High-Low Thread Countersunk Tapping Screw

Name: High-Low Thread Countersunk Tapping Screw
Brand: ZINSN
SKU: hi-lo-thread-countersunk-tapping-screw

Alternating high and low thread profile in a countersunk head — superior holding in plastic and softer substrates.

High-Low thread countersunk head tapping screw in grey phosphate finish

Self-Tapping Screws

Specification

Thread	High-Low, alternating profile
Head	Countersunk
Drive	Phillips, Pozi, Torx, hex socket
Point	Type AB or Type 17 sharp point
Diameter	2.9 – 6.3 mm
Length	9.5 – 80 mm
Material	SAE 1022 carbon steel; 304 / 316 stainless
Finish	White zinc, yellow zinc, black phosphate, plain

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Custom sizes, finishes and OEM packaging available. Samples shipped within 5 working days of approval.

Why it is built this way

Engineering notes

Plastic is the hardest substrate to fasten into reliably. Drive a conventional thread into a moulded boss and the hoop stress cracks it; drive it too shallow and it pulls out under vibration. The High-Low profile solves both at once — the tall thread reaches deep for holding power while the low thread keeps the displaced material supported and the boss wall intact.

The countersunk head suits recessed and flush-mount applications where nothing can stand proud of the surface: enclosure lids, trim panels and assemblies that receive a cover afterwards.

Key features

High-Low thread reduces hoop stress in moulded plastic bosses
Higher withdrawal resistance in soft and friable substrates
Countersunk head for flush and recessed assemblies
Available in stainless for corrosive service

Typical applications

Sheet metal fabrication
HVAC ducting
Electrical enclosures
Signage
Plastic enclosures
General assembly

Buyer questions

Frequently asked

Why does High-Low work better in plastic?

The low thread supports the boss wall while the high thread carries the load, so you get engagement without the hoop stress that cracks a moulded boss.

Can it be used in wood as well?

Yes, particularly in soft and engineered timber. For gypsum and cement board see our Hi-Lo drywall variant.

Is stainless available?

304 and 316 stainless are both available across the self-tapping family.

Ordering information. FOB Shanghai or Ningbo as standard; CIF and DDP available. Mill test certificates, SGS reports and dimensional inspection records are issued on request. See available documents.

Same family