College of Engineering Shop Procedure LATHE PROCEDURE. Dept: Multi-department Laboratory: Student Machine Shop Rm: HML 113

Transcription

1 College of Engineering Shop Procedure LATHE PROCEDURE Dept: Multi-department Laboratory: Student Machine Shop Rm: HML 113 Authored by: Adam Spiegelman, Support Technician Date: Reviewed and Approved by: Matt Lundgren, EH&S Lab Safety Officer Date: Filename: Lathe SOP 29-Nov-11.doc Revision: 1 Procedure Type Process/Protocol Chemical Hazard Class Brief Overview & Scope Potential Hazards Engr. Controls PPE Add'l Equipment, Tools: Mat ls, Supplies: Add l Training Requirements This procedure provides general instructions on how to use the Monarch, Tida and Jet lathes in the student shop. The lathe is a versatile tool that is used to create cylindrical external and internal profiles on workpieces. The workpiece is held to the spindle by chuck or collet and rotated. A cutting tool is held by a tool post that can move parallel and at right angles to the axis of rotation. Thus, the workpiece may be shaped or bored as the tool is moved relative to the spinning workpiece. This document describes typical operations only. Consult a shop supervisor if you need to perform an operation not described here. Maintenance operations of the tool are beyond the scope of this document due to the skill required and diversity of tools and processes associated with these operations. Entanglement with cutting tool, spindle or chuck resulting in injury or death. Injury due to workpiece thrown from spindle. Eye injury due to debris ejected from turning, facing or boring. Burns due to cutting or workpiece becoming hot. Injury due to heavy workpiece or fixture falling off lathe or dropped while moving. Safety glasses, non-slip, close-toed shoes Cutting tools, holders, drill bits, hand broom, dust pan Cutting lubricant, towels (as needed) All mandatory shop training modules Hands-on training for mill Special Requirements: Handling & Facilities n/a Spill & Incident Decontamination/ Waste Disposal Sources/ References n/a All shop consumables to be disposed of per Shop Waste Materials Disposal SOP. Some content for this procedure have been taken from the other sources. See citing in specific areas.

2 TABLE OF CONTENTS MILLING MACHINE TOOL COMPONENTS... 3 GENERAL LATHE SAFETY RULES... 8 COMMON TASKS Stopping the Tool Applying Power to Machine Facing Turning Drilling Boring Parting Tapping Workholding Tool Setup Speeds and Feeds Clean Up Oct-11 Page 2 of 18

3 TOOL COMPONENTS Spindle Speed Controls 3-Jaw Chuck Quickchange Tool Post Compound Slide Cross Slide Drill Chuck Tailstock Feed Controls Apron Carriage Handwheel Cross Feed Handwheel Automatic Feed Lever Starting Shaft Lever Tida Lathe 21-Oct-11 Page 3 of 18

4 21-Oct-11 Page 4 of 18

5 Cross Slide Handwheel Feed Control Lever Carriage Handwheel Half Nut Lever Tida Controls 21-Oct-11 Page 5 of 18

6 Spindle Speed Controls Collet Chuck Quick- Change Tool Post Compound Rest Drill Tailstoc Cross Slide Cross Feed Handwheel Feed Controls Carriage Handwheel Apron Automatic Feed Starting Shaft Lever Monarch Lathe 21-Oct-11 Page 6 of 18

7 Carriage Handwheel Cross Slide Handwheel Compound Handwheel Half Nut Feed Direction Lever Cross Feed Lever Longitudinal Feed Lever Starting Shaft Lever Monarch Controls 21-Oct-11 Page 7 of 18

8 a. Safety glasses are required to use this tool. GENERAL LATHE SAFETY RULES b. Do not operate a lathe until you fully understand its controls c. To prevent entanglement with the cutting tool, chuck or collet: - Tie back long hair and tuck under shirt, roll up long sleeves, remove gloves or loose clothing. - Remove any gloves, rings, or other jewelry. - Keep hands away from work area when tool is turned on. - Keep your hand away from the cutting tool or workpiece when the tool is on.. d. Always remove chuck key before starting the machine. e. Know the location of start and stop switches or buttons for this machine. Never attempt to stop the lathe chuck by hand. f. Never use a rag while the lathe is in operation; it may be drawn into the rotating machine. g. Do not use any machine in which a guard or cover has been removed. Contact the shop supervisor immediately. h. Keep the working area free of tools and other materials; cluttered areas can lead to accidents i. Always rotate spindle by hand to ensure that gears are meshed properly and parts will clear without jamming. j. Keep floor around machine free of oil, tools, chips etc. k. Get help when lifting heavy chucks, workpieces or other tooling. l. Use only properly sharpened cutting tools and drill bits or other cutting tools. Bring dull tools to supervisor for sharpening or replacement. m. Do not remove metal or chips from work area when lathe is running. Use brushes or other tools to properly remove chips after the tool has been turned off and has come to a stop. n. Do not attempt to make adjustments to the cutting tool or measurements of the workpiece while the machine is turned on. o. Always install and remove the cutting tool using the proper wrenches or other tools. 21-Oct-11 Page 8 of 18

