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Evidence Guide: CUVOPA06B - Cut and polish an opal doublet/triplet

Student: __________________________________________________

Signature: _________________________________________________

Tips for gathering evidence to demonstrate your skills

The important thing to remember when gathering evidence is that the more evidence the better - that is, the more evidence you gather to demonstrate your skills, the more confident an assessor can be that you have learned the skills not just at one point in time, but are continuing to apply and develop those skills (as opposed to just learning for the test!). Furthermore, one piece of evidence that you collect will not usualy demonstrate all the required criteria for a unit of competency, whereas multiple overlapping pieces of evidence will usually do the trick!

From the Wiki University

 

CUVOPA06B - Cut and polish an opal doublet/triplet

What evidence can you provide to prove your understanding of each of the following citeria?

Prepare to cut an opal doublet.

  1. Identify and obtain consumables required for cutting and polishing an opal doublet or triplet.
  2. Identify equipment to be used.
  3. Determine jewellers' cutting angle requirements.
  4. Dop preform on appropriate dop stick using waxor adhesive.
Identify and obtain consumables required for cutting and polishing an opal doublet or triplet.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Identify equipment to be used.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Determine jewellers' cutting angle requirements.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Dop preform on appropriate dop stick using waxor adhesive.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Cut and polish an opal doublet.

  1. Grind to relevant shape using colour pattern and play as a guide.
  2. Grind to shape incorporating jewellers side angles, including backing into shape.
  3. Dome the top of doublet, leaving a minimum of 1mm above join at side angle.
  4. Sand and polish top and sides of opal doublet.
  5. Turn stone over and re-dop.
  6. Grind, sand and polish backing at jewellers angles.
  7. Remove stone from dop and clean.
Grind to relevant shape using colour pattern and play as a guide.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Grind to shape incorporating jewellers side angles, including backing into shape.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Dome the top of doublet, leaving a minimum of 1mm above join at side angle.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Sand and polish top and sides of opal doublet.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Turn stone over and re-dop.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Grind, sand and polish backing at jewellers angles.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Remove stone from dop and clean.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Cut and polish an opal triplet (commercial top).

  1. Dop stone on top of triplet top.
  2. Grind backing thickness down to approximately 1mm.
  3. Grind edge of backing at approx. 30º until the edge of the triplet top is met.
  4. Sand and polish backing.
  5. Remove stone from dop and clean.
Dop stone on top of triplet top.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Grind backing thickness down to approximately 1mm.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Grind edge of backing at approx. 30º until the edge of the triplet top is met.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Sand and polish backing.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Remove stone from dop and clean.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Cut and polish an opal triplet (non commercial top).

  1. Dop pre-form with glass/quartz on top.
  2. Shape stone like high domed doublet on grinder.
  3. Transform opal colour optically into whole of dome.
  4. Sand and polish top and sides of stone.
  5. Turn stone over and re-dop on top surface.
  6. Grind backing thickness to 1mm.
  7. Grind setting edge angle at 30º, until 1mm into top, under- cutting backing.
  8. Sand and polish bottom and setting edge and remove any chipping that may occur around edge of top.
  9. Remove stone from dop and clean.
Dop pre-form with glass/quartz on top.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Shape stone like high domed doublet on grinder.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Transform opal colour optically into whole of dome.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Sand and polish top and sides of stone.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Turn stone over and re-dop on top surface.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Grind backing thickness to 1mm.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Grind setting edge angle at 30º, until 1mm into top, under- cutting backing.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Sand and polish bottom and setting edge and remove any chipping that may occur around edge of top.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Remove stone from dop and clean.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Follow OHS principles when operating opal cutting and polishing equipment.

  1. Follow general principles of OHS for working in an opal cutting workshop.
Follow general principles of OHS for working in an opal cutting workshop.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Assessed

Teacher: ___________________________________ Date: _________

Signature: ________________________________________________

Comments:

 

 

 

 

 

 

 

 

Instructions to Assessors

Evidence Guide

The evidence guide provides advice on assessment and must be read in conjunction with the performance criteria, required skills and knowledge, range statement and the Assessment Guidelines for the Training Package.

Critical aspects for assessment and evidence required to demonstrate competency in this unit

To achieve competency in this unit, a person must be able to cut and polish doublets and triplets from a range of types of opal using appropriate consumables and equipment.

Assessment must confirm knowledge of the use of appropriate consumables and equipment to produce opal doublets and triplets using commercial and non-commercial triplet tops to accepted industry standards. Assessment must confirm the safe completion of the cutting, polishing and cleaning processes and safe use of the equipment and consumables.

Competence in this unit must be assessed over a period of time in order to ensure consistency of performance over the range of variables and contexts applicable to the work environment.

Context of and specific resources for assessment

This unit may be assessed in a work environment or in a simulated work environment or in a combination of these situations.

Method of assessment

For valid and reliable assessment of this unit, evidence should be gathered through a range of methods to indicate consistent performance.

Assessment of this unit of competence will usually include observation of processes and procedures, oral and/or written questioning on underpinning knowledge and skills, evaluation of the final product and other methods as required.

Assessment methods should closely reflect workplace demands (e.g. literacy) and the needs of particular groups (e.g. people with disabilities, and people who may have literacy or numeracy difficulties such as speakers of languages other than English, remote communities and those with interrupted schooling).

Assessment of this competency requires access to:

an opal cutting workshop

a qualified workplace assessor or assessment team.

Required Skills and Knowledge

Required skills:

safe use of appropriate equipment

grinding, sanding and polishing skills

Opal Cutting and Polishing

Required knowledge:

the characteristics of opal that make it suitable for use as a doublet or triplet

knowledge of the materials used in doublets and triplets

processes to be used in making a doublet or triplet.

Range Statement

The range statement relates to the unit of competency as a whole. It allows for different work environments and situations that may affect performance. Bold italicised wording, if used in the performance criteria, is detailed below. Essential operating conditions that may be present with training and assessment (depending on the work situation needs of the candidate, accessibility of the item, and local industry and regional contexts) may also be included.

Consumables may include:

cerium or tin oxide

cleaning spirit

diamond or silicon-carbide wheels #220 or #360

diamond polishing compound #2400 to #100000

diamond polishing wheels #3000 to #50000

diamond sanding wheels #280 to #1200

felt or leather buffs

personal protective equipment

silicon-carbide sanding paper #180 to #600.

Equipment may include:

grinding machinery

polishing machinery

sanding machinery

saw.

Jewellers' cutting angle requirements may include:

10º to 12º side angle (from setting edge to start of dome)

all sharp edges or acute angles be slightly rounded (optional)

flat or domed back

high overall polish and free of defects

sanded or polished back

setting edge to be straight and parallel to back

tolerance for standard millimetre sizes, 0.2mil. + or -

Wax or adhesives for dopping may include:

any 5min. adhesive, using aluminium dop-sticks

AQUADERE wood glue

hot wax sticks (hot glue gun)

super glues

vacuum dopping

wax (medium to low melting)

Note: stone should be kept cool - heat may damage opal.

Shape may include:

a variety of other shapes

cabochon

dome - high, medium, low

free form

rectangles.

Triplet top materials may include:

clear quartz

commercial standards size triplet tops

glass, plain or plate

lead crystal glass

material of the triplet top should be disclosed

synthetic spinel, corundum, topaz.

General OHS principles and Safe Operating Procedures may include:

complying with the safe operating procedures for each machine and materials

good housekeeping

using personal protection equipment where required.