COREN Craftsman cheat sheet

Marking out: datum surfaces are established first; scriber lines are cut on the workpiece only after the surface plate, angle plate and surface gauge are proven square.

Filing: a double-cut file removes metal on the forward stroke only; draw filing is used for finishing because the file is drawn along the work with both hands.

Drilling speed rule: cutting speed V = πDN/1000, so N (rpm) = 1000V/(πD); halve V for high-carbon steel relative to mild steel.

Tapping drill size for metric threads: core diameter ≈ major diameter − pitch (e.g. M10 × 1.5 needs an 8.5 mm tapping drill).

Lathe turning: spindle speed and feed set from material and tool grade; depth of cut per pass should not exceed the tool nose radius capability.

Welding: arc length is kept roughly equal to electrode core diameter; a long arc gives spatter, undercut and poor penetration.

Limits and fits: clearance fit always leaves a gap, interference fit always overlaps, transition fit may give either depending on actual sizes.

Torque wrench calibration and bench vice jaws are checked before use; a worn vice jaw causes taper in hand-filed and hacksawed work.

Safety rule of thumb: rotating machinery is never adjusted by hand; guards are interlocked and the emergency stop is tested before each shift.

First-angle projection: the object sits between observer and plane, so the view from the front is placed below the top view and the left view goes on the right.

Third-angle projection: the plane sits between observer and object, so the top view is above the front view and the right-side view is on the right.

Line convention: visible outlines are continuous thick, hidden edges are short dashes, centre lines are long-short-long, and dimension lines are thin continuous.

Scale: drawing scale = drawing length ÷ actual length; a 1:50 drawing of a 10 m wall measures 200 mm on paper.

Dimensioning: dimensions are given once, never repeated on another view, and are placed outside the outline where possible with arrowheads touching extension lines.

Section views: hatching at 45° indicates cut material; adjacent parts are hatched in opposite directions to keep boundaries legible.

Tolerance notation: a limit dimension such as 25 +0.05/−0.02 gives a maximum of 25.05 mm and a minimum of 24.98 mm.

Surface finish symbol Ra is the arithmetic mean roughness in micrometres; a smaller Ra number means a smoother surface.

Plain carbon steel is classified by carbon content: low carbon up to about 0.3%, medium 0.3–0.6%, high carbon 0.6–1.4%; higher carbon raises hardness and lowers ductility.

Stress σ = F/A and strain ε = ΔL/L; Young's modulus E = σ/ε applies only in the elastic region.

Annealing softens and relieves stress by slow cooling; normalising refines grain structure by air cooling; quenching hardens by rapid cooling and is followed by tempering.

Cast iron contains roughly 2–4% carbon; grey iron is brittle in tension but good in compression and damping, so it suits machine bases.

Non-ferrous alloys: aluminium is light and corrosion resistant but low in stiffness; copper alloys conduct heat and electricity well and resist marine corrosion.

Hardness scales are not interchangeable directly; a conversion table is needed to compare Brinell, Vickers and Rockwell values.

Galvanic corrosion occurs when two dissimilar metals are joined in the presence of an electrolyte; the less noble metal becomes the anode and corrodes.

Micrometer screw gauge: least count = pitch ÷ number of divisions on the thimble; a 0.5 mm pitch with a 50-division thimble reads to 0.01 mm.

Vernier calliper: least count = smallest main-scale division ÷ number of vernier divisions; a 1 mm main scale with 50 vernier divisions reads to 0.02 mm.

Zero error: a micrometer or vernier that does not read zero when closed must have its error added or subtracted from every reading.

A dial test indicator measures small displacements and run-out; it is not a direct-reading size gauge for the workpiece diameter.

Torque wrench range must cover the target torque; a wrench used below 20% of its range gives poor accuracy.

Hacksaw blade selection: 14–18 teeth per inch for thick sections, 24–32 for thin tube and sheet, so at least two teeth stay in contact with the work.

Grinding wheel marking gives abrasive type, grit size, grade and bond; a softer grade is used on hard materials so worn grit is released.