9 1. Be sure the chuck, workpiece and cutting tool are mounted securely before starting the lathe. p. All stock must be properly secured with chuck or collett prior to a machining process. q. Use the correct speed, cutting tool and lubricant for the type of stock being machined. Ask a supervisor for help if you don't know. r. If any part of the tool makes an unexpected noise, malfunctions or has been damaged or broken, notify the supervisor immediately. s. If you have any questions about this tool or its use, stop what you are doing and ask a shop supervisor. 21-Oct-11 Page 9 of 18

10 COMMON TASKS 1. Stopping the Tool In the course of normal operation or in the event of an emergency, stop the mill as shown: Sharp CNC Mill (left): Press red emergency stop button a. Manual Sharp Mill (below): Turn power switch lever to middle (OFF) position Emergency Stop 2. Applying Power to Machine The Sharp manual mill is connected directly to a power receptacle so power is normally always on. However, the Sharp CNC mill is connected through a power shutoff panel on the right side of the base. If the digital readout is not illuminated, the power shutoff is probably turned off. Turn back on by rotating the red switch to the ON position and pressing the green button as shown in left figure. In addition, the Sharp CNC mill has an emergency shut off. If the shut off has been pushed, it must be reset by rotating counterclockwise as shown in right figure. 21-Oct-11 Page 10 of 18

11 3. Facing Facing is the removal of material on the end of a workpiece using the cross feed. This creates a flat and square cut in relation to the axis of rotation of the spindle. Figure 1: Facing operation ( 4. Turning Turning is the removal of material diametrically on a workpiece using the longitudinal feed. This creates a smaller diameter that is concentric with the axis of rotation of the spindle. Figure 2: Turning Operation ( 5. Drilling Drilling is done on the lathe with the use of the drill chuck and tailstock. A drill is placed into the drill chuck and fed into the work using the tailstock while the workpiece is spinning. 21-Oct-11 Page 11 of 18

12 6. Boring Boring is the removal of material diametrically on the internal wall of a hole. Boring allows holes to be created more accurately than drills and at any size. Figure 3: Boring Bar Set ( Boring operation (web.mit.edu) 7. Parting Parting uses a thin cutting tool that plunges directly into the workpiece. This operation is normally used to removed the finished work from the bar stock clamped in the chuck. Figure 4: Parting Tool Holder Figure 5: Parting Operation 8. Tapping Tapping is creating threads in a drilled hole. This can be done on the lathe with the use of a tap, T- handle, and spring-loaded tap guide as shown in the figure below. The tap guide is placed into the tailstock and the tap is placed into the T-handle. The tap guide is used to keep the tap straight during the tapping process. Cutting oil is used during tapping to prolong the tap s life. 21-Oct-11 Page 12 of 18

13 9. Workholding Figure 6: Offset tapping with 4-Jaw and Spring-loaded tap guide ( a. 3-Jaw Chuck The three-jaw universal chuck is used to hold round and hexagonal work. All three jaws move in simultaneously to grasp the work within a few thousandths of an inch. This simultaneous motion is the result of a scroll plate within the chuck that the jaws fit into. If the three-jaw chuck is opened too widely the jaws will come off the scroll completely. Care must be taken putting the jaws back into plate since they must be placed back in the correct order. There is a removable portion of the jaws that can be rotated around to accommodate larger diameter work pieces. There are two socket headed cap screws holding each removable jaw in place. Figure 7: Three-Jaw Chuck b. 3-Jaw Chuck The three-jaw universal chuck is used to hold round and hexagonal work. All three jaws move in simultaneously to grasp the work within a few thousandths of an inch. This simultaneous motion is the result of a scroll plate within the chuck that the jaws fit into. If the three-jaw chuck is opened too widely the jaws will come off the scroll completely. Care must be taken putting the jaws back into plate since they must be placed back in the correct order. There is a removable portion of the jaws that can be rotated around to accommodate larger diameter work pieces. There are two socket headed cap screws holding each removable jaw in place. Figure 8: Three-Jaw Chuck 21-Oct-11 Page 13 of 18

