EngineeringEngineering drawingdrawing

SemesterSemester I/III/II MechanicalMechanical EngineeringEngineering DepartmentDepartment TechnicalTechnical UniversityUniversity ofof GdaGda ńńsksk

Lecture 1 0 ThreeThree methodsmethods commonlycommonly usedused inin fasteningfastening

MechanicalMechanical FasteningFastening •• Bolts,Bolts, screws,screws, rivets,rivets, keys,keys, pinspins

BondingBonding •• Welding,Welding, soldering,soldering, brazing,brazing, gluinggluing

FormingForming •• SheetSheet metal,metal, plasticplastic snapsnap partsparts FastenersFasteners

• nuts, • bolts, • screws, • washers, • nails, • pins, • keys, • rivets, • clips Self-weight approx.ThrededThreded 250kg, load fastenersfasteners capacity up to 150kg, additional accelerationUseful joining forces technique that allows disassembly • but need to guard against loosening • most screw threads are right-handed • widely used throughout industry: – 2.5 million fasteners in a Boeing 747 – most are rivets

More than 125 Nm Great braking forces of torque have to be resulting from emergency transmitted at the wheels. braking (300 km/h!) SizesSizes ofof boletdboletd jointsjoints Huge screws

Midget screws

Screws in a clock Holding screws in a compressor ThreadedThreaded FastenersFasteners –– terminologyterminology

Bolt – head on one end, threads on other end, used with a nut

Stud – rod threaded at both ends

Cap screw – head on one end, threads on other end, NOT used with a nut

Machine screw – similar to cap screw but smaller

Set screw – used to prevent 2 rotating parts from moving separately ThreadedThreaded FastenersFasteners –– terminologyterminology

Internal threads • Threads inside a hole • Made by drill & tap:
drill smooth hole
make threads with a tap

External threads • Threads outside a cylinder • Made with a die • Made by rolling ThreadedThreaded FastenersFasteners –– terminologyterminology

External thread ThreadThread typestypes

Unified Coarse- Thread TypeSeries of (UNC thread or UNRC)Designation Sample Most commonly used inMetric the bulk (coarse) production of bolts,M screws,M16 nuts for general engineering applications. Metric (fine) M M16 x 1,5 Unified Fine-Thread SeriesUnified (UNFscrew orthread UNRF) ½ Use when more threads per inch are required (i.e. where are Pipe thread G G1/4 short length of engagement is available). Pipe taper thread R R1/4 M-Series Trapezoidal thread Tr Tr24x5 Metric system of diameters,(symetric) pitches, and tolerance/allowances. Buttres thread S S24x5 Knuckle thread Rd Rd32x1/8 Lefthand thread LH M16LH Multiple thread P… M60x4(P3) ScrewScrew threadsthreads –– metricmetric typestypes

• thread angle = 60 o • symmetric profiles • identified as M • coarse and fine pitch • specification of the thread:

M12 x 1.75

• the metric thread designation (M) • nominal major diameter (12 mm) • pitch (1,75 mm) MetricMetric threadsthreads

Thread P Thread P diameter it Thread diameter it Thread series c dimensions series c dimensions h h ThreadedThreaded fastenersfasteners -- sectionssections SimplifiedSimplified representationrepresentation ofof boltsbolts andand screwsscrews

Agreed Exact drawing Simplified drawing drawin g SimplifiedSimplified representationrepresentation ofof nutsnuts andand washerswashers

Agreed Exact drawing Simplified drawing drawing SimplifiedSimplified representationrepresentation ofof boltsbolts andand nutsnuts inin assemblingassembling

Agreed Exact drawing Simplified drawing drawing ThreadsThreads forfor powerpower screwsscrews

• Used for power transmission • These have preferred sizes but also can vary • Modifications to these threads are easy

(a) Single, (b) double, (c) triple threaded screws. ScrewScrew classclass propertyproperty 4.6 5.6 6.8 8.8 10.9 12.9

Bolt materials are identifiedBolts withstanding according to property class. • The designation for eachthe same property load class consists of two figures which are separated by a full-stop • The first figure is equal to a hundredth of the nominal tensile strenght Rm in MPA • The second figure indicates 10 times the ratio of the nominal yield stress Rp02 to the nominal tensile stress Rm (ratio yield point) • If the two figures are multiplied together the result is a tenth of the nominal yield stress in MPa 5 – Rm=500MPa, 5.6 6 – Re=0.6*500MPa=300 MPa ThreadThread dimensioningdimensioning

1413,0.SLDPRT ZłoŜenie1.SLDASM