Apply Quality Control, Testing, and Troubleshooting Techniques

Applying Quality Control, Testing, and Troubleshooting Techniques

This chapter covers the essential skills of Red Seal competency block 11 for the Tool and Die Maker trade. You will learn dimensional verification methods, testing procedures, systematic troubleshooting techniques, and the application of relevant Canadian standards. Mastering these techniques is crucial: it distinguishes the machine operator from the qualified tool maker.

1. Fundamentals of Quality Control in Tool Making

1.1 Definitions and Principles

Quality control (QC) is a systematic process aimed at verifying that parts and tooling meet technical specifications. In tool making, these specifications are often expressed as tolerances — the allowable deviation between a nominal dimension and the actual measured dimension.

The three fundamental principles of QC in tool making are:

Traceability: each measurement must be linked to a certified reference standard (e.g., grade 0 or AAA gauge blocks).

Repeatability: the same operator, using the same instrument, must obtain the same results on the same part.

Reproducibility: two different operators must obtain comparable results using the same instrument.

1.2 International System of Units (SI) and Tolerances

In Canada, the metric system is the legal standard, but the tool making industry frequently uses the imperial system (inches). The Red Seal exam requires mastery of both systems and their conversions.

System	Base Unit	Common Sub-units	Equivalence
Metric	Millimetre (mm)	0.001 mm = 1 µm	1 mm = 0.03937 in
Imperial	Inch (in)	0.001 in = 1 mil	1 in = 25.4 mm

Quick conversion rule: to convert inches to millimetres, multiply by 25.4. To convert millimetres to inches, divide by 25.4. Example: 0.500 in × 25.4 = 12.70 mm.

1.3 Applicable Canadian Standards

Quality control in tool making relies on several national standards:

CSA W47.1: Certification of fusion welding — applicable if you must inspect welded tooling.

CSA B149.1: Natural gas and propane code — relevant for tooling used in environments where gases are present.

CSA B44: Elevator safety code — applicable to maintenance tooling in this field.

ISO 9001: Quality management systems — although not mandatory for the Red Seal, this standard is often required by employers.

For the tooling itself, tolerances are generally defined according to ISO 286 classes (fit system). Common fits are:

H7/g6: sliding fit (minimal clearance)

H7/k6: uncertain fit (transition)

H7/p6: tight fit (interference)

2. Measuring Instruments and Their Use

2.1 Direct Measuring Instruments

The caliper: typical accuracy of 0.02 mm or 0.001 in. It measures outside dimensions, inside dimensions, and depths. Common pitfall: never use a caliper to measure a rotating part (risk of jaw wear).

The micrometre: accuracy of 0.001 mm (0.0001 in). It comes in outside, inside, and depth versions. Reading is done in three steps:

28.Read the main graduation (sleeve scale).

29.Read the thimble graduation (100 divisions = 0.01 mm per revolution).

30.Add the two values together.

Reading example: Sleeve at 12.50 mm, thimble at 0.37 mm → total reading = 12.87 mm.

The dial indicator: used for comparative measurements (difference from a standard). Its typical resolution is 0.01 mm or 0.001 mm.

2.2 Optical and Electronic Measuring Instruments

Optical comparator: magnifies the part's profile onto a screen for comparison with a template. Ideal for complex shapes.

Coordinate measuring machine (CMM): measures the X, Y, Z coordinates of a part with an accuracy of approximately 0.001 mm. It is indispensable for precision tooling.

Laser interferometer: used for very high precision measurements (nanometric), primarily in reference dimensional metrology.

2.3 Instrument Verification

Before each use, instruments must be verified against a reference standard. The reference temperature is 20 °C (68 °F). A temperature variation of 1 °C on a 100 mm steel part causes an expansion of approximately 0.0012 mm — a significant error for tolerances of 0.005 mm.

Verification procedure:

40.Clean the measuring surfaces with a non-abrasive solvent.

41.Check the instrument zero (using a gauge block for micrometres).

42.Take three measurements on a certified gauge block.

43.If the deviation exceeds half the resolution, the instrument must be recalibrated.

