Our partially threaded hex head bolts use a fine pitch thread with a plain shank under the head. The fine thread gives finer tension control and better hold against loosening, while the plain shank locates parts and carries shear across the joint. Available in class 8.8, 10.9 and 12.9 steel and A2/A4 stainless.

Hex Head Bolt Fine Thread Partially Threaded: Metric Sizes

What Is a Fine Thread Partially Threaded Hex Head Bolt?

A fine thread partially threaded hex head bolt is a six sided fastener that mixes two useful traits. First, it has a fine pitch thread, meaning the threads sit closer together than on a coarse bolt. Second, it has a partial thread, so there is a smooth plain shank between the head and the threaded end. The fine pitch gives you a smaller advance per turn, which means finer control over how much tension you set and a shallower helix that tends to hold better against loosening. The plain shank locates parts precisely and carries shear load across its solid cross section rather than across the threads.

That pairing suits joints that see load in more than one direction, or that need the plain shank to act as a locating pin. It is a familiar choice in automotive, machinery, and structural connections where the plain shank sets alignment and the fine thread lets you dial in clamp load. Higher property classes let the bolt carry heavy static and shifting loads, and the six sided head takes a standard wrench or socket for repeatable torque.

Fine thread also matters when the bolt threads into a thin wall or a harder material. More threads per length of engagement means more contact area carrying the load, so the joint holds better in a shallow tapped hole. The trade off is that a fine thread is a little more sensitive to dirt and damage on the crest, so the threads should be clean before assembly. In return you get a bolt that is easier to set precisely and that resists loosening well once torqued.

Key Features and Benefits

• Fine Pitch Thread: The closer thread spacing gives finer tension control and a shallow helix that resists loosening.
• Plain Shank: The smooth shank locates parts and carries shear across a solid section, not the threads.
• Six Sided Drive: The hex head takes a standard wrench or socket for high, repeatable torque.
• High Strength Classes: Class 8.8, 10.9 and 12.9 carry heavy static and shifting loads.
• Steel and Stainless: Plated and alloy steel for strength and stainless for corrosion resistant work.

Materials and Finishes

• Alloy Steel (Class 8.8, 10.9, 12.9): Heat treated for higher tensile strength in loaded joints.
• Carbon Steel (Zinc Plated): A plated finish for general assembly and indoor use.
• Stainless Steel (A2 / A4): For marine, outdoor, and corrosion prone environments.

Fine Thread Versus Coarse Thread

Coarse and fine are the two common metric thread pitches, and each has its place. A coarse thread has fewer threads per length, so it goes on faster, shrugs off nicks and light rust, and is the default for most general work. A fine thread packs more threads into the same length, which gives finer control over tension, a stronger hold in thin or hard material, and better resistance to vibration loosening.

Pick fine thread when the joint calls for careful preload, when the bolt threads into a limited depth of harder metal, or when steady vibration is a concern, as it often is in engines, gear housings, and moving machinery. Keep in mind that a fine thread bolt must mate with a fine thread nut or hole of the same pitch, so plan the whole joint around one pitch.

Common Applications

Fine thread partially threaded hex bolts are widely used in automotive and machinery work. They join engine and transmission housings, hold suspension and steering parts, and fasten machine frames and bearing carriers where the plain shank lines the parts up and takes side load. In structural and equipment building, they connect plates and members that must stay aligned under load. Anywhere a joint needs both precise clamp load and a locating shank, this bolt is a strong fit.

Standards Compliance

• DIN 960 / ISO 8765: Partially threaded hex bolts, fine pitch
• ISO 898-1: Mechanical properties for steel fasteners

Size Range and Availability

Available in M8 through M24 in metric fine thread, in class 8.8, 10.9 and 12.9 alloy steel and A2/A4 stainless steel. If you need a size, pitch, or finish that is not shown, reach out and we will help you source it.

Frequently Asked Questions (FAQs)

1. What is a fine thread partially threaded hex bolt used for?

It is used in automotive, machinery, and structural joints where the plain shank sets alignment and carries shear, and the fine thread lets you set clamp load with more control.

2. Why choose a fine thread over coarse?

A fine thread advances less per turn, so you get finer tension control, and its shallow helix tends to hold better against loosening in the right joint.

3. What does the plain shank do?

The smooth shank locates parts precisely and carries shear across its solid cross section rather than across the threads, which suits joints loaded in more than one direction.

4. When should I choose partial thread?

Choose partial thread when you want a plain shank to act as a locating pin or to take shear, rather than thread running the full length.

5. What property classes do you stock?

We stock class 8.8, 10.9 and 12.9 in alloy steel, along with A2 and A4 stainless for corrosion resistant work.

6. Do these take a standard wrench?

Yes. The six sided head takes a standard metric wrench or socket for repeatable torque.

7. Are these available in stainless steel?

Yes. We stock them in A2 and A4 stainless along with plated and alloy steel.

8. What sizes do you stock?

We stock M8 through M24 in metric fine thread across steel and stainless.