18-8 vs. 304 Stainless Steel
If you have a project that needs fasteners, you have several options to choose from. Screws come in a wide range of sizes, threads, heads and tips. Before you start to narrow your choices down, however, you need to know what type of screw to buy. The 18-8 stainless and 304 stainless screws are some of the most popular fasteners on the market, but they have a few differences that can affect the long-term performance of your finished project.
Getting to Know 18-8 Stainless Steel vs. 304 Stainless Steel
Screws made from 18-8 and 304 stainless steel are both made using stainless steel, but their compositions vary. The differences between 18-8 stainless steel vs. 304 stainless steel may seem minor, but they can have a measurable impact.
18-8 Stainless Steel
This iron alloy earns its name due to its makeup. It is produced using approximate quantities of 18% chromium and 8% nickel, and it covers a family of fittings that include 302, 304, 305 and 384 stainless screws. These fittings all use 18-8 stainless steel as a base before they are modified with additional alloys. Screws made from 18-8 stainless steel are non-magnetic and have excellent resistance to rust and corrosion.
304 Stainless Steel
This stainless steel (SS) type is austenitic and the most widely used alloy in the AISI (American Iron and Steel Institute) 300 series. It has the chromium and nickel content of 18-8 stainless steel but contains a maximum of 0.08% carbon as well. It also shares many similar properties to 18-8 stainless steel, including resistance to corrosion and oxidation. The addition of carbon provides this alloy with extra strength and hardness that sets it apart from other alloys.
The Applications of 18-8 SS vs. 304 SS
With different chemical structures, fasteners made with 18-8 vs. 304 stainless steel offer distinct advantages. Before you make your purchase, consider the ideal applications of 18-8 vs. 304 stainless steel:
- 18-8 stainless steel: The chemical composition of 18-8 grade stainless steel makes it suitable across many industries. Fasteners made with this alloy will perform well in chemical, high-temperature and high-moisture environments. These screws will react to chlorides, like salt, and are, therefore, not recommended for use in marine applications.
- 304 stainless steel: 304 stainless steel is an alloy with a slightly different composition. This alloy provides some of the best corrosion resistance in the 300 series. The extra hardness from the carbon, combined with the benefits of chromium and nickel, makes these screws a favorite for HVAC use and construction applications like deck, gutter or roofing installation.
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Screw Point Types
Screws consist of a head, shank, threads and the tip or point. The point of a screw is the first part of the screw to make contact with the material you’re working with. Different types of screw points serve different purposes. For example, some are better suited for sheet metal or soft materials than others, while other points are designed for misaligned holes or minimizing the risk for surface cracking. Use this screw point type chart to find the best screw for your project.
Tapping Screw Points
If you’re looking for thin sheet metal screw point types, tapping screws are a popular choice because they do not require a pilot hole to begin. These screws are externally threaded and create — or “tap” — their own threads in thin sheet metals and non-metal materials.
Some types of tapping screws include:
- Type A: Type A screws have coarse threads that make them useful when you need to drill or nest a hole in thin sheet metal, resin plywood, asbestos combinations and other materials. They are threading screws and not recommended for new designs.
- Type B: You can use a fine-thread Type B screw for non-ferrous lightweight and heavy metals, plastics, resin plywood and other materials.
- Type AB: Type AB screws are thread forming screws similar to both Type A and Type B points. It has the pointed tip of a Type A point screw but the threads of a Type B point screw. This combination makes them ideal for thin sheet metal, resin plywood, composite materials and several other industry-spanning applications.
- Type BP: These screws have a similar thread style to Type B points but with a slightly longer and more pointed tip. If you’re working on a project with misaligned holes, a Type BP point is a thread forming screw suitable for use in heavy and lightweight sheet metal, plastic and other materials.
Thread Cutting Screw Points
Thread cutting screws work like self-tapping screws and can help you create new holes in different materials like wood and metal. Due to the way a thread cutting screw is designed, it doesn’t take much torque to apply them. Minimal stress is placed on the material, decreasing the chance for product damage.
