MACOR®

MACHINABLE CERAMIC FOR ENGINEERING APPLICATIONS Traditional ceramic materials can normally only be machined by diamond grinding once they have been fired, which can be costly. MACOR® machinable glass ceramic offers a potentially lower cost solution to this problem. MACOR® is an extremely versatile engineering material, offering researchers, product designers and machinists the opportunity to quickly, accurately and economically make high precision components which are machinable with ordinary metalworking tools and do not require any post-firing after machining has been completed, removing a production process and potentially reducing costs. MACOR® machinable glass ceramic exhibits good strength, electrical & thermal insulation, has zero porosity and can be machined to very high tolerances. This allows the performance of a technical ceramic to be achieved whilst reducing the time necessary between design and realization. Goodfellow Ceramic and Glass Division is able to offer MACOR® machinable glass ceramic as rods, bars, sheets and finished components. Characteristics of MACOR® machinable glass ceramic > Excellent Machinability High precision and complex shapes can be achieved, limited only by available equipment and the experience of the machinist. > Excellent electrical properties Good electrical insulation is achieved at high voltages, various frequencies and high temperatures. When properly baked out the material will not outgas in vacuum environments. > Sealing, Joining & Metallizing MACOR® machinable glass ceramic can be joined or sealed, both to itself and to other materials in a number of ways. It can also be thick film metallized using metal inks, or thin film metallized by sputtering. > Maximum use temperature of 1000°C > Strong and rigid > Radiation resistant > Low thermal conductivity > Can be highly polished

MACOR® machinable glass ceramic is a white, odorless material composed of approximately 55% fluorophlogopite mica and 45% borosilicate glass.

Manufacturing Applications of MACOR® machinable glass ceramic > Precision Coil Formers (Electronic / Semiconductor industry) > Spacers, cavities and reflectors (Laser industry) > Thermal breaks, coil supports, vacuum feedthroughs (High Vacuum industry) > Retaining rings, supports and components (Aerospace / Space industry) > Fixtures and reference blocks in power generation (Nuclear industry)

MACOR® is a registered trademark of Corning Incorporated

Maximum available size MACOR® machinable glass ceramic is manufactured in two standard sizes. The following should be referred to as the maximum possible dimensions when considering the use of MACOR® machinable glass ceramic:

Standard Block: 340 x 330 x 57mm Standard Rods: 76mm diameter x 300mm long

Properties Thermal

Coefficient of Expansion -200 to 25°C 74x10-7/°C 25 to 300°C 93x10-7/°C 25 to 600°C 114x10-7/°C 25 to 800°C 126x10-7/°C

Specific Heat, 25°C

.79KJ/kg°C

Thermal Conductivity, 25°C

1.46 W/m°C

Thermal Diffusivity, 25°C

7.3x10-7m2/s

Continuous Operating Temperature

800°C

Maximum No Load Temperature

1000°C

Mechanical

Density 2.52 g/cm3 Porosity

0%

Young’s Modulus, 25°C (Modulus of Elasticity)

66.9 GPa

Poisson’s Ratio

0.29

Shear Modulus, 25°C

25.5 GPa

Hardness, Knoop, 100g Rockwell A

250 48

Modulus of Rupture, 25°C

94 MPa

(Flexural Strength) (minimum specified average value) Compressive strength

345 MPa

Fracture Toughness

1.53 MPa m0.5

Properties Electrical Dielectric Constant, 25°C

1 KHz 8.5 GHz

6.03 5.67

Loss Tangent, 25°C

1KHz 8.5 GHz

4.7x10-3 7.1x10-3

Dielectric Strength (AC) avg. (at 0.3mm thickness and 25°C)

9.4 KV/mm

Dielectric Strength (DC) avg. (at 0.3mm thickness and 25°C)

62.4 KV/mm

DC Volume Resistivity, 25°C

>1016 ohm-cm

Chemical

Tests

Results Weight Loss (mg/cm

2)

Solution pH Time Temp. Gravimetric 5% HCl

(Hydrochloric Acid) 0.1 24 hrs 95°C ~ 100

0.002 N HNO3 (Nitric Acid)

2.8 24 hrs 95°C ~ 0.6

0.1 N NaHCO3 (Sodium Bicarbonate)

8.4 24 hrs 95°C ~ 0.3

0.02 N Na2CO3 (Sodium Carbonate)

10.9 6 hrs 95°C ~ 0.1

5% NaOH (Sodium Hydroxide)

