazard.

∑ All machines must be thoroughly cleaned and excess coolant dried off after use.

∑ If the machine is making a strange noise, vibratiing, or is not cutting as it shouldalways stop and check for the cause or ask the instructor for assistance. Do notproceed regardless.

General Techniques Used for Milling.

∑ It is important to pay attention to the following details. Failure to do so will oftenresult in a finished part not conforming to specification. This is often only recognisedat the completion of the part or worse yet in the final assembly resulting in a timeconsuming re-make or rework of the part.

∑ Note: There is no “ Undo “ command in machining.

∑ Ensure the vise jaws and base are thoroughly clean before installing parts (use theair-gun or shop towels if necessary). A tiny metal chip left sandwiched between thepart and the vise jaw or parallels will result in an out of square part and can alsoleave indentations in the part.

∑ De-burr and remove all sharp corners of parts with a file after milling or cutting.This will ensure parts seat properly when re-installed in the vise, also for safety andcosmetic reasons.

∑ Always ensure the cutter is spinning when bringing it into contact with theworkpiece. This prevents the cutter edges from being damaged.

∑ Most parts clamped in the vise only require the vise handle to be tightened 1/6 to 1/8

of a turn past finger tight. (This exerts a clamping force of approximately 2000 lbs onthe part.)

∑ When making a finish cut in one axis always lock the opposite axis table using thelocking handles. This will prevent any drift occurring in the opposite axis.Remember to unlock the handles after.

∑ Only clamp one part at time. If it is necessary to clamp more than one part at a timeto improve efficiency, only clamp in series, not in parallel (Fig 2). Parts clamped inparallel can not be held with even force which can cause one part to come looseduring milling.

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series clamping parts- recommended -

vise back jaw

vise

part 2 part 1

parallel clamping parts- not recommended -

vise

vise back jawpart 1 part 2

Fig. 2 Parallel Clamping Parts and Series Clamping Parts

∑ Always check the diameter of the drill you have selected with a dial caliper to verifythat it is the correct size (previous users may have incorrectly replaced the drill in thedrill index). The accurate method of measuring a drill is to measure across thecutting flutes tips using the broad section of the dial caliper as shown in (Fig. 3).

Fig 3 Correct Method for Accurately Measuring Drill Diameter

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The Project: Pillow Blocks

Procedure:

1.0 Setting the X-Y Datum Corner Of Vise.

Note: All dials on machines and dimensions are in inches.

∑ Instructions for setting the Digital Read Out (DRO) systems are located on theindividual machines.

∑ Positioning the Mill uses an X,Y,Z Cartesian plane axis system as shown in (Fig. 4).

Fig. 4 Mill Axes of Motion (Tool Motion Orientation)

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stationary back jaw

movable jaw

vise

datumcorner

+X+Y

+X-Y

-X-Y

-X+Y

Fig. 5 Datum Corner of Vise and the “X”, “Y” Coordinates

∑ An “Edge Finder” centripetal probe will be used to accurately locate the datumcorner of the vise with respect to the centre of the Mill spindle. (Fig. 5).

∑ The milling machine vise must first be initialised to obtain a datum corner. This isusually the top left corner of the vise back jaw as shown in (Fig.5).

∑ Install the 1/2” collet into the Mill spindle and install the 0.200” diameter probe EdgeFinder into the collet with approximately 1” total protruding (Fig.6a).

∑ Turn the Mill on, setting the speed to approximately 1800 RPM.

∑ Open the vise up to approximately 2”.

∑ Note: The Edge Finder probe is 0.200” dia. therefore a radius of 0.100” is used to setthe X and Y positions with respect to the edge of the vise.

∑ Position the Edge Finder as shown in (Fig. 6a) and move the Y table slowly towardsthe Edge Finder until the Edge Finder probe is barely touching the edge of the vise.Continue slowly moving the Y table in the same direction until the Edge Finderprobe flicks to the side (running eccentric with respect to the body).

∑ This position will be Y = -0.100”, set the DRO to Y -0.100.

∑ Repeat this operation to confirm that the correct position has been obtained.

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∑ Move the X table with respect Edge Finder shown in (Fig. 6b)

∑ Repeat step 5 in the X axis. This position will be X= -0.100”, input this position to theDRO.

