Articles 

Loose Change

2011-02-23

1.Paint and foreign material causes difficult assembly. Are there features on fasteners that can clean out this material. How good are they at this job? Jamming, low clamp loads, hard to install problems due to excessive torque to drive and seat, resistance to finger starting are but a few of the problems that are caused by dross and various debris in the threads. The problem has been further exacerbated by the increased use of thick corrosion resistant coatings and very hard paint primers. The first solution that may occur to the designer is to use a paint cleaner feature on the bolt. There are several types available as shown on the attached illustration. The most common type is the Type 23 shown. This type is used for tapping into medium to thick metal and for cleaning out partially filled holes. Like all the types of cleaning features mentioned below, the feature functions by the cutting action of a sharp, exposed edge of the thread cross-section. This feature is usually cut, slit, or formed in the part as a secondary manufacture step.