Screws on IndustryNet

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The concept of screw dates back to around 200 AC. The screw known today was not developed until the Renaissance.

A screw is a type of fastener, which is typically made of metal and characterized by a helical ridge known as a male thread or thread wrapped around a cylinder. A screw will almost always have a head on one end, which contains a specially formed shape that allows it to be turned or driven with a tool.

Screws are generally made from low to medium carbon steel wire. However, other tough and inexpensive metals maybe substituted such as stainless steel, bras, nickel alloys or aluminum alloy.The quality of the metal used is of utmost importance so that cracking is avoided.

There are two types of screws, machine and wood screws, which are both made of metal. The machine screw has a constant diameter and joins with nuts, while the wood screw is tapered and grips to the actual wood surface.

Manufacturing Process:

Screws are usually mass manufactured using the thread rolling method.Machining is only used on unique design or with screws too small to be made any other way.

Method:

1. Wire is fed from a mechanical coil through a pre-straightening machine

2. The straightened wire flows directly into a machine that automatically cuts the wire at a designated length and die cuts the head of the screw blank into a preprogrammed shape

3. The heading machine utilizes either an open or closed die that either requires one punch or two punches to create the screw head

4. The closed or (solid) die creates a more accurate screw blank

5. On an average, the cold heading machine produces 100 to 550 screw blanks per minute

6. Once cold headed, the screw blanks are automatically fed to the thread-cutting dies from a vibrating hopper. The hopper guides the screw blanks down a chute to the dies, while ensuring they are in the correct feed position

7. The blank is then cut using one of three technologies

8. In the reciprocating die, to flat dies are used to cut the screw thread. One die is stationary while the other moves in a reciprocating manner. The screw blank is then rolled between the two. When the center-less cylindrical die is used, the screw blank is rolled between two or three round dies in order to create finished thread.

9. The final method is the planetary rotary die process. It holds the screw blank stationary, while several die-cutting machines roll around the blank.

Choosing The Right Screw For The Project:

Know the kinds of screws and their purpose:

Round - head is rounded and often settles above the secured surface

Pan - head is flatter than a round head but thicker at the edges, has more surface for a screwdriver to grip into

Flat – often found on wood screws, enables the screw to be embedded into the surface

Oval – commonly used on wood screws instead of being embedded in the wood, the head protrudes above the surface as decoration

It is also important to know the various types of screws for different surfaces.

Woodscrews –also known as flatheads are usually used on wood

Sheet Metal Screws – used to secure thin metal object

Drywall Screws - designed to secure drywall to wood or to metal studs

Masonry And Other Screws – works ell with hard material such as concrete or brick

Prior to placing your order, you should have the following information available for a quote:

• Machine type

• Machine size

• Screw diameter

• L/D- ratio is the ratio of he flighted length of the screw it is to outside diameter

• Whether a high wear resistance package is required

Other purchasing tips:

• Obtain several quotes

• Supplier/manufacturer should be willing to provide certification of all materials used.

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