13.2 6 hrs 95°C ~ 10

Resistance to water over time H2O 7.6 1 day* 95°C 0.01

3 days* 95°C 0.07 7 days* 95°C 9.4

* Water not freshened daily 3 days** 95°C 0.06 ** Water freshened daily 6 days** 95°C 0.11

MACOR® MACHINABLE GLASS CERAMIC - MACHINING INFORMATION

Machining

MACOR® can be machined to make precision components but its machining characteristics are different to metals and plastics. MACOR® consists of interlocking plate-like mica crystals in a glassy matrix. It is these crystals which stop microscopic fractures at the tool tip from spreading through the material, thus making it machinable in a controlled way. During machining the tool pulverizes and tears the MACOR® surface producing a fine powder of crystals and glass. The crystals are so small that, when machined, MACOR® has a good surface finish. When machining is complete, the component is cleaned ready for use, no further treatment (e.g. firing) is required.

Setting Up

MACOR® machinable glass ceramic is not resilient so, when small or delicate pieces are being machined, make sure that the load is uniformly distributed. Use soft jaws if possible.

It is well worthwhile taking some time to learn how the material behaves during machining. Try some simple tasks such as drilling, turning and milling and you will see how the material machines. This information gives a basis for good machining practice, but do not be afraid to experiment with tools and speeds to obtain the optimum machining performance from your equipment.

MACOR® can be machined with high speed steel tools but the use of tungsten carbide tools is highly recommended (ceramic tipped tools are not advised). If the tool squeaks, if the MACOR® surface turns greyish through tool wear or if too much force is needed – then stop and sharpen the tool.

As a general rule, machine at lower speeds (keeping the work piece cool) and take smaller depths of cut until you become more confident in machining the material. It is normally the requirement to maintain a surface finish which controls machining speeds. Remember, you are machining a brittle material so always avoid physical shock.

Using Coolant

Although MACOR® is a high temperature material, the best machining results are obtained when both the material and tool are kept cool. Water soluble cutting fluids will improve the cutting action, trap and wash away the debris produced during machining and protect machine tools. If the fluid is to be recirculated, the use of a settling tank is recommended. The powder generated during machining is somewhat abrasive and so attention must be given to cleanliness and machine maintenance.

Sawing

Use a carbide grit blade with a 30 m/min band speed, or a diamond or silicon carbide cut-off wheel.

More...

MACOR® MACHINABLE GLASS CERAMIC – MACHINING INFORMATION (Continued)

Turning

Using carbide tipped tools, suggested turning speeds are around 600 rpm for ø 5mm–10mm rod, reducing to around 400 rpm for ø 25mm rod. Feed rates are 20–30 mm/minute with a depth of cut of 2–4mm for roughing and less than 1mm for finishing.

Side and back rake angle, end and side relief angles should be around 5°. The recommended side cutting edge angle is 15°–45° and the nose radius should be larger than 0.8mm.

Thread cutting can also be done at low spindle speeds, a typical cutting depth is 0.025–0.040mm per pass.

Milling

Typical head speeds are 1000–1500 rpm with a chip load of 0.05mm per tooth. Depths of cut are as for turning. Climb milling prevents material being pulled off the edge of the MACOR®.

Drilling

For holes up to about ø 5mm a spindle speed of 1000–1500 rpm and a feed rate of 20–30 mm/min. has been found to be effective. Relieve the drill flutes constantly, especially for small diameter holes. Check the sharpness of the drill every 25–50 holes. A slow feed is recommended at the start and finish of each hole. To prevent breakout, use a backing plate or chamfer the hole entrance and exit before drilling through thickness. It is possible to ultrasonically drill MACOR®.

Tapping

Make the clearance hole one size larger than that recommended for metal (typically 0.1–0.2mm larger). Chamfer both ends of the hole to prevent chipping. A 4 flute tap is preferable to a 2 flute tap. Run the tap slowly in the same direction (turning the tap back and forth can cause chipping) and flush with water or coolant to remove dust. Wire thread inserts can be used with MACOR®.

Grinding and polishing Diamond grinding wheels give the best results although silicon carbide and alumina wheels can be used. Always use water cooling. Start polishing with a 400 grit silicon carbide, prior to using alumina or cerium oxide powders for the final finish.

