The present invention concerns methods and compositions for the treatment of cancer and cancer cells using altered poxviruses, including a vaccinia virus that has been altered to generate a more effective therapeutic agent. This regulative member press-contacts one end of the gear to maintain the gear exactly perpendicular to an axis of the rotary shaft. The pathway captures a plurality of spherical balls between the ball nut and the ball screw, the balls being configured for circulation through the return passage and around a portion of the helically extending retention grooves. Compared with the currently-used roasting method, the method has the advantages of decreasing the reaction temperature by about 700\xb0 C. A secondary threaded element follows the primary threaded drive and is configured to support the mold cover if the primary threaded drive fails.