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Countersunk or Flat Head Screws
SCREWS
Countersunk screws are also called Flat head or CSK screws. These screws have a flat head which tapers along the shaft.
Flat head screws are used for flush mounting of sections, usually where one part slides over another or one part is mounted on another. They are used with a countersunk hole to provide a flush, snag free fit.
Countersunk head screws, like button heads and low heads, are limited by configuration in their tensile strength capability. Because of this, they should not be used in applications requiring full strength, where Socket Head Cap Screws should be used.
Flat head screws require a matching counter in the workpiece.
The Countersunk head is preferred to obtain a flush and level finish without any projection in metal or plastic. They sink into the surface to give a smooth exterior finish.
The head angle for metric countersunk socket screws is 90 degrees up to & including M20 and 60 degrees over M20.
The head angle for Imperial is different – Unified is 82 degrees and British thread forms are 90 degrees.
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Pan Head Screws
The pan head is a commonly used head style for screws.
It looks like an upside down frying pan – pan head screws have a cylindrical head with a slightly rounded top surface and a flat bearing surface underneath.
Pan head screws are visually appealing and can take higher torque and provide better clamping force.
This head style is ideal for most applications where a protruding head is acceptable.
Pan Head Machine Screws
Pan Phillips Screws
The Phillips screw drive (specified as an ANSI Type I Cross Recess and type H in ISO documentation) is among the most popular drive style for screws.
Cross recess H (Phillips) according to ISO 4757 has a conventional cruciform recess with all walls inclined, the end of the screwdriver having trapezoid webs.
The design is often criticized for its tendency to cam out at lower torque levels than other “cross head” designs.
Applicable standards
- IS 7483 – Indian Standard
- DIN 7985 – DIN [German] standard
- ISO 7045 – International Standards Organisation
- JIS B1111 – Japanese standard
DIN Sizes from M1.6
Micro Sizes now available starting from M1.0Materials – Steel, Stainless Steel AISI 304 and 316, Titanium on request.
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