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MODEL G4791 12" x 39" LARGE COMBO LATHE/MILL OWNER'S MANUAL WARNING: NO PORTION OF THIS MANUAL MAY BE REPRODUCED IN ANY SHAPE OR FORM WITHOUT THE WRITTEN APPROVAL OF GRIZZLY INDUSTRIAL, INC.
Machine Data Sheet Customer Service #: (570) 546-9663 · To Order Call: (800) 523-4777 · Fax #: (800) 438-5901 MODEL G4791 12" X 39" LARGE COMBO LATHE/MILL Product Dimensions: Weight... 1110 lbs. Length/Width/Height... 69 x 25 x 69 in. Foot Print (Length/Width)... 56 x 19-1/2 in.
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No. Of Change Gears... 14 Swing Over Bed... 12 in. Swing Over Saddle... 6-7/8 in. Dist. Between Centers...39 in. Spindle Bore...1-1/2 in. Lathe Spindle Taper...MT#5 Mill Info Drill Press Taper... MT#3 Mill Drill Spindle Travel...5 in. Mill Drill Swing... 21 in.
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Construction Bed Const... Hardened and Ground Cast Iron Headstock Const... Cast Iron Body Const... Cast Iron Frame Const...Cast Iron Headstock Gears Const...Steel Stand Const...Cast Iron Paint... Epoxy Other Bed Width...6-1/8 in. Floor To Center Height...43 in. Lead Screw Diameter...0.950 in. Lead Screw TPI...8 Lead Screw Length...
Additional Safety Instructions For Mills UNDERSTANDING CONTROLS. SAFETY ACCESSORIES. WORK HOLDING. CHUCK KEY SAFETY. SPINDLE SPEEDS. POWER DISRUPTION. STOPPING SPINDLE. CLEAN-UP. BE ATTENTIVE. Like all machinery there is potential danger when operating this machine. Accidents are frequent- ly caused by lack of familiarity or failure to pay attention. Use this mill with respect and caution to reduce the risk of operator injury.
Additional Safety Instructions for Lathes UNDERSTANDING CONTROLS. CLEANING MACHINE: USING CORRECT TOOLING: ELIMINATING A PROJECTILE HAZARD: SECURING A WORKPIECE: AVOIDING OVERLOADS: AVOIDING ENTANGLEMENT INJURIES: No list of safety guidelines can be complete. Every shop environment is different. Always con- sider safety first, as it applies to your individual working conditions. Use this and other machin- ery with caution and respect.
SECTION 2: CIRCUIT REQUIREMENTS 220V Operation Serious personal injury could occur if you connect the machine to power before com- pleting the setup process. DO NOT connect the machine to the power until instructed later in this manual. Electrocution or fire could result if machine is not grounded and installed in compliance with electrical...
Wear safety glasses dur- ing the entire setup pro- cess! The Model G4791 is a heavy machine. Serious personal injury may occur if safe moving methods are not used. To be safe, get assistance and use power equipment rated for at least 2000 lbs.
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Inventory Note: If you can't find an item on this list, check the mounting location on the machine or examine the packaging materials carefully. Occasionally we pre-install certain components for shipping purposes. Inventory: (Figures 3–4) Figure 3. Figure 4. SUFFOCATION HAZARD! Immediately discard all plas- tic bags and packing materi- als to eliminate choking/suf-...
Clean Up Figure 5 For optimum performance, clean all moving parts or sliding contact surfaces. Gasoline and petroleum products have low flash points and can explode or cause fire if used to clean machinery. NOT use these products to clean the machinery. Many cleaning solvents toxic Minimize your risk by only...
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Placement & Assembly The Model G4791 is a heavy machine. Serious personal injury may occur if safe moving methods are not used. To be safe, get assistance and use power equipment rated for at least 2000 lbs. to move the shipping crate and remove the machine from the crate.
