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NIMS CNC practice questions

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Question 1Safety, Health, and Environmental Practices

When operating a CNC lathe that sprays coolant, which eye protection is appropriate?

  1. Safety glasses with side shields Correct answer.
  2. Tinted sunglasses
  3. Prescription reading glasses without side shields
  4. A face shield only

Explanation

Safety glasses with side shields protect against coolant droplets and flying chips from the front and side. Prescription eyewear without shields and ordinary sunglasses do not meet impact-protection requirements. A face shield alone does not provide adequate primary eye protection.

Question 2Safety, Health, and Environmental Practices

Oil and coolant accumulate on the floor around a CNC mill. What is the best control?

  1. Cover the puddle with cardboard
  2. Clean it up and repair the leak Correct answer.
  3. Mark the area with tape
  4. Wait for the end of the shift

Explanation

Slips are prevented by removing the hazard at its source, so the spill should be cleaned and the leak repaired. Covering or marking the puddle leaves the slip hazard in place. Waiting until the end of the shift leaves workers exposed.

Question 3Safety, Health, and Environmental Practices

Before reaching into a CNC machine's work enclosure, what should you do first?

  1. Open the enclosure door and look inside
  2. Press E-stop and wait for zero motion Correct answer.
  3. Ask a nearby coworker to observe
  4. Reduce spindle speed to its lowest setting

Explanation

The emergency stop removes power from the drives, and the operator must wait until all motion has stopped before reaching in. Low spindle speed is not a safe substitute for a full stop. A coworker watching does not protect the operator's hands.

Question 4Safety, Health, and Environmental Practices

Where should you find the hazards of a coolant concentrate before mixing it?

  1. The drum's shipping label
  2. The supplier invoice file
  3. Its safety data sheet Correct answer.
  4. The machine maintenance log

Explanation

A safety data sheet lists the product's health hazards, handling precautions, and first-aid measures. Shipping labels and invoices carry only limited information. Maintenance logs do not describe chemical hazards.

Question 5Safety, Health, and Environmental Practices

What is the safest way to lift a heavy CNC toolholder from a cart?

  1. Bend at the waist and keep your arms straight
  2. Twist your torso during the lift
  3. Bend your knees and keep load close Correct answer.
  4. Lift quickly with a jerking motion

Explanation

Bending the knees and holding the load close uses the leg muscles and reduces strain on the lower back. Bending at the waist or twisting while lifting loads the spine in a vulnerable position. Jerking motions increase the force on the back.

Question 6Safety, Health, and Environmental Practices

Prolonged skin contact with metalworking coolant can cause dermatitis. What is the best preventive practice?

  1. Use mild soap and barrier cream Correct answer.
  2. Rinse hands in solvent after work
  3. Wear cotton gloves kept soaked in coolant
  4. Skip washing and let hands air-dry

Explanation

Mild soap removes coolant without stripping the skin, and barrier cream helps protect against contact dermatitis. Solvents defat the skin and worsen irritation. Gloves that stay wet hold coolant against the skin.

Question 7Safety, Health, and Environmental Practices

A maintenance task requires reaching past the guard of a CNC mill. What must be done before the guard is removed?

  1. Lock out and verify zero energy Correct answer.
  2. Place a warning sign on the door
  3. Reduce the feed rate override to zero
  4. Notify the shift supervisor and wait

Explanation

Lockout/tagout isolates hazardous energy, and verification confirms that the machine cannot start or move. Reducing the feed override does not remove stored or electrical energy. A warning sign is only an administrative control.

Question 8Safety, Health, and Environmental Practices

Why must a CNC machine's interlocked door not be bypassed?

  1. It raises tool wear rates
  2. It keeps hands from moving parts Correct answer.
  3. It increases the cycle time
  4. It voids the machine's coolant warranty

Explanation

The interlock stops spindle and axis motion when the door opens, preventing access to moving parts. Bypassing it allows the machine to run with the enclosure open. Warranty, cycle time, and tool wear are not the safety reason for the interlock.

Question 9Safety, Health, and Environmental Practices

What is the correct way to remove stringy chips from around a CNC lathe chuck?

  1. Blow them off with the coolant hose
  2. Grab them with a gloved hand
  3. Use compressed air at high pressure
  4. Use a hook or brush, not hands Correct answer.

