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66 Cards in this Set
- Front
- Back
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For maximum strength of the formed sheet metal fitting, should the bend be along or across the grain of the metal? |
Across |
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What determines the minimum bend radius that can be used when forming a sheet metal structural fitting? |
The alloy, the metal thickness, and its hardness. |
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What is meant by the neutral axis in a sheet of metal? |
A plane within the metal that neither stretches or shrinks when the metal is being bent |
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What is a mold line in the development of a flat pattern for a formed metal part ? |
An extension of the flat sides beyond the radius |
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What is the bend tangent line? |
Where the bend starts in a flat pattern layout |
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What is a setback? |
The distance the jaws of a brake must be set back from the mold line to form a bend |
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What is bend allowance? |
The actual amount of metal in a bend. The distance between the bend tangent lines in a flat pattern layout |
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What is a sight line? |
A line drawn on a flat pattern layout within the bend allowance that is one bend radius from the bend tangent line |
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What type of device is a Cleco fastener? |
It’s a device that’s inserted into the river hole that holds together the two pieces of metal until it can be riveted |
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What is the main function of throatless shears in an aircraft sheet metal shop? |
Used to cut mild carbon steel and stainless steel in irregular curves |
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What kind of metal forming is done by a slip roll former? |
Simple curves with a large radius |
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What kind of metal forming is done by bumping? |
Compound curves in sheet metal |
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When forming a curved angle, what must be done to the flanges? |
The flanges must be stretched for a convex curve and shrunk for a concave curve? |
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When handforming a piece of sheet metal that has a concave curve, should the forming be started in the center of the curve, or at the edges ? |
Start at the edges and work towards the center |
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What is meant by a joggle in a piece of sheet metal? |
A joggle is a small offset best the edge of a piece of a piece of sheet metal that allows the sheet to overlap another piece of metal |
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What is the minimum edge distance allowed when installing rivets in a sheet metal structure? |
Two times the diameter of the river shank (2D) |
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What is the purpose of the beehive spring on a rivet gun? |
It holds the rivet set in the gun and allows the gun to vibrate the set |
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What is the recommended transverse pitch to use when making a riveted two row splice in a piece of sheet metal? |
3/4 the distance between the rivets in the row |
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Why should aluminum alloy rivets be driven with as few blows as is practical? |
You will work harden the rivets which will make them difficult to drive |
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What determines whether a piece of sheet metal should be dimpled or countersunk when installing flush rivets ? |
Depends on the thickness of the sheet. Countersinking should only be done when the thickness of the sheet is greater than the thickness of the rivet head |
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What type of metal should be hot-dimpled ? |
7075-T6, 2024-T81 aluminum alloys, and magnesium alloys |
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What should be done to protect a riveted joint between aluminum alloy and magnesium alloy from corrosion? |
Coat the surface with a corrosion inhibiting primer, dip the rivets in the primer and drive them while wet |
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Which stringer attached to a wing skin would require the greatest number of rivets for a splice? |
A stringer in the lower surface |
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What type of rivet may be used to replace a round head rivet in an aircraft structure? |
Universal head rivet |
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How long should a rivet be to join two pieces of sheet metal ? |
The combined thickness of the metal sheets plus 1 1/2 times the rivet shank diameter |
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Should a riveted joint fail in shear or in bearing? |
Shear. The rivets should shear before the sheet tears at the rivet holes |
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What is the major type of damage to aluminum structures that is caused by exposure to the weather? |
Corrosion |
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What is the major type of damage to aluminum structures that is caused by exposure to the weather? |
Corrosion |
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Name several methods for forming sheet metal |
Bending or folding , stretching , shrinking, bumping , crimping |
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Describe the markings on the heads of A,B,D,AD, and DD rivets |
A- plain B- cross D- raised dot AD- dimple DD- double dash |
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What happens to the stem of a self plugging (friction lock) rivet when it’s installed ? |
The stem needs to be pulled until it snaps off then cut to be flush |
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Why is it important to use the proper size and weight bucking bar when performing sheet metal riveting? |
Too large/heavy- could lose control and damage structure Too light- will work harden the rivet before you’re able to buck it |
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What procedures should be followed to properly remove a solid shank rivet ? |
Center punch the rivet, then drill it using same size drill or one size smaller to the base of the rivet head. Then use a punch to take off the head , then drive out the rest of the rivet |
