An experimental machine using elastomer rod has been developed for the forming of tee-junction on metal tubes. This was achieved by applying loading-unloading cycles to the tube and the elastomer simultaneously. The success of the operation is governed by the so called “clearance height” which controls the relationship between the displaced volume of the elastomer and the reduced length of the tube. Present experiments have confirmed the validity of the empirical expression previously found. The upper-bound theory is found to be in good agreement with experimental results, for predicting the total forming load. The experiments were performed on materials with different work-hardening characteristics. In addition, the effects of other variables on the process are examined.