Hex Tap Bolts (Full Thread Hex Cap Screws)

18-8 Stainless Steel Hex Tap Bolts

316 Stainless Steel Hex Tap Bolts

Metric A2 Stainless Steel Hex Tap Bolts

What Are Hex Tap Bolts (Full Thread Hex Cap Screws)?

Hex tap bolts—also called full thread hex cap screws—are hex-head fasteners with threads running the entire length of the shank. They can be used with a nut or driven into a tapped hole when maximum thread engagement through the joint is required.

What Are Hex Tap Bolts (Full Thread Hex Cap Screws) Used For?

Through-bolting thin or variable material stacks where a partially threaded shoulder would reduce engagement.
Fastening into pre-tapped holes that require full-depth engagement across the joint thickness.
Equipment mounting, brackets, guards, and fixtures in machinery and OEM assembly.
Automotive and repair work, metal-to-metal and wood-to-metal assemblies with a mating nut.

Benefits of Hex Tap Bolts (Full Thread Hex Cap Screws)

Full engagement: threads span the entire grip for maximum contact in thin or layered joints.
Versatile fit: works with nuts, tapped plates, and inserts without worrying about shoulder length.
Standard tools: installs with common wrenches/sockets; easy to remove for service.
Material choices: available in stainless, silicon bronze, and coated or zinc-plated carbon steel to match environment and appearance.

Hex Tap Bolts (Full Thread Hex Cap Screws) Sizes & Threads

Order by diameter × thread × length (e.g., 3/8"-16 × 2" or M8-1.25 × 50 mm). Inch series commonly use UNC (coarse) or UNF (fine) threads; metric uses standard pitches (e.g., M6-1.0, M8-1.25). Length is measured from under the head to the tip.

Materials & Finishes for Hex Tap Bolts (Full Thread Hex Cap Screws)

18-8 / 304 stainless: general corrosion resistance for most outdoor/indoor applications.
316 stainless: upgraded resistance for marine and chemically aggressive environments.
Zinc plated carbon steel: economical protection for dry interior service.
Silicon bronze: corrosion resistance with a warm appearance for marine/architectural use.
Metric A2/A4 stainless: the common metric equivalents to 304/316.

Installation Tips for Hex Tap Bolts (Full Thread Hex Cap Screws)

Match nuts and washers to the bolt’s grade/material and thread (UNC/UNF or metric).
Select a length that allows 1–3 threads to project beyond the nut after tightening.
Use appropriate torque methods; for stainless, consider anti-seize to reduce the risk of galling.
Add flat or flange washers to increase bearing area on softer materials and protect finishes.
For vibration, consider prevailing-torque lock nuts or a compatible threadlocker.

Related Hardware for Hex Tap Bolts (Full Thread Hex Cap Screws)

Hex nuts (matching grade/material), nylon-insert lock nuts, and flange nuts
Flat, fender, and lock washers; finish washers for appearance-critical installs
Threaded inserts or tapped plates when a nut is not accessible

Hex Tap Bolts (Full Thread Hex Cap Screws) FAQs

See the accordion below for selection, sizing, and installation answers.

Disclaimer: This content is general guidance. Always follow product datasheets and the governing project specification.

What’s the difference between a hex tap bolt and a standard hex cap screw?

A tap bolt is fully threaded from head to tip. A standard hex cap screw may be partially threaded with a smooth shoulder under the head.

When should I choose a fully threaded tap bolt instead of a partially threaded hex cap screw?

Use a tap bolt when the joint is thin or layered and needs full thread engagement through the entire grip, or when installing into pre-tapped holes with varying thickness.

Can I use hex tap bolts in tapped holes and with nuts?

Yes. They’re suitable for both—ensure the thread series and pitch match the mating threads.

UNC vs. UNF: which should I pick for tap bolts?

UNC (coarse) is the most common and more forgiving in field assembly. UNF (fine) is used where finer adjustment or higher clamp per turn is desired and the mating parts support it.

How do I measure the length of a tap bolt?

From under the head to the tip—same as other hex bolts/cap screws.

What sizes are common for tap bolts?

Popular inch sizes include 1/4"-20, 5/16"-18, 3/8"-16, and 1/2"-13; metric examples include M6-1.0, M8-1.25, and M10-1.5. Availability depends on material/finish.

Are stainless hex tap bolts magnetic?

18-8/304 and 316 are typically low-magnetic; some magnetism can appear from cold working or thread rolling.

Which material should I choose—zinc plated, stainless, or silicon bronze?

Use zinc plated for dry interior, stainless for general outdoor or corrosive settings (316 for harsher/marine), and silicon bronze where corrosion resistance and appearance are priorities.

Do I need washers with tap bolts?

Washers are recommended on softer materials or painted surfaces to spread load and protect finishes. Flange nuts can also increase bearing area.

How tight should I make the joint?

Torque depends on diameter, grade/material, lubrication, and finish. Use the product’s torque table or project specification.

Can I use threadlocker with tap bolts?

Yes, when compatible with the materials and service temperature. For repeated service, consider prevailing-torque lock nuts instead.

Are tap bolts suitable for structural steel connections?

Structural connections typically require heavy-hex structural bolts specified by the project or code. Use tap bolts only where allowed by the design.

Can I mix stainless nuts with carbon-steel tap bolts (or vice versa)?

Best practice is to match materials and finishes to avoid galvanic corrosion and strength mismatches.

Why did my stainless tap bolt gall or seize during tightening?

Stainless threads can gall under high friction. Use proper lubrication/anti-seize, avoid over-speeding, and don’t back-and-forth rapidly under high load.