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Figure 9 Note: It may be necessary to slightly re- position the cabinets and chip pan during this step. Figure 9. Note: Re-check the bedway for levelness after the first 24 hours, the first two weeks, then annually after that. Mounting to Shop Floor Bolting to Concrete Floors...
Using Machine Mounts Figure 11 NOTICE We strongly recommend securing your machine to the floor if it is hardwired to the power source. Consult with your electrician to ensure compliance with local codes. Check Gearbox Oil Lubrication GEARBOXES MUST BE FILLED WITH OIL! NO OIL SHIPPED WITH MACHINE! Requires ISO 68...
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Before starting the machine, make sure you have performed the preceding assembly and adjustment instructions, and you have read through the rest of the manual and are familiar with the various functions and safety features on this machine. Failure to follow this warning could result in serious personal injury or even death! Figure 13...
Spindle Break-In NOTICE Successfully complete all of the spindle break-in steps for both the lathe and mill to avoid rapid deterioration of the spindle bearings and other related parts. To perform the spindle break-in for this machine: Lubrication Page 54 Setting Mill Speed Steps 4–6...
WE STRONGLY RECOMMEND that you read books, trade magazines, or get formal training before beginning any projects. Regardless of the content in this section, Grizzly Industrial will not be held liable for accidents caused by lack of training. Basic Mill Controls Figures 14–15...
N. Main Power EMERGENCY Button: O. Main Power Lamp: P. Motor Position Crank: Turning the mill and lathe ON at the same time presents an entanglement hazard and could cause serious personal injury or damage to the machine. To prevent this condition, DO NOT have the mill and lathe running at the same time.
Table Movement Figure 16 Figure 16. Handwheel Dial Increments twice Figure 17 Figure 17. Head Movement Rotating the Mill Head Resolution Figure 18. Elevating the Mill Head Unexpected head movement when the mill is running can cause the cutting tool to move into the operator or damage the workpiece.
Setting Mill Speed Calculating Mill Spindle Speed Figure 19 Note: Cutting speed is the rotational speed that the cutter moves over/into the workpiece, and is expressed in surface feet per minute (SFM). Cutting Speeds for High Speed Steel (HSS) Cutting Tools Note: For carbide cutting tools, double the cutting speed.
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Note: This chart is also on the front of the machine. In most cases, the calculated spindle speed will be between the available speeds. Use your best judgement when choosing either a higher or lower spindle speed. Example with HSS Cutting Tool Step 1: Figure 19 Page 23...
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Quill Downfeed Figure 23 Figure 23. To use the downfeed controls: Note: It may be necessary to move the quill slightly up or down to push the downfeed selector knob all the way in. Note: Since the spring that automatically raises the quill is fairly strong, we recommend raising the quill in a controlled manner by hand to avoid premature wear to the mecha-...
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Unloading Tooling With the Drawbar Unloading Tooling With the Drift Key Figure 25 Figure 25. Cutting tools are sharp and can quickly injure your hands. Always protect your hands when handling cutting tools.
WE STRONGLY RECOMMEND that you read books, trade magazines, or get formal training before beginning any projects. Regardless of the content in this section, Grizzly Industrial will not be held liable for accidents caused by lack of training. Basic Lathe Controls Figures 26–28...
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H. Change Gear Cabinet: Main Power ON Button: Main Power EMERGENCY Button: Carriage Figure 27. K. Table (Cross Feed) Handwheel: Compound Slide Mounting Bolt: M. Compound Slide Rotational Adjustment Nut: N. 4-Way Tool Post: O. Compound Slide Handwheel: P. Thread Dial: Q.
Mounting/Removing Chuck or Faceplate ACCESSORIES Page 50 Tools Needed Mounting a Chuck or Faceplate Figure 29 Figure 29. Debris or grit on the mating surfaces will not allow the chuck or faceplate to evenly seat onto the spindle back plate. This con- dition could allow the chuck or faceplate to vibrate loose during use and cause serious personal injury.