Explanation

A hook or brush keeps hands away from sharp chips and the chuck. Compressed air can drive chips into the eyes or skin, and a gloved hand can be cut or pulled in. The coolant hose spreads chips and creates a slip hazard.

Question 10Safety, Health, and Environmental Practices

Why is it unsafe to use compressed air to clean metal chips off your clothing?

  1. It cools the skin far too quickly
  2. It wastes expensive shop air pressure
  3. It can drive chips into skin or eyes Correct answer.
  4. It leaves an oily film on clothing

Explanation

Compressed air can propel chips and debris into the eyes or through the skin. Air should not be used for cleaning clothing or body parts. Air pressure costs and oily residue are not the primary safety concerns.

Question 11Safety, Health, and Environmental Practices

A CNC grinder runs above 85 dBA for a full shift. What is the employer's first obligation?

  1. Post a warning sign and take no action
  2. Rotate workers between machines hourly
  3. Hand out earplugs at the end of the shift
  4. Measure exposure and protect hearing Correct answer.

Explanation

Noise exposure must be assessed and, where it exceeds the action level, a hearing conservation program with hearing protection is required. Distributing protection after the shift provides no benefit. Rotation and signs alone do not control the hazard.

Question 12Safety, Health, and Environmental Practices

A small pail of coolant tips over on the shop floor. What is the first step?

  1. Cover the puddle with a tarp
  2. Absorb it with sawdust and sweep
  3. Hose it into the nearest floor drain
  4. Stop the source and block the area Correct answer.

Explanation

Controlling the source and keeping people away prevents the spill from spreading and protects others from slipping. Draining coolant to the floor drain may violate discharge rules. Absorbing is a later step, and a tarp over a puddle creates a hidden slip hazard.

Question 13Safety, Health, and Environmental Practices

Before opening an electrical cabinet on a CNC machine, what should you do?

  1. Wear rubber gloves and proceed
  2. Lock out and test for voltage Correct answer.
  3. Turn off the coolant pump only
  4. Stand on a dry wooden pallet

Explanation

Electrical work requires isolating the supply, applying lockout, and verifying the absence of voltage with a meter. Rubber gloves and a wooden pallet do not substitute for de-energizing. Turning off only the coolant pump leaves the cabinet energized.

Question 14Safety, Health, and Environmental Practices

A small fire starts in a CNC's coolant sump. Which extinguisher class is designed for flammable liquids?

  1. Class C
  2. Class B Correct answer.
  3. Class A
  4. Class D

Explanation

Class B extinguishers are rated for flammable liquids such as oils and coolants. Class A is for ordinary combustibles, Class C for energized electrical equipment, and Class D for combustible metals.

Question 15Safety, Health, and Environmental Practices

Machining with coolant produces fine mist. What is the most effective control?

  1. Wear a disposable dust mask
  2. Run a floor fan to blow mist away
  3. Open a nearby window for air
  4. Use local exhaust ventilation Correct answer.

Explanation

Local exhaust at the enclosure captures mist before it reaches the operator's breathing zone. A window or floor fan only moves contaminated air around the shop. A dust mask is not appropriate for oil mist.

Question 16Safety, Health, and Environmental Practices

When using an overhead hoist to load a heavy workpiece into a CNC, what should you do?

  1. Walk the load quickly across the shop floor
  2. Stand under the load to guide it
  3. Use the hoist to lift beyond its rating
  4. Keep the load low and stand clear Correct answer.

Explanation

Keeping the load low limits the fall distance, and standing clear keeps the operator out of the drop zone. Walking a load quickly or exceeding the rated capacity increases the chance of a swing or failure. No one should stand beneath a suspended load.

Question 17Safety, Health, and Environmental Practices

A CNC machine has a vertical axis that can fall when power is removed. What must be done during lockout?

  1. Block or pin the axis against gravity Correct answer.
  2. Lower the axis by hand quickly
  3. Leave the axis in its raised position
  4. Rely on the servo brake alone

Explanation

Gravity is stored energy, so the axis must be blocked or pinned before work begins. A servo brake may not hold the load once power is removed. Lowering by hand or leaving the axis raised does not control the stored energy.

Question 18Safety, Health, and Environmental Practices

Which health effect is most associated with long-term exposure to metalworking fluid mist?

