Wood Screw Manufacturing - China Auto Transponder Key - Automotive Key Blanks
Briefs
In the manufacturing of wood screws, normally, steel with low carbon contents is used as a metal, manufactured by steel mills in the shape of billets which are purchased by wire rod manufacturing mills. This wire rod is further drawn by wire drawing units into different sizes of wire, required by screws, fasteners manufacturing factories. Drawn wire has a variety of other uses as well. Brass is another metal which is used in the manufacture of Brass wood screws.
Wood screws are made in various sizes and thickness. Size of a wood screw is normally expressed by inches or milli-meters and thickness by numbers. x 4 means a wood screw of half inch length having 4 gauge thickness. Regarding the length of the threads, in general terms, it is known as half threaded or full threaded (Twinfast) wood screw. In Twinfast type of wood screws, two threads are moving parallel with each other to penetrate into wood at a faster rate with the help of a screw driver.
Process
A wood screw passes through the following processes before coming to the packing department in a wood screw manufacturing factory where three separate machines are used to manufacture wood screws.
Heading
Slotting
Threading
Polishing
Galvanization, Blackening, Coating (these processes are omitted when not required by users or sellers)
Heading
This process is called cold forging. Wire coil is put on a stand and wire is fed into a heading machine known as the Header. This wire should not be rusty. The wire is cut into a specified size by a cutting mechanism and is pushed forward towards a die hole. A punch, fixed on a moving block, punches this wire into a die made of Carbide, encased by a protective steel covering or a die of any other suitable material to make a plug. Then a second punch presses this plug to form a blank. The shape of the head is formed according to the design of the second punch. For a flat head wood screw, a flat punch is fixed. Half round or phillips head wood screws are manufactured by grooving or embossing the shape as required on second punch. When the blank is made, a pin moving in the round die, pushes the blank out. This heading machine is also known as the Double-stroke Header. Frequent lubrication is necessary to all parts of the heading machine. Before introduction of the Double-stroke Heading machines, Single-stroke Headers were used to make blanks but are obsolete now.
For working of a Single-stroke header or "former" also see bolt manufacturing process.
Slotting
Blanks made by the heading machine are sent to the slotting machine after polishing. Polishing is a necessary process to clean oil, dust or rust from the blanks. Rust or corrosion can damage or reduce the life of the cutter used to make slots. Blanks are put in the hopper fixed on the slotting machine, and they slide down through railing towards the rotating grooved dial which moves them towards the round cutter which is fixed on rotating adjustable shaft. Regarding the cutting speed, it is constantly proportion to the rotation of the dial.The cutter is controlled by a separate motor in some other models of slotting machines. The cutter makes the slot in the centre of the blank's head. When the blanks reach down they are dropped. Continuous lubrication is needed to increase life of the cutter. The process of slotting is skipped when the slot is made on the head by second punch on the heading machine. Slotting machines perform their function at high speed reaching up to 1600 pcs per minute (theoretically). In practice, however, a much less number of pieces is manufactured than claimed by the manufacturers of machines.
Threading
Feeding Finger at work
There are two ways of making threads
Rolling
Cutting
Rolling
The slotted blanks are polished again. Blanks are put in the hopper fixed on the threading machine, and they slide down the railing towards dies. Two flat dies are used, one is stationary and other is moving and the rolling faces of the dies are located opposite each other. One blank at a time is pushed towards the dies with the help of a plate known as the feeding or the starter finger.
Flat die moving direction
When it is gripped between hardened steel dies, the moving die rotates it and threads are formed[] and a point[] is made as per threading dies. The moving die is fixed in a die pocket on the block which moves further ahead and the screw is dropped[]. Threading machines perform their function at a high speed. The process is called cold forming and continuous lubrication is required to keep the dies below certain temperature.
Notes
[] The threaded faces of these dies are pressed against the periphery of the plain cylindrical blank and re-form the surface of the blank into threads as the blank rolls on the die faces. The working faces of the dies have a thread form, which is the reverse of the thread to be manufactured. While penetrating the surface of the blank, the dies displace the material to form the root of the thread and force the displaced material radially outward to form the crests of the thread. The blank has a diameter part way between the major and minor diameter of the thread. There is no appreciable axial movement of the blank during rolling. The diameter of the finished thread is controlled by the diameter of the blank and the distance between the faces of the dies and the finish end of the stroke.
[] A small material is cut-off from the point.
[] On some type of work, it is necessary to employ a "Knock-off" device to prevent the finished screw etc. from being caught by a return motion of the dies. Some machines are equipped with such a device, if not, then it is a simple matter to make one and attach it to the machine.
Cutting
The other method of making threads is cut-thread. These machines are different form Thread-rolling machines. Blanks slide though rail from the hopper (different than the hopper used in thread rolling machines) and are gripped by feeding finger one by one. The feeding finger presses down and pushes the blank into spindle head and moves up to grip the next blank. The timing of this mechanism is controlled by gears and a rotating cam along with other cams. As soon as the spindle head is closed, and the head of blank is gripped, a cutting tool moves forward to cut the other side of blank to make a point. While this tool is moving back, another tool fixed on a shaft starts cutting the threads. Cutting of threads is a three to five steps process depending upon the length and the diameter of blank. When the threads are cut and the spindle is opened, the feeding finger comes down, pulls out the screw, feeds in the next blank, moves up and before it reaches its original position, a shoot ahead part takes the screw from it.
Polishing
Polishing of blanks is repeated after they are made, slotted and threaded. A hexagonal steel drum is used for blanks polishing and a hexagonal drum made of wood is used for polishing after threads are cut or formed. Wood and leather waste is jointly or separately put inside the drum along with blanks in humid weather. Wood waste alone can do the work in dry weather. When these drums rotate, wood and leather waste absorb oil and continuous rubbing cleans and polishes the surface of blanks and screws.
Galvanization, Blackening, Coating
Hot-dip galvanizing, blackening or coating is done only when it is required by wholesalers, retailers or is desired by users.
Packing
Generally, a hundred numbers or One Gross of wood screws are packed in each packet. A bundle of six packet is made up to size 1 x 9. Above this size, a bundle of three or less packets is made. Craft paper (60-80 grams preferable) is used for wrapping. These bundles are packed in wooden boxes or cartons as per the requirement of wholesalers or importers.
Specifications
The following are suggested blank (thread rolling portion) specifications for wood screws, made to American Standards Association (ASA) B18.6.1 - 1961. * reference Reed thread rolling dies catalogue
Nominal
Size
Treads
(TPI)
Rolling
Dia
0
32
.044
1
28
.055
2
26
.066
3
24
.077
4
22
.088
5
20
.099
6
18
.108
7
16
.118
8
15
.128
9
14
.141
10
13
.151
12
11
.169
14
10
.190
16
9
.210
18
8
.228
20
8
.254
24
7
.296
See also
Blackening
Coating
Galvanization
Heading
Low carbon steel
Milling cutter
Tungsten carbide
Categories: Metalworking | ScrewsHidden categories: Articles that need to be wikified from July 2009 | All articles that need to be wikified | Articles lacking sources from July 2009 | All articles lacking sources
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