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Evidence Guide: CUVOPA206A - Cut and polish opal doublets and triplets

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

 

CUVOPA206A - Cut and polish opal doublets and triplets

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

Prepare to cut an opal doublet or triplet

  1. Identify and obtain consumables required for cutting and polishing an opal doublet or triplet
  2. Select tools and equipment to be used
  3. Determine jewellers’ cutting angle requirements
  4. Dop pre-form on appropriate dop stick using wax or adhesive
Identify and obtain consumables required for cutting and polishing an opal doublet or triplet

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Select tools and equipment to be used

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Determine jewellers’ cutting angle requirements

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Dop pre-form on appropriate dop stick using wax or adhesive

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Cut and polish an opal doublet or triplet

  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 approximately 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 approximately 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:

 

 

 

 

 

 

 

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.

Overview of assessment

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

Evidence of the ability to:

cut and polish doublets and triplets from a range of types of opal using appropriate consumables and equipment and using commercial and non-commercial triplet tops to accepted industry standards

safely complete the cutting, polishing and cleaning processes, using equipment and consumables safely.

Context of and specific resources for assessment

Assessment must ensure access to an opal-cutting workshop.

Method of assessment

A range of assessment methods should be used to assess practical skills and knowledge. The following examples are appropriate for this unit:

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

review of portfolios of evidence

review of third-party workplace reports of on-the-job performance by candidate.

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).

Guidance information for assessment

Holistic assessment with other units relevant to the industry sector workplace and job role is recommended.

Required Skills and Knowledge

Required skills

planning and organising skills to prepare materials for cutting and polishing

problem-solving skills to identify and address common cutting and polishing problems

numeracy skills to use numerical features of machinery

technical skills to:

cut and polish opals using correct technique

work safely with opal-cutting equipment and materials.

Required knowledge

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

general principles of OHS for working in an opal-cutting workshop, including:

complying with the safe operating procedures for each machine and materials

good housekeeping

using personal protective equipment (PPE) where required

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

silicon carbide sanding paper #180 to #600.

Equipment may include:

grinding machinery

PPE

polishing machinery

sanding machinery

saw.

Jewellers’ cutting angle requirements may include:

10º to 12º side angle

all sharp edges or acute angles be slightly rounded

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 5 minute adhesive, using aluminium dop sticks

wood glue

hot wax sticks (hot glue gun)

super glues

vacuum dopping

wax (medium to low melting).

Shape may include:

a variety of other shapes

cabochon

dome – high, medium and 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 and topaz.