  1. Hearing loss from noise
  2. Lung irritation and asthma Correct answer.
  3. Carpal tunnel syndrome
  4. Skin sensitivity to sunlight

Explanation

Inhaled metalworking fluid mist can irritate the respiratory tract and is linked to occupational asthma. Hearing loss comes from noise, and carpal tunnel syndrome from repetitive hand motion. Sun sensitivity is not the characteristic effect of fluid mist.

Question 19Safety, Health, and Environmental Practices

Used metalworking coolant is best managed as which type of waste?

  1. Recyclable paper waste
  2. Regulated industrial waste Correct answer.
  3. Clean water sent to the drain
  4. Regular trash in sealed bags

Explanation

Spent coolant contains oils, additives, and metal fines, so it is managed as regulated industrial or hazardous waste under the applicable rules. It must not go into regular trash or a drain. It is not a paper recyclable.

Question 20Safety, Health, and Environmental Practices

An operator wears a loose long-sleeved shirt while polishing a rotating shaft on a lathe. What is the primary hazard?

  1. Static electricity buildup on the shirt
  2. Coolant splashing the face
  3. Clothing caught by the rotating part Correct answer.
  4. Chip burns on the arms

Explanation

Loose clothing can be grabbed by a rotating shaft and pull the operator into the machine. This entanglement hazard is why sleeves must be secured and polishing near rotating parts is controlled. Static, splashing coolant, and chip burns are not the main risk in this situation.

Question 21Blueprint Reading, GD&T, and Drawing Interpretation

On a multi-view mechanical drawing, what does a hidden line (a line of short dashes) represent?

  1. An edge or surface not visible in that view Correct answer.
  2. The path of a part that moves during operation
  3. The centerline of a symmetrical feature
  4. A surface that has already been machined away

Explanation

Hidden lines show edges and surfaces that lie behind visible material in a given view, so internal or obscured features can still be located. They are drawn as short dashes to distinguish them from visible object lines.

Question 22Blueprint Reading, GD&T, and Drawing Interpretation

Reading from left to right, what is the correct order of the entries in a feature control frame?

  1. Geometric symbol, tolerance zone, datums Correct answer.
  2. Geometric symbol, datums, tolerance zone
  3. Tolerance zone, geometric symbol, datum references
  4. Datum references, geometric symbol, tolerance zone

Explanation

A feature control frame is read left to right as the geometric characteristic symbol, the tolerance zone (with any material condition modifier), and the datum references given in order of precedence.

Question 23Blueprint Reading, GD&T, and Drawing Interpretation

A hole is dimensioned as ⌀0.500 / ⌀0.490. What are the maximum hole size and the total tolerance?

  1. 0.490 and 0.010
  2. 0.500 and 0.020
  3. 0.495 and 0.005
  4. 0.500 and 0.010 Correct answer.

Explanation

In a limit dimension the larger number is the maximum permissible size and the smaller number is the minimum. The total tolerance is their difference, 0.500 minus 0.490, which is 0.010.

Question 24Blueprint Reading, GD&T, and Drawing Interpretation

A thread callout reads 1/4-20 UNC 2B. What does the 20 specify?

  1. The class of fit
  2. The major diameter in millimetres
  3. The threads per inch Correct answer.
  4. The thread length in inches

Explanation

In a unified thread callout the number following the nominal diameter is the pitch expressed as threads per inch. UNC denotes the coarse series and 2B denotes a class of fit for an internal thread.

Question 25Blueprint Reading, GD&T, and Drawing Interpretation

A drawing note states SCALE 2:1. What does this mean?

  1. All dimensions must be doubled to get true size
  2. Two views are needed to define the part
  3. The part is twice the size of the drawing
  4. The view is drawn twice actual size Correct answer.

Explanation

In a drawing scale the first number refers to the drawing and the second to the real part, so 2:1 means the drawn geometry is twice full size. Dimensions always state true size regardless of the scale used.

Question 26Blueprint Reading, GD&T, and Drawing Interpretation

A dimension value enclosed in a rectangle on a drawing is a:

  1. datum target dimension
  2. limit dimension
  3. basic dimension Correct answer.
  4. reference dimension

Explanation

A boxed value is a basic dimension: a theoretically exact size carrying no tolerance of its own, used to establish true profile or true position. Its permissible variation comes from the associated geometric tolerance.

