Presentation on theme: "Lesson 3 Applying Cold Metalworking Techniques. Bell Work! zIdentify the types of steel stock. zIdentify the tools used in cold metal work. zDescribe."— Presentation transcript:
Lesson 3 Applying Cold Metalworking Techniques
Bell Work! zIdentify the types of steel stock. zIdentify the tools used in cold metal work. zDescribe how cold metal stock is marked, bent, shaped, cut, drilled, filed, and punched. zDescribe the methods used in tapping, threading, bolting, and riveting metal. zIdentify safety practices that should be observed in working with cold metal.
Next Generation Science/Common Core Standards Addressed! zMP.4 Model with mathematics. (HS ‐ PS1 ‐ 4) zCCSS.Math.Content.HSGCO.D.13 Construct an equilateral triangle, a square, and a regular hexagon inscribed in a circle CCSS. zCCSS.Math.Content.HSGCO.D.12 Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.). Copying a segment; copying an angle; bisecting a segment; bisecting an angle; constructing perpendicular lines, including the perpendicular bisector of a line segment; and constructing a line parallel to a given line through a point not on the line. zCCSS.ELALiteracy.RST.9 ‐ 10.3 Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text.
Interest Approach zTake this piece of metal and place it in a vise. zAsk for a volunteer to take a ball peen hammer and try to bend the piece of metal. zWhat happens? zAre there special techniques and/or tools that should be used when working with cold metal?
How is steel stock identified and how is metal that can be worked cold identified?
Metals can be purchased in several different shapes, sizes, hardness, weights, by linear foot, by the pound 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. zKnow the hardness of your metal before trying to drill, chisel, shear, or saw. zTwist 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: yUsing 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. yIf the file does not dig in readily or if it rings or chatters, this an indication that the metal 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. zStrike the punch with a hammer, and then observe the depth of penetration in the metal. zRepeat this several times.
There are different methods of determining the hardness of metals. zTry a piece of metal that you are certain is soft enough to work. zTry a piece of car or truck spring and observe the depth of penetration of the punch. zCompare the metal you tested to the metal you plan to work.
What are the tools used in cold metal work?
The first step in any project is measuring and marking the stock to get the desired size and proper location of holes.
A. A metal worker needs access to several tools.
Measuring Cold Steel zSelect a rule or tape that is long enough to measure the entire distance at one time. zThe 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.
3. Some rules and tapes utilize both the English and Metric systems.
B. Several types of squares are suitable for layout work.
Squares z1. The framing square is used for squaring large pieces. z2. The Try-square is used for squaring small objects.
Squares z3. The combination square has a blade to which three different heads may be attached. yThese heads consist of one square and miter head, one centering head, and one bevel protractor head.
C. There are several different types of marking devices used with cold steel.
Marking Devices z1. A straight edge is used for marking straight lines between two points.
Marking Devices z1. A straight edge is used for marking straight lines between twon points. z2. The steel square, steel rule, or any metal or wood straight edge is satisfactory for most shop work.
Marking Devices z3. A chalk line may be used when working with large sheets of metal. z4. The scriber is made of high carbon steel in different patterns and shapes, and is sharpened to a needle point.
Marking Devices z5. 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 z6. The prick punch and center punch are ground to a sharp point.
The Prick Punch zThe 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 especially on thin metal.
The Prick Punch zIt 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 zThe 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 z7. Dividers are used for marking circles, dividing circles, and stepping off equal lengths for spacing of holes.
Dividers zThe two legs of the dividers are sharpened to needle points; they can be adjusted to varying widths. zThe size of dividers is determined by the length from the pivot to the point of the leg.
D. Machinist’s hammers are available in three types of peens: ball peen, straight peen, and cross peen.
Machinist’s Hammers zThe flat face of the machinist’s hammer is used for striking punches or chisels and for bending or shaping metal. zThe peen is used for drawing and bending metal, as in ornamental work, and for forming curved shapes on thin metal.
Machinist’s Hammers zSelect the proper-sized hammer for the type of work being done. zThe size of a hammer is determined by its weight, which ranges from ¼ lb. to 4 lbs.
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. zMarks for holes to be drilled are made with a center punch. zLines on metal are made with a scriber, which is a sharp-pointed tool. zA sharp prick punch or a nail sharpened to a point, may also be used for marking metal.
B. Light pieces of metal can often be bent cold.
Bending Cold Metal zA vise is used in bending metal rods and bars. zIf 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. zSlip a piece of pipe over the strap iron to provide leverage.
Bending Cold Metal zThe bend can also be made by hammering after the piece of strap iron has been clamped in the vise. zA sharp bend in a piece of strap iron can be made by clamping it in a vise against a piece of round stock. yThen, hammer or pull the piece of strap iron around the piece of round stock.
Bending Cold Metal zA large bend can be made in a piece of strap iron by placing it between the jaws of a vise. zDo not clamp the jaws against the piece of strap iron. zSlip the piece down between the jaws of the vise as it is bent.
C. Cold metal may be cut with a hacksaw, a bolt cutter, or a cold chisel.
Cutting Cold Metal zWhen using a hacksaw, cut a notch at the mark with a file. zApply slight pressure on the forward strokes and release the pressure on the return strokes to insure proper cutting.
Cutting Cold Metal zRun the saw evenly, using long strokes, with all the teeth cutting to prevent wear on a small portion of the blade. zThin metal can be cut more easily with a hacksaw if a thin piece of wood is clamped on each side of the metal. zSaw through the metal and wood pieces simultaneously.
Cutting Cold Metal zA cold chisel can also be used to cut coldA bolt cutter can be used to cut small pieces of iron quickly and easily. z metal. yWatch the edge of the chisel and use sharp, quick blows.
