Combination of friction drilling and form tapping processes on dissimilar materials for making nutless joints

In this article, a new method for the rapid and economical production of ‘nutless’ bolted joins is presented, using a combination of two hole-making techniques, namely, form drilling and form tapping. The combined method achieves a quick way for the production of threaded holes on couples of dissimilar metal alloys, as it is the case of steels and aluminium alloys. After the simultaneous form drilling on the aluminium–steel pairs and followed by form tapping, a fastener can be introduced and screwed for achieving a tight bolted joint, without any necessity of nut. However, form drilling and threading are performed consecutively in the same machine tool, reducing the whole process time. The process parameters were studied for reducing the gap between surfaces and producing a good cup for making the posterior threading. Then, mechanical testing of several test pieces resulted in a similar behaviour than traditional bolted joints. Finally, corrosion tests were performed for a better understanding of the joint manufactured. In this way, savings in time and money are derived from the application of the approach. Target markets for the new approach are the light boilermaking industry in order to eliminate either welding beads or classical bolted joints using nuts.

Analysis of Intermittent Metal Forming with Planetary Rollers by Numerical Simulation

Processing profiles through form tapping process with planetary rollers is used in industry, especially in the automotive industry. Even though this process exists for several decades, few studies dealing with this topic were published. The main objective of this paper was to determine the influence of the two process parameters on three important values which influence the quality of profiles: the rolling force, the state of stresses in the deformed material and on the rolling time. The material used was carbon steel AISI 1015.

Finite Element Modeling for Tap Design Improvement in Form Tapping

The form tapping process typically yields unfinished threads known as split crests. Thread quality can be greatly improved by reducing the size and severity of split crest formation. This paper develops a finite element model to simulate form tapping with an eye towards the reduction of split crests. The model is validated against linear scratch experiments, and simulations are compared to actual tapping. The effects of various tap design parameters and tapping process conditions on the formation of split crests are investigated to strive toward an optimal tap design.