∑ Note: The top left corner is commonly used as the machining datum, therefore it isalso useful to dimension parts on the drawings from this corner.

∑ Note: There are other methods to locate datum edges, enquire with the shopinstructor.

edge finder

back vise jaw

edge finder

Fig. 6a Front View to set “Y” Axis Datum Fig. 6b Side View to set “X” Axis Datum

2.0 Preparation Of Workpiece Stock For Pillow Block

∑ The pillow blocks will be made from: Aluminum 6061-T6 Bar Stock 1/2” x 2 “.

∑ Cut one piece 3 3/8” ± 1/16” long using the Metal Cutting Chop Saw.

∑ Remove all burrs using a file.

3.0 Milling of Pillow Blocks

Squaring-up blocks∑ (Fig. 7) shows the evolution and milling sequences of the pillow blocks from the

initial bar stock.

∑ Install the 1/2” wide parallels in the vise and place the workpiece on top of theparallels. Lightly clamp the workpiece and hit it with the rubber mallet to ensure it iswell seated on the parallels, then tighten up the vise. A second hit with the malletmay be necessary to ensure good seating of the part.

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∑ Use a 1/2” diameter, 2 flute, HSS (high speed steel) milling cutter (approximately2000 rpm) to “end mill” the top face of the aluminum block as shown (Fig. 7, step 1).Move the workpiece under the cutter and slowly move it up using the Z axis crankhandle until the cutter contacts. Set the Z dial to “0”, then raise the tableapproximately 0.100” (one full revolution = 0.100”) for the first cut, this will be a“plunge mill.” Traverse the table back and forward to remove all the material onthis plane.

∑ Remove an additional 0.025” of material for a finishing cut. Remove the workpiecefrom the vise and de-burr edges.

∑ Replace the workpiece in the vise with the last machined side facing down. Removeapproximately 0.100” of material in the Z axis.

∑ Move the workpiece in the X axis approximately 3” away from the cutter. Do notmove the Z axis from its last cutting position and measure the height of theworkpiece using a dial caliper.

∑ Crank the table up the required amount and mill the workpiece to its finished heightof 1.750” ± 0.005”.

∑ Always check the workpiece to ensure that the correct dimension and squarenesshas been obtained before proceeding to the next step.

∑ Place the workpiece in the vise as shown in (Fig. 7 step 3) with the bottom of themilling cutter protruding approximately 3/8” below the workpiece. This will reducetool deflection.

∑ Using the “Y” axis table “ side mill ” the part removing max. 0.125” per pass. Makethe last cut a “climb mill “ removing less than .005” of material using a slow steadyfeed rate. This will produce a superior finish.

Note: “Climb milling” is when the workpiece travels with the direction of the cutterrotation. “Conventional milling” is when the workpiece travels against the rotationof the cutter. See (Fig. 8).Climb milling is used on manual milling machines only when machining soft metalsand plastics. Do not use climb milling when milling steel, conventionalmilling is used when milling steel on a manual milling machine. Climb milling isused predominantly in CNC machining on all metals and materials, this is due to anegligible amount of “backlash” on these machines.Note: Backlash is the play between the screw (driving element) and nut (drivenelement) of the machine.

∑ Remove the part and de-burr the last cut edge. Insert the workpiece with theopposite end (unfinished end) protruding approximately 1/2’’. Side mill this edgeremoving the least amount of material to obtain a completely finished edge makingthe last cut a climb mill removing less than 0.005’’. Total length of part shouldmeasure approximately 3 1/4” long.

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∑ Remove the part from the vise and scribe a line dividing the part into two equalsections lengthwise. Using the Band Saw (small Delta band saw), cut the part in twothru this line.

Note: Consult the instructor on the correct and safe use of the Band Saw prior to use.

∑ Place one of the previously cut pieces in the vise protruding approximately 1/2’’with the rough cut edge facing up as shown in (Fig. 7, step 5). Face mill this piece toa height of 1.425” ±0.005”. Repeat this step for the 2nd piece. De-burr with a file andcheck parts for squareness.