SHAPAL™ Hi-M SOFT MACHINABLE ALUMINIUM NITRIDE CERAMIC

Ceramic materials are distinguished from metals and polymers by their unique characteristics. Unfortunately, two of these characteristics, brittleness and hardness, make them difficult to machine and this can limit their applications. Grades of ceramic have been developed which can be machined, but they are not suitable for all engineering applications due to their low flexural strength. SHAPAL™Hi-M soft was developed by Tokuyama Corporation to specifically address these issues and is a machinable ceramic which offers both high mechanical strength and thermal conductivity. SHAPAL™Hi-M soft is based upon the first translucent aluminium nitride developed by Tokuyama Soda Co. Ltd. and is a composite sintered body of AlN and BN. This material has unique characteristics which make it suitable for a wide range of applications. Goodfellow Ceramic and Glass Division are able to offer SHAPAL™Hi-M soft as rods, sheets and finished components.

Characteristics of SHAPALTM-M soft > Excellent machinability High precision, close tolerance components can be machined from SHAPAL™Hi-M soft using a wide range of techniques including drilling, grinding, turning and milling. > High Thermal Conductivity The thermal conductivity of SHAPAL™Hi-M soft is approximately 5x that of alumina. > High Mechanical Strength SHAPAL™Hi-M soft has a flexural strength of 30kg/mm2 which is comparable to that of alumina In addition to the above mechanical properties, SHAPAL™Hi-M soft offers the following: > Excellent electrical insulation > Low thermal expansion > Low dielectric loss > Excellent high temperature properties > Suitability for vacuum applications

Typical Applications: Prototyping & small volume production Vacuum components

Electrical components Jigs & Fixtures

Heat sinks Crucibles for vacum applications For more information and advice please discuss your application with our sales staff. SHAPAL™Hi-M soft is a trademark of Tokuyama Corp.

SHAPAL™ Hi-M SOFT - PROPERTIES MACHINABLE ALUMINIUM NITRIDE CERAMIC

Property/Test Conditions Shapal™ Hi-M soft Units GENERAL Density Corrected to 4°C 2.88 g/cm³ Porosity 25°C 0 % ELECTRICAL Volume Resistivity 25°C, DC 1.0 x 1015 Ωcm Dissipation Factor (tan δ) 25°C, 1MHz 10 x 10-4 Dielectric Constant (ε) 25°C, 1MHz 6.8 Dielectric Strength 65 kV/mm THERMAL Thermal Expansion Coefficient RT~400°C 4.8 x 10-6 /°C Thermal Expansion Coefficient RT~600°C 4.9 x 10-6 /°C Thermal Expansion Coefficient RT~800°C 5.0 x 10-6 /°C Thermal Conductivity 25°C 92 W/mK Maximum Use Temp. (in air) 1000 °C Maximum Use Temp (in non-oxidizing atmosphere) 1900 °C Thermal Shock Resistance ∆t water quench 400 °C MECHANICAL Bending Strength 25°C 300 MPa Compressive Strength 25°C 100 kg/mm2 Young's Modulus 25°C 1.8 x 104 kg/mm2 Poisson's Ratio 25°C 0.31 Vickers Hardness (Hv) 25°C, 300g 380 kg/mm2 CHEMICAL DURABILITY Resistance to Acid 10%HCI 24Hrs, 25°C 0.2 mg/cm2 wt loss Resistance to Base 10%NaOH 24Hrs, 25°C 60 mg/cm2 wt loss

IMPURITIES C 300ppm Ca 1300ppm Cr 1ppm Mg 1ppm Ni 2ppm Fe 8ppm Si 40ppm O 0.9% Ti <20ppm

Properties shown are typical values, they are not absolute material properties, and should be used for guidance only. It is recommended that materials and components are tested for their suitability for a specific application. For more information and advice please discuss your application with our sales staff.

