Four Locating Pin Families — One Decision Framework
Locating pins come in four distinct families, each engineered for a specific fixture scenario. Choosing the wrong family wastes budget and compromises accuracy. This guide walks you through the selection process in three steps.
Step 1 — Identify Your Primary Function
| Pin Family | Primary Function | Best For | Product Count |
|---|---|---|---|
| Standard Dowel Pins | Fixed-position datum reference | CNC fixtures, assembly jigs, inspection gauges | 360 |
| Height Adjusting Pins | Variable-height workpiece support | Fixtures handling multiple part variants with different datum heights | 69 |
| Jig & Drill Bushings | Guided tool positioning | Drilling jigs, reaming fixtures, boring guides | 79 |
| Welding Locating Pins | Spatter-resistant positioning | Robotic welding cells, resistance welding, BIW assembly | 76 |
Step 2 — Check Environmental Conditions
Even after identifying the primary function, environmental factors may shift your selection:
- Weld spatter exposure: Any fixture within 300 mm of a weld arc needs spatter-resistant pins. Standard dowels will seize within days. Use DLC-coated or ceramic-sleeved welding pins.
- Corrosive coolant: Water-based coolants corrode standard SKD11 pins. Switch to SUS304 stainless steel, accepting the lower hardness (~187 HB vs 58-62 HRC).
- Thermal cycling: Fixtures near heat sources (welding, forging) expand and contract. Use diamond pins for the secondary locator to accommodate thermal expansion along one axis.
- Cleanroom requirements: Food and medical manufacturing may prohibit lubricants. Specify oil-free bushing materials.
Step 3 — Verify Tolerance and Fit Requirements
Each pin family supports different tolerance grades:
| Fit Type | Pin Tolerance | Bushing Bore | Application |
|---|---|---|---|
| Press-fit (permanent) | m6 | H7 | Permanent datum pins, never removed |
| Transition (semi-permanent) | h7 | H7 | Replaceable pins, periodic maintenance |
| Clearance (removable) | g6 | H7 | Spring pins, retractable locators, thermal compensation |
Decision Flowchart Summary
Follow this sequence for rapid selection:
- Is the fixture exposed to weld spatter? → Welding Locating Pins
- Does the fixture need guided drilling/reaming? → Jig & Drill Bushings
- Does the workpiece datum height vary by >±0.5 mm between variants? → Height Adjusting Pins
- None of the above? → Standard Dowel Pins (cylindrical + diamond pair)
For the standard dowel pin selection, use the cylindrical vs diamond comparison to choose between pin geometries.