COREN is the Council for the Regulation of Engineering in Nigeria, established by Decree 55 of 1970, now the Engineers (Registration, etc.) Act; it registers engineers, technologists and technicians.

Only persons registered with COREN may practise or use the title engineer in Nigeria; practising without registration is an offence under the Act.

Registration categories include registered engineer, registered engineering technologist and registered engineering technician, each with defined qualifications and experience.

COREN enforces a code of conduct: competence within one's field, no misrepresentation of qualifications, confidentiality of client information and disclosure of conflicts of interest.

Professional misconduct can lead to inquiry, suspension or withdrawal of registration by the Council's disciplinary tribunal.

Factories Act (Nigeria) requires guarding of dangerous machinery, safe means of access, and reporting of accidents; the employer owes a duty of care to workers.

Personal protective equipment is the last line of defence: hazard is first eliminated, substituted, engineered out, or administratively controlled before PPE is relied on.

Site safety: permit-to-work systems govern hot work, confined-space entry and electrical isolation; lock-out/tag-out prevents unexpected energisation.

Marking out: datum surfaces are established first; scriber lines are cut on the workpiece only after the surface plate, angle plate and surface gauge are proven square.

Filing: a double-cut file removes metal on the forward stroke only; draw filing is used for finishing because the file is drawn along the work with both hands.

Drilling speed rule: cutting speed V = πDN/1000, so N (rpm) = 1000V/(πD); halve V for high-carbon steel relative to mild steel.

Tapping drill size for metric threads: core diameter ≈ major diameter − pitch (e.g. M10 × 1.5 needs an 8.5 mm tapping drill).

Lathe turning: spindle speed and feed set from material and tool grade; depth of cut per pass should not exceed the tool nose radius capability.

Welding: arc length is kept roughly equal to electrode core diameter; a long arc gives spatter, undercut and poor penetration.

Limits and fits: clearance fit always leaves a gap, interference fit always overlaps, transition fit may give either depending on actual sizes.

Torque wrench calibration and bench vice jaws are checked before use; a worn vice jaw causes taper in hand-filed and hacksawed work.

Safety rule of thumb: rotating machinery is never adjusted by hand; guards are interlocked and the emergency stop is tested before each shift.

First-angle projection: the object sits between observer and plane, so the view from the front is placed below the top view and the left view goes on the right.

Third-angle projection: the plane sits between observer and object, so the top view is above the front view and the right-side view is on the right.

Line convention: visible outlines are continuous thick, hidden edges are short dashes, centre lines are long-short-long, and dimension lines are thin continuous.

Scale: drawing scale = drawing length ÷ actual length; a 1:50 drawing of a 10 m wall measures 200 mm on paper.

Dimensioning: dimensions are given once, never repeated on another view, and are placed outside the outline where possible with arrowheads touching extension lines.

Section views: hatching at 45° indicates cut material; adjacent parts are hatched in opposite directions to keep boundaries legible.

Tolerance notation: a limit dimension such as 25 +0.05/−0.02 gives a maximum of 25.05 mm and a minimum of 24.98 mm.

Surface finish symbol Ra is the arithmetic mean roughness in micrometres; a smaller Ra number means a smoother surface.

Plain carbon steel is classified by carbon content: low carbon up to about 0.3%, medium 0.3–0.6%, high carbon 0.6–1.4%; higher carbon raises hardness and lowers ductility.

Stress σ = F/A and strain ε = ΔL/L; Young's modulus E = σ/ε applies only in the elastic region.

Annealing softens and relieves stress by slow cooling; normalising refines grain structure by air cooling; quenching hardens by rapid cooling and is followed by tempering.

Cast iron contains roughly 2–4% carbon; grey iron is brittle in tension but good in compression and damping, so it suits machine bases.

Non-ferrous alloys: aluminium is light and corrosion resistant but low in stiffness; copper alloys conduct heat and electricity well and resist marine corrosion.

Hardness scales are not interchangeable directly; a conversion table is needed to compare Brinell, Vickers and Rockwell values.

