Mechanical Engineering Drawing MENG 204

Summer Semester 2015By:

Dr. Ghassan Mousa

Fasteners & shafts

Thread standards & definition

• d: major diameter

• p: pitch

• l: lead

• Multiple threads

• Die for external threading.https://www.youtube.com/watch?v=gVcwjjBAT4Q

• Tab for internal threading

Fig. 8.1 Terminology of screw threads

http://www.gizmology.net/nutsbolts.htm

Threaded fastenersUsed to non-permanently join one or more objectstogether.

http://www.walter-tools.com/en-gb/tools/standard_products/threading/overview/hss_tap/eco_ht/Pages/default.aspx

Types

Three types of threaded fastener. (a) Bolt and nut; (c) Cap screw; (c) stud.

Metric thread

• Thread angle is 60˚

• M8 × 1.25

Imperial thread

• Thread angle is 60˚

• 3/8 – 24 UNF

Table 8-1 Geometrical data for Standard Bolts (SI)

Power screw

Trapezoidal thread

• Thread angle is 30˚

• Tr 36 X 10

Buttress Thread

• Thread angle is 30˚

• S 40 X 7

Loading Direction

Strength

Bolts in axial loading fail at the:

• Fillet under the head.

• Thread runout.

• 1st thread engaged in the nut.

Table 8-11 Material properties of steel bolts

• Setscrew

• washer

• Nuts• Slotted nut jam nut

• Prevailing torque locknut

Design (Configuration)

Design (Head Style)

Design (Drive Type)

Thread dimension

Threaded Fasteners Preferred

Sizes (Length):

• 2, 3, 4, 5, 6, 8, 10

• 12, 16, 20, 25, 30

• 35-60, 65, 70, 80

• 90-140, 150, 160, 180, 200

Shafts

• Used to transmit power (torque).

• The shorter the better.

• Load carrying components should be placed near the bearing.

• Means of transmitting power through:• Gears• Belts• Chains

• Torque is transmitted by using keys

• Axial force is supported by using Pins

Stepped shaft

Retaining rings

External ringE ring

Keys

Tapered keyGib head tapered key

Woodruff key

Pins

Spring pin

Dowel pinHairpin cotter

Cotter pin Tapered pin