Safety Practices: Cold Metal Keep work area clean, wipe spills immediately. Use approved safety glasses or face shield. Store oily/greasy rags in a fireproof metal container. Use proper lifting techniques to prevent injury.

Safety Practices: Cold Metal Use the proper size of tools and equipment. Obtain permission of instructor before using tools. Do not wear loose or bulky clothing. Tie back long hair, or put into a band or cap.

Safety Practices: Cold Metal Securely fasten stock to be cut, filed, or chiseled in a vise or by clamps to prevent tools from slipping.

Types of Steel Stock Metals can be purchased in several shapes, sizes, hardnesses, and weights. In addition, they can be purchased by lineal foot or by piece. Knowing the shapes, sizes, and standard lengths of commonly used stocks can be beneficial in planning repair projects.

Types of Steel Stock The metal being worked with should be softer than the cutting tool. Know the hardness of the metal before trying to drill, chisel, shear, or saw. Twist drills, saw blades, cold chisels, and shear cutting parts of equipment are easily broken or worn out in a matter of minutes on hardened stock.

Determining the Hardness of Metals Various methods exist for determining the hardness of metals. One method is by using the corner of a file. Make three 6-inch filing strokes, using half your pushing strength on the metal to be cut, drilled, or worked. When a file does not dig in readily or if it rings or chatters, it is an indication that the material is too hard to work when cold.

Determining the Hardness of Metals Another method is to use a center punch, which is a tool used to mark the middle spot. Strike the punch with a hammer. Then observe the depth of penetration. This should be repeated several times. It is best to try a piece of metal that is soft enough to work.

Joining Metal & Other Materials Various ways exist to join metal & other materials. A common metalworking job in agricultural mechanics is the cutting of threads on bolts and nuts. Taps and dies are used for thread cutting.

Joining Metal & Other Materials A tap is a screw-like tool used to cut inside threads. Three types of taps exist: Taper Plug Bottoming

TYPES OF TAPS AND ORDER OF USE FOR A BLIND HOLE

Joining Metal & Other Materials A die is a tool used for cutting outside threads, such as those found on the threads of bolts. Three common types of dies are The round-split die (can adjust) The two-piece die (can adjust) The solid die (not adjustable) Taps and dies have their sizes and classifications stamped on them.

USING THE DIE TO CUT OUTSIDE THREADS

Thread Classifications NC threads are commonly used on parts of machinery where there is little vibration. NF threads are used where vibration is excessive. Fine threads will withstand more vibration than coarse threads before the nut loosens. NPT is a U.S. standard for tapered threads used on threaded pipes and pipe fittings.

Procedure for Threading Bolts Place the rod in a perpendicular position in a vise, and clamp it securely. File off any projections on the end of the rod or bolt, slightly tapering it. Select the proper size of die. The tool used for holding and turning the die is called the die stock. Use the die stock, not any other tool.

Procedure for Threading Bolts Place the die squarely on the rod or bolt. Apply pressure evenly as the die is turned. Apply oil so the die will run through it while cutting. Move the die back and forth so the chips of metal fall out. Remove the die by turning it counterclockwise after the required number of threads is cut.

Procedure for Tapping a Hole Drill the proper size hole for the tap you plan to use. Select the proper taper tap, and insert the square end in a tap wrench. Place the item to be tapped in a vise, and clamp it securely.

Procedure for Tapping a Hole Grasp the tap wrench with your hand directly over the tap, and place the end of the tap in the hole. Apply downward pressure on the wrench, and turn it clockwise to start the tap. Continue turning the wrench in this manner until the tap starts to feed itself.

Procedure for Tapping a Hole When the tap begins to feed itself, grasp the tap wrench handles with both hands, and continue turning slowly. Apply the same turning power on each handle to prevent breaking the tap. Apply the proper lubricant to keep the tap cool so it will cut properly.

Procedure for Tapping a Hole After the tap has been properly started, turn it one full turn forward. Then back it up one quarter turn to break and clear away the chips. This will help make a smoother thread. Continue in this manner until the tap reaches the bottom or turns freely in the hole.

Procedure for Tapping a Hole Back the tap out slowly. Thoroughly clean the tap before placing it in the rack.

Squaring a Tap with the Work