Fillister head screws are specialized fasteners with a tall, narrow, cylindrical head and a flat or slightly rounded top. Their head design provides a relatively deep drive recess and a concentrated bearing area, making them useful in machinery, tooling, precision equipment, and applications where the fastener head needs to fit into a counterbored hole.
Unlike pan head, truss head, or flat head screws, fillister head screws have a distinctive high-profile head. They are commonly available in both metric and imperial sizes and can be manufactured with Phillips, slotted, hex socket, or other drive configurations.
This complete fillister head screw size chart and guide explains common sizes, thread specifications, head dimensions, measurement methods, materials, applications, installation, and how to select the correct fillister head screw.
What Is a Fillister Head Screw?
A fillister head screw is a machine screw with a deep cylindrical head and a relatively small head diameter compared with its height.
The head is designed to provide a useful combination of:
- High head profile
- Narrow head diameter
- Deep drive area
- Concentrated bearing surface
- Strong mechanical appearance
- Compatibility with counterbored holes
Fillister head screws are frequently used in applications where a standard low-profile screw head would not provide the required geometry.
Typical applications include:
- Machinery
- Machine tools
- Precision equipment
- Metal assemblies
- Tooling
- Industrial equipment
- Mechanical components
- Instrumentation
- Die and mold equipment
- Engineering assemblies
Understanding Fillister Head Screw Dimensions
Several measurements are used to identify a fillister head screw.
Screw Diameter
The nominal diameter identifies the threaded portion.
Common metric sizes include:
- M3
- M4
- M5
- M6
- M8
- M10
Common imperial sizes include:
- #4
- #6
- #8
- #10
- #12
- 1/4 inch
- 5/16 inch
- 3/8 inch
The exact sizes available depend on the applicable screw standard.
Screw Length
For a fillister head screw, length is generally measured from the underside of the head to the tip.
For example:
M6 × 30 mm
means a nominal 6 mm thread diameter and a 30 mm screw length.
Head Diameter
Head diameter is measured across the widest portion of the cylindrical head.
Fillister heads are generally narrower than many other raised screw heads.
Head Height
Head height is measured from the underside of the head to the top of the head.
The relatively tall head is one of the defining characteristics of a fillister screw.
Thread Pitch
Metric machine screws are identified by thread pitch.
For example:
M6 × 1.0
means a 6 mm nominal diameter and 1.0 mm thread pitch.
Imperial versions are generally specified using threads per inch.
Metric Fillister Head Screw Size Chart
The following table shows common metric fillister head screw thread sizes.
| Screw Size | Nominal Diameter | Common Coarse Pitch | Typical Application |
|---|---|---|---|
| M3 | 3 mm | 0.50 mm | Precision equipment |
| M4 | 4 mm | 0.70 mm | Machinery |
| M5 | 5 mm | 0.80 mm | Mechanical assemblies |
| M6 | 6 mm | 1.00 mm | Machine components |
| M8 | 8 mm | 1.25 mm | Machinery and tooling |
| M10 | 10 mm | 1.50 mm | Heavy mechanical assemblies |
| M12 | 12 mm | 1.75 mm | Large machinery |
Exact head diameter, head height, and drive dimensions depend on the applicable fastener standard and manufacturer.
Imperial Fillister Head Screw Size Chart
Common imperial fillister head screw sizes include numbered screw sizes and fractional diameters.
| Screw Size | Approx. Major Diameter | Common Thread | Typical Application |
|---|---|---|---|
| #4 | 0.112 in | 40 TPI | Small machinery |
| #6 | 0.138 in | 32 TPI | Equipment |
| #8 | 0.164 in | 32 TPI | Mechanical assemblies |
| #10 | 0.190 in | 24 TPI | Machinery |
| #12 | 0.216 in | 24 TPI | Mechanical equipment |
| 1/4 in | 0.250 in | 20 TPI | Machinery |
| 5/16 in | 0.313 in | 18 TPI | Heavy assemblies |
| 3/8 in | 0.375 in | 16 TPI | Large equipment |
Fine-thread versions may be available for certain sizes.
How to Read Fillister Head Screw Sizes
A typical metric designation looks like:
M5 × 20 mm
This means:
- M = metric thread
- 5 = nominal diameter
- 20 mm = screw length
A complete specification may be written as:
M5 × 0.8 × 20 mm
where:
- 5 mm = nominal thread diameter
- 0.8 mm = thread pitch
- 20 mm = screw length
An imperial example is:
#10-24 × 1 in
This identifies:
- #10 screw size
- 24 threads per inch
- 1-inch length
The specification may also include the material, finish, drive type, and applicable standard.
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How to Measure a Fillister Head Screw
If you have an existing screw and need to identify its replacement, measure the important dimensions carefully.
Step 1: Measure the Thread Diameter
Use a caliper to measure the outside diameter of the threaded section.
Compare the result with a metric or imperial size chart.
Step 2: Measure the Screw Length
Measure from the underside of the head to the tip.
Do not normally include the head height.
Step 3: Measure Head Diameter
Measure across the widest part of the cylindrical head.
Step 4: Measure Head Height
Measure from the underside of the head to its highest point.
Step 5: Determine Thread Pitch
Use a thread gauge to identify metric pitch or imperial threads per inch.
Step 6: Identify the Drive
Determine whether the screw uses:
- Slotted
- Phillips
- Hex socket
- Torx
- Combination drive
Fillister Head Screw Head Dimensions
The head design is one of the most important features of a fillister screw.
Unlike a pan head screw, the fillister head is generally taller and narrower.
Important head measurements include:
- Head diameter
- Head height
- Top profile
- Underside profile
- Drive recess dimensions
Because these dimensions can vary by standard, the screw should be matched to the appropriate engineering specification when exact interchangeability is required.
Fillister Head Screw vs Pan Head Screw
Fillister and pan head screws are both raised-head machine screws, but their proportions are different.
| Feature | Fillister Head | Pan Head |
|---|---|---|
| Head profile | Tall and narrow | Rounded and broader |
| Head height | Relatively high | Moderate |
| Head diameter | Relatively small | Larger |
| Common use | Machinery and tooling | General fastening |
| Counterboring | Often useful | Usually unnecessary |
| Appearance | Cylindrical | Rounded |
Fillister head screws are particularly useful when the screw head needs to fit into a counterbored recess.
Fillister Head Screw vs Socket Head Cap Screw
Fillister and socket head cap screws can both have relatively tall heads, but they are not the same fastener.
A socket head cap screw typically has a larger cylindrical head and an internal hexagonal socket.
Fillister screws have their own standardized head geometry and may use different drive styles.
For high-strength applications, the fastener grade and applicable standard should be checked rather than substituting one screw type for another based only on appearance.
Fillister Head Screw vs Flat Head Screw
The two designs have very different head geometries.
| Feature | Fillister Head | Flat Head |
|---|---|---|
| Head shape | Tall cylindrical | Tapered countersunk |
| Head position | Above surface or in counterbore | Can sit flush |
| Countersinking | Normally not required | Required |
| Typical use | Machinery | Flush fastening |
| Head profile | High | Low after installation |
A fillister screw is generally selected when a raised head or counterbored installation is appropriate.
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Fillister Head Machine Screws
Most fillister head screws are machine screws designed for threaded connections.
They may be installed into:
- Tapped holes
- Nuts
- Threaded inserts
- Machine components
- Metal assemblies
They are particularly useful in precision mechanical construction because the head geometry can be incorporated into a counterbored design.
Counterbore for Fillister Head Screws
A counterbore is a cylindrical recess machined into a material to allow a fastener head to sit below or near the surface.
Fillister head screws are often suitable for counterbored applications because their cylindrical head can fit into a matching round recess.
A properly designed counterbore should account for:
- Head diameter
- Head height
- Required seating depth
- Tool access
- Material thickness
- Screw length
The counterbore should not be deeper than necessary because excessive material removal can weaken the component.
Fillister Head Screw Drive Types
Fillister screws are available with several drive configurations.
Slotted Fillister Head Screw
Slotted fillister screws have a single straight recess and are commonly found in traditional machinery and engineering applications.
Phillips Fillister Head Screw
Phillips versions are available for applications requiring a cross-shaped driver recess.
Hex Socket Fillister Head Screw
An internal hexagonal drive provides strong tool engagement and can be useful where access is limited.
Torx Fillister Head Screw
Torx drives provide a multi-lobed recess designed for good driver engagement and torque transfer.
Fillister Head Screw Materials
The material determines strength, corrosion resistance, and suitability for the operating environment.
Steel
Steel fillister screws are commonly used in machinery and general mechanical applications.
Alloy Steel
High-strength alloy steel versions may be used in demanding mechanical applications where increased tensile strength is required.
Stainless Steel
Stainless steel fillister screws provide improved corrosion resistance.
They are useful for:
- Outdoor equipment
- Moist environments
- Marine applications
- Food-processing equipment
- Corrosion-sensitive assemblies
Zinc-Plated Steel
Zinc-plated steel provides additional surface protection against corrosion and is common in general-purpose applications.
Fillister Head Screw Thread Types
Fillister screws may be available with different thread configurations.
Coarse Thread
Coarse metric and imperial threads are widely used for general machine screw applications.
Fine Thread
Fine threads may be selected for particular mechanical applications where their thread geometry is beneficial.
Metric Thread
Metric fillister screws use a nominal diameter in millimeters and a specified thread pitch.
Imperial Thread
Imperial versions use numbered or fractional diameters and specify threads per inch.
Metric and imperial threads should not be mixed.
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Fillister Head Screw Length Guide
The correct length depends on the thickness and design of the joint.
Consider:
- Material thickness
- Counterbore depth
- Thread engagement
- Washer thickness
- Nut thickness
- Blind-hole depth
- Clearance behind the component
For a screw installed into a blind threaded hole, the screw should not be so long that it bottoms out before the head is properly seated.
For through-fastening applications, ensure sufficient thread extends into the nut or threaded component.
How to Choose the Correct Fillister Head Screw Size
Selecting a fillister screw involves several specifications.
1. Select the Diameter
Identify the nominal thread diameter required by the tapped hole or nut.
2. Select the Thread Pitch
Match the exact pitch of the mating thread.
3. Choose the Length
Determine the required thread engagement and account for any counterbore.
4. Check Head Diameter
Make sure the head fits the available counterbore.
5. Check Head Height
Verify that the head will sit at the intended depth.
6. Select the Drive
Choose a drive appropriate for the available installation space and torque requirements.
7. Select the Material
Choose steel, alloy steel, stainless steel, or another suitable material.
8. Choose the Finish
Select a finish appropriate for the environment and required corrosion resistance.
Fillister Head Screw Applications
Fillister head screws are particularly common in engineering and industrial environments.
Applications include:
- Machine tools
- Machinery
- Precision instruments
- Industrial equipment
- Tooling
- Dies and molds
- Mechanical assemblies
- Metal components
- Electrical equipment
- Instrumentation
- Manufacturing equipment
Their distinctive head shape makes them useful where standard screw heads are unsuitable.
Advantages of Fillister Head Screws
Fillister screws offer several useful characteristics.
Tall Head Design
The relatively high head can provide useful material around the drive recess.
Narrow Head Diameter
The smaller head diameter can fit into compact areas.
Counterbore Compatibility
Their cylindrical geometry works well with counterbored holes.
Mechanical Appearance
They are commonly used in precision machinery where a traditional machine-screw appearance is desirable.
Wide Size Selection
They are available in multiple metric and imperial thread sizes.
Limitations of Fillister Head Screws
Fillister screws are not ideal for every application.
Their limitations may include:
- High head profile
- Need for additional clearance
- Less suitable where a flush surface is required
- Limited suitability for very thin materials
- Exact dimensions vary by standard
If a flush installation is required, a countersunk screw may be more appropriate.
If a low-profile head is required, a button or low-head fastener may be preferable.
Common Fillister Head Screw Problems
Using the Wrong Counterbore
A counterbore that is too small will prevent proper seating.
Choosing the Wrong Length
An excessively long screw can bottom out in a blind hole.
Incorrect Thread Pitch
A screw with the wrong pitch can damage the mating thread.
Using an Incorrect Drive
A poorly fitting driver can damage the recess.
Over-Tightening
Excessive torque can damage the screw, threads, or component.
Ignoring Head Clearance
The tall head requires sufficient space above the component.
Fillister Head Screw Size Chart Quick Reference
| Size | Nominal Diameter | Common Pitch / TPI | Typical Application |
|---|---|---|---|
| M3 | 3 mm | 0.50 mm | Precision equipment |
| M4 | 4 mm | 0.70 mm | Machinery |
| M5 | 5 mm | 0.80 mm | Mechanical assemblies |
| M6 | 6 mm | 1.00 mm | Machine components |
| M8 | 8 mm | 1.25 mm | Machinery and tooling |
| M10 | 10 mm | 1.50 mm | Heavy assemblies |
| M12 | 12 mm | 1.75 mm | Large machinery |
| #4 | 0.112 in | 40 TPI | Small equipment |
| #6 | 0.138 in | 32 TPI | Machinery |
| #8 | 0.164 in | 32 TPI | Mechanical assemblies |
| #10 | 0.190 in | 24 TPI | Machinery |
| #12 | 0.216 in | 24 TPI | Industrial equipment |
| 1/4 in | 0.250 in | 20 TPI | Mechanical assemblies |
| 5/16 in | 0.313 in | 18 TPI | Heavy equipment |
| 3/8 in | 0.375 in | 16 TPI | Large machinery |
These are common thread-size references. Exact fillister head diameter, head height, drive dimensions, and available lengths depend on the applicable standard and manufacturer.
Frequently Asked Questions About Fillister Head Screw Sizes
What is a fillister head screw?
A fillister head screw is a machine screw with a tall, narrow cylindrical head. Its geometry makes it useful for machinery, tooling, precision equipment, and counterbored installations. Fillister screws are available in different diameters, lengths, thread pitches, materials, and drive configurations.
What are the common fillister head screw sizes?
Common metric sizes include M3, M4, M5, M6, M8, M10, and M12. Common imperial sizes include #4, #6, #8, #10, #12, 1/4 inch, 5/16 inch, and 3/8 inch. Exact availability varies by manufacturer and standard.
How are fillister head screws measured?
Fillister head screws are measured by thread diameter, screw length, thread pitch, head diameter, and head height. Length is normally measured from the underside of the head to the tip. A caliper and thread gauge can help identify the correct replacement.
What is the difference between a fillister head and pan head screw?
A fillister head is taller and narrower, while a pan head is generally broader and more rounded. Fillister screws are commonly used in machinery and counterbored applications, while pan head screws are widely used for general-purpose fastening.
Do fillister head screws require a counterbore?
Not necessarily, but they are well suited to counterbored holes because their cylindrical heads can fit inside a matching round recess. Whether a counterbore is required depends on the component design and whether the head needs to sit below or near the surface.
What is a fillister screw used for?
Fillister screws are commonly used in machinery, tooling, machine tools, precision instruments, industrial equipment, dies, molds, and mechanical assemblies. Their tall, narrow head is useful where a traditional raised machine-screw head and counterbored installation are appropriate.
Are fillister head screws available in metric sizes?
Yes. Metric fillister head screws are commonly available in sizes such as M3, M4, M5, M6, M8, M10, and M12. They use metric thread pitches and should be matched to the exact pitch of the mating threaded hole or nut.
How are fillister head screw lengths measured?
For a standard fillister head screw, length is normally measured from the underside of the head to the tip. The head height is not included in the stated screw length. Always confirm the manufacturer’s measurement method when exact dimensions are required.
Final Thoughts
A fillister head screw size chart is useful for identifying common metric and imperial thread sizes, but choosing the correct fastener requires consideration of the complete screw specification.
The most important factors include diameter, length, thread pitch, head diameter, head height, drive type, material, finish, and counterbore requirements.
Common metric sizes include M3 through M12, while common imperial sizes include #4 through 3/8 inch.
The defining feature of a fillister head screw is its tall, narrow cylindrical head, which makes it especially useful for machinery, precision equipment, tooling, and counterbored mechanical assemblies.
When replacing a fillister screw, measure the existing fastener carefully and verify both the thread dimensions and head dimensions. For precision or high-load applications, always use the appropriate engineering standard and manufacturer’s specifications rather than relying solely on a general size chart.
Engineer Hassan is a Mechanical Engineer with 16+ years of hands-on experience in mechanical hardware, fasteners, and workshop tools. He focuses on size selection, thread identification, and measurement, helping users choose the correct components with accuracy and safety.