1.75

.125

scribe line thru centre, cut with band saw

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3.15 +- 0.5

1.75

end milling 2nd edge

2

.125

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1.425

1.75

end milling 1st edge

outline of pillow blocks in bar stock

3

5

end mill blocks individually

side mill both sides using climb milling for finish cut

Fig. 7 Steps for Milling Blocks

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rotation of cutter

feed directionof part

Climb milling

rotation of cutter

Conventional milling

feed directionof part

Fig. 8 Top View of Climb Milling and Conventional Milling

7.0 Boring the Bushing Hole

The hole boring operation will be done while the pillow blocks are in a rectangularshape (prior to removing the material on the side). This allows a more accommodatingshape for clamping the part in the vise.Precision diameter holes can be bored using various techniques:

Boring head reamer plunging with a calibrated diameter end mill.

The latter will be used in this lab as it requires the least amount of set up.When a precise diameter hole is to be plunge bored with an end mill a hole must first bedrilled approximately 85% of the diameter of the finished hole size.

∑ Clamp one block in the vise as shown in Fig. 12 butting the block up to the magneton the left side of the back jaw. (The magnet acts as the position stop for the X axis.)

∑ Do not use excessive force as the vise is capable of exerting thousands of pounds offorce on the part which can force the back jaw (“Y” datum) backwards up to .004”.(This will happen on even the best vises). This will result in the hole position of1.000” ± 0.0005” to be out of tolerance, ultimately causing the Rotor Assembly tobind.

∑ Insert the drill chuck in the spindle and drill a 7/16” dia. hole (approximately 1000rpm) at the X=0.875”, Y=1.000” position ensuring the table locks are locked.Remove the part and repeat the drilling process for the 2nd block.

∑ Insert the designated 1/2” diameter end mill into the collet (approximately 1800 rpm)and plunge the cutter through the drilled hole using a steady ”Z” feed. Repeat forthe 2nd block.

∑ The Instructor will check the hole height position relative to the base using the DialIndicator installed on the Height Gauge.

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4.0 Milling the Side Recesses

∑ In order to mill the side recesses “cutter radius offset” will be used (Fig. 9). Cutterradius offset is the amount the cutter must be offset from the cut line to compensatefor its radius. This is also commonly referred to as cutter compensation.

cutter radius offset = 1/2 cutterdia.

cutter diameter

0.5

0.25

∑ Lines will be scribed on the blocks to give the student a visual reference whenmilling this step. As the student becomes more proficient with cutter tool offsets thescribing of visual references will not be necessary. Using the height gauge on thesurface plate with the scriber tip, scribe lines in the position as shown in (Fig. 10).

∑ Using a 1/2” dia. cutter, mill the block as shown in (Fig. 10). 0.375” is required to beremoved from the side of the block, as a 1/2” dia. cutter is to be used cutter radiusoffset will be 0.250”.

∑ Place the work piece in the vise as shown. (Fig. 10)

∑ While the spindle is rotating, bring the tip of the cutter lightly into contact with thetop of the block using the “Z” crank handle. Zero the “Z” dial.Milling the side recesses in the pillow blocks will use a combination of side millingand end milling.

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∑ Remove approximately 0.25” vertically (“Z”) and approximately 0.35” horizontally(“Y”) simultaneously in each pass (lock the “X” axis while cutting in the “Y”).Increment the “Z” with the cutter to the side of the block. In this case do not plungethe cutter into the block.

∑ Once the final depth has been achieved move the block over in “X” to the finalposition and make the finishing cut in a climb mill direction which will result in asuperior finish on the side.

.35

0.25

1.625

1st cut to rough out material

datum X=0 edge

.125

scribed lines for milling side recesses

1.75

1.425

0.925

1.375

0.375

position of cutter for clean up cut showing cutter offset positionposition of cutter for clean up cut showing

cutter offset position

Fig. 10 Steps for Milling Side Recessess in Pillow Block

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5.0 Drilling Screw Clearance Holes

∑ Install the drill chuck into the spindle, using a #7 drill = 0.201” dia. (approximately1500 rpm) to drill the #10 screw clearance holes as indicated in the drawing.

Note: Ensure that the parallels under the part are set to the side as far as possible toavoid drilling into them.Note: Tool offset is not used when drilling holes as holes are only point positions withthe drill being centred to the machine spindle.

