7.8: Riveting Flashcards
Rivet allowance is 1.5 times rivet diameter
Rivet allowance
When fitting a rivet, sufficient shank must be left protruding above the plate to take up the clearance and form the head.
The faying surface
'’In the construction of metal airframe structure, most permanent joints are made with either rivets or bolts. These hold the structural components together; the contact areas being referred to as ‘faying surfaces’. To securely attach faying surfaces together, rivets are cheaper, lighter and more rapidly fastened than nuts and bolts.’’
A max of .003’’ clearance
Rivet clearance
Rivet clearance is the amount that the rivet hole diameter exceeds the rivet diameter
This is a desirable condition
Rivet Sphere of influence
The sphere of influence of a rivet is the area in which the closed rivet maintains the plates in close proximity and this is approximately five times the diameter of the fastener or 5D. When the pitch of rivets is 4D, the sphere of influence of each rivet overlaps, providing a fluid-tight joint.
Note: Rivet Pitch is the distance between adjacent rivets in a row. Minimum spacing is 3D
Is an alternate for a multiple chain
Rivet Layout
Single chain - Used chiefly on attachment and lightly stressed joints
Multiple chain - Used on watertight joints and in places of high stress where thick gauge plate is used.
Staggered riveting - Used as an alternative to multiple chains in watertight joints, circular patches etc.
118 degree drill bit at slow speed
'’When drilling hard metals, the twist drill should have an included angle of 118^ and should be operated at low speeds; but for soft metals, use a twist drill with an included angle of 90^ operated at higher speeds. Thin sheets of aluminium alloy are drilled with greater accuracy by a drill having an included angle of 118^ because the large angle of the frill has less tendency to tear or elongate the hole’’
Hard material - 118 degree drill bit at slow speed
Soft material - 90 degree at high speed
Based on two above, without knowing material property, only 1 possible answer. Don’t confuse this question with 90 degree which is the angle you hold the drill to the work piece.
Unacceptable
'’Form countersinking or dimpling can be used on thin material although thicker sheet will tend to crack, while if a cut countersink is too deep in relation to the skin thickness, the resultant knife-edge hole is prone to cracking and the strength of the joint is also reduced’’
Below 0.048’’ thick
Dimpling
This is a process for indenting thin sheet material (not normally thicker than 18 SWG, 0.048’’) around a drilled hole to accomodate a countersunk rivet. If correctly performed, dimpling has a beneficial effect on the strength of a joint as the material is not thinned, but the method of dimpling must be related to the ductility of the material to prevent overstressing and cracking.
Never
Mechanically locked blind rivet
'’CherryMax and CherryLock are commercial names for self-plugging mechanical lock blind rivets. Both rivets (CherryMax and CherryLock) are blind rivets, meaning that they can both be installed without access to the inside’’
Note: CherryMax less popular as need special equipment to install, whereas don’t with CherryLock
Medium / average stress
Lap joint - Used in places where stress is not particularly high and where flush surfaces are not required. Often used in longitudinal aircraft skin joints.
Joggled lap joint - The under plate is joggled to preserve the continuity of the upper surface. This provides a flush surface and can be used in radial or longitudinal skin joints
Butt joint - Single strap, used on flush surfaces where high stress is encountered, requiring the use of heavy gauge plate. Can be used in radial skin joints
Double strap butt joint - Double strap, used in places of very high stress, where strength is more important than streamlining such as internal structures.
Flange joints - Used on internal structural members, such as ribs, frames, etc, where loads are chiefly compression
3D
Rivet Pitch - The distance between rivets in a row measurd from centre to centre. 3D minimum
2D
Land - The distance between the rivet centre and the edge of the material. 2D minimum
75%
75%
4D
Spacing - The distance between adjacent rows of rivets is 3-4D minimum
where D = shank diameter in 1/32’s
4D
Pitch - The distance between rivets in a row measured from centre to centre. 3D minimum
3D is min however, sphere of influence best practice is 4D
where D = rivet shank diameter (1/32’s)
1/16
Rivet diameter (1/32’s ‘’)
Rivet length (1/16’s ‘’)
Diameter comes first in ident
3/16 inch
The length of the rivet should be 3 times the size of the thickest piece of material to be riveted
Note: For diameter it’s x2.5
Length = 3T
Diameter = 2.5T
where T is the thickness of the thickest section to be riveted
Both of the above are correct
'’The length is measured only on the cylindrical shank for universal head rivets. In the cause of countersunk-head rivets, the length is given to include the head of the rivet
The diameter of a rivet is standardised in 1/32’’
The rivet lengths are graduated by 1/16’’
Separations of the sheets may occur
Too small a hole causes buckling, too large causes separation
four 1/16 inch rivets would be required
Three times
150 hours
a broaching process
'’Avdel rivets are a range of British blind fasteners. They are hollow rivets which are closed by a broaching process, each rivet being threaded on a mandrel of the break stem type, the head of which applies a squeezing force, whilst the shank expands the rivets to fill the rivet tube hole.’’
To test the tightness of the pin in the rivet.
'’On application of a force by the rivet gun, the shank of the mandrel is pulled into the bore of the rivet and the mandrel then breaks so that part of its shank remains in the rivet bore and thus plugs the rivet and improves its shear strength. The protruding length of the mandrel is then cut off and milled flush with the skin surface.
The firmness of the mandrel should be tested with an Avdel Pin tester, which has a spring loaded retractable pin which is pre-set to 15 lbsf
nipped off and milled flush with the head
'’On application of a force by the rivet gun, the shank of the mandrel is pulled into the bore of the rivet and the mandrel then breaks so that part of its shank remains in the rivet bore and thus plugs the rivet and improves its shear strength. The protruding length of the mandrel is then cut off and milled flush with the skin surface.’’
60 to 80 lbs per sq. inch
Avdel Hydro-pneumatic pull tool Type 734 series
'’The Avdel Hydro-Pneumatic Tool Type 734 is a robust, high production tool developed for the easy and rapid installation of up to and including 3/16’’ Avdel rivets. A compressed air supply of between 70 PSI and 100 PSI is required for placing rivets, however, a minimum of 85 PSI is required to place rivets of 5/32’’ and above’’
A special countersinking bit with a stop to prevent drilling too deep should be used.
the snap was not square
The amount of material required to form the rivet on installation
Rivet allance - The amount of shank left protruding above the plate to take up the clearance and form the head
Note: Other option in this Q. Rivet Pitch is the distance between rivets in the same row. Minimum 3D
5D
Rivet allowance is 1.5 times rivet diameter
The faying surface
A max of .003’’ clearance
This is a desirable condition
Is an alternate for a multiple chain
What is the ‘’Grip’’ of a rivet?
‘’Grip’’ of a rivet is the thickness of the plates which can be fastened
56
The rivet Pt number is irrelevant, the repair patch is double the length than the width.
20 rivets length x 10 rivets width. Minus the corners = 56
Copper
The same size as the rivet head
The hole was too small
Solution treatment
