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newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › CNC Machining › Certification Exam Preparation: NIMS, Mastercam Associate & Haas › Lesson 2
MFG-CNC14-10 · Lesson 2 · 28 clock hours · lab

NIMS Machining L1 & L2 Domain Review and Performance Skill Practice

Objective. Students achieve at or above the NIMS passing standard on all NIMS blueprint domains by working through targeted written-item banks and completing hands-on performance tasks that mirror NIMS credentialing-activity requirements.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed engineer or certified journey-level tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

NIMS Machining L1 & L2 Domain Review and Performance Skill Practice

This lab session is designed to close any remaining gaps between what you know and what NIMS requires you to demonstrate. NIMS credentials are industry-written, portable, and employer-recognized. Passing them means meeting a national standard—not just a classroom standard. Today you work through every domain NIMS tests and practice the hands-on performance skills that mirror actual credentialing activities.

The Six NIMS Domains

NIMS organizes its machining knowledge into domains. You will rotate through six stations today:

1. Measurement and Quality Control. You must select and correctly use precision instruments—digital calipers, micrometers, depth micrometers, and dial test indicators. Read an instrument to its stated resolution, apply proper measuring technique (consistent contact pressure, part temperature stabilized), and interpret whether a dimension is within tolerance. A part at the high or low limit of tolerance is still acceptable; a part outside tolerance is scrap or rework.

2. Print Reading and GD&T. Engineering drawings communicate every requirement for a part. GD&T (Geometric Dimensioning and Tolerancing) symbols define form, orientation, location, and runout controls. Know the common symbols: flatness, straightness, circularity, cylindricity, perpendicularity, parallelism, angularity, true position, concentricity, and runout. A feature control frame reads left to right: geometric characteristic symbol, tolerance value, and datum references.

3. Milling Operations. This domain covers setup, tooling selection, speeds and feeds, and the sequence of cuts on a manual or CNC milling machine. Know how to calculate spindle speed (RPM = (cutting speed × 12) ÷ (π × diameter)) and feed rate. Understand climb milling versus conventional milling and when each is appropriate.

4. Turning Operations. Lathe work includes facing, turning, boring, threading, parting, and taper turning. Apply the same RPM formula. Know tool geometry terms: rake angle, relief angle, and nose radius. Understand how nose radius affects surface finish and how depth of cut and feed interact.

5. CNC Operations. G-code and M-code fundamentals, program structure, work offsets (G54–G59), tool length offsets, canned cycles (G81 drilling, G83 peck drilling, G84 tapping, G76 threading on a lathe), and safe startup procedures. You must be able to read a short program and identify errors or describe what each block does.

6. Workplace Safety and Material Properties. Federal OSHA standards and shop-specific rules govern your behavior around machines. Know the hierarchy of controls: elimination, substitution, engineering controls, administrative controls, PPE. Understand Lockout/Tagout (LOTO): before any maintenance, cleaning, or unjamming task, shut down the machine, isolate the energy source, apply a personal lock, and verify zero energy state before touching any moving part. Know common work materials—low-carbon steel, aluminum, stainless steel, brass—and how machinability, hardness, and chip character differ among them.

Performance Skill Tasks: What NIMS Expects

NIMS credentials include both a written exam and a performance skill component. During performance tasks you will:

Accuracy is non-negotiable. A dimension outside tolerance fails the task regardless of how well the rest of the part looks.

Safety Before You Touch Any Machine

The Timed Practice Exam

The 80-question, 45-minute written practice exam runs under actual test conditions: no notes, no phone, instructor proctored. After scoring, every missed item is logged by domain in your remediation log. Match each missed item to the corresponding section in the NIMS study guide and work through that section before your retest. The published NIMS passing threshold is 70% or higher—confirm the current standard with your instructor or the NIMS website before your credentialing exam, as policies can be updated.

Remediation Path

If you score below threshold or miss a performance task dimension, you receive one structured remediation session focused on your specific weak domains, followed by one retest attempt within this lesson block. Track your scores honestly in your remediation log; that record is your roadmap to passing.

