Dowel pins
Parallel locating pins, length datums, material conditions, extraction features and the limits of nominal-size fit comparisons.
Tags: components, fasteners, assembly, locating
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Elesa+Ganter's DIN 6325 drawing measures l1 end to end, including shaped ends, with length class js14. Pinstructure's DIN7m6 nominal length excludes the radiused ends. Elesa+Ganter says its m6 dowel with an H7 location hole can produce a transition fit. Compare actual diameter limits and usable cylindrical engagement before assuming interference or blind-hole depth. DIN 6325, p. 1, Pinstructure DIN7m6.
Identity and purpose
The cylindrical outside surface locates mating parts. Elesa+Ganter describes DIN 7979 pins for positioning and connecting machine parts. Elesa+Ganter DIN 7979.
ISO 2338 covers unhardened steel and austenitic stainless. ISO 8734 covers hardened steel and martensitic stainless. ISO 2338 catalog, ISO 8734 catalog.
Dimensions and the length datum
Diameter and length need their own tolerances and units. In the Elesa+Ganter DIN 6325 drawing, d is the diameter, while l1 spans the end-to-end length, including the shaped ends. The table identifies diameter class m6 and length class js14; the end features have separate dimensions. This drawing interpretation applies to that product sheet. DIN 6325, p. 1
A different convention appears in Pinstructure's DIN7m6 offering: its stated nominal length measures only the parallel surface, excluding the radiused ends. The supplier lists mild steel, A1 stainless and A4 stainless versions. These are supplier-specific descriptions, not additional material claims about ISO 2338. Pinstructure DIN7m6
Synthesis: equal catalog diameter and length numbers can therefore describe different overall envelopes or locating lengths. Overall length, usable cylindrical engagement, end relief and blind-hole depth are separate quantities. A diameter tolerance symbol does not define any of those axial quantities. The distinction follows from the two length conventions above. DIN 6325 drawing, DIN7m6 length note
Material condition and construction
The following distinctions describe the named sources; they are not an interchangeability table.
| Form or condition | What the source establishes | Applicability boundary |
|---|---|---|
| Unhardened parallel pins | ISO 2338:1997 names unhardened steel and austenitic stainless steel. | The public catalog does not supply this article with the standard's detailed hardness, finish or dimensional requirements. ISO catalog |
| Hardened parallel dowels | ISO 8734:1997 names hardened steel and martensitic stainless steel. | “Stainless” without its family or grade does not identify this condition. ISO catalog |
| Ground hollow alignment dowels | SPIROL's GD100 is made from strip steel with a ground outside diameter. The product page describes low-carbon steel and optional case hardening for wear resistance or heat-treated high-carbon steel for improved shear strength. | SPIROL's replacement claim concerns ISO 8734 solid dowels in alignment applications; it is not a universal strength equivalence. SPIROL GD100 |
| Spring alignment dowels and dowel bushings | SPIROL describes roll-formed hollow parts with lead-in chamfers and flexibility to accommodate hole variation. Its dowel bushings allow a fastening bolt through the inside diameter; its spring dowels are not intended for use with bolts. | These are distinct SPIROL product functions. A hollow bore alone does not establish spring behavior, bolt clearance or a suitable hole tolerance. SPIROL spring alignment products |
Synthesis: solid versus hollow describes construction; hardened versus unhardened describes material condition; ground describes surface manufacture. These properties answer different questions. A common outside diameter is insufficient to transfer a load rating between constructions, and a material label alone does not establish wear life or corrosion suitability. SPIROL GD100 material options, ISO material-family titles
Extractable pins and blind holes
An extraction thread is another independent feature. Elesa+Ganter's DIN 7979 steel dowel has an internal thread for removal with a puller handle or slide hammer. Its flat section vents trapped air, and a protective countersink guards the thread during installation. The supplier describes blind-hole use, hardened steel at HRC 60 ±2, and a ground locating diameter. It states that the dimensions correspond to ISO 8735. These statements apply to this offering, rather than every internally threaded pin. Elesa+Ganter DIN 7979
Synthesis: the internal thread provides extraction access; it does not turn the pin into a through-bolt or prove that the assembled joint has axial retention. Whether extraction remains possible also depends on access to that end after assembly. DIN 7979 removal description
Fit is a relationship between two actual limits
Elesa+Ganter states that its DIN 6325 dowel with an H7 location hole can produce a transition fit. It also warns that its dimensions do not conform to ISO 8734, although partial replacement is possible. Thus neither “m6” nor a DIN/ISO cross-reference means guaranteed interference. DIN 6325, p. 1
Dimensional synthesis: for circular pin and hole diameter limits expressed in the same unit, define diametral clearance as hole diameter minus pin diameter:
- Minimum clearance = minimum hole diameter − maximum pin diameter.
- Maximum clearance = maximum hole diameter − minimum pin diameter.
A wholly positive interval indicates clearance; a wholly negative interval indicates interference; an interval crossing zero permits both. Zero is the limiting line-to-line case. These are size comparisons, not installation-force calculations. They assume that the stated limits apply to the surfaces and condition being assembled; they do not include position error, form error, surface texture or temperature effects. The algebra explains why nominal size alone cannot settle the transition-fit case described by the supplier. DIN 6325 fit statement
Coverage and source versions
This reference addresses metallic locating and alignment parts. It establishes no universal interference allowance, hole-preparation method, engagement ratio, installation force, shear capacity or structural approval. Those outcomes remain dependent on the selected product, mating components, loading and environment. Supplier dimensional correspondence is narrower than complete interchangeability.
Sources were accessed October 30, 2026 PDT. The inspected Elesa DIN 6325 PDF carries 2/2026 in its page-1 footer; its drawing and table were visually inspected. The linked DIN 7979, Pinstructure and SPIROL web pages have no displayed technical revision date in the cited descriptions, so their applicability is bounded by the named offerings and access date.
Only public ISO catalog metadata was used: ISO 8734:1997 is listed as edition 2, confirmed in 2023; ISO 2338:1997 is listed as edition 3, confirmed in 2023. These catalog labels do not substitute for inspection of the full standards, whose tables and normative requirements were not used here. ISO 8734 metadata, ISO 2338 metadata