Home Random Page


CATEGORIES:

BiologyChemistryConstructionCultureEcologyEconomyElectronicsFinanceGeographyHistoryInformaticsLawMathematicsMechanicsMedicineOtherPedagogyPhilosophyPhysicsPolicyPsychologySociologySportTourism






External stamped circlip (A), internal

Stamped circlip (B), machined circlip (C)

and wirecirclip (D)

 

• Always use circlip pliers to remove and install circiips; expand or compress them just enough to remove them. After installation, rotate the circlip in its groove to ensure it is securely seated. If installing a circlip on a splined shaft, always align its opening with a shaft channel to ensure the circlip ends are well supported and unlikely to catch (see illustration 2.10).

THRUST LOAD

---------- ►

THRUST WASHER

/

"SHARP EDGE

CHAMFERED EDGE

Correct fitting of a stamped circlip


 

Align circlip opening with shaft channel

 

• Circiips can wear due to the thrust of components and become loose in their grooves, with the subsequent danger of becoming dislodged in operation. For this reason, renewal is advised every time a circlip is disturbed.

• Wire circiips are commonly used as piston pin retaining clips. If a removal tang is provided, long-nosed pliers can be used to dislodge them, otherwise careful use of a small flat-bladed screwdriver is necessary. Wire circiips should be renewed every time they are disturbed.

Thread diameter and pitch

 

2.11 Fastener length (L), thread diameter (D), thread pitch (P) and head size (AF)

• Diameter of a male thread (screw, bolt or stud) is the outside diameter of the threaded portion (see illustration 2.11).Most motorcycle manufacturers use the ISO (International Standards Organisation) metric system expressed in millimetres, eg M6 refers to a 6 mm diameter thread. Sizing is the same for nuts, except that the thread diameter is measured across the valleys of the nut.

• Pitch is the distance between the peaks of the thread (see illustration 2.11). It isexpressed in millimetres, thus a common bolt size may be expressed as 6.0 x 1.0 mm (6 mm thread diameter and 1 mm pitch). Generally pitch increases in proportion to thread diameter, although there are always exceptions.

• Thread diameter and pitch are related for conventional fastener applications and the accompanying table can be used as a guide. Additionally, the AF (Across Flats), spanner or socket size dimension of the bolt or nut (see illustration 2.11)is linked to thread and pitch specification. Thread pitch can be measured with a thread gauge (see illustration 2.12).


Using a thread gauge to measure pitch

 

AF size Thread diameter x pitch (mm)
8mm M5x 0.8
8 mm M6x 1.0
10mm M6x1.0
12mm M8 x 1.25
14mm M10x1.25
17mm M12x1.25

 

Thethreads of most fasteners are of the
right-hand type, ie they are turned clockwise
to tighten and anti-clockwise to loosen. The
reverse situation applies to left-hand thread
fasteners, which are turned anti-clockwise to
tighten and clockwise to loosen. Left-hand
threads are used where rotation of a
component might loosen a conventional right-
hand thread fastener.



Seized fasteners

 

2.13 A sharp tap on the head of a fastener will often break free a corroded thread

• Corrosion of external fasteners due to water or reaction between two dissimilar metals can occur over a period of time. It will build up sooner in wet conditions or in countries where salt is used on the roads during the winter. If a fastener is severely corroded it is likely that normal methods of removal will fail and result In its head being ruined. When you attempt removal, the fastener thread should be heard to crack free and unscrew easily - if it doesn't, stop there before damaging something.

• A smart tap on the head of the fastener will often succeed in breaking free corrosion which has occurred in the threads (see illustration 2.13).

• An aerosol penetrating fluid (such as WD-40) applied the night beforehand may work its way down into the thread and ease removal. Depending on the location, you may be able to make up a Plasticine well around the fastener head and fill it with penetrating fluid.


Tools and


Workshop Tips ref-7


 


• If you are working on an engine internal component, corrosion will most likely not be a problem due to the well lubricated environment. However, components can be very tight and an impact driver is a useful tool in freeing them (see illustration 2.14).


Date: 2016-01-14; view: 697


<== previous page | next page ==>
Nuts and split pins | And sealing compounds
doclecture.net - lectures - 2014-2024 year. Copyright infringement or personal data (0.007 sec.)