Key terms10

NIMS passing thresholdThe minimum score required to earn a NIMS credential on the written exam component; currently published at 70% or higher—verify the current figure with NIMS before your credentialing exam.
Feature control frameA rectangular box on an engineering drawing that specifies a GD&T requirement; read left to right it contains the geometric characteristic symbol, the tolerance value, and any datum references.
Lockout/Tagout (LOTO)An OSHA-required procedure to isolate and de-energize a machine before maintenance or setup work; involves shutting down, isolating the energy source, applying a personal lock, and verifying zero energy state.
Spindle speed (RPM)The rotational speed of a machine spindle in revolutions per minute, calculated from the workpiece or cutter diameter and the recommended cutting speed for the material being machined.
Canned cycleA pre-programmed G-code routine that executes a repetitive machining operation—such as drilling, peck drilling, or tapping—in a single program block, simplifying CNC programming.
True positionA GD&T control that defines the theoretically exact location of a feature and specifies a cylindrical (or other shaped) tolerance zone within which the feature's axis or center plane must lie.
First-article inspectionA complete dimensional and attribute check of the first part produced from a setup, performed to verify that the machine, tooling, and program produce parts within all drawing requirements before running a batch.
MachinabilityA relative rating of how easily a material can be cut to a good surface finish and acceptable tool life; free-machining alloys rate high, hardened steels and stainless steels rate lower.
Work offset (G54–G59)CNC controller registers that store the distance from the machine home position to the workpiece datum, allowing the program to reference part coordinates rather than machine coordinates.
Dial test indicatorA precision measuring instrument with a pivoting contact point and a graduated dial, used to check runout, flatness, and alignment to within 0.0005 in or finer.

Worked examples4

1. Calculate the spindle speed (RPM) for milling 6061 aluminum with a 0.500-inch-diameter end mill. The recommended cutting speed for aluminum with HSS tooling is 300 SFM.
  1. Write the RPM formula: RPM = (Cutting Speed × 12) ÷ (π × Diameter)
  2. Substitute values: RPM = (300 × 12) ÷ (3.1416 × 0.500)
  3. Numerator: 300 × 12 = 3600
  4. Denominator: 3.1416 × 0.500 = 1.5708
  5. Divide: 3600 ÷ 1.5708 ≈ 2292 RPM
  6. Round to the nearest available spindle speed on the machine, typically 2300 RPM or the closest setting.
Answer: Approximately 2292 RPM; use 2300 RPM or the nearest available machine speed.
2. A turned diameter measures 1.2480 in on a 0–2 in outside micrometer. The drawing calls for 1.250 in ±0.002 in. Determine whether the part is within tolerance.
  1. Identify the upper limit: 1.250 + 0.002 = 1.252 in
  2. Identify the lower limit: 1.250 − 0.002 = 1.248 in
  3. Compare the measured value (1.2480 in) to the limits: 1.248 ≤ 1.2480 ≤ 1.252
  4. 1.2480 equals the lower limit exactly, which is the boundary of acceptability.
Answer: 1.2480 in is exactly at the lower limit of 1.248 in and is therefore acceptable—the part passes this dimension.
3. A CNC program block reads: G83 X1.500 Y0.750 Z-1.000 R0.100 Q0.250 F5.0. Identify what each address does.
  1. G83 activates the peck-drilling canned cycle, which drills in incremental pecks and retracts to the R plane between each peck to clear chips.
  2. X1.500 Y0.750 defines the XY position where the hole will be drilled in the workpiece coordinate system.
  3. Z-1.000 sets the final hole depth below the workpiece zero (Z0) datum.
  4. R0.100 sets the R-plane (retract plane) height above Z0 where the tool retracts between pecks.
  5. Q0.250 sets the peck increment—the tool advances 0.250 in per peck before retracting.
  6. F5.0 sets the feed rate to 5.0 inches per minute for the drilling motion.
Answer: G83 peck-drills a hole at X1.500, Y0.750 to a depth of 1.000 in below datum, with 0.250 in pecks, retracting to 0.100 in above datum between pecks, at 5.0 IPM.
4. A drawing shows a hole diameter with a true position callout of ⌀0.010 in at MMC, referenced to datