ISO 2338 Dowel Pins: Differences and Relationships with DIN 7, ISO 8734, and DIN 6325
- 翰君 陳
- 1 day ago
- 6 min read
ISO 2338 is an international standard for unhardened parallel pins (Parallel Pins, Unhardened). In practical applications and supplier catalogs, it is often compared alongside the German DIN 7 standard.
However, the two are not completely identical. ISO 2338 measures length end-to-end (including chamfers), while DIN 7 nominal length excludes the end form, meaning the actual total length may be 0.3–8.0 mm longer than the nominal size. In addition, DIN 7 allows three end styles—flat, rounded, and chamfered—while ISO 2338 is typically chamfered-end.
Their tolerance grades and material specifications are similar, which is why they are frequently discussed together, but purchasing decisions should still follow the actual drawing specification and dimensional definition.
Another common question when seeing “ISO 2338” on a drawing is:
“How is it different from DIN 6325? Can they be directly substituted?”
The answer is: not necessarily.
Although they look similar externally, their hardness, tolerance, and intended applications are different.
In simple terms, these four standards can be divided into two groups:
ISO 2338 and DIN 7 → unhardened parallel pins
ISO 8734 and DIN 6325 → hardened and ground dowel pins
Although the appearance is similar, hardness, heat treatment condition, and application scenarios differ, so they should not be replaced based solely on appearance or dimensions.
From the standards perspective:
ISO 2338 and ISO 8734 belong to ISO international standards
DIN 7 and DIN 6325 belong to German DIN standards
ISO standards are commonly seen in international drawings, European equipment, and global procurement documents, while DIN standards are frequently used in German machinery, European industrial drawings, and Taiwanese industry references.
In practice:
ISO 2338 is often compared with DIN 7
ISO 8734 is often compared with DIN 6325
Therefore, these four names are commonly reviewed together during sourcing and specification verification.
Quick Comparison of the Four Standards
Standard Group | Standard Source | Pin Type | Main Difference |
ISO 2338 (often compared with DIN 7) | ISO / German DIN | Unhardened parallel pins | Lower hardness, commonly m6 / h8, suitable for general positioning, slip-fit, and removable structures |
ISO 8734 / DIN 6325 | ISO / German DIN | Hardened and ground dowel pins | Higher hardness, commonly m6, suitable for precision press-fit, molds, fixtures, and high wear resistance |
ISO 2338 Dowel Pin Specification Summary
Item | Description |
Standard | ISO 2338; DIN 7 often used as comparable specification |
English Name | Parallel Pin / Dowel Pin |
Standard Materials | Carbon steel, austenitic stainless steel (SUS303 / SUS304 / SUS316) |
Tolerance Grades | m6, h8 (special tolerances such as g6 may also be specified) |
Diameter Range | 0.6–30 mm |
Common Applications | Machinery positioning, fixtures, equipment assembly, removable structures |
Comparable Standard | ISO 8734 / DIN 6325 are hardened dowel pins |
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1. What is ISO 2338?
ISO 2338 specifies unhardened carbon steel and austenitic stainless steel dowel pins, with diameter ranges from Φ0.6 mm to Φ50 mm.
Compared with hardened dowel pins such as DIN 6325, ISO 2338 pins have lower hardness but lower manufacturing cost and are more suitable for removable structures.
Common ISO 2338 tolerances include m6 and h8, while some drawings may specify special tolerances such as g6.
Tolerance Grade | Fit Type | Application | Description |
m6 | Tight fit | Press-fit, fixed structures | Pin diameter slightly larger than nominal size |
h8 | Loose fit | Slip-fit, removable assemblies | Pin diameter equal to or slightly smaller than nominal size |
g6 | Precision clearance fit | Precision sliding assemblies | Smaller and more precise clearance than h8 |
Actual selection should always be based on hole tolerance and drawing requirements.
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2. Differences Between ISO 2338 and ISO 8734 / DIN 6325
This is one of the most common questions.
Although ISO 2338, DIN 7, ISO 8734, and DIN 6325 all appear as cylindrical dowel pins, the specifications are different.
Item | ISO 2338 (DIN 7 comparable) | ISO 8734 / DIN 6325 |
Heat Treatment | Unhardened | Hardened and ground |
Typical Hardness | Carbon steel approx. 125–245 HV30 | Approx. HRC 58–62 |
Tolerance | m6 / h8 | Mainly m6 |
Material | Carbon steel, stainless steel | Usually SUJ2 or heat-treated S45C |
Application | General positioning, removable structures | Precision press-fit, molds, fixtures |
Wear Resistance | Standard | High |
The key difference is hardness and heat treatment condition.
ISO 2338 pins are unhardened and suitable for structures without high impact or wear demands.
ISO 8734 / DIN 6325 are hardened and ground, making them suitable for molds and precision positioning applications.
If a drawing specifies ISO 2338 or DIN 7, directly replacing it with DIN 6325 or ISO 8734 is not recommended.
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3. Common ISO 2338 Sizes
Diameter d | Standard Length Range |
Φ0.8 | 3–12 |
Φ1 | 3–20 |
Φ1.5 | 3–32 |
Φ2 | 4–40 |
Φ2.5 | 4–40 |
Φ3 | 4–50 |
Φ4 | 6–60 |
Φ5 | 6–60 |
Φ6 | 6–60 |
Φ8 | 10–80 |
Φ10 | 12–100 |
Φ12 | 12–120 |
Φ16 | 20–120 |
Φ20 | 24–120 |
Φ25 | 30–120 |
Φ30 | 30–120 |
These are common ISO 2338 standard ranges.