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What are two special calculations that must be made when bending sheet metal? |
Bend allowance and setback |
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What factors must be considered in order to determine setback? |
Thickness of the metal and the bend radius |
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What is done to a corner where two bends intersect, to prevent cracking ? |
Drill relief holes in the corner |
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What are two reasons for installing a lightening hole in a sheet metal wing rib ? |
Reduce weight and increase stiffness |
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Describe a joggle and it’s function |
An offset formed at an intersection of two or more sheets of metal to allow multiple sheets to be stacked flat against each other |
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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 |
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Name at least three types of self plugging mechanical lock rivets |
CherryMAX , CherryLOCK, OlympicLOK, and HuckLOK rivets |
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What is the difference between the tools used to pull a CherryLOCK rivet and a CherryMAX rivet ? |
With a CherryLOCK rivet, you need the correct size and head shape With a CherryMAX rivet, there’s one tool |
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Which of the 5 stresses is the most common cause of rivet failure? |
Shear Stresses - shearing (rivets /plates, tension (plates), bearing (btwn rivets and plates ) |
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If a 2024 rivet must be replaced with a 2117 rivet, how do you determine the size to be used? |
For 5/32 & under, use the next larger size of 2117 rivet |
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Describe the process for determining the total length of a solid rivet for a particular installation. |
Add the grip length (thickness of materials being joined) PLUS 1 1/2 x rivet diameter |
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What minimum edge distance and spacing should be used for a single row of protruding head rivets ? |
Greater than or equal to 2D x 3D |
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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, thick sheets countersunk |
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What action is taken to prevent cracks from forming while dimpling magnesium or some hard sheet metals? |
Hot dimpling equipment is used to preheat and soften the metal before the dimple is formed |
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What type of damage can occur when using a rivet set that doesn’t properly fit? |
Too small, it will damage the rivet Too big, it will damage the sheet |
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What happens to the stem of a self plugging (friction lock) rivet when it’s installed ? |
The stem needs to be pulled until it snaps off then cut to be flush |
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Why is it important to use the proper size and weight bucking bar when performing sheet metal riveting? |
Too large/heavy- could lose control and damage structure Too light- will work harden the rivet before you’re able to buck it |
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What procedures should be followed to properly remove a solid shank rivet ? |
Center punch the rivet, then drill it using same size drill or one size smaller to the base of the rivet head. Then use a punch to take off the head , then drive out the rest of the rivet |
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What are two special calculations that must be made when bending sheet metal? |
Bend allowance and setback |
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What factors must be considered in order to determine setback? |
Thickness of the metal and the bend radius |
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What is done to a corner where two bends intersect, to prevent cracking ? |
Drill relief holes in the corner |
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What are two reasons for installing a lightening hole in a sheet metal wing rib ? |
Reduce weight and increase stiffness |
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Describe a joggle and it’s function |
An offset formed at an intersection of two or more sheets of metal to allow multiple sheets to be stacked flat against each other |
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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 |
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Name at least three types of self plugging mechanical lock rivets |
CherryMAX , CherryLOCK, OlympicLOK, and HuckLOK rivets |
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What is the difference between the tools used to pull a CherryLOCK rivet and a CherryMAX rivet ? |
With a CherryLOCK rivet, you need the correct size and head shape With a CherryMAX rivet, there’s one tool |
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Which of the 5 stresses is the most common cause of rivet failure? |
Shear Stresses - shearing (rivets /plates, tension (plates), bearing (btwn rivets and plates ) |
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If a 2024 rivet must be replaced with a 2117 rivet, how do you determine the size to be used? |
For 5/32 & under, use the next larger size of 2117 rivet |
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Describe the process for determining the total length of a solid rivet for a particular installation. |
Add the grip length (thickness of materials being joined) PLUS 1 1/2 x rivet diameter |
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What minimum edge distance and spacing should be used for a single row of protruding head rivets ? |
Greater than or equal to 2D x 3D |
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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, thick sheets countersunk |
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What action is taken to prevent cracks from forming while dimpling magnesium or some hard sheet metals? |
Hot dimpling equipment is used to preheat and soften the metal before the dimple is formed |
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What type of damage can occur when using a rivet set that doesn’t properly fit? |
Too small, it will damage the rivet Too big, it will damage the sheet |
