How to Select Locating Pins Info Types of locating fixturing pins dowels alignment How to Select Locating Pins

Images credits: John Sam Tool Co.; Misumi USA; Olson Machining, Inc. 

 

Locating and fixturing pins are press-fit, removable hardware devices designed to align or affix two work pieces to very small tolerances. When translation mechanisms are not stable or precise enough to place objects in position for a particular process, locating and fixturing pins can ensure an accurate alignment. They can be activated manually, pneumatically, hydraulically, or electrically. Spring locating pins are not covered in this tutorial, but these devices and their specifications can be examined on GlobalSpec's Spring Locating Pin Selection Guide

 

Locating and Fixturing Pin Operation

Locating and fixturing pins are typically meant to be used in conjunction with a mating anchor or bushing. They align components in many high-stress applications along their longitudinal axis. Two pins--of different styles and lengths--are usually used together to compensate for dimensional differences between mounting holes, and to correctly position the workpiece during pin insertion. This repeatability is useful when machining interchangeable components. Most pins have a tapered or conical shape to ease insertion. It may be necessary to adopt a pin mounting technique that will allow replacement if the locating or fixturing pin becomes worn.

 

Images credit: Misumi Corp.

 

Locating and Fixturing Pin Production

Like many cylindrical hardware devices consisting of metal, locating and fixturing pins are roll formed with minor alterations to change individual specifications. The production method is visualized in the infographic below.

 

 

Pin Material

Common locating and fixturing pin materials include:

  • Aluminum is light, malleable, ductile, thermally and electrically conductive, and resistant to oxidation. It is not suitable for heavy loads.
  • Brass has good temperature ductility, is electrically conductive, has excellent corrosion resistance, and is relatively strong.
  • Plastic is lightweight, easily molded, corrosion resistant, and inexpensive, but it can only handle light loads.
  • Hardened, ground steel undergoes a heat treatment process that compacts carbon atoms, resulting in a stronger but more brittle version of the metal. If uncoated, it is likely to oxidize under certain conditions.
  • Unhardened steel is more malleable and less expensive than hardened steel, but also cannot handle extreme loads. It is vulnerable to corrosion.
  • Stainless steel is corrosion resistant, aesthetically appealing, and exceptionally strong, but is also more expensive than other steel options.
  • Exotic metals, like titanium, have properties that are especially suited for the application. These are the most expensive option as well.

 

Locating and Fixturing Pin Configurations

Varieties of locating and fixturing pins are produced for specific applications, or to be used cooperatively to promise a correct alignment.

 

Pin Head Styles

The head is the portion of the pin that is inserted into the bushing or anchor, but provides no positive grip. Some heads may have a small air vent to relieve pneumatic pressure.

 

 

Image credit: Alliance Communications Inc.

 

Pin Shank Styles

The shank is the section of the pin that is installed in the mounting fixture, but does not come in contact with the workpiece. Bottom-mount shanks are the most common and easiest to install, but side-mount and top-mount shanks are available as well.

 

 

 

 

 

Types of Locating and Fixturing Pins

  • Bullet-nose dowels have a long, tapered nose. They are similar to bullet-nose pins, explained below, but have a smaller locating shoulder. They are almost always used with a bushing.

How to Select Bullet-nose Dowels

Image credit: Carr Lane 

  • Bullet-nose pins have a short, round, or diamond tip to align two pieces of a fixture. Usually, round and diamond bullet-nose pins are used together, providing location on two axes. These are almost always used with a bushing.

 How to Select Bullet-nose Diamond Pin

Image credit: Carr Lane    

      

  • Clamping pins use a collar-adjustable type of locating pin that can clamp materials of varying thicknesses. Some clamping pins have a lock mechanism.

 How to Select Clamping Pins Locate Fixture   

Image credit: Carr Lane

  • Cone locator pins can compensate for a moderate amount of misalignment. They are similar to round or diamond locating pins, but have cone-shaped tips.

 How to Select Cone Locator Pins

Image credit: Carr Lane

 

  • Diamond locating pins have four flat, diamond-shaped edges on the head. They are often used with a round pin to provide multi-axis alignment.

 How to Select Diamond Locating Pins Fixture

Image credit: Carr Lane

  • Drift pins have a tapered end that are placed into bolt holes that are somewhat aligned. As the pin is driven through the holes the pieces become aligned, allowing for bolting or riveting.

 How to Select Drift Pin Locate Fixture

Image credit: Klein Tools

  • Floating locating pins are similar to diamond pins. They provide precise, single-axis location while floating in the perpendicular axis. This is usually used with a round pin, as well.

 How to Select Floating Locating Pins Fixture axis single

Image credit: Carr Lane

  • Indexing/pop pins are spring-loaded alignment devices. These hardware pieces could be threaded, but nearly always have a handle or grip

 How to Select Indexing Pop Pins Locate fixture

Image credit: Riteon Corp.

  • L-pins are removable locating pins with an offset handle. A cable can be attached to the pin handle.

 How to Select L pin locate fixture pins

Image credit: Carr Lane

 

  • Powered pins are sophisticated locating pins that are actuated via electric, hydraulic, or pneumatic power. These pins can actively compensate for misalignment.

 

Image credit: Welker Engineered Products

  • Quick-release pins (ball lock) use a spring-loaded steel ball to provide positive gripping action. A button or lever releases the pin for removal.

 How to Select ball lock quick release locate fixture pins

Image credit: Jergens Inc.

  • Round locating pins use a round, tapered tip. They are often used in conjunction with a diamond-tipped pin, and a bushing as well, to align components on multiple axes.

 How to Select Round Locating Pin Fixture Taper

Image credit: Carr Lane

  • T-pins are similar to L-pins, but with a T-shaped grip and the option of having a locking mechanism interacting with the bushing.

 How to Select T-pins locate fixture

Image credit: Carr Lane

 

Resources

 

Carr Lane - Alignment Pins; Locating Pins

 

Misumi USA Inc. - Locating Pins and How They Are Used; How to Use Locating Pins

 

ShopWiki - Press Fit Locating Pins