Sheng Fong Precision supplies from Φ0.8 mm and also supports custom lengths and non-standard dimensions.
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4. Material Selection for ISO 2338 Dowel Pins
Standard Materials
Material | Feature | Application |
S45C | Balanced strength, low cost | General machinery |
12L14 | Excellent machinability | Mass production |
SUS303 | Free-machining stainless steel | General anti-rust applications |
SUS304 | Standard corrosion resistance | Automation equipment |
SUS316 | High corrosion resistance | Medical, food, semiconductor |
Custom Materials Available
Material | Feature | Application |
SUS416 | Heat-treatable martensitic stainless | High-machining efficiency |
SUS420 | High hardness after heat treatment | Wear-resistant applications |
SUS630 | High-strength precipitation-hardening stainless | High-load structures |
Carbon steel pins may also receive:
Zinc plating
Black oxide
Phosphate coating
Stainless steel pins may receive passivation treatment.
Special tolerances such as h6 / h7 / m6 / g6 are also available.
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5. When Should ISO 2338 Be Used?
Not all dowel pins require hardened specifications.
ISO 2338 is suitable for:
Removable structures
Easy maintenance and repeated assembly/disassembly
Stainless steel applications
SUS304 / SUS316 versions provide corrosion resistance
Cost-sensitive applications
Lower manufacturing cost than hardened pins
General positioning and alignment
Suitable when high wear or heavy impact is not required
ISO 2338 Recommended Application Quick Guide
Suitable Situation | Recommended Reason | Common Configuration | Additional Notes |
Structures requiring repeated assembly and disassembly | h8 slip fit is easier to remove and reassemble repeatedly | h8 tolerance, stainless steel material | Suitable for maintenance, fixture assembly/disassembly, or equipment adjustment |
General positioning and alignment | Unhardened dowel pins are sufficient for standard assembly applications | m6 or h8 depending on hole tolerance | For high loads or repeated impact, specifications should be further confirmed |
Applications requiring corrosion resistance | ISO 2338 can use austenitic stainless steel materials | SUS303 / SUS304 / SUS316 | Suitable for automation equipment, semiconductors, medical equipment, and general anti-corrosion environments |
Cost considerations | Unhardened pins generally have lower manufacturing costs than hardened dowel pins | Carbon steel S45C or stainless steel | More suitable when high hardness or high wear resistance is not required |
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6. Sheng Fong Precision ISO 2338 Dowel Pins
Sheng Fong Precision supplies ISO 2338 dowel pins and can also assist with DIN 7 equivalent specifications.
Available options include:
Tolerances: m6, h8, g6, h6, h7
Materials: S45C, SUS303, SUS304, SUS316
Custom materials: SUS416, SUS420, SUS630
Diameter range: Φ0.8 mm – Φ30 mm
End machining: chamfered ends, 15° taper, deburring, internal threads
Surface treatment: zinc plating, black oxide, passivation
Delivery: standard stock items and urgent custom orders
If you have drawings specifying ISO 2338 or DIN 7, feel free to provide the PDF drawing for quotation and specification review.
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7. Frequently Asked Questions
1. Q: Are ISO 2338 and DIN 7 the same?
A: They are very similar and both belong to unhardened parallel pins. Their tolerance grades and material specifications are close, which is why they are often discussed together.
However, there are two important differences:
ISO 2338 measures total length including chamfers
DIN 7 nominal length excludes the end form, making actual length 0.3–8.0 mm longer
DIN 7 also allows flat, rounded, and chamfered ends, while ISO 2338 is typically chamfered-end.
2. Q: Can DIN 6325 replace ISO 2338?
A: Direct substitution is not recommended.
DIN 6325 is hardened and ground, with significantly higher hardness. It becomes harder to remove after press fitting and may damage hole walls.
3. Q: How should I choose between m6, h8, and g6?
A:
m6 → tight fit / press-fit
h8 → removable / slip-fit
g6 → precision sliding fit
Selection should match hole tolerances.
4. Q: Does ISO 2338 mean “non-heat-treated”?
A: Yes.
ISO 2338 specifically defines unhardened dowel pins.
For hardened versions, ISO 8734 should be used.
5. Q: What is the difference between DIN 7 and DIN 6325?
A:
DIN 7 → unhardened dowel pin standard
DIN 6325 → hardened and ground dowel pin standard
DIN 7 is for general positioning and removable structures, while DIN 6325 is for precision press-fit and wear-resistant applications.
6. Q: Why can’t ISO 2338 and ISO 8734 be directly interchanged?
A: Because they define different types of pins.
ISO 2338 → unhardened pins
ISO 8734 → hardened pins
Hardness, manufacturing methods, and intended applications differ.
7. Q: The drawing only says “Dowel Pin.” How can I identify the correct standard?
A: Check:
Material
Hardness
Tolerance
Surface treatment
General removable structures are usually closer to ISO 2338 / DIN 7.
Molds, fixtures, and precision press-fit applications are usually closer to ISO 8734 / DIN 6325.
If you need ISO 2338 or DIN 7 dowel pins, or need assistance confirming ISO 8734 / DIN 6325 specifications, feel free to contact Sheng Fong Precision.
LINE: @s9000
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