Galvanic corrosion occurs when two dissimilar metals are joined in the presence of an electrolyte; the less noble metal becomes the anode and corrodes.

Micrometer screw gauge: least count = pitch ÷ number of divisions on the thimble; a 0.5 mm pitch with a 50-division thimble reads to 0.01 mm.

Vernier calliper: least count = smallest main-scale division ÷ number of vernier divisions; a 1 mm main scale with 50 vernier divisions reads to 0.02 mm.

Zero error: a micrometer or vernier that does not read zero when closed must have its error added or subtracted from every reading.

A dial test indicator measures small displacements and run-out; it is not a direct-reading size gauge for the workpiece diameter.

Torque wrench range must cover the target torque; a wrench used below 20% of its range gives poor accuracy.

Hacksaw blade selection: 14–18 teeth per inch for thick sections, 24–32 for thin tube and sheet, so at least two teeth stay in contact with the work.

Grinding wheel marking gives abrasive type, grit size, grade and bond; a softer grade is used on hard materials so worn grit is released.

COREN is the Council for the Regulation of Engineering in Nigeria, established by Decree 55 of 1970, now the Engineers (Registration, etc.) Act; it registers engineers, technologists and technicians.

Only persons registered with COREN may practise or use the title engineer in Nigeria; practising without registration is an offence under the Act.

Registration categories include registered engineer, registered engineering technologist and registered engineering technician, each with defined qualifications and experience.

COREN enforces a code of conduct: competence within one's field, no misrepresentation of qualifications, confidentiality of client information and disclosure of conflicts of interest.

Professional misconduct can lead to inquiry, suspension or withdrawal of registration by the Council's disciplinary tribunal.

Factories Act (Nigeria) requires guarding of dangerous machinery, safe means of access, and reporting of accidents; the employer owes a duty of care to workers.

Personal protective equipment is the last line of defence: hazard is first eliminated, substituted, engineered out, or administratively controlled before PPE is relied on.

Site safety: permit-to-work systems govern hot work, confined-space entry and electrical isolation; lock-out/tag-out prevents unexpected energisation.

Marking out: datum surfaces are established first; scriber lines are cut on the workpiece only after the surface plate, angle plate and surface gauge are proven square.

Filing: a double-cut file removes metal on the forward stroke only; draw filing is used for finishing because the file is drawn along the work with both hands.

Drilling speed rule: cutting speed V = πDN/1000, so N (rpm) = 1000V/(πD); halve V for high-carbon steel relative to mild steel.

Tapping drill size for metric threads: core diameter ≈ major diameter − pitch (e.g. M10 × 1.5 needs an 8.5 mm tapping drill).

Lathe turning: spindle speed and feed set from material and tool grade; depth of cut per pass should not exceed the tool nose radius capability.

Welding: arc length is kept roughly equal to electrode core diameter; a long arc gives spatter, undercut and poor penetration.

Limits and fits: clearance fit always leaves a gap, interference fit always overlaps, transition fit may give either depending on actual sizes.

Torque wrench calibration and bench vice jaws are checked before use; a worn vice jaw causes taper in hand-filed and hacksawed work.

Safety rule of thumb: rotating machinery is never adjusted by hand; guards are interlocked and the emergency stop is tested before each shift.

First-angle projection: the object sits between observer and plane, so the view from the front is placed below the top view and the left view goes on the right.

Third-angle projection: the plane sits between observer and object, so the top view is above the front view and the right-side view is on the right.

Line convention: visible outlines are continuous thick, hidden edges are short dashes, centre lines are long-short-long, and dimension lines are thin continuous.

Scale: drawing scale = drawing length ÷ actual length; a 1:50 drawing of a 10 m wall measures 200 mm on paper.

Dimensioning: dimensions are given once, never repeated on another view, and are placed outside the outline where possible with arrowheads touching extension lines.

Section views: hatching at 45° indicates cut material; adjacent parts are hatched in opposite directions to keep boundaries legible.

Tolerance notation: a limit dimension such as 25 +0.05/−0.02 gives a maximum of 25.05 mm and a minimum of 24.98 mm.