∑ A general rule for determining screw clearance holes:Drill is approximately 5% larger than the outer diameter of the screw.For example, #10 screw = 0.190 O.D. 0.190” x 1.05 = 0.200”. As there is no 0.200”dia.drill select the next larger size = 0.201 dia. (#7 drill). See the attached chart for tapdrill holes and screw clearance holes.

6.0 CNC Machining of Base Plate

∑ The base plate machining will be a demonstration of CNC (computer numericalcontrol) machining by the shop instructor. This demonstration will replicate aproduction method of machining the base plate.

∑ All milling operations will be performed with the workpiece screwed to a preparedjig with all milled edges, faces and drilled holes machined in one set-up.The base plate will be machined from a piece of 1/4” x 3” extruded aluminum cut toapproximately 3.75” long (approximately 1/8” longer than final size).

∑ Initially two screw down holes (0.200” dia.) will be drilled through the plate in thepositions shown in the drawing. These two holes will serve as the machining fixturescrew down holes and the base plate’s hold down holes.

∑ Note how the design incorporates the final holes in the design to be used asmachining fixture hold down holes, therefore not requiring the workpiece to beclamped down using a vise or clamps.

∑ The CNC machine will cut out the outside contour first, then mill a pocket 0.050”deep. This pocket is to create a flat surface for the pillow blocks to mate to in order toassure alignment. Aluminum extrusion does not come flat often having a slightconvex or concave surface.

∑ Four tap drill holes will be drilled into the base plate in the positions indicated onthe drawing using a #20 drill (See attached Tap Drill Cart for the selection of TapDrills). These holes will be tapped (internally threaded) using a #10-32 tap. All holesand edges to be de-burred to assure a good mating surface of pillow block and baseplate.

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Manual Lathe

Manual Lathe Safety Procedures

∑ Only one student to operate the machine at any one time. Multiple people working on amachine leads to confusion and inadvertent operations which can endanger otheroperators. Non-operating members of the group can watch, advise the operator and canadd coolant to the work piece (part being machined) if required.

∑ The operator and those watching must always stand to the side of the chuck, out of theline of rotation.

∑ Always remove the chuck key from the lathe chuck immediately after use and replace itin the chuck key holder (on the back splash guard). Do not even leave the chuck key inthe lathe chuck for a moment while your hand is not holding it. If a chuck key is left inthe chuck and the lathe turned on the results can be very serious.

∑ Always ensure the workpiece is held securely in the chuck. Ask the instructor if you arenot sure.

∑ Always wait for the lathe chuck to come to a complete stop before touching the chuck orworkpiece.

∑ Never remove swarf (long stringy cuttings) from the lathe tool or work piece with yourfingers. These can cause nasty cuts to your hands and fingers. Use the long nosed pliersor air gun to remove the swarf and cuttings.

∑ Do not allow an accumulation of swarf in the vicinity of the chuck and the work area.Remove it , and put in in the recycle bin.

∑ Remove the lathe tool when drilling or using the tailstock. Conversely remove any drillsfrom the drill chuck or the pointed live centre when they are not being used.

∑ Always stop the lathe while changing tools.

∑ Ask the instructor before using sandpaper on the lathe.

∑ Ask the instructor before using a hand file on the lathe.

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Fig. 1 A Manual Lathe(Courtesy of the Dorian Tool Catalog, 2001)

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Use and Care of the Lathe

∑ Refer to (Fig. 1) to familiarise yourself with the names and parts of the lathe.

∑ Oil the lathe first. Inject oil from the oil can into the oil fittings. Apply oil to the bedways.

∑ When changing speeds using the gears, always turn the chuck by hand before switchingon the lathe to ensure that the gears are properly engaged.

∑ Do not machine too close to the chuck. Keep the cutting tool tip a minimum of 1/8”away from the chuck.

∑ Ensure that sufficient stock is held in the chuck to prevent the workpiece from beingpulled out of the chuck while being machined.

∑ Use caution when using the long nosed pliers to remove swarf from around theworkpiece and cutting tool, so as not to knock the pliers against the cutting tool.

