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Engineering Technologies
ArticleName Ensuring precision for small arms lock assembly with consideration for interface contact stiffness
DOI 10.17580/cisisr.2018.01.08
ArticleAuthor A. S. Yamnikov, A. A. Malikov, O. S. Kashmin, D. I. Troitsky.

Tula State University (Tula, Russia):

A. S. Yamnikov, Dr. Eng., Prof., Chair of Manufacturing Technology, e-mail:
A. A. Malikov, Dr. Eng., Prof., Head of the Chair of Manufacturing Technology
O. S. Kashmin, Cand. Eng., Associate Prof., Chair of Manufacturing Technology


TTS Translation and Software Agency (Tula, Russia):
D. I. Troitsky, Cand. Eng., Associate Prof., Director


In small arms manufacturing the lock dimensional chain final link precision is secured with manual file fitting and removing the tolerance intentionally left on the recoil lugs. The manual process reduces the contact stiffness of the lock components, and the final link dimension (between the cylindrical gauge end that simulates a cartridge, and the breeching lock face) set during the assembly is distorted when the breech lock components are exposed to shot impact loads. For this reason, the cylindrical cartridge dummy used for the initial assembly is sized to allow for subsequent plastic deformation at the breech lock component interfaces. The deformation value is determined experimentally on an ad hoc basis. The study shows that the plastic deformation value depends of the force applied to the interface surfaces, and on the loaded contact area. The area, in its turn, depends on the physical and chemical properties of the interface materials and the surface finish (roughness, undulation, geometric shape precision.) Polynomial expressions have been obtained experimentally for the interface plastic deformation vs. relative positioning errors and surface finish relation for parts made of typical military steel grades. To study the relation between the interface surface machining methods and contact stiffness flat specimens, 50RA steel quenched to HRC 40–45 (the roughness RZ is 10–15 μm) were machined as follows: peripheral pregrinding; flank milling; file crosswise (at 45°) movements. The results and curves generated after processing the measurements made with a HOMMEL TESTER W55 instrument show that finish flank milling yields the best results.

keywords Rifles, contact stiffness, dimension chain, plastic deformation at part interfaces, Abbott-Firestone curve, finish machining, quenched steel specimens

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