Repair Methods And Skills; Chiseling, Filing And Scraping; Rivet Joint And Welding; Drilling And Reaming - ZONGSHEN ZS250GY-3 Service Manual

[2] Instrument Inspection
Instrument inspection is to measure the size and geometry shape of parts by gauge and apparatus;then
compare the measured value with limiting value to figure out the condition of parts.This method can get
an accurate judgement,but it needs careful inspection for the precision of instrument and reasonable
selection of parts.
[3] Troubleshooting
To find the latent fault of parts，we can apply troubleshooting.Usually we adopt the method of oil
immersion and knock during maintenance.The process of this method is as following.First,immerse
the parts into coal oil or diesel oil for several minutes.Second,take out and wipe the parts.Third,spread
talcum powder on the surface of parts. Finally, knock the non-working surface of parts gently with a small
hammer . In this way,the knock can produce vibration and oil that has remained in crack will splash for
vibration.The splashed oil will dye the talcum powder yellow,so we can easily find a yellow mark in crack
place.
Cleaning methods for non-metal parts differ in different materials.The best detergent for rubber parts
is alcohol.Do not use coal oil or gasoline to clean rubber parts,because they can cause inflation and
deformity of rubber parts.Gasoline is suitable for clutch disc and brake pads friction disc,while aqueous
alkali is forbidden.
（4）Repair methods and skills
After disassembly,cleaning and inspection,the following is the principal stage.Mastering the basic skill
well is the key to ensure a good quality of maintenance.The skills for maintenance are as following:
[1] Chiseling,filing and scraping
Chiseling is to process metal parts by hammer and chisel. The functions are cutting and parting.
Filing is to rasp off the surface of parts by a file.It includes rasp and delicate filing.Teeth of a file directly
decide the roughness degree when filing metal parts.The operation of file is different because of different
shape surface of parts.
Scraping is a process which scrapes off a thin layer from the surface of parts. It is a delicate work, so
we should scrape the parts bit by bit with great care.Usually,scraping off 0.005～0.01mm each time.
Before scraping,we need to spread red lead on the surface of parts.Then,match the parts with standard
one.The unmatched parts are the aim of scraping.After several match and scraping,the contact surface of
parts is bigger.So it reaches the requirement and achieves the purpose.
[2] Rubbing
Rubbing is to rub out a thin layer from the surface of parts by grinder and crocus.This is a fine finish
for the surface of parts,which can provide a precise size ,exact geometrical shape and the lowest degree of
roughness.It includes flat rubbing,internal rubbing and external rubbing.The rubbing tool for flat rubbing is
a plane plate,while internal rubbing tool is a pestle.During maintenance,rubbing methods are usually used
for rubbing the flat of crankcase and internal hole of connecting rod.

[3] Rivet joint and welding

Rivet joint is a process which can join two parts or more together with rivets.It is widely used in
maintenance,such as rivet joint of clutch disc and so on. Classified by its function,rivet joint can be divided
into fixed rivet joint,active rivet joint and seal rivet joint.
Welding is a process which can bring into close union of two metal parts with welding tool and solder.
It is also widely used in maintenance,such as repairing the crack of frame and other metal parts.

[4] Drilling and Reaming

Drilling is a process which drills holes on parts or materials with drill bit.The drilling tools mainly
include beam drill、bench drill、electric hand drill、rotary hand drill、drill bit and clamp.
Reaming is a fine finish by reamer,which can increase the precision degree of holes on parts and
decrease the roughness degree.It improves the match precision between hole and shaft and the precision
can reach grade 6 to grade 8. The basic tool for reaming is a reamer,such as fixed reamer,adjustable
reamer,conical reamer and so on.Before reaming,we need to drill a bottom hole in advance,which is for
the precision requirement of hole shaped and making room for reaming procedure.
[5]Tapping and thread die cutting
Tapping is to Process internal thread with screw tap and thread die cutting is to process external thread
with threading die. The essential tools for tapping is screw tap. Generally, screw tap consist of master tap
and plug tap. The difference between these Two kinds of tap is that master tap adopt a slight bevel angle
on cutting part,instead , plug tap adopt a steeply bevel angle. After tapping,we should drill a bottom hole
with chamfer.
6