Figure 29 PINCH HAZARD! Get assistance and pro- tect your hands and the precision ground bedways with plywood or a chuck cradle when removing the lathe chuck! The heavy weight of a falling chuck can cause serious injury. 3-Jaw Chuck Figure 31 Figure 31.
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Tools Needed Mounting Workpiece in 3-Jaw Chuck Securely workpiece and remove the chuck key! Thrown objects from a lathe can cause serious injury or death to the operator and to bystanders many feet away. Removing Jaws from 3-Jaw Chuck Note: Each jaw will move until it becomes loose from the scroll gear threads, then it can be removed by hand.
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Installing Jaws into 3-Jaw Chuck Figure 33 Figure 33. Steps 4–5 It is important to follow these points when replacing jaws in your 3-jaw chuck: 4-Jaw Chuck Page 29 Tools Needed To mount a workpiece in the 4-jaw chuck:...
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Figure 34 Figure 34. Figure 35 Figure 35. Always use a low spindle speed when machining non-cylindrical or off-center workpieces to avoid ejecting the workpiece from the holding device at a high rate of speed. Failure to heed this warning could lead to serious personal injury, death or property damage.
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Centers Figure 37 Figure 37. Figure 38 Figure 38. ACCESSORIES Page 50 Using a Dead Center in the Spindle Note: Hold onto the center as you tap it loose to avoid dropping it and damaging the tip or the bedways. Figure 38...
Using a Dead Center in the Tailstock Note: For stability and accuracy, the tailstock quill with the dead center mounted should protrude between ⁄ " and 1 Note: The force against the mounted workpiece will fully seat the center's taper. However, do not overly force the center into the workpiece—this will make removing the center very difficult.
Aligning Tailstock To align the tailstock: Page 16 Note: If the tailstock is slightly out of align- ment by a few thousands of an inch, the center drill will find the center point during the drilling process. If the tailstock appears gross- ly out of alignment, move the tailstock until it appears to be centered (refer to the previous subsection for detailed instructions).
thinner Drilling with away Tailstock half Figure 43 Note: Refer to Offsetting Tailstock on Page 35 for making adjustments to the tailstock position. Figure 44 Figure 43. Figure 44.
Follow Rest Figure 45. Tools Needed To use the follow rest: Tip: To further avoid deflection of the workpiece during setup, use the method Figure 45 shown in Figure 46. The test indicator is set directly opposite the brass fingers on the workpiece, then the brass finger is moved into the workpiece until the dial on the indi- cator begins to move.
Steady Rest Tools Needed To use the steady rest: Figure 47 Figure 47. Figure 48 Figure 48. Note: See the Tip on Page 38 for a method to further minimize deflection during steady rest setup.
Tool Post Figure 52 Figure 52. Tools Needed To load and use the 4-way tool post: Step 1 When securing a tool into the tool post, always remember these rules: Figure 53 Figure 53.
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Setting Lathe Speed Calculating Correct Spindle Speed Figure 54 Note: Cutting speeds are expressed in sur- face feet cut per minute (SFM). Recommended Cutting Speeds Rough Cuts Note: These values are based on HSS cutting tools. For carbide cutting tools, double the aver- age speed.
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Note: Your lathe/mill ships with three V-belts of varying length for the lathe spindle speed configuration: 1) 26", 2) 28", and 3) 29". Use your best judgement when deciding which length of V-belt to use for each pulley con- nection.
Example Step 1: Figure 54 Step 2: Step 3: Step 4: Step 5: Figure 57 Figure 57. Setting Feed Rate Figure 55 Figure 58. Note: The feed rate configuration chart is also on the inside of the change gear cabinet door. Figure 58...
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"II" position, point the arrow at 2/HI (high). Attempting to move the feed rate range lever when the lathe is running will damage the internal gears of the power feed mecha- nism and will void the warranty. NEVER attempt to move the feed rate range lever when the lathe is running.