3. Dimensional Control Techniques

3.1 Measuring Geometric Characteristics

Geometric tolerances (GD&T) are governed by the ASME Y14.5 standard (adopted in Canada). The essential symbols are:

Symbol	Characteristic	Definition
⏤	Straightness	The line must be straight within a given plane
⏥	Flatness	All points on the surface must lie within two parallel planes
⭘	Circularity	All points on the circumference must be equidistant from the centre
⌭	Concentricity	The centres of the circles must coincide
⊥	Perpendicularity	The surface or axis must be at 90° to a datum

Specification example: ⏤ 0.005 A means the straightness of the surface must be within a zone of 0.005 mm relative to datum A.

3.2 Thread Measurement Methods

Threads are measured with thread gauges (go/no-go) or by the three-wire method. The three-wire method is the most accurate for measuring the pitch diameter.

Pitch diameter formula (for ISO metric threads):

Dp = M - 3 × (d_w) + 0.866 × P

Where:

Dp = pitch diameter

M = measurement over wires

d_w = wire diameter

P = thread pitch

Example: For an M12 × 1.75 thread with wires of 1.008 mm diameter, if M = 12.50 mm:

Dp = 12.50 - 3 × 1.008 + 0.866 × 1.75 = 12.50 - 3.024 + 1.516 = 10.992 mm

3.3 Surface Inspection

Surface roughness (Ra) is measured with a profilometer. Typical values for tool making are:

Application	Ra (µm)	Ra (µin)
Roughing	3.2 - 6.3	125 - 250
Standard finishing	0.8 - 1.6	32 - 63
Precision finishing	0.2 - 0.4	8 - 16
Mirror polishing	< 0.1	< 4

Common pitfall: Ra roughness does not provide information about the surface form (waviness, isolated peaks). A low Ra does not guarantee good sealing.

4. Tooling Testing

4.1 Functional Testing

Functional testing verifies that the tooling produces conforming parts under real operating conditions. The standard procedure is:

67.Setup: install the tooling in the press or machine according to the instructions.

68.Initial adjustment: adjust the shut height, centring, and stops.

69.Dry run: perform a cycle without material to verify component movement.

70.Test with material: produce 5 to 10 test parts.

71.Inspection of test parts: measure critical dimensions and compare to specifications.

72.Adjustments: correct deviations by grinding, machining, or adjusting components.

4.2 Hardness Testing

Hardness is an essential property of tooling. Common scales are:

Scale	Indenter	Load	Application
Rockwell C (HRC)	Diamond cone	150 kgf	Hardened steels
Rockwell B (HRB)	1/16 in ball	100 kgf	Mild steels
Brinell (HB)	10 mm ball	3000 kgf	Cast parts
Vickers (HV)	Diamond pyramid	Variable	Thin materials

Approximate conversion rule: HRC ≈ (HV / 10) - 10. Example: HV 600 → HRC ≈ 50.

Common pitfall: never perform a hardness test on a cylindrical surface without proper support — the result will be inaccurate.

4.3 Non-Destructive Testing (NDT)

NDT methods detect internal defects without destroying the part. Common methods in tool making:

Liquid penetrant testing (PT): detects surface cracks. Applicable to non-porous materials.

Magnetic particle testing (MT): detects surface and near-surface cracks in ferromagnetic materials.

Ultrasonic testing (UT): detects internal defects (porosity, inclusions) through sound wave reflection.

Radiographic testing (RT): uses X-rays or gamma rays to visualize internal defects.

Regulatory requirement: NDT testing must be performed by personnel certified according to CSA W178.2 for welding. For non-welded tooling, certification is not mandatory, but competence is expected.

5. Systematic Troubleshooting

5.1 Problem-Solving Methodology

Troubleshooting in tool making follows a logical five-step approach:

88.Define the problem: describe the symptom precisely (e.g., excessive burr on the part, premature punch wear).

89.Collect data: measure, observe, and document operating conditions.

90.Identify possible causes: use an Ishikawa diagram (fishbone) to organize causes into categories (method, material, machine, manpower, measurement, environment).

91.Test hypotheses: change one variable at a time and observe the effect.

92.Apply the correction: implement the solution and verify its effectiveness over several cycles.

