STAINLESS STEEL ALLEN CSK

Product Specification :
Product Specification: Stainless Steel Allen CSK (Countersunk Socket Screws)
Stainless Steel Allen CSK screws, also known as Flat Head Socket Cap Screws, are designed for applications where the fastener head must sit flush with or below the surface of the material. They feature a conical under-head and an internal hexagonal (Allen) drive.
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1. Material Grades
Since these are stainless steel, they are primarily chosen for their rust resistance and aesthetic appeal:
Grade    Common Name    Properties
A2-70 (304)    18-8 Stainless    Most common; excellent for general outdoor and food-grade use.
A4-70 (316)    Marine Grade    High resistance to chlorides and salt spray; ideal for coastal or chemical environments.

2. Physical Design & Dimensions
Head Shape: 90° countersunk (conical) angle (Note: Imperial/SAE versions often use an 82° angle).
Drive Type: Internal Hexagonal (Allen) socket.
Standards:
Metric: ISO 10642 or DIN 7991.
Imperial: ASME B18.3.
Length Measurement: Unlike standard bolts, the length of a CSK screw is measured from the top of the head to the tip of the thread (Total Length).

3. Technical Specifications
Tensile Strength: Usually 700 MPa (for Class 70 stainless).
Thread Pitch: Available in Coarse (Standard) and Fine threads.
Surface Finish: Generally supplied in a "Bright" or "Passivated" finish for maximum corrosion resistance.
Non-Magnetic: A2 and A4 grades are typically non-magnetic or only slightly magnetic due to cold working.

4. Application Considerations
Pros    Cons
Flush Finish: Prevents snagging and allows parts to slide over the fastener.    Smaller Drive: The socket is smaller than a standard Cap screw, increasing the risk of stripping if over-torqued.
Aesthetics: Provides a clean, professional "flat" look.    Weakened Head: The countersunk geometry makes the head slightly less strong than a cylindrical cap head.

5. Installation Best Practices
Countersinking: The hole must be pre-drilled and then beveled with a countersink bit to the exact diameter and angle of the screw head ($90^\circ$ for Metric).
Anti-Galling: Just like other stainless fasteners, use an Anti-Seize lubricant to prevent the threads from "cold-welding" to the mating part.
Torque Warning: Because the socket depth is shallower than a standard Allen Cap, ensure the Allen key is fully seated to avoid "rounding out" the internal hex.

6. Common Sizes (Metric)
Diameter    Recommended Allen Key Size
M3    2.0 mm
M4    2.5 mm
M5    3.0 mm
M6    4.0 mm
M8    5.0 mm
M10    6.0 mm