This document discusses quality assurance for metric thread screw production. It defines quality assurance as activities that ensure a product will meet quality requirements. It describes implementing quality assurance through mechanical integrity testing and conforming to applicable standards. It also provides an overview of screw threads, describing the nominal contour and tolerance series for ISO metric screw threads. It discusses material selection factors and conducting tests to measure thread geometrical accuracy and preload force during the manufacturing process.

1. A CASE STUDY ON QUALITY
ASSURANCE OF A METRIC THREAD
SCREW
SHANKHA SHUBHRA
G0SWAMI
Roll No- 17101203011

2. What is QUALITY ASSURANCE?
Quality assurance is defined as activities implemented
within the quality system that can be demonstrated to
ensure that a product will fulfil requirements with regard to
quality. Quality itself can be related to reduction of
variation, value-added, and conformance to specifications.

3. HOW TO IMPLEMENTATION ‘QUALITY ASSURANCE’
 Mechanical Integrit And Testing
• Must Conform to the Requirements of the
• Applicable Code such as:
• ASME
• ANSI
• ASTM
• NFPA
• CGA
• ISO
• And any other applicable codes

4. OVERVIEW OF SCREW
In the case of ISO general purpose metric screw thread production,
which is the most commonly applied thread in machine
construction and technology, the surfaces of the thread are
described with parameters defined in ISO 68-1:1998, which are
subsequently tolerated into the material, assuming as the zero line
the nominal contour of the thread. A set of tolerance series and
tolerance fields of the tolerated diameters.

5. The material selection is influenced by required strength,
temperature, resistance to corrorsion, joint materials, and cost. To
keep costs down, use standard materials. Specifying a fastener
material with a specific chemical analysis adds time and cost. Often,
a standard fastener can be altered by heat treating, cold working, or
coating to meet special needs.
• machined object: external thread diameter is ready-made, and will not be machined
again,
• -machined material is EN 41Cr4 steel,
•
• -tools: cutting edge with universal metric screw thread shape with 1 mm pitch,
•
• -machining tool: universal lathe with thread turning option by use of kinematic
coupling method,
•
• -manufacturing methods: thread turning by use of kinematic coupling method,
• -feed: feed equal to thread pitch,
• -in feed: radial plunge, used for smaller thread leads and strongly hardening
• materials, was conducted in several passes, as recommended: 5 passes, infeed
•
• depth per pass: 0.20, 0.15, 0.13, 0.10, 0.08 mm,
•
• -machining speed: as recommended by the tool producer: triangular one-side insert
made of coated cemented carbide – vc ϵ (80,160) m/min.

6. THEORY AND CALCULATIONS
• Testing the geometrical accuracy of the
thread during the manufacturing
PROCESS

7. Measurement of the preload force on
screw
• Vibration tests:

8. ULTRASONIC METHOD
• The basic feature of the ultrasonic method is to determine the
running time of a shock wave as it travels through the bolt or stud.
• A number of material factors, such as density, Young’s modulus,
• sound velocity (which depends also on the tension), temperature,
• etc., influence this measurement. Especially the sound velocity
• varies from batch to batch of material.

9. PROBLEM FORMULATION
• There are many quality related problems which were
observed during the work in industry. The Rejection
observed was some amount(9.45%) which was
alarming due to some critical manufacturing defects.
Raw material was also rusty. The screw dislocation
is slightly more difficult to visualize. The motion of a
screw dislocation is also a result of shear stress, but
the defect line movement is perpendicular to
direction of the stress and the atom displacement,
rather than parallel. To visualize a screw dislocation,
imagine a block of metal with a shear stress applied
across one end so that the metal begins to rip.
• Screw positioning error. Wear and damages on
screw fastening bits.

10. RESULTS AND DISCUSSION

12. CONCLUSIONS
• The model of the manufacturing system was
elaborated and the influence of factors affecting
the technological quality assurance of the
product was analyzed. A more thorough analysis
was made to assess the effect of tool flank wear
on the accuracy of the metric screw thread in the
manufacturing process model. At the same time,
capacity analysis was performed for the entire
manufacturing system