5.2 Troubleshooting Blanking Dies

Symptom	Probable Cause	Corrective Action
Excessive burr	Punch-die clearance too large	Reduce clearance or grind the edges
Material tearing	Clearance too small	Increase clearance or sharpen the edges
Premature wear	Insufficient lubrication	Improve the lubrication system
Broken punch	Misalignment	Check centring and guidance
Deformed part	Insufficient holding pressure	Increase the blank holder force

5.3 Troubleshooting Injection Moulds

Symptom	Probable Cause	Corrective Action
Part stuck on core	Insufficient draft	Increase the draft angle (1° to 3°)
Ejection marks	Ejection surface too small	Enlarge ejectors or add more
Weld line	Material temperature too low	Increase the barrel temperature
Sink mark	Insufficient holding pressure	Increase the pressure or hold time
Flash	Damaged parting line	Grind the parting line or check clamping force

5.4 Troubleshooting Forming Tooling

Springback problem: the metal returns to its original shape after forming. Corrective actions are:

Over-bend the curvature (compensate for springback).

Use a punch with a more pronounced angle.

Apply a coining operation to compress the material.

Springback compensation formula:

Corrected angle = Desired angle + (Desired angle × Springback factor)

The springback factor depends on the material: approximately 2% for mild steel, 5% for stainless steel, 10% for hardened aluminium.

6. Documentation and Traceability

6.1 Inspection Reports

Each inspection must be documented. The report must contain:

Part identification (drawing number, serial number)

Date and time of inspection

Inspector's name

Instruments used (with their certification numbers)

Measurement results (with applicable tolerances)

Decision (conforming / non-conforming)

Corrective actions if necessary

6.2 Certificates of Conformity

The certificate of conformity (C of C) attests that the tooling meets contractual specifications. It must be signed by an authorized person and accompanied by detailed inspection reports.

6.3 Non-Conformance Management

In the event of a non-conforming part, the standard procedure is:

119.Isolate the non-conforming part (red tagging).

120.Document the non-conformance (description, measurement, deviation).

121.Analyze the root cause (5 Whys method).

122.Decide: scrap, repair, or accept with deviation (if approved by the customer).

123.Follow up on the effectiveness of corrective actions.

7. Safety During Testing and Quality Control

7.1 Specific Hazards

Moving machinery: never measure a part while it is rotating.

Chemicals: cleaning solvents and penetrant testing products must be used with adequate ventilation.

Radiation: radiographic testing requires controlled areas and dosimeters.

Noise: ultrasonic testing can generate high noise levels — wear hearing protection.

7.2 Personal Protective Equipment (PPE)

Safety glasses with side shields (mandatory at all times).

Cut-resistant gloves when handling parts.

Safety shoes with steel toe caps.

Hearing protection in areas above 85 dB(A).

Summary

Quality control in tool making relies on the traceability, repeatability, and reproducibility of measurements.

Measuring instruments must be verified against certified standards at 20 °C.

The inch-to-millimetre conversion uses the factor 25.4.

Geometric tolerances follow the ASME Y14.5 standard.

Functional testing follows a six-step procedure: setup, adjustment, dry run, test with material, inspection, adjustments.

Rockwell C hardness (HRC) is the most common measurement for hardened tool steels.

Non-destructive testing (liquid penetrant, magnetic particle, ultrasonic) detects defects without destroying the part.

Systematic troubleshooting follows five steps: define, collect, identify, test, correct.

Each inspection must be documented with a complete and traceable report.

Pitfalls to Avoid

146.Confusing resolution and accuracy: a resolution of 0.001 mm does not guarantee an accuracy of 0.001 mm. Accuracy depends on calibration and technique.

147.Neglecting temperature: measuring a hot part gives inaccurate results. Wait until the part reaches 20 °C.

148.Using a damaged instrument: a micrometre with a scratched thimble or a caliper with worn jaws gives erroneous measurements.

149.Forgetting the zero: always check the zero before each series of measurements.

150.Confusing hardness scales: HRC and HRB are not interchangeable. An HRC of 60 is very hard, but an HRB of 60 is very soft.

151.Ignoring springback: never assume that forming produces exactly the punch angle.

152.Changing multiple variables at once: when troubleshooting, change only one variable at a time to identify the real cause.

153.Not documenting: a measurement that is not documented is a lost measurement. Always record results immediately.

154.Using the wrong ISO fit: H7/g6 is a sliding fit, H7/p6 is an interference fit. Confusing them causes failures.

155.Neglecting safety: never bypass safety devices to take a measurement or perform a test.

This chapter covers all the knowledge required for Red Seal competency block 11. Review the conversion tables, calculation formulas, and troubleshooting procedures — these are the elements most frequently tested on the exam.