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Configure Change Gears Tools Needed To configure the change gears: Figure 60 Note: Your lathe/mill is shipped with the fol- lowing change gears installed: Figure 60. Figure 58 Page 44 Column D Note: Before you install or store the gears,...
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Change Gear "B" or "C" Note: Be sure to retain the T-nut behind the pivot arm that the bolt threads into. Change Gear "D" Example of Setting Feed Rate Step 1: Figure 58 Step 2: 2/HI Step 3: Page 44...
Threading Controls Half-Nut Lever Figure 61 Figure 61. Thread Dial Figure 62. NOTICE Use lower spindle speeds (RPM) when threading. A slower RPM will give you more time to engage/disengage the half-nut, especially if threading over a short distance or threading up to a shoulder. Figure 62...
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Follow these rules and refer to the chart in Figure 63 when using the thread dial: Note: The thread pitch of the longitudinal leadscrew is 8. Figure 64 Thread Pitch Thread Dial Setting Figure 63. Figure 64. Note: The thread dial is not used when cutting metric threads.
SECTION 6: ACCESSORIES H8257—Primrose Armor Plate with Moly-D Machine and Way Oil 1 Quart S. Balolia – President Figure 65. G9849—Magnetic Base/Dial Indicator Combo Figure 66. G1076—52-PC. Clamping Kit, Figure 67. G1070—MT3 Live Center Set Figure 68. ⁄ " T-Nut...
Annually: Page 56 DO NOT use compressed air to blow away chips from the lathe to avoid the risk of flying metal debris injuring yourself or oth- ers, or driving the chips deep into the lathe mechanisms resulting in damage or prema- ture wear.
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Daily Lubrication Procedures Figure 77 Description Figure Follow reasonable lubrication practices as outlined in this manual for your lathe. Failure to do so could lead to premature failure of your lathe and will void the warranty. Lubrication Figures 78–90 Lubricant Figure 77.
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Figure 86. Figure 90. Checking/Adding Lathe Gearbox Oil Reservoir Lubricant Frequency Figure 87. Tools Needed To check and add oil to the reservoir: Figure 91 Figure 88. Figure 91. Figure 89.
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Figure 92 Figure 92. NOTICE The lathe gearbox oil must be changed after the first three months of operation, then annually after that. Semi-Annual Lubrication Tools Needed To perform the semi-annual procedure: Figure 93 Figure 93. Note: If necessary to pry the end cap off,...
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Figures 94–95 Figure 94. Figure 95. Note: To avoid damage to the bevel gears, make sure the teeth of the bevel gears mesh while inserting the end cap and gear without forcing them into the head. Figure 96 Figure 96. Figure 97 Figure 97.
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Note: If you have difficulty removing the fill plug, do not remove the drain plug to drain the reservoir until you can successfully remove the fill plug. This way you can still operate the lathe until the difficulty is resolved. Figure 92...
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Tools Needed To adjust the motor V-belt tension: Figure 100 Note: Moving the motor toward the lathe head will reduce V-belt tension. Conversely, pulling the motor away from the lathe head will increase V-belt tension. Figure 100. Figure 101 Figure 101.
Adjusting Gibs NOTICE Excessively loose gibs may cause poor workpiece finishes, and may cause undue wear of the sliding surfaces. Over-tightening the gibs may cause premature wear of these sliding surfaces. Saddle and Table Gibs Tools Needed To adjust the saddle and table gibs: Figure 102.
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Note: Turning the screws clockwise will tighten the gib, and turning them counter- clockwise will loosen the gib. Steps 2–4 Tailstock Gib Tools Needed To adjust the tailstock gib: Note: Turning the set screws clockwise will tighten the gib, and turning them counter- clockwise will loosen the gib.
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Adjusting Half-Nut Tools Needed To adjust the half-nut: Note: Turn the screws clockwise to tighten the gib, and counterclockwise to loosen it. Figure 106. Replacing Shear Figure Figure 107. Tools Needed To replace a shear pin: Pins Figure 107...
