Lesson Applying Cold Metalworking Techniques
Interest Approach • Take this piece of metal and place it in a vise. • Ask for a volunteer to take a ball peen hammer and try to bend the piece of metal. • What happens? • Are there special techniques and/or tools that should be used when working with cold metal?
Student Learning Objectives • Identify the types of steel stock. • Identify the tools used in cold metal work. • Describe how cold metal stock is marked, bent, shaped, cut, drilled, filed, and punched. • Describe the methods used in tapping, threading, bolting, and riveting metal. • Identify safety practices that should be observed in working with cold metal.
Carriage bolts Die Die stock Machine bolts Rivet Stove bolts Stud bolts Tap Terms
How is steel stock identified and how is metal that can be worked cold identified?
Metals can be purchased in several different shapes, sizes, hardnesses, weights, by lineal foot, or by piece.
A. Knowing the shapes, sizes, and standard lengths of commonly used stocks can be beneficial in planning repair projects.
Be certain the metal you are working with is softer than your cutting tool. • Know the hardness of your 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.
There are different methods of determining the hardness of metals. 1. One method of determining the hardness: • 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. • If the file does not dig in readily or if it rings or chatters, this an indication that it is too hard to work when cold.
There are different methods of determining the hardness of metals. 2. Another method is to use a center punch. • Strike the punch with a hammer, and then observe the depth of penetration. • Repeat this several times.
There are different methods of determining the hardness of metals. • Try a piece of metal that you are certain is soft enough to work. • Try a piece of car or truck spring and observe the depth of penetration of the punch. • Compare the metal you tested to the metal you plan to work.
The first step in any project is measuring and marking the stock to get the desired size and proper location of holes.
Instruments used to measure cold steel are a push-pull rule and steel tapes. • These tapes and rules are thin and flexible and must be laid flat and straight for accurate measurement.
Measuring Cold Steel • Select a rule or tape that is long enough to measure the entire distance at one time. • The most suitable rules and tapes are those in which the inches are divided into one or more of the following: 1/2, 1/4, 1/8 , 1/16 , 1/32 , and 1/64 . A 1/10 and 1/12 rule is used for special jobs.
Squares • 1. The framing square is used for squaring large pieces. • 2. The T-square is used for squaring small objects.
Squares • 3. The combination square has a blade to which three different heads may be attached. • These heads consist of one square and miter head, one centering head, and one bevel protractor head.
Squares • The heads may be purchased as a set or separately and can be attached quickly and locked in any position along the blade.
C. There are several different types of marking devices used with cold steel.
Marking Devices • 1. A straight edge is used for marking straight lines between two points.
Marking Devices • 2. The steel square, steel rule, or any metal or wood straight edge is satisfactory for most shop work.
Marking Devices • 3. A chalk line can be used for marking long lines.
Marking Devices • 4. The scriber is made of high carbon steel in different patterns and shapes, and is sharpened to a needle point.
Marking Devices • 5. The scratch awl is made of high carbon steel and a hardwood handle, and is used to scribe lines on metal. Since the metal of the awl protrudes through the handle, it can be tapped with a hammer to make a light center punch.
Marking Devices • 6. The prick punch and center punch are ground to a sharp point.
The Prick Punch • The prick punch is ground to about a 15 degree angle to the center line and is used for marking reference points, locating the centers of holes, and making small marks along the layout lines.
The Prick Punch • It can be used to transfer a layout from paper to metal by placing the paper over the metal and punching through the paper to locate holes, curves and other layout lines.
The Center Punch • The center punch is ground to about a 60 degree angle to the center lines and is used to mark the location of holes and to make a starting hole for a drill .
Marking Devices • 7. Dividers are used for marking circles, dividing circles, and stepping off equal lengths for spacing of holes.
Dividers • The two legs of the dividers are sharpened to needle points; they can be adjusted to varying widths. • The size of dividers is determined by the length from the pivot to the point of the leg.
Marking Devices • 8. Layout fluid is a quick-drying liquid that may be painted on metal to form a colored surface for marking.
D. Machinist’s hammers are available in three types of peens: ball peen, straight peen, and cross peen.
Machinist’s Hammers • The flat face of the machinist’s hammer is used for striking punches or chisels and for bending or shaping metal. • The peen is used for drawing and bending metal, as in ornamental work, and for forming curved shapes on thin metal.
Machinist’s Hammers • Select the proper-sized hammer for the type of work being done. • The size of a hammer is determined by its weight, which ranges from ¼ lb. to 4 lbs.
1. Framing Square 2. Combination Square 3. T-Square 4. Center Punch 5. Scratch Awl 6. Scriber 7. Spring Dividers 8. Ball Peen Hammer 9. Straight Edge Layout Tools
How is cold metal stock marked, bent, shaped, cut, drilled, filed, and punched?
Working with cold metal requires different techniques depending upon the type of work to be completed.
Metal needs to be marked for cutting, welding, bending, and drilling. • Marks for holes to be drilled are made with a center punch. • Lines on metal are made with a scriber, which is a sharp-pointed tool. • A sharp prick punch or a nail sharpened to a point, may also be used for marking metal.
Bending Cold Metal • A vise is used in bending metal rods and bars. • If a heavy piece of strap iron is to be bent cold, clamp it in a machinist’s or black-smith’s vise of adequate size. • Slip a piece of pipe over the strap iron to provide leverage.