screwfitmentdatabase

Screw head shapes and when each one is right

Head shape decides whether a cover closes, whether the screw sits flush, and how much clamping force it spreads. Swapping shapes is a common cause of a lid that will not shut.

The common shapes

  • Pan head — slightly domed, wide bearing surface, the general-purpose default.
  • Button head — lower dome, softer look, less driver engagement so it strips more easily.
  • Countersunk (flat) head — 90 degree cone, sits flush in a chamfered hole. Only works with a matching countersink.
  • Socket cap — tall cylindrical head with a hex socket, highest strength.
  • Cheese head — tall and straight-sided, common in instruments and older machines.
  • Wafer / low-profile head — very thin, very wide, made for thin panels and tight clearances.
  • Flange head — built-in washer face, spreads load and resists loosening.

Low profile is a real spec, not a style

Laptop and camera assemblies often need a head under 1 mm tall. Fitting a standard pan head in that spot can stop a cover seating or short a board underneath.

If a part shipped with a low-profile head, replace it with a low-profile head.

Countersunk mistakes

A countersunk screw in a flat-drilled hole only touches on the edge, and it will pull through or crack thin plastic.

Metric countersunk heads are 90 degrees; imperial flat heads are often 82 degrees. They do not seat the same way.

Common questions

Which head is strongest?

Socket cap heads take the most torque because the hex socket is deep and hard to strip.

Can I swap a countersunk for a pan head?

Only if the extra head height fits and the hole is not chamfered. In an electronics housing the answer is usually no.

Why do button heads strip so often?

The socket is shallow to keep the head low, so the bit has less to grip.

Keep reading

How to measure a screw and work out its metric sizeRemoving a stripped tiny screw without wrecking the deviceLaptop screw sizes explainedMetric vs imperial screws — the sizes that fool everyoneThread locker and torque on small screwsPutting screws into plastic without stripping itChoosing the right screw lengthWhich screw material to use, and what rustsSecurity screws and how to get them outKeeping track of tiny screws during a repairCross-threaded, seized and spinning screwsWashers, locking methods and screws that will not stay tightHow to buy the right screws onlineOpening a laptop, phone or console without damageScrew standards: ISO, DIN, ANSI and JISIdentifying a screw when the manufacturer never published the sizeChoosing and fitting screws in 3D printed partsEyeglass, watch and hearing aid screwsLicense plate, trim and small automotive screwsAll tools

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