Surface finish symbol Ra is the arithmetic mean roughness in micrometres; a smaller Ra number means a smoother surface.

Plain carbon steel is classified by carbon content: low carbon up to about 0.3%, medium 0.3–0.6%, high carbon 0.6–1.4%; higher carbon raises hardness and lowers ductility.

Stress σ = F/A and strain ε = ΔL/L; Young's modulus E = σ/ε applies only in the elastic region.

Annealing softens and relieves stress by slow cooling; normalising refines grain structure by air cooling; quenching hardens by rapid cooling and is followed by tempering.

Cast iron contains roughly 2–4% carbon; grey iron is brittle in tension but good in compression and damping, so it suits machine bases.

Non-ferrous alloys: aluminium is light and corrosion resistant but low in stiffness; copper alloys conduct heat and electricity well and resist marine corrosion.

Hardness scales are not interchangeable directly; a conversion table is needed to compare Brinell, Vickers and Rockwell values.

Galvanic corrosion occurs when two dissimilar metals are joined in the presence of an electrolyte; the less noble metal becomes the anode and corrodes.

Micrometer screw gauge: least count = pitch ÷ number of divisions on the thimble; a 0.5 mm pitch with a 50-division thimble reads to 0.01 mm.

Vernier calliper: least count = smallest main-scale division ÷ number of vernier divisions; a 1 mm main scale with 50 vernier divisions reads to 0.02 mm.

Zero error: a micrometer or vernier that does not read zero when closed must have its error added or subtracted from every reading.

A dial test indicator measures small displacements and run-out; it is not a direct-reading size gauge for the workpiece diameter.

Torque wrench range must cover the target torque; a wrench used below 20% of its range gives poor accuracy.

Hacksaw blade selection: 14–18 teeth per inch for thick sections, 24–32 for thin tube and sheet, so at least two teeth stay in contact with the work.

Grinding wheel marking gives abrasive type, grit size, grade and bond; a softer grade is used on hard materials so worn grit is released.

COREN is the Council for the Regulation of Engineering in Nigeria, established by Decree 55 of 1970, now the Engineers (Registration, etc.) Act; it registers engineers, technologists and technicians.

Only persons registered with COREN may practise or use the title engineer in Nigeria; practising without registration is an offence under the Act.

Registration categories include registered engineer, registered engineering technologist and registered engineering technician, each with defined qualifications and experience.

COREN enforces a code of conduct: competence within one's field, no misrepresentation of qualifications, confidentiality of client information and disclosure of conflicts of interest.

Professional misconduct can lead to inquiry, suspension or withdrawal of registration by the Council's disciplinary tribunal.

Factories Act (Nigeria) requires guarding of dangerous machinery, safe means of access, and reporting of accidents; the employer owes a duty of care to workers.

Personal protective equipment is the last line of defence: hazard is first eliminated, substituted, engineered out, or administratively controlled before PPE is relied on.

Site safety: permit-to-work systems govern hot work, confined-space entry and electrical isolation; lock-out/tag-out prevents unexpected energisation.

Marking out: datum surfaces are established first; scriber lines are cut on the workpiece only after the surface plate, angle plate and surface gauge are proven square.

Filing: a double-cut file removes metal on the forward stroke only; draw filing is used for finishing because the file is drawn along the work with both hands.

Drilling speed rule: cutting speed V = πDN/1000, so N (rpm) = 1000V/(πD); halve V for high-carbon steel relative to mild steel.

Tapping drill size for metric threads: core diameter ≈ major diameter − pitch (e.g. M10 × 1.5 needs an 8.5 mm tapping drill).

Lathe turning: spindle speed and feed set from material and tool grade; depth of cut per pass should not exceed the tool nose radius capability.

Welding: arc length is kept roughly equal to electrode core diameter; a long arc gives spatter, undercut and poor penetration.

Limits and fits: clearance fit always leaves a gap, interference fit always overlaps, transition fit may give either depending on actual sizes.

Torque wrench calibration and bench vice jaws are checked before use; a worn vice jaw causes taper in hand-filed and hacksawed work.

