The 15.01.352 bar main collet clamping tube is the version designed for machining bars up to maximum diameter 20 mm on Gildemeister-DMG Mori AS20, GS20 and GM20AC multi-spindle automatic lathes. The 9012E bar collet is mounted on the main collet clamping tube and provides bar clamping inside the main spindle during the work cycle. The function of the main collet clamping tube is to transmit the axial movement required to close the collet, converting the backward movement of the actuating unit into controlled clamping force on the material. During the closing phase the main collet clamping tube moves axially backwards through clamping fingers 0801303 on AS20 machines and through clamping fingers 3101108 on GS20 and GM20AC machines; this movement closes the collet and keeps the bar locked in the correct position for turning and front machining operations. The two left-hand threads are essential for locking the system and for adjusting the closing force of the bar collet by means of threaded nut 0801401. Correct adjustment provides a clamping force suitable for the bar diameter, avoiding both insufficient gripping, which may cause slipping or dimensional variation, and excessive load, which may accelerate wear of the collet, disc spring 1501003, nut and connected axial elements. From a kinematic point of view, the main collet clamping tube works within the chain formed by the actuating sleeve, clamping fingers, bar main collet clamping tube, nut 0801401, spring 1501003, collet 9012E and main bar spindle. Its geometric accuracy, thread quality and coupling stability directly affect clamping repeatability, bar concentricity, cutting stability and finished part quality. A worn, deformed or incorrectly adjusted main collet clamping tube can cause material micro movements, turned diameter variations, form errors, loss of repeatability, vibration, tool breakage, damage to the bar collet and increased production scrap. During preventive and extraordinary maintenance it is important to check the condition of both left-hand threads, support surfaces, the 9012E collet mounting area, coupling with nut 0801401, main collet clamping tube straightness and the absence of deformation or seizure marks. Replacement is recommended when wear, adjustment difficulty, abnormal play, inconsistent collet closing or loss of accuracy on machined parts is detected. For production departments and maintenance technicians operating AS20, GS20 and GM20AC machines, availability of the 15.01.352 bar main collet clamping tube allows quick restoration of the bar clamping assembly and helps reduce machine downtime.