SHAPAL™ Hi-M SOFT MACHINABLE ALUMINIUM NITRIDE CERAMIC

MACHINING INSTRUCTIONS Shapal™ Hi-M soft can be machined to make precision components, but its machining characteristics are different to metals and plastics. Shapal™ Hi-M soft has a special crystal structure which makes it strong and hard - yet machinable. It is the crystals which prevent the microscopic fractures at the tool tip from spreading throughout the material so making it machinable in a controlled way. During machining, the tool pulverizes and tears the Shapal™ Hi-M soft surface producing a fine powder. The crystals are so small that, when machined, Shapal™ Hi-M soft has a good surface finish. When finished, the component is cleaned and used; no further treatment (e.g. firing) is required. Do not use acids or alkalis to clean components. Setting Up Shapal™ Hi-M soft is not resilient so, when small or delicate pieces are being machined, make sure the clamping load is uniformly distributed. Use soft jaws, if possible. Machining It is well worthwhile taking sometime to learn how the material behaves during machining. Try some simple tasks such as drilling, turning and milling and you will See how the material machines. This information gives a basis for good machining practice, but do not be afraid to experiment with tools and speeds to obtain your optimum machining performance. Shapal™ Hi-M soft must be machined with carbide tools, do not use high speed steel tools. Ceramic tip tools are not advised. Always keep tools sharp and check regularly throughout the machining process. If the tool squeaks or too much force is needed - then stop and sharpen the tool. As a general rule, machine with slower speeds (keeping the work piece cool) and take smaller depths of cut until you become more confident in machining the material. Always machine from the edge to the center to avoid edge chipping. Remember, you are machining a brittle material so always avoid physical shock. It is normally the requirement to maintain a surface finish which controls machining speeds. Use coolant generously Although Shapal™ Hi-M soft is a high-temperature material, the best machining results are obtained when both the material and tool are kept cool. Water soluble cutting fluids improve the cutting action, trap and wash away the powder during machining and protect machine tools. If the fluid is to be recirculated, the use of a Settling pot is recommended. The powder generated during machining is somewhat abrasive so attention must be given to cleanliness and machine maintenance. Turning Suggested turning speeds are up to 320 rpm for 5 and 10mm diameter rod, reducing to around 150 rpm for 25mm diameter rod. Feed rates are 0.lmm/rev with a 0.1-0.5mm depth of cut. Side and back rack angle, end and side relief angles are to be around 5°. The recommended side cutting edge;angle is 15 - 45° and the nose radius is to be larger than 0.8mm. Thread cutting can also be done at low spindle speeds; a typical cutting depth is 0.025 - 0.040mm per path.

SHAPAL™ Hi-M SOFT MACHINABLE ALUMINIUM NITRIDE CERAMIC

MACHINING INSTRUCTIONS continued…. Milling Typical head speeds are around 1000 rpm for end mill diameters up to 5mm, reducing to as low as 100 rpm for larger tool diameters. Feed rates are 50-20mm/min with a 0.1-0.5mm depth of cut. Mill top faces first before side faces and climb mill to minimise chipping. Drilling For holes up to about 5mm diameter a spindle speed of 1000-1500 rpm and a feed rate of 10-15mm/min has been found to be effective. Relieve the drill flutes constantly, especially for small diameter holes. Check the sharpness of the drill every few holes. Slow feed is recommended at the start and the finishing of holes. To prevent breakout, use a backing plate or bevel the hole entrance and exit before drilling. It is possible to ultrasonically drill Shapal™ Hi-M soft. Sawing Use a carbide grit blade with a 30m/min band speed, or a diamond or silicon carbide cut off wheel. Tapping Make the clearance hole one size larger than recommended for metal (typically 0.1 - 0.2mm larger). Chamfer both ends of the hole to prevent chipping. Carbide or titanium nitride coated taps can be used for sizes up to M4. For larger sizes, better results are obtained by machine cutting the thread using carbide tips. Wire thread inserts, e.g. Helicoil can be used with Shapal™ Hi-M soft. Grinding and Polishing Diamond grinding wheels are best although silicon carbide and alumina can be used. Always use water cooling. Polishing is started with a 400 grit silicon carbide prior to using alumina powders for the final finish. Design considerations Shapal™ Hi-M soft is a brittle material and, as such, certain design considerations will help achieve the best performance of the material. If possible and practical:

Avoid sudden changes in section or thickness. Avoid sharp edges, if possible chamfer or round any changes in direction. If possible, ensure that the distance between a hole and an edge or second hole is twice the diameter of the hole. For thermal applications, try to ensure that wall thicknesses are uniform to reduce thermal expansion strains during heating and cooling.

SHAPAL™Hi-M soft is a trademark of Tokuyama Corp.