∑ Use caution when placing any metal tools near the lathe cutting tools that are not in use.The lathe cutting tool used in this shop are expensive tungsten carbide inserts whichhave very sharp brittle tips and can be damaged easily if knocked against other metalobjects. Therefore, do not place the chuck key on the headstock ledge; return itimmediately to its designated holder on the back panel.

∑ Do not allow any tools or measuring instruments to lay protruding from the latheheadstock ledge, as they could accidentally drop onto the rotating chuck.

General Techniques for Turning on a Manual Lathe

∑ Important! Failure to pay attention to the following details will often result in a finishedpart not conforming to specification. This is often only recognised after completion ofthe part, or worse yet, in the final assembly, resulting in a time consuming re-make orrework.

∑ Note: there is no “Undo“ command in machining, therefore measure correctly and checkyour work.

∑ Removal, cutting or machining of material on a lathe with a lathe tool is referred to as“turning.”

∑ Always ensure the workpiece is rotating at full speed when engaging the cutting toolinto the workpiece or exiting the cutting tool from the workpiece. Do not stop the chuckrotation with the cutting tool in the workpiece or when it is touching the workpiece.

∑ Always move the lathe tool to its cutting position off of the workpiece then proceed withthe cut into the workpiece.

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∑ Always clean the chuck jaws with a shop cloth prior to installing the workpiece toprevent eccentric chucking and indentation of the workpiece by previous cuttings.

∑ Have the least amount of material protruding from the chuck as possible in order tomachine the part. Rigidity is the key factor to achieving a good machined finish on thepart.

A general rule: Do not have more than 2 times the diameter of the work protruding fromthe chuck, and a minimum length of one times the diameter held in the chuck. See (Fig. 2).If more of the workpiece is to protrude from the chuck, a live centre must be used tosupport the end. The cutting tool must be centred with respect to the centre of the spindle.See (Fig. 3).

x 2x

xlathe chuck workpiece

Fig. 2 Maximum protrusion of workpiece from the chuck without end support.

0.1

tool

depth of cut

spindle centreheight

1.0 dia.

1.2 dia.

Fig. 3 When the tool tip is set to spindle centre height 0.1”, the depth of cutdecreases diameter by 0.2”

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∑ Feeding in or out the cross slide (“X” axis) will determine the diameter of the workpieceand the feeding in or out the carriage (“Z’’ axis) will determine the length of the part.

∑ A physical movement or cut of x in the cross slide “X axis” will result in a physicaldiameter reduction on the workpiece of 2x. (i.e. when a cut depth of 0.100” is made, thisresults in a diameter reduction of 0.200”). The digital readouts (DRO’s) on the lathes areset to read in “diameter.” See (Fig. 3).

∑ If an overshoot occurs when turning the cross slide (“X” axis) to its desired position thecross slide must be backed out approximately half-a-turn and then repositioned to thedesired position. This will eliminate “backlash.” Backlash is the play or slack betweenthe driving element (screw) and the driven element (nut).

∑ An small initial cut and measurement must always be made on the diameter of the “X”axis and another on the “Z” axis to establish a datum point from which the diameter(“X” axis) and length (“Z” axis) can be set. This is a crucial measurement as allsubsequent measurements will be based on these initial cuts.

∑ When measuring the diameter of the part in the chuck, move the carriage well out of theway to allow unconfined access to the part.

∑ The lathe tool used in this Machining Lab is set in the same position for longitudinal cuts(cuts along the “Z” axis) and for facing cuts (cuts along the “X” axis).Note: Often when using older style lathe tools, the tool angle must be changed for afacing cut or a longitudinal cut.

∑ Use two hands when feeding during a cut. This will result in more control and willproviding a uniform finish on the workpiece.

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The Project: Aluminum Rotor and Brass Bushings

Procedure:

1.0 Preparation of Workpiece for Aluminum Rotor and Brass Bushing

∑ The Rotor will be machined from Aluminum 6061-T6 1 1/2” diameter bar stock.

∑ The brass bushing will be machined from Brass 3/4” diameter bar stock.

∑ These pieces must each be a minimum of 2” long to ensure that a sufficient amount ofmaterial can be held in the chuck for safety and rigidity.