Safety rule of thumb: rotating machinery is never adjusted by hand; guards are interlocked and the emergency stop is tested before each shift.

First-angle projection: the object sits between observer and plane, so the view from the front is placed below the top view and the left view goes on the right.

Third-angle projection: the plane sits between observer and object, so the top view is above the front view and the right-side view is on the right.

Line convention: visible outlines are continuous thick, hidden edges are short dashes, centre lines are long-short-long, and dimension lines are thin continuous.

Scale: drawing scale = drawing length ÷ actual length; a 1:50 drawing of a 10 m wall measures 200 mm on paper.

Dimensioning: dimensions are given once, never repeated on another view, and are placed outside the outline where possible with arrowheads touching extension lines.

Section views: hatching at 45° indicates cut material; adjacent parts are hatched in opposite directions to keep boundaries legible.

Tolerance notation: a limit dimension such as 25 +0.05/−0.02 gives a maximum of 25.05 mm and a minimum of 24.98 mm.

Surface finish symbol Ra is the arithmetic mean roughness in micrometres; a smaller Ra number means a smoother surface.

Plain carbon steel is classified by carbon content: low carbon up to about 0.3%, medium 0.3–0.6%, high carbon 0.6–1.4%; higher carbon raises hardness and lowers ductility.

Stress σ = F/A and strain ε = ΔL/L; Young's modulus E = σ/ε applies only in the elastic region.

Annealing softens and relieves stress by slow cooling; normalising refines grain structure by air cooling; quenching hardens by rapid cooling and is followed by tempering.

Cast iron contains roughly 2–4% carbon; grey iron is brittle in tension but good in compression and damping, so it suits machine bases.

Non-ferrous alloys: aluminium is light and corrosion resistant but low in stiffness; copper alloys conduct heat and electricity well and resist marine corrosion.

Hardness scales are not interchangeable directly; a conversion table is needed to compare Brinell, Vickers and Rockwell values.

Galvanic corrosion occurs when two dissimilar metals are joined in the presence of an electrolyte; the less noble metal becomes the anode and corrodes.

Micrometer screw gauge: least count = pitch ÷ number of divisions on the thimble; a 0.5 mm pitch with a 50-division thimble reads to 0.01 mm.

Vernier calliper: least count = smallest main-scale division ÷ number of vernier divisions; a 1 mm main scale with 50 vernier divisions reads to 0.02 mm.

Zero error: a micrometer or vernier that does not read zero when closed must have its error added or subtracted from every reading.

A dial test indicator measures small displacements and run-out; it is not a direct-reading size gauge for the workpiece diameter.

Torque wrench range must cover the target torque; a wrench used below 20% of its range gives poor accuracy.

Hacksaw blade selection: 14–18 teeth per inch for thick sections, 24–32 for thin tube and sheet, so at least two teeth stay in contact with the work.

Grinding wheel marking gives abrasive type, grit size, grade and bond; a softer grade is used on hard materials so worn grit is released.

COREN is the Council for the Regulation of Engineering in Nigeria, established by Decree 55 of 1970, now the Engineers (Registration, etc.) Act; it registers engineers, technologists and technicians.

Only persons registered with COREN may practise or use the title engineer in Nigeria; practising without registration is an offence under the Act.

Registration categories include registered engineer, registered engineering technologist and registered engineering technician, each with defined qualifications and experience.

COREN enforces a code of conduct: competence within one's field, no misrepresentation of qualifications, confidentiality of client information and disclosure of conflicts of interest.

Professional misconduct can lead to inquiry, suspension or withdrawal of registration by the Council's disciplinary tribunal.

Factories Act (Nigeria) requires guarding of dangerous machinery, safe means of access, and reporting of accidents; the employer owes a duty of care to workers.

Personal protective equipment is the last line of defence: hazard is first eliminated, substituted, engineered out, or administratively controlled before PPE is relied on.

Site safety: permit-to-work systems govern hot work, confined-space entry and electrical isolation; lock-out/tag-out prevents unexpected energisation.