CLASS POWERPOINT - 150102a - HAND GRINDING MACHINES.pdf

MACHINIST PROGRAM - FIRST PERIOD HAND GRINDING MACHINES 150102a SAFETY  Workers Death What potentially happened? 1. A worker steps up to an abrasive wheel grinder and places a piece of metal against the wheel’s spinning surface. 2. Due to incorrect adjustment, the metal...

MACHINIST PROGRAM - FIRST PERIOD HAND GRINDING MACHINES 150102a SAFETY  Workers Death What potentially happened? 1. A worker steps up to an abrasive wheel grinder and places a piece of metal against the wheel’s spinning surface. 2. Due to incorrect adjustment, the metal catches in the grinder. 3. A split-second later, the grinding wheel explodes, sending stony chunks as deadly shrapnel shooting through the shop. 4. The worker drops lifeless to the floor. Warning Graphic Photo alert ! Safety Procedures Fasten pedestal and bench grinders on a solid surface securely. Ensure all the guards are in place and secure before using a grinder. Safety Procedures Check electrical cables for possible damage from metal debris and sparks, and poor connections. Safety Procedures Stand to one side of the grinder upon start up and until the wheel reaches operating speed before engaging in work. Grinder Safety Apply gradual pressure to allow the wheel to warm up evenly. Dull wheels are the largest contributing factor in placing too much pressure on the wheel. Grinder safety Tool Rest The tool rest on any bench or pedestal grinder must not exceed 1/8” gap. (OH&S) When setting up a new wheel , it should be no more than 1/16” away from the wheel periphery GRINDER TYPES Bench Mounted Grinder Bench Mounted Grinder Typical wheel size of 6,8 10 Inches in diameter Wheel grits are typically coarse grit ( 60 – 80 grit) on the left hand side and 120 – 180 grit on the right hand side. Common – 1” wide wheel Rpm average is 3600 Commonly used for finish or general purpose shop type applications Pedestal Grinder Pedestal Grinders - Wheels are generally 10 – 24 “ diameter and 1 – 3 “ wide. - RPM – 1800 is commonly the maximum RPM. - Used for snagging, removing large amounts of materials, rough grinding operations Side Grinders Side grinders are tools that are designed to grind on the face of the wheel. Special wheels are required for this operation with steel backing plates. The advantage of this type of grinder is a tool can be sharpened on a flat face, rather than the periphery of a round wheel.  WHEEL SELECTION  Grinding wheels are available Wheel Grit Selection in a variety of grit (cutting abrasive ) sizes The lower the number the larger the pieces of grit are. Coarse grit (36- 80) is used for roughing operations. Fine grit (100 – 240) is often used for finish operations such as sharpening drill bits, or other tooling. Wheel Grit Types Aluminum Oxide Wheels Ferrous materials only will be ground on Aluminum Oxide Grinding Wheels. Caution: Grinding Non-ferrous material will fill the spaces or voids on these wheel surfaces. This creates a potential for the wheel to break or crack. Grinding Wheel Types Silicon Carbide Wheels These green coloured wheel are use to grind non ferrous materials. Sharpening Carbide cutting tools, Brass, Bronze Wheel Selection Wheel Hardness is based upon the bonding agent that is used to hold the grit in place. The softer the bond the more rapidly the wheel will wear, but the wheel will also have new grit exposed much more rapidly allowing for freer cutting action and cooler work pieces. Hard bonded wheels will last longer and may be more economical for the business, but at the expense of the cutting action. GRINDING WHEEL MOUNTING Wheel Installation Check for wheel appropriate blotters. Check the wheel fit Tighten a fasteners before you turn the grinder on. Manually spin the wheel to make sure it spins freely. Grinding Wheel Spindles Left Side of grinder Right side of Grinder Flanges Left Hand Right hand Thread Thread Nut Wheel Safety – Ring Test Wheel Inspection ( NEW) New wheels must be ring tested to test for cracks Ensure the correct plastic wheel bushings are used to take up the space between the hole in the wheel and the diameter of the motor shaft Wheel Blotter and Maximum RPM Wheel Blotter When installing a new Wheel on the grinder. Look carefully at the Blotter glued to the wheel to ensure the Rpm of the Machine is slower that the Grinding wheel maximum RPM Blotters must be in place on both sides of the wheel prior to mounting Wheel to Spindle Bushing Selection Wheel Bushings These devices take up the space between the spindle of the grinder and the hole size of the wheel. Note. Must be the same width of the wheel Wheel Flange Inspection Flanges Important for the safety and stability of the wheels. They provide cushioning area for the blotter. They provide increased drive power. Inspection Always check for nicks and marks on the surface of the flange. A nick can cause a pressure point of contact and breakage of a wheel. Flanges must contact the blotter. Wheel Spindle Tightening Left hand thread on the left hand side of the spindle Right hand thread on the right hand side of the Spindle. Initial tensioning must be not overly tightened to prevent wheel breakage. Use a wood stick between the wheel and tool rest to provide rotational locking during the tightening operation. WHEEL MAINTENANCE DRESSING AND TRUING  Glazed Wheel: Wheel Issues Condition where the wheel takes on a glass like appearance. Caused by grain wearing away faster than the wheel bonding material. Poor performance and an increase amount of pressure required to grind Loaded Grinding Wheel: When work piece chips adhere to the cutting face of the wheel. Caused by grinding non- ferrous materials and wheels that are too hard Wheel Dressing Dressing removes the top surface of the grinding wheel periphery to expose new grit. Do this When: The wheel looks glazed ( glossy) The wheel is not cutting freely The wheel surface appears to be loaded Truing a Wheel Performed when an out of round wheel causes a vibration throughout the grinder. The truing process ensures the wheel is running true to the axis of the spindle. To true a wheel , a diamond tip is used to cut across the wheel surface. Truing A Grinding Wheel Operation Start wheel Touch the diamond onto the running wheel Using very small depth of cuts, run the diamond across the wheel surface Repeat until the wheel and grinder are running smoothly. Stop the grinder and readjust the tool rest to the 1/16” distance  GRINDING OPERATIONS Grinder Operations Pedestal Grinder - Video Grinding a Prick or Center Punch Repairing a Flat Screw Driver Drill Bit Sharpening END