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Lathe Bearing Preload Note: Lathe spindle end-play can be felt when attempting to move the spindle toward and away from the headstock. Tools Needed To adjust the lathe spindle bearing preload: Figure 108 Figure 108. Note: You may have to tap on the outboard...
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NOTICE Adjusting the lathe spindle preload is a fair- ly complex procedure that requires precise measurements. If you are not comfortable performing this procedure, get assistance from an experienced professional. Figure 110 Figure 110. Note: While tightening the spanner nut, rock...
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Figure 111. Note: It may only be possible to partially engage a lock washer tang with the spanner nut, which will be sufficient. To confirm that the spindle bearings are cor- rectly preloaded: Figure 111 Step 10...
GROUNDED CIRCUIT. WARNING! SHOCK HAZARD! Disconnect power before working on wiring. MOTOR WIRING. 5. EXPERIENCING DIFFICULTIES. NOTICE The photos and diagrams included in this section are best viewed in color. You can view these pages in color at www.grizzly.com.
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Mill Head Parts List REF PART # DESCRIPTION P4791001 SPANNER NUT M30-1.5 P4791002 BEVEL GEAR 46T P4791003 SPACER P8107 THRUST BEARING 8107 P4791005 LEADSCREW NUT BRACKET PSB13M CAP SCREW M8-1.25 X 30 P4791007 ELEVATION LEADSCREW NUT PK60M KEY 8 X 8 X 15 P4791009 MILL COLUMN P4791010...
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Downfeed Breakdown REF PART # DESCRIPTION P4791101 SPRING COVER P4791102 COILED SPRING 0.8 X 20 X 1000 P4791103 SPRING SEAT PS17M PHLP HD SCR M4-.7 x 6 P4791105 GEAR SHAFT 18T PK99M KEY 6 X 6 X 15 P4791107 PIN 5 X 28 P4791108 WORM SEAT P4791109...
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Mill Motor Breakdown REF PART # DESCRIPTION P4791201 MOTOR PULLEY PK99M KEY 6 X 6 X 15 PSS05M SET SCREW M5-.8 X 10 PB85M HEX BOLT M8-1.25 X 18 P4791205 MILL MOTOR 3/4HP 220V 1-PH 205-1 P4791205-1 CAPACITOR COVER 205-2 P4791205-2 S CAPACITOR 75M 250V 1-1/4 X 3-1/8 205-3 P4791205-3 R CAPACITOR 16M 450V 1-5/8 X 2-7/8...
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Lathe Head Parts List REF PART # DESCRIPTION P4791572 LATHE SWITCH ASSEMBLY 572-1 P479174-1 ELECTRICAL BOX 572-2 P479174-2 SWITCH COVER 572-3 PS36 PHLP HD SCR 10-24 X 2-1/2 572-4 P479174-4 FWD/REV SWITCH 572-5 P479174-5 ON SWITCH 572-6 P479174-6 OFF SWITCH...
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P4791704 STAR GRIP KNOB 8 X 32 P4791705 BUSHING P4791706 DOOR P4791707 BUTT HINGE P4791708 LATHE DRIVE SYSTEM CABINET P4791709 PIVOT PLATE P4791710 BUSHING PFH05M FLAT HD SCR M5-.8 X 12 P4791712 TENSION SPRING 2 X 12 X 61.5 REF PART #...
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Lathe Motor Breakdown REF PART # DESCRIPTION PB07M HEX BOLT M8-1.25 X 25 PK41M KEY 8 X 8 X 40 P4791803 MOTOR 1-1/2HP 220V 1-PH 803-1 P4791803-1 CAPACITOR COVER 803-2 P4791803-2 S CAP. 150M 250V 1-1/4 X 3-1/8 803-3 P4791803-3 R CAP.
MUST maintain the original location and readability of the labels on the machine. If any label is removed or becomes unreadable, REPLACE that label before using the machine again. Contact Grizzly at (800) 523-4777 or www.grizzly.com to order new labels. Label Placement...