DURATEC® MACHINABLE CERAMIC FOR ENGINEERING APPLICATIONS

Duratec® materials are versatile, asbestos free, machinable technical ceramics manufactured from calcium silicate. With a maximum service temperature of 1000°C, these materials provide excellent thermal and electrical insulation. Duratec® materials have been designed to be easily machined with appropriate tooling to give high definition finishes without chipping or breaking. High speed steel, carbide or diamond tipped tools can all be used to machine Duratec®, by following traditional engineering techniques. Goodfellow Ceramic and Glass Division can offer Duratec® materials as rods, bars, sheets and finished components.

CHARACTERISTICS Duratec® 750 Duratec® 1000

Maximum available size 1220x1500x75mm 1220x1500x50mm

Nominal Density 1400kg/m3 1400kg/m3

Flexural Strength 23MPa 16MPa

Hardness 80 (Shore D) 70 (Shore D)

Compressive strength at 10% compaction 55MPa 31MPa

Maximum service temperature 1000°C 1000°C

Thermal conductivity at 750°C 0.49W/mK 0.37W/mK

Shrinkage at 750°C for 12 hours (length, width, thickness) 0.14/1.1% 0.12/0.8%

Loss on ignition 7.3% 5.3%

Coefficient of thermal expansion at 100-750°C 6.6 x 10-6 6.4 x 10-6

Flatwise electrical strength 7300kV/m 4700kV/m

Arc resistance, Stage 40 (40mA) >420 seconds >420 seconds Volume resistivity 25°C 600°C

9.0 x 1010 Ωcm 1.0 x 1010 Ωcm

7.5 x 1010 Ωcm 3.1 x 1010 Ωcm

Surface resistivity 25°C 600°C

10.0 x 1010 Ωcm 7.0 x 109 Ωcm

4.1 x 1010 Ωcm 3.9 x 109 Ωcm

Relative permittivity 25°C 600°C

7.6 21.0

4.7 4.0

Dissipation factor 25°C 600°C

250 400

640 510

Properties shown are typical values, they are not absolute material properties, and should be used for guidance only. It is recommended that materials and components are tested for their suitability for a specific application. For more information and advice please discuss your application with our sales staff.

Typical applications: Arc shields and chutes Heater housings

Electrical formers Component mounting plates

Element supports Furnace door linings and gaskets

DURATEC® MACHINABLE CERAMIC – MACHINING INSTRUCTIONS

1.0 Straight Line Cutting

DRY CUTTING Duratec® panels should be worked and cut dry. A total thickness of up to 75mm can be cut at one time. The use of the following equipment and procedures will ensure clean, chip free edges. Saw: Overhead Radial saw/Flat bed beam saw, with hold down clamps to stop panel vibration and movement that could cause chipping. The use of a slotted board support beneath the panel is also necessary to minimize chipping. Blade: Carbide Tipped

• 460mm diameter/48 Teeth – 400mm diameter/32 Teeth

• 10 degree positive Rake

• 3.8 to 4mm Plate

• 5mm Kerf

Blade Drive: Variable depending on sharpness of blade.

• 900 rpm (Sharp)

• 600 rpm (worn)

This can be obtained either by Gearing, or an Inverter drive.

Blade Penetration: 10-12mm beyond material Feed: Variable hydraulic motor for controlling the traverse speed of saw. The Duratec® remains stationary, the saw travels. Feed Speed: Depending on thickness of board:

Thickness Feed Speed 1 Feed Speed 2

6-12mm 10 meters per minute 7 meters per minute

15-25mm 8 meters per minute 5 meters per minute

30-50mm 6 meters per minute 4 meters per minute

60-100mm 3 meters per minute 1 meter per minute

Using a sharp blade, take Feed Speed 1 with reductions as blade wears. Speed is controlled to assure clean cuts, as the cut edge deteriorates the speed is reduced until the rate dictates that a new or sharpened blade be used. Feed Speed 2 is recommended as a minimum feed rate before changing blade. Duratec® can also be cut using carbide tipped circular saws running at low revs and carbide bladed band saws. As Duratec® is abrasive, carbide tipped hand saws are recommended.