14 c. Spring collets MILLING MACHINE Spring collets are used in conjunction with the collet chuck to hold workpieces. Collets are the most accurate work holding device. Each collet has a range of only a couple thousandths within the nominal size stamped onto the collet. Spring collets are held in place by the draw bar. The draw bar goes through the headstock and screws into the back of the collet. The draw bar is tightened to draw the collet into the collet chuck, clamping onto the work piece. The draw bar is loosened to release the work piece. 10. Tool Setup a. Tool Grinding Improper tool geometry and dull cutting edges are the most common causes of poor surface finishes on lathe parts. A great resource for grinding and sharpening lathe tools can be viewed at this website: A basic turning-facing tool can be seen below: Figure 9: Turning-Facing tool and cutter terminology (web.mit.edu) 21-Oct-11 Page 14 of 18

15 b. Setting tool height The quick change tool holders have a height adjustment to accommodate different size tools. The cutting edge of tools must be on center with the axis of rotation of the lathe to cut properly. If the tool is too high the front end clearance of the tool will be rubbing on the workpiece instead of the cutting edge. If the tool is too low the workpiece has a tendency to climb the tool. Proper tool height is most critical on small diameter parts. The easiest way to set tool height is to use a standard steel rule as shown in the figure below. Carefully pinch a steel rule between the cutting edge of the tool and the work piece and observe the angle of the steel rule. If the steel rule is not vertical the tool height must be adjusted. Tool too low Figure 10: Using a Steel Rule to adjust Tool Height 21-Oct-11 Page 15 of 18

16 11. Speeds and Feeds Lathes are designed to operate at various spindle speeds and feed rates. Spindle speeds are measured in revolutions per minute of the workpiece. Feed rates are measured in inches per revolution. To change spindle speeds and feed rates the lathe must be turned OFF. Attempting to change gears while the lathe is running will result in damage to the lathe. a. Cutting speed Cutting speed or surface feet is the tangential velocity of the cutting edge of the toolbit in relation to the workpiece. The optimal cutting speed varies for different cutter materials and workpiece materials. Table 1 below shows recommended cutting speeds for a variety of workpiece materials using a High Speed Steel (HSS) cutter. Lathe Cutting Speeds in Feet per Minute using High Speed Steel (HSS) Toolbit Turning and Boring Material Rough Cut Finish Cut Threading Carbon Steel Tool Steel Cast Iron Bronze Aluminum Table 1: Cutting Speeds 21-Oct-11 Page 16 of 18

17 a. Spindle Speed The following equation is used to calculate the lathe s angular velocity or speed in revolutions per minute: Where CS is cutting speed in feet per minute D is diameter of workpiece in inches To change RPMs on the lathe, position the spindle speed control levers to the settings identified on the lathe s nameplate. If the levers do not move easily slowly rotate the chuck with one hand while adjusting the levers with the other. Be sure the gears are fully engaged before starting the lathe, failure to do so may result in grinding between the gears. Spindle Speed Control Levers Nameplate a. Feed Rates Feed rate is the distance the toolbit travels into the workpiece as it rotates one full revolution. Recommended feed rates for roughing and finishing are located in Table 2 below. The feed controls for the Tida and the Monarch lathe can be seen in the figures below. Lathe Feed Rates in inches per revolution using High Speed Steel (HSS) Toolbit Material Rough Cut Finish Cut Carbon Steel Tool Steel Cast Iron Bronze Aluminum Table 2: Feed Rates 21-Oct-11 Page 17 of 18

18 Figure 11: Tida Feed Controls Figure 12: Monarch Feed Controls 12. Clean Up a. Wipe table and vise clean and sweep up chips and debris off the floor. b. Use vacuum to clear chip from the table and other crevices. Use of compressed air is discouraged as it may embed chips into the table ways and other moving parts. c. Wipe end mills, collets, bits, clamps and other tools clean and put back in their proper place. d. Return mill speed range to HIGH if you changed it to LOW. e. Make sure the table is set at the horizontal position so it is ready for the next user. Restore any other settings to their nominal positions as needed. f. Shop towels, etc. to be disposed of in accordance with the Shop Waste Disposal SOP. 21-Oct-11 Page 18 of 18