2.0 Turning Aluminum Rotor

∑ See (Fig.4) for the names associated with the various features of the Rotor.

SHOULDER

BOSS

ROTOR O.D.

.25" SHAFT HOLE

BORE CHAMFER

BORE

BORE FACE

Fig. 4 Features of the Rotor

∑ Set the “Metosa” lathe to 1075 rpm and the smaller “Standard and Modern” lathe to 900rpm.

∑ Place the Aluminum designated lathe tool in the quick-change tool holder.

∑ See (Fig. 5a, 5b) for the machining steps of the aluminum Rotor.

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1.25

1.45

5

4

turn O.D.

.49

1.05

.49

6

1.5

rough stock removal

rough stock removal

1.5

2

1

initial bar stock placement in chuck

0

0.25

approx. 1.48

1.25

3

inital skim cut cut to establish "X" datum

iInitial facing cut, set "Z" datum

Fig. 5a Machining Steps for the Rotor

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0.75

0.5

chamfer edges

10

shoulder face cut

9

8

rough stock removal

7

turn to final 0.75"dia.

.49

0.85

0.75

.49

Fig. 5b Machining Steps for the Rotor

∑ Place the 1 1/2” diameter aluminum bar in the chuck with approximately 1 1/2”protruding and facing the end (X axis feed). Set the Digital Read Out (DRO) on the “Z”to 0.000. This will be the datum point for the length of the part.

∑ Make a small skim cut (approximately 0.25” long) on the diameter of the workpiece, andmove the lathe tool back off the part in the “Z” axis without moving the position of the“X” axis.

∑ Measure the diameter of this cut with the dial calipers, and input this value into theDRO for the “X” axis.

∑ Turn the diameter to 1.450” ±0.005” and to a length of 1.25”.

∑ Refer to (Fig.5) for the steps to turn the boss to 0.750” diameter by 0.500” long. Only turnto 0.480” ±0.010” in length ( Z axis) for the rough cuts.The final 0.500” length cut of the boss will be made using a facing cut by positioning theZ axis at 0.500” ±0.005” and feeding the X axis in to 0.750” ±0.005”.

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∑ Remove the tool from the quick-change tool holder and replace with the chamfering tooland lightly chamfer the two corners as required.

∑ Note: These corners are only “cosmetic” chamfers, and therefore do not need to beaccurate.

3.0 Drilling the Shaft Hole

∑ A centre drill is always used in a lathe drilling operation. If the regular drill was usedwithout the centre drilled hole, it would deflect to the side.

∑ Insert the drill chuck into the tail stock and using the centre drill (Fig. 6), drill a centrehole in the aluminum workpiece to the depth shown in (Fig. 6b).

∑ Drill the shaft hole with a 1/4’’ diameter drill approximately 1 1/4’’ deep, backing outevery 3/8’’ to clear the cuttings and inject coolant down the hole.

∑ All holes should be deburred. Insert the countersink tool in the drill chuck, gentlybringing it into contact with the part. Rotate the chuck by hand. This will remove theburr at the entrance of the hole and create a small chamfer.

centre drill

Fig. 6 Showing drill depth for the centre drill

4.0 Cutting Off the Rotor

∑ Insert the cut-off tool into the tool holder and align its front right tip to the front face ofthe part as shown in (Fig. 7). Move the “Z” carriage forward to approximately Z=1.05”and feed the cut-off tool into the work at a medium steady pace ensuring coolant isbeing injected liberally into the cut-off groove. Once the cut-off tool penetrates to thedrilled hole the part will simply fall away. Do not attempt to catch it.

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align right edge of cut-off tool withfront face of part

1.05

tool at cut-offpostion

Fig. 7 Cut-off tool positioning

5.0 Facing the Rotor to Finished Length

∑ Remove the bar stock from the chuck and insert the Rotor part as shown in (Fig. 8). Shimstock (brass foil) can be wrapped around the part so as to prevent the hard jaws of thechuck from indenting the part.

∑ Insert the regular lathe tool (diamond shaped) into tool holder and face the part,removing as little material as possible. Back the tool out in the “X” axis without movingthe “Z” carriage.

∑ Measure the total length of the part and input this value into the “Z” DRO.