D. When cutting round stock, cut halfway through. Turn the stock and make the rest of the cut from the opposite side.
E. Cutting sheet metal with a chisel should be avoided because it will stretch the metal.
F. Holes may be drilled in metal with a twist drill. zDrilling may be done with a hand drill, a portable power drill, or a drill press. zMark the location of the hole with a center punch and place a drop of oil in the center punch mark.
F. Holes may be drilled in metal with a twist drill. zEase the pressure and drill slowly when the point of the drill is about to break through the bottom. zWhen drilling holes in round stock, hold the work in V-blocks.
G. Small amounts of metal may be removed where needed with a file. zUse pressure on the forward stroke only, and use only enough pressure to make the file cut evenly. zFiles are classified by the coarseness of their teeth, length, and shape.
Parts of a File
What are the methods used in tapping, threading, bolting, and riveting metal?
There are different ways to join metal and other materials
A. A common metalworking job in agricultural mechanics is the cutting of threads on bolts and nuts. Taps and dies are used for thread cutting.
A tap zA screw-like tool used to cut inside threads. zThere are three types of taps.
A tap zThe taper tap, with the first 0 to 10 threads that do not cut full- depth threads, is used alone for tapping a hole that is drilled completely through the metal. zWhen tapping a blind hole all three taps must be used.
A tap zThe plug tap, with five or six partial threads, is used after the taper tap. zIt is screwed down to the bottom of the hole.
A tap zThe bottoming tap is used after the plug tap to cut full-size threads to the bottom of the hole.
A die zUsed for cutting outside threads, like those found on the threads of bolts. zThere are three common types of dies: yround-split die ytwo-piece die ysolid die.
A die zThe round-split and two-piece dies can be adjusted to vary the depth of cut, but the solid die is not adjustable.
3. Taps and dies have their sizes and classifications stamped on them.
There are three classifications of threads: zNational Coarse (NC) zNational Fine (NF) zNational Pipe Thread (NPT).
1.NC threads are commonly used on parts of machinery where there is very little vibration.
2. NF threads are used where vibration is excessive. Fine threads will stand more vibration than coarse threads before the nut loosens.
C. There is a precise procedure to follow when threading bolts.
Bolt Threading Procedure z1. Place the rod in a perpendicular position in a vise and clamp securely. z2. File off any projections on the end of the rod or bolt, slightly tapering it. z3. Select the proper size of die. yThe tool used for holding and turning the die is called the die stock.
Bolt Threading Procedure z4. Place the die squarely on the rod or bolt and apply pressure evenly as the die is turned. z5. Apply oil so that the die will run through it while cutting.
Bolt Threading Procedure z6. Move the die back and forth so the chips of metal will fall out. z7. Remove the die by turning it counterclockwise after the required number of threads are made.
D. A precise procedure must be followed when tapping a hole.
Hole Tapping Procedure z1. Drill the proper sized hole for tapping. z2. Select the proper taper tap and insert the square end in a tap wrench. z3. Place the item to be tapped in a vise and clamp securely. z4. Grasp the tap wrench with the hand directly over the tap and place the end of the tap in the hole.
Hole Tapping Procedure z5. Apply downward pressure on the wrench, and turn it clockwise to start the tap. yContinue turning the wrench in this manner until the tap starts to feed itself.
Hole Tapping Procedure z6. When the tap begins to feed itself, grasp the tap wrench handles with both hands, and continue turning slowly. yApply the same turning power on each handle to prevent breaking the tap. Apply the proper lubricant to keep the tap cool so that it will cut properly.
Hole Tapping Procedure z7. After the tap has been properly started, turn it one full turn forward. yThen, back it up one-quarter turn to break and clear away the chips. yThis will help to make a smoother thread. yContinue in this manner until the tap reaches the bottom or turns freely in the hole.
Hole Tapping Procedure z8. Back the tap out slowly. z9. Thoroughly clean the tap before placing it in the rack.
E. Bolts are used in heavy construction work in which permanency and strength are desired or in which an object may need to be dismantled frequently.
Bolts may be purchased with fine or coarse threads. The bolt head can be held with a wrench when the nut is tightened or loosened.
1. Machine bolts zHave hexagonal heads and are used to fasten wood or metal in places where the protruding head is not objectionable. zMachine bolts are preferred for fastening wood where the bolt needs periodic retightening or removing.
2. Carriage bolts zHave a rounded head and a square shank to fit square slotted holes in machinery or in heavy wood construction. zCarriage bolts are used when the protruding head of a machine bolt would be objectionable.
3. Stove bolts zHave round or flat heads and are used for lightweight structures of either metal or wood. zStove bolts are threaded their full length.
4. Stud bolts zUsed for fastening frequently removed metal parts, such as cylinder heads or cover plates. zOne end of the stud bolt is screwed into a tapped hole, and a nut is screwed on the other end.
F. When two pieces of metal cannot be welded satisfactorily, they are often riveted together.
Riveting z1. A rivet is a bolt-shaped piece of iron used to fasten sheet metal, or to fasten knife sections on a sickle, by peening the end to form a head.
Riveting 2. There is a procedure for properly riveting materials. yMake holes the same diameter as the size of the rivets selected. ySelect rivets which are slightly longer than the metal thickness so that they will extend 1 /8 to ¼ inch beyond the pieces being riveted.
Riveting zInsert the rivets and place the heads on the face of the anvil. zPlace the washers on the rivets if washers are used.
Riveting zDeliver several blows to the center of each rivet, first with the peen of the hammer and then with the face of the hammer, until the pieces are closely united. zRound the edges of the head and finish to an oval shape or to the shape the manufacturer recommends. zUse a rivet set to obtain a smooth finish.