Question 27Blueprint Reading, GD&T, and Drawing Interpretation

In a section view, evenly spaced parallel hatch lines indicate:

  1. the location of the cutting plane
  2. areas that require surface grinding
  3. internal threads in the part
  4. solid material cut by the plane Correct answer.

Explanation

Hatching represents the solid material intersected by the imaginary cutting plane, which reveals internal features that would otherwise be hidden. In an assembly, adjacent parts are hatched at different angles or spacings.

Question 28Blueprint Reading, GD&T, and Drawing Interpretation

In third-angle projection, where is the right-side view placed on the drawing?

  1. to the right of the front view Correct answer.
  2. on the left side of the front view
  3. directly below the front view
  4. directly above the front view

Explanation

Third-angle projection places each view on the side of the front view from which it is observed, so the right-side view goes to the right. First-angle projection reverses this arrangement.

Question 29Blueprint Reading, GD&T, and Drawing Interpretation

A primary datum plane established by three points of contact removes how many degrees of freedom from a part?

  1. One
  2. Three Correct answer.
  3. Six
  4. Two

Explanation

A primary datum plane contacts the part at a minimum of three points, preventing translation along the plane normal and rotation about two axes. That is three of the six degrees of freedom available to a free body.

Question 30Blueprint Reading, GD&T, and Drawing Interpretation

Which statement correctly distinguishes flatness from parallelism?

  1. Flatness requires a datum; parallelism does not
  2. Both are orientation tolerances, but flatness applies only to cylindrical features
  3. Flatness is a form tolerance; parallelism is an orientation tolerance Correct answer.
  4. Flatness controls surface texture and parallelism controls size

Explanation

Form tolerances such as flatness are self-referencing and never cite a datum, because they control only the shape of the feature itself. Parallelism is an orientation tolerance, so it must reference a datum to establish the direction the surface must follow.

Question 31Blueprint Reading, GD&T, and Drawing Interpretation

A hole is dimensioned ⌀10.0 ±0.2 and carries a position tolerance of ⌀0.4 Ⓜ. If the hole is produced at ⌀10.4, what total position tolerance applies?

  1. ⌀0.4
  2. ⌀0.8
  3. ⌀1.0 Correct answer.
  4. ⌀0.6

Explanation

For an internal feature at MMC the maximum material condition is the smallest permitted size, here 9.8. The bonus is the departure from MMC, 10.4 minus 9.8 equals 0.6, which is added to the stated ⌀0.4 for a total of ⌀1.0.

Question 32Blueprint Reading, GD&T, and Drawing Interpretation

Circular runout differs from total runout in that circular runout:

  1. controls the entire surface in a single continuous sweep
  2. is checked one cross-section at a time Correct answer.
  3. applies only to faces perpendicular to the datum axis
  4. does not require a datum axis

Explanation

Circular runout is measured with the indicator held at one axial position while the part makes a full rotation, so each circular element is judged separately. Total runout moves the indicator along the surface while the part rotates, controlling the whole feature at once.

Question 33Blueprint Reading, GD&T, and Drawing Interpretation

A profile of a surface tolerance of 0.5 is applied to a curved surface. The tolerance zone is bounded by:

  1. a cylinder 0.5 in diameter
  2. two surfaces 0.5 apart about the true profile Correct answer.
  3. a sphere of radius 0.5 centred on the profile
  4. two parallel planes 0.5 apart

Explanation

Profile of a surface creates a three-dimensional zone between two boundaries offset from the true profile, which is why basic dimensions define the profile. Unless otherwise specified, the tolerance is divided equally, 0.25 on each side.

Question 34Blueprint Reading, GD&T, and Drawing Interpretation

Perpendicularity applied to a flat surface with respect to a datum plane creates a zone of:

  1. two concentric circles centred on the datum axis
  2. a cylinder perpendicular to the datum
  3. a single plane at exactly 90°
  4. two parallel planes at 90° to the datum Correct answer.

Explanation

When perpendicularity is applied to a surface, the tolerance zone is two parallel planes exactly perpendicular to the datum and separated by the tolerance value. Every point of the controlled surface must lie between those planes.

Question 35Blueprint Reading, GD&T, and Drawing Interpretation

A surface texture symbol specifies Ra 1.6. What does Ra describe?

