The 15.01.601 bar main collet clamping tube is the version designed for machining bars up to maximum diameter 25 mm on Gildemeister-DMG Mori AS20, GS20 and GM20AC multi-spindle automatic lathes. The 9017E bar collet is mounted on the main collet clamping tube, sized for clamping larger bar diameters than the 20 mm version and intended to keep the bar stable inside the main spindle during machining phases. 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 machine cycle 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 backward movement closes the collet and locks the bar in the correct position for turning, drilling, front machining and operations connected to the multi-spindle cycle. 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 allows the clamping force to be matched to the bar being machined, avoiding insufficient gripping that may cause slipping, dimensional variation and loss of concentricity, but also avoiding excessive loads that may stress collet 9017E, the main collet clamping tube, disc spring 1501003, nut 0801401 and the axial control 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, adjustment nut, disc spring, bar collet and main bar spindle. Its efficiency directly affects bar stability, clamping repeatability, turned diameter accuracy, cutting regularity and finished part quality. In the version for bars up to 25 mm, clamping control is especially important because the increased material section involves higher loads, greater inertia and a greater need for stability during metal removal. A worn, deformed or incorrectly adjusted main collet clamping tube can cause bar micro movements, measurement errors, form defects, vibration, cutting instability, tool breakage, damage to the bar collet and increased scrap. The component also has an indirect function in the entire kinematics of the multi-spindle lathe, because correct bar locking is required for synchronization with the main spindles mounted in the spindle drum, with radial and axial slides, with front toolholder spindles and with auxiliary systems for feeding, machining and unloading. During preventive and extraordinary maintenance it is important to check the condition of the two left-hand threads, support surfaces, the 9017E collet mounting area, coupling with nut 0801401, main collet clamping tube straightness and the absence of deformation, wear or seizure marks. Replacement is recommended when adjustment difficulty, loss of closing force, abnormal play, thread wear or loss of accuracy on machined parts appears. For production departments and maintenance technicians working on AS20, GS20 and GM20AC machines, availability of main collet clamping tube 15.01.601 allows quick restoration of the bar clamping assembly and reduces the risk of extended machine downtime.