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DURATEC® MACHINABLE CERAMIC – MACHINING INSTRUCTIONS WET CUTTING Duratec® can be cut wet, but it is not the preferred method of cutting. The advantages are a better surface finish and less tool wear. The disadvantage is the care needed during drying to prevent shrinkage and cracking of the material. The Duratec ® is totally submerged in water until saturated then cut while still wet. Blade: 450mm segmented Diamond 36/44 grade. Alternatively, a polycrystalline tipped blade can be used (but tend to be expensive). These will give an excellent cutting finish which in most instances will not need to be machine finished. Blade Drive: 2500-3000 rpm Blade Penetration: 10 to 12mm Feed: Variable hydraulic or cable Feed Speed: Depending on thickness of board:

Thickness Feed Speed 6-12mm 5 meters per minute

15-25mm 3 meters per minute 30-50mm 1.5 meters per minute

60-100mm 0.5 meters per minute

2.0 Drilling Duratec® is drilled dry. Use carbide (solid/tipped) drills only

Sizes Speed 1mm to 12mm diameter 2000 to 2300 rpm

14mm to 25mm diameter 1000 to 1200 rpm 26mm to 50mm diameter 500 to 700 rpm

Feed Speed: Peck drill to stop dust build up, this will stop overheating at the drill tip, prolonging the life of the drill. The feed is determined by the diameter of the drill, and is governed by the sharpness of the tip (cutting edge). The nature of the material is very abrasive, shortening the life of the tip, hole to hole. Feed is achieved by judging the resistance against the tip on drilling (touch). Guide line speeds: Through holes

Sizes Speed 1mm – 3mm 300mm – 400mm per minute

4mm – 12mm 400mm – 500mm per minute 13mm - 20mm 400mm – 500mm per minute 21mm – 25mm 300mm – 400mm per minute

Larger holes can be drilled using two flue (carbide tipped) router cutters, but must be piloted first with a drill to clear bottom cut clearance. Holes exceeding 40mm – 50mm should be drilled using a Boring Head with carbide tipped tools, or trepanning tools, keeping speeds down to a maximum of 100 rpm.

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DURATEC® MACHINABLE CERAMIC – MACHINING INSTRUCTIONS

3.0 Turning

Duratec is turned dry.

Tooling: All solid or carbide tipped tools to be used (replaceable tips recommended)

Holding: In the majority of cases engineering practices can be applied, except when turning tubes, rings and washers.

Boring tubes can be especially difficult to hold and machine.

Typical procedure guide: (example size 50mm OD x 40mm ID x 300mm long)

• Cut piece to 55mm x 55mm x 302mm

• Place in a four jaw self-centring chuck and tail stock with revolving center

• Turn oversize, from both ends approximately 58mm OD

• Leave in chuck and drill from tail stock all the way through with 20mm-25mm drill, (peck drilling to eliminate dust

build up)

• Bore out center to 40mm using tipped boring bar placed in tool post

• Machine a plug (metal/tufnol) to fit each end, one with a square flange, one with a round flange

• Place a plug in each end, the square end into the self-centring four jaw, the round one with a round flange

• Compress with tail stock until everything rotates together

• Turn OD to size with tipped tool in the tool post

Speeds: All speeds need to be kept to an approximate 500 rpm with the exception of finished cuts, where fine cuts can

be achieved at higher speeds.

Traverse Speeds: Kept to a minimum allowing for the fragility of the piece

Tips: Use hard grade (k) cast iron or similar with angles and rakes used in engineering practices.

DURATEC® MACHINABLE CERAMIC – MACHINING INSTRUCTIONS

4.0 Tapping

Machine tapping tends to be too fierce (hand tapping is recommended)

5.0 Fasteners and Fastening

Self-tapping screws can be used (holes must be piloted to the body size of the screw) eg. a 4mm screw will need a 3mm/3.5mm pilot hole. For edge construction (box) wire helicoils are recommended

Clearance Holes: Sufficient clearance is required to allow for thermal movement of the fastener and board. 1mm minimum on

diameters for steel screw fastenings is recommended

6.0 Hand Tools

Cutting: Carbide blades recommended

Drilling: Variables speed required

Finishing Tools: Filing/sanding can be achieved, but tool life is short

7.0 Health and Safety

It is recommended that an adequate extraction system is installed adjacent to the cutting tools to remove nuisance dust

The instructions are for guidance only. We suggest that machining trials are carried out on a test piece prior to machining finished components.

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