Common types of thread cutting screws include:
- Type F: Type F screw points are a type of thread cutting and self-tapping screw with cutting edges and a blunt and tapered end at the tip. These features make it useful for heavy materials, like cast iron, sheet metal, brass and some plastics.
- Type D/Type 1: Type D screw points — also known as Type 1 points — are a thread cutting point with a single flute. Type D tips are suitable for field replacement and general use applications.
- Type G: Type G screw points are blunt and have singular slots to create sharp cutting edges.
- Type 17: You can use a coarse, sharp Type 17 screw tip for wood and field replacement applications.
- Type 23/Type T: Type 23 points, also known as Type T points, require minimum tightening torque and are good for chip clearing and maximum thread cutting.
- Type 25/Type BT: Type 25 points, called Type BT points, are similar to Type 23 points, except they have coarser threads for use with softer materials, like plastic.
Thread Forming Screw Points
Thread forming screws have a high and low thread. These screws displace and shape the material while in motion, securing it. They typically have a blunt end for use with high-performance thermoplastics, sheet metal, plastic and composite materials.
Thread forming screw points include:
- Type C: Type C screws have a blunt and tapered point and require a higher driving torque. You can use these with heavy sheet metals, die castings and similar materials.
- Type CA: Type CA screw points have either fine or coarse threads and a pointed, gimlet tip.
- Type PT: Type PT screw tips are the ideal solution for low-density materials, such as nylon or wood, that you want to avoid cracking or chipping during screw installation.
- Type “TT”: “TT” tips, or “tri-round” tips, roll materials to form matching threads without producing any chips. This means you can drive the screw in with less torque than you would with other thread forming screws.
Self Drilling and Self Piercing Screw Points
Self-drilling and self-piercing screws are similar, but different points make them suitable for different applications and materials:
- Self-drilling: Self-drilling screws are also known as Tek screws and eliminate the need for hole preparation. They are suitable for metal, plastic and wooden material applications and minimize the amount of build-up or foreign debris common in pre-drilled holes.
- Self-piercing: Self-piercing screws are similar to self-drilling screws, except they have a pointed tip that allows them to quickly pierce through sheet metal without sacrificing any stability. They are also called needle point, speed point and spring point screws.
Machine Screw Points
Machine screws are small and uniform, with either fine or coarse threads. They are intended for use in electronics, casings, manufacturing equipment and other precise applications. Some machine screw point types include:
- Dog point: Dog point, or extended point, machine screws have a protruding tip and a flat end for permanent application.
- Cone point: Cone points are smooth and shaped like their name, ideal for contoured surfaces or applications that require an angle.
- Cupped point: Cupped point machine screws have a gripped, cup-shaped end for quick assembly or temporary projects.
- Header point: Header point machine screws have large thread roots and are small in diameter.
- Pinched nail point: Pinched nail point machine screws have a sharp, squared nail-like tip that can pair wood with softer materials.
- Rolled point: Rolled points are long with a cone-like end known as a chamfer.
- Round point: These screw points are rounded and allow you to apply pressure and create friction without damaging or deforming the material you’re working with.
- Rounded pinch point: Rounded pinch point screw tips are slightly rounded with pinched sides.
- Type U drive point: The tip of these screws is flat with rounded edges, and you can use them for permanent application in plastic and metal material.
What Type of Point Does a Hex Lag Screw Have?
Hex lags — also known as hex bolts and lag screws — are strong, sturdy screws with deep threads and a nut on one side that you can use to hold heavy-duty materials together. You need to pre-drill a hole before using a hex lag screw. All hex lag screws have the same six-sided head, and the most common hex lag screw point type is a pointed gimlet shape.
All Points Fasteners Has the Fasteners You Need
All Points Fasteners has the screws, nails, drill bits, anchors and other top-quality fasteners you need to complete your project. Browse our inventory today and ask us about getting a free sample of our stocked items before you place your order, so you can be confident you’ve made the right decision for your project and your budget.
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