Return pass practice for the high mill of a seamless-pipe mill

In the production of seamless tubing, wherein a shell is transferred to a plug rolling mill and said shell is rolled through work-rolls in a first plug-rolling pass consisting of pushing the shell over a plug attached to a supported mandrel bar, said plug lying within a roll groove of the work rolls, the entry side of said plug being tapered in a direction counter to the travel of said shell, whereby the entirety of said shell is drawn over the plug by the rolling friction of the roll groove, thereafter repeating the rolling operation for at least one additional pass on said shell, the improvement for significantly decreasing the time required for completion of said additional pass, which comprises,

• (a) subsequent to said first pass, reversing the rotation of said work-rolls, rotating the shell about 90.degree. around its longitudinal axis, and
• (b) pushing the shell back through said reverse-rotating work-rolls to effect the additional pass over the same plug, said plug being connected to the mandrel so as to transmit the tension force on the plug to the mandrel, the exit side of said plug being provided with a taper in a direction counter to the reverse travel of said shell, whereby said shell is drawn over said plug by said work-rolls to perform said additional pass.