  1. the average spacing between adjacent peaks
  2. the arithmetic average roughness of the profile Correct answer.
  3. the waviness of the surface over its full length
  4. the maximum peak-to-valley height of the profile

Explanation

Ra is the arithmetical mean roughness, calculated as the average absolute deviation of the filtered profile from its mean line. It is the parameter most commonly specified on drawings.

Question 36Blueprint Reading, GD&T, and Drawing Interpretation

Why is baseline (ordinate) dimensioning usually preferred over chain dimensioning for a row of holes?

  1. it avoids tolerance build-up between holes Correct answer.
  2. it removes the need to reference datum features
  3. it permits much larger tolerances on each hole
  4. it removes the need for a tolerance title block

Explanation

With chain dimensioning each feature is located from the previous one, so tolerances accumulate and the last feature carries the greatest error. Baseline dimensioning locates every feature from a single datum, so each tolerance applies independently.

Question 37Blueprint Reading, GD&T, and Drawing Interpretation

A datum feature symbol attached to a size dimension such as ⌀30 identifies:

  1. the dimension as a reference dimension
  2. the axis or centre plane of that feature Correct answer.
  3. the surface of the feature closest to the symbol
  4. the feature as one requiring full inspection

Explanation

When the datum feature symbol is placed on the dimension line, aligned with an extension line or attached to the dimension, the datum is the axis or centre plane of the feature of size. Attaching the symbol directly to a surface instead makes that surface the datum.

Question 38Blueprint Reading, GD&T, and Drawing Interpretation

An auxiliary view is added to a drawing mainly to:

  1. show the part as it appears after assembly
  2. show an inclined surface in true shape and size Correct answer.
  3. indicate the sequence of machining operations
  4. enlarge a small feature for clarity

Explanation

Auxiliary views are projected perpendicular to an inclined surface so that surface appears in true shape and size, which ordinary orthographic views cannot provide. They are commonly used for angled faces carrying holes or slots.

Question 39Blueprint Reading, GD&T, and Drawing Interpretation

A pin is dimensioned ⌀0.500 ±0.002 and is limited by a position tolerance of ⌀0.010 Ⓜ. What is its virtual condition size?

  1. ⌀0.512 Correct answer.
  2. ⌀0.488
  3. ⌀0.522
  4. ⌀0.498

Explanation

For an external feature the maximum material condition is the largest permitted size, 0.502. The virtual condition is the MMC size plus the geometric tolerance, giving 0.512, which is the boundary the mating part must clear.

Question 40Blueprint Reading, GD&T, and Drawing Interpretation

A position tolerance on a hole that receives a stud or press-fit pin uses the projected tolerance zone modifier Ⓟ. Why?

  1. to transfer the tolerance to the mating part
  2. to allow the hole to be checked with a go/no-go plug gauge
  3. to control the axis beyond the feature so a mating part fits Correct answer.
  4. to relax the tolerance on the hole in proportion to its length

Explanation

The projected tolerance zone extends the controlled axis out of the part by a stated distance, covering the region where the mating pin or stud actually engages. This prevents a fastener that is within tolerance at the hole exit from binding in the mating part.

Question 41Blueprint Reading, GD&T, and Drawing Interpretation

In a composite position tolerance, the upper segment of the frame controls:

  1. the surface finish inside each hole
  2. only the size of the individual holes
  3. the orientation of each feature within the pattern, ignoring location
  4. the location of the pattern relative to all the referenced datums Correct answer.

Explanation

The upper segment of a composite frame is the pattern-locating control, governing the position of the pattern as a group relative to the full datum reference frame. The lower segment, carrying a tighter tolerance, controls only the orientation and spacing of the features to each other.

Question 42Blueprint Reading, GD&T, and Drawing Interpretation

Under the envelope requirement (Rule #1), a shaft dimensioned ⌀20.0 ±0.1 must at every permissible size:

  1. have an axis that is perfectly straight regardless of size
  2. be inspected for size only and not for form
  3. fit inside a ⌀20.1 perfect cylinder at all sizes Correct answer.
  4. never measure larger than ⌀19.9

Explanation

Rule #1 states that the limits of size also control form, so the surface may not violate the envelope of a perfect cylinder at the maximum material condition, here ⌀20.1. As the feature departs from MMC, additional form variation is permitted within the size limits.

