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OP Sheet Metal
| Question | Answer |
|---|---|
| What is the major type of damage to aluminum structures that is caused by exposure to the weather? | Corrosion. |
| Name several methods for forming sheet metal? | Bending or folding, stretching, shrinking, bumping, crimping. |
| What are the dimensions of a properly formed rivet head? | The head should be 1 1/2 times the shank diameter in width and 1/2 the shank diameter in height. |
| Describe the markings found on the heads of A, B, D, AD, DD rivets. | A rivets are plain, B rivets have a cross, D rivets have a raised dot, AD rivets have a dimple, DD rivets have a double dash. |
| What happens to the stem of a self-plugging {friction lock} rivet when the rivet is installed? | The stem is pulled until it snaps off and the remaining projecting part is trimmed flush with the head. |
| Name at least three types of self plugging mechanical lock rivets? | Cherry MAX, Cherry LOCK, Olympic LOCK, Huck LOCK. |
| What is the difference between the tools required to pull a Cherry LOCK rivet and a Cherry MAX rivet? | Cherry LOCK rivets require a tool for each different size and head shape while one pulling tool will set any size Cherry MAX. |
| Which of the five stresses is the most common cause of rivet failure? | Shear. |
| If a 2024 rivet must replaced with a 2117 rivet, how do you determine the size to be used? | For 5/32 or smaller diameter, use the next larger size 2117 rivet, assuming that the edge distance and spacing meet minimum requirements. |
| Describe the process for determining the total length of a solid rivet for a particular installation. | Add the grip length [thickness of the materials being joined] plus 1 1/2 times the rivet diameter. |
| What minimum edge distance and spacing should be used for a single row of protruding head rivets? | Not less than 2 rivet diameters from the edge and no less than 3 rivet diameters apart. |
| How can a mechanic determine whether the countersink for a flush rivet should be dimpled or drilled? | By the thickness of the top sheet; thin sheets are dimpled while thick sheets may be countersunk. |
| What action is taken to prevent cracks from forming while dimpling magnesium or some hard sheet metals? | Hot dimpling equipment is used to pre heat and soften the metal before the dimple is formed. |
| What type of damage can occur when using a rivet set that does not properly fit the rivet. | If the set is to small damage to the rivet head can occur, if to large damage to the sheet metal. |
| Why is it important to use the proper size and weight bucking bar when performing sheet metal riveting? | If a bucking bar is to big or heavy it may be difficult to control and cause damage to the surrounding area, a bar to light will not properly upset the rivet before work hardening occurs. |
| What procedures should be followed to properly remove a solid shank rivet? | Center punch the rivet then drill just to the base of the rivet head with same size or one size smaller drill bit. Use a pin punch to tip off the head of the rivet. Drive out the remaining shank with a punch while supporting the surrounding metal. |
| What are the two special calculations that must be made when bending sheet metal? | Bend allowance and set back. |
| What factors must be considered in order to determine set back? | The thickness of the metal and the bend radius. |
| What is done to a corner where two bends intersect to prevent cracking? | Relief holes are drilled in the corners. |
| What are the two reasons for installing a lightening hole in a sheet metal rib? | Lightening holes reduce the weight and increase stifness |
| Describe a joggle and explain its function? | A joggle is an offset formed at an intersection of two or more sheets of metal to allow the multiple sheets to be stacked flat against each other. |
| When repairing an all metal aircraft, how do you determine what metals should be used? | Always use metal of the same type and thickness as the original structure. |
| What is the grip length of a rivet? | The combined thickness of the materials being joined. |
| Where are special rivets such as huck and cherry loc used? | Where it is impossible to reach both sides of the rivet or space is so tight you can fit tooling in place. |
| When bending sheet metal how should the grain be in relation to the bend? | Grain should be perpendicular to the bend. |
| What is the bend tangent line? | The line at which the metal begins to bend. |
| What type of forming is done by bumping? | Compound curves. |
| Describe the anodizing process for aluminum? | Metal is soaked in an electrolytic bath which causes a hydroxide film to form on the surface. |
| What size drill should be used for the common 3/32 4/32 and 5/32 diameter rivets? | Number 40, 30 and 21 bit respectively. |
| What are three requirements for a repair to a piece of sheet metal aircraft structure? | The repair must restore strength and rigidity and not change the aerodynamic shape of the part. |
| When making a riveted repair to an aircraft sheet metal structure, which should be the stronger, the shear strength of the rivet, or the bearing strength of the metal sheet? | The two should be close but the bearing strength of the metal should be greater. |
| What type of device is a Cleco fastener? | A patented fastener that is inserted in the rivet holes and is used to hold two pieces of sheet metal together until they can be riveted. |
| What is the main function of throatless shears in an aircraft sheet metal shop? | Throatless shears are used to cut mild carbon steel up to 10-gage, and stainless steel up to 12-gage. They can be used to cut irregular curves in the metal. |
| What is the purpose of a sight line when laying out sheet metal to be bent in a cornice brake? | The sight line allows the jaws of a cornice brake to be positioned so the bend made by the brake will start at the bend tangent line. |
| What kind of metal forming is done by a slip roll former? | Simple curves with a large radius. |
| What must be done to the flanges of an angle for it to be curved? | The flanges must be stretched for a convex curve and shrunk for a concave curve. |
| What is meant by the bend allowance used in making a bend in a piece of sheet metal? | The bend allowance is the amount of metal that is actually used in making the bend in a piece of sheet metal. |
| What determines the minimum bend radius that can be used with a piece of sheet metal? | The thickness of the material and its hardness. |
| When hand-forming a piece of sheet metal that has a concave curve, should the forming be started in the center of the curve, or at its edges? | Start at the edges and work toward the center. |
| What is the recommended transverse pitch to use when making a riveted two-row splice in a piece of sheet metal? | Three-fourths of the pitch of the rivets in the rows. |
| Why should aluminum alloy rivets be driven with as few blows as is practical? | Excessive hammering will work-harden the rivets and make them difficult to drive. |
| What type of metal should be hot-dimpled? | 7075-T6, 2024-T81 aluminum alloys, and magnesium alloys should be hot-dimpled. |
Created by:
g153511
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