∑ Move the “Z” carriage to 1.00” and face the part. This will produce the 1.00” finishedlength of the part.

∑ Insert the chamfering tool and turn a small chamfer on the part.

tool cuttingdirection

tool

chuck jaws

Fig. 8 Facing Rotor

25

6.0 Boring the Recess in the Rotor

∑ Insert the boring tool into the tool holder and very lightly touch the tip of the boring barto the front face of the part near the centre with the lathe on. Set the DRO in the “Z”axis to 0.000”. See (Fig. 9).

∑ Move the tip of the boring tool out in the “X” axis approximately 1/8” beyond the centrehole and bore in the “Z” axis to a maximum depth of 0.24”. Repeat this operationincreasing the diameter of the bore by approximately 0.200” per cut.

∑ After the 2nd cut, back out the boring tool in the “Z” axis, ensuring not to move the “X’axis from its last cut. Measure the internal diameter of the bored hole, and input thisvalue in “X” DRO. Continue boring out the recess in increments of approximately0.100” until the diameter 1.00” ±0.005” is achieved.

∑ Return the tip of the boring tool to the centre of the part (“X” = 0.000”) at a depth of “Z”= 0.250” ±0.005” and feed the tool out (facing cut) to a diameter of 0.995”. Retract thetool in the “Z” ( the tool is only taken to 0.995” diameter so it does not contact the innerdiameter wall, which would produce chatter marks).

∑ The internal chamfer on the 1.00” bore diameter can be achieved by feeding the boringtool in at a 45 degree angle. Internal chamfers can not be turned using the regular lathetool.

initial boring tool start position

boring tool

chuck jaws

Fig. 9 Boring tool set-up

26

7.0 Turning the Brass Bushing

∑ Insert the 3/4” diameter brass bar stock into the chuck with approximately 1.00”protruding.

∑ Using the diamond shaped lathe tool face the workpiece and set the DRO to Z=0.000”.

∑ Do a small skim cut (approximately 0.25” long) on the diameter of the workpiece andmove the lathe tool back off the part in the “Z” axis without moving the position of the“X” axis.

∑ Measure the diameter of this cut with the dial calipers and input this value into the DROfor the “X” axis.

∑ Note: The brass bar stock is 0.75” dia. therefore the “0.75” Nom.” dia section of thebushing is already to size and does not required to be machined. ( Nom. is short fornominal which means: leave the pre-sized stock at its original size or as it comes fromthe supplier). Keeping this practice in mind where ever feasible will save much time andexpense in designing and manufacturing parts.

∑ Turn the shoulder of the bushing to 0.510” ±0.005” dia. and 0.440” deep inapproximately 0.100” diameter increments. See (Fig. 10a, 10b).

∑ In order to obtain the high tolerance on the bushing O.D. (0.501” ±0.0003”) a micrometermust be used to measure the O.D. Input this micrometer measured diameter into theDRO.

∑ Turn the bushing down to 0.5050” and measure the dia. again using the micrometer, if itreads different to the DRO reading update the DRO with this latest measurement.

∑ Make a cut at O.5020” diameter, measure again to check.

∑ Now cut diameter to the required size 0.501”, +0.0000, -0.0003” and check the size usingthe micrometer.

∑ Position the tool at “Z”= 0.450” and feed in the “X” axis to a diameter of 0.490”. Thiswill face cut a clean square shoulder and produce an undercut at the junction of theflange and the shoulder. See (Fig. 10b, step 12).

∑ Turn the small reduced diameter of 0.490” x 0.07 long. This reduced diameter isdesigned into the part to allow for ease of initial insertion of the bushing into the pillowblock bore.

∑ Insert the chamfering tool. Cut the small chamfers on the front edge and the shoulderedge.

27

8.0 Drilling and Reaming the Bushing Bore

∑ Refer to the section on drilling the Rotor shaft hole (section 3).

∑ As this is a precision hole of 0.2510” ±0.0003 it must be reamed to attain the tolerancesrequired. A hole of approximately 0.240” is drilled to a depth of 0.75”, drilling inincrements of approximately 1/4” deep and retracting to clear the cuttings.