Question 43Blueprint Reading, GD&T, and Drawing Interpretation

A datum feature of size is referenced at Ⓜ in the feature control frame. What does this permit?

  1. no movement at all between the part and the datum simulator
  2. datum shift equal to the departure from MMB Correct answer.
  3. the datum to be treated as a single point rather than an axis
  4. the datum to be established from the least material boundary

Explanation

Referencing a datum feature of size at MMB fixes the datum simulator at the virtual condition boundary and allows the part to shift within the resulting clearance. The amount of available shift equals the datum feature's departure from its maximum material boundary size.

Question 44Blueprint Reading, GD&T, and Drawing Interpretation

A hole is located by coordinate tolerances of ±0.1 in X and Y. Compared with a position callout of ⌀0.2, the coordinate method:

  1. produces a circular tolerance zone of the same diameter
  2. has no effect on whether the part is accepted
  3. permits corner locations outside the ⌀0.2 circle Correct answer.
  4. is always more restrictive on the produced part

Explanation

Square coordinate tolerances of ±0.1 give a 0.2 by 0.2 zone whose diagonally located corners lie about 0.141 from true position, beyond the 0.1 radius of a ⌀0.2 position zone. Because position defines a cylindrical zone, the two methods are not equivalent.

Question 45Precision Measurement and Inspection

A vernier caliper has a main scale graduated in 1 mm and a vernier plate divided into 50 equal divisions. What is the smallest value the instrument can read?

  1. 0.01 mm
  2. 0.10 mm
  3. 0.05 mm
  4. 0.02 mm Correct answer.

Explanation

The vernier spreads one main-scale millimetre over 50 divisions, so one vernier division represents 1 mm divided by 50, which is 0.02 mm. This least count is the smallest difference the caliper can resolve.

Question 46Precision Measurement and Inspection

A metric outside micrometer advances the spindle 0.5 mm per revolution, and the thimble carries 50 graduations. What value does one thimble division represent?

  1. 0.005 mm
  2. 0.05 mm
  3. 0.01 mm Correct answer.
  4. 0.02 mm

Explanation

One division equals the spindle advance per revolution divided by the number of thimble divisions, so 0.5 mm divided by 50 gives 0.01 mm. That is why a standard metric micrometer reads directly to hundredths of a millimetre.

Question 47Precision Measurement and Inspection

A dial indicator is graduated at 0.01 mm per division. After contacting a part, the needle stops 14 divisions from the zero mark. What displacement does the indicator show?

  1. 0.014 mm
  2. 0.14 mm Correct answer.
  3. 1.4 mm
  4. 0.0014 mm

Explanation

Multiply the number of graduations travelled by the value of one division: 14 multiplied by 0.01 mm gives 0.14 mm. The displacement is read directly from the number of graduations the needle has passed.

Question 48Precision Measurement and Inspection

What is the primary role of gauge blocks in a precision shop?

  1. To measure the depth of a blind hole without a depth gauge
  2. To provide a certified length standard for calibration Correct answer.
  3. To check the hardness of a heat-treated workpiece surface
  4. To verify the surface roughness of a machined face

Explanation

Gauge blocks are precision length standards that are wrung together to build a known dimension. They are used to set or verify calipers, micrometers, height gauges and sine bars rather than to measure a part directly.

Question 49Precision Measurement and Inspection

Why is granite commonly chosen for precision surface plates?

  1. It expands more than steel when the shop warms up
  2. It can be ground to a sharp edge for layout work
  3. It is softer than cast iron and will not scratch parts
  4. It resists corrosion and holds its flatness over time Correct answer.

Explanation

Granite is hard, corrosion resistant and dimensionally stable, so a lapped granite plate keeps its flat reference surface for many years. It also does not rust or raise burrs when parts are slid across it.

Question 50Precision Measurement and Inspection

In metric practice, precision dimensional measurements are conventionally referenced to which temperature?

  1. 20 °C Correct answer.
  2. 0 °C
  3. 10 °C
  4. 25 °C

Explanation

International practice defines 20 °C as the reference temperature for dimensional measurement, so a part and a gauge at 20 °C both carry their stated size. Measuring far from this temperature introduces expansion or contraction error.