∑ Insert the 0.2510” diameter reamer into the drill chuck and change the lathe speed to 275rpm for Metosa, and 200 rpm for Standard and Modern.Note: The more cutting flutes the tool, has the slower the rotational speed.

∑ While applying coolant, slowly feed the reamer into the drilled hole until the reamerbottoms out. Retract slowly.

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.44

0.51

.44

.55

rough stock removal

rough stock removal

6

5

.44

.505

.44

1

measure dia. with micrometer and input into DRO

measure dia. again after this cut and re-clibrate DRO if required

8

7

0

chuck jaws

bar stock

2

1 0.75

.44

face front and set "Z" datum to 0.000

insert brass bar stock as shown

0.65

initial skim cut to establish "X" datum

rough stock removal

4

3

0.125

?

Fig. 10a Machining steps for the brass bushing

29

0.45

.4811

12

face shoulder square and undercut corner

0.07

0.49

0.501

.44

turn down step on leading edge chamfer edges

10

9

turn to final 0.501" dia

Fig. 10b Machining steps for the brass bushing

9.0 Cutting Off the Brass Bushing

∑ It is important that all the necessary operations are performed on this side of the partprior to it being separated from its mother piece, as it is often very difficult to hold thepart in this orientation again and maintain concentricity.

∑ Refer to (section 4) - Cutting off the Rotor.

∑ Cut the bushing off longer than stated in the drawing, to a length of0.600” ±0.010”. This extra length will allow a small amount of material to be removed fora facing cut, as the cut-off tool will not always produce a flat smooth face on the part.

10.0 Facing the Bushing To Finished Length

∑ Refer to (section 5) Facing the Bushing To Finished Length.

∑ Face the bushing to a length of 0.575” and chamfer O.D. using the chamfering tool andI.D. using the countersink tool in the drill chuck.

∑ The completed part should now conform to the drawing.

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Appendix ADepartment of Mechanical Engineering

MACHINING / DESIGN FACILITY USE POLICY

May 2001

Safety

Safe working procedures must be adhered to at all times.

∑ Familiarization with the document: Department of Mechanical Engineering Basic SafetyRegulations for Instructors and Students is required. A copy is on hand in the Facility aswell as on the Mech Eng website: http://www.me.uvic.ca/undergrad/index.htm

∑ Safety Glasses must be worn at all times while using any tools and equipment orwhile observing.

∑ Care and attention must be exercised so as not to cause injury to self or others.Rushing is the main cause of accidents.

∑ Any equipment or area requiring attention or which may cause a hazardoussituation must be addressed immediately or reported to the Facility Supervisor.

∑ Shop personnel must be consulted before using any tool or method consideredunsafe or with which a user is not familiar. Users are encouraged to ask questionsfromthe Facility Manager or the Teaching Assistant at any time.

Facility Dress Code

∑ No open toe footwear is permitted.

∑ Minimum shirt attire can be a T-shirt. No sleeveless vests are permitted.

∑ Shop aprons are to be worn and straps must be tied.

∑ Name tags are to be worn whenever possible.

∑ Long hair must be tied back and restrained.

∑ All loose jewelry and finger rings are to be removed before using movingequipment.

∑ The supplied Barrier Cream should be used to protect hands from the coolant andoils.

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General

∑ Care must be exercised so as not to cause damage or undue wear and tear to theFacility. This includes protecting and maintaining equipment and fixtures asinstructed by the Manager.

∑ Users of equipment should clean all areas of work and equipment after use to thelevel at which it was found. Machine tools and equipment used for the projects areto be thoroughly cleaned and oiled after use. Workbenches and the areassurrounding the equipment must be swept and vacuumed after use.

∑ Hand tools taken from the racks must be placed back following their use.

∑ All tools or materials borrowed from the Design Facility must be signed out withconsent of the Facility personnel.

Mechanical Engineering Machining Facility Standards

∑ Drawings must be made for all work being performed in the Design Facility andsubmitted to the Facility personnel prior to commencing with any work.

∑ Only course related or approved projects can be worked on in the Design Facility.

∑ Machine Tools, equipment, and supplies in Room B111 are for use by the DesignFacility Personnel only. Please consult first with the Facility personnel if you requiresupplies or tools from Room B111.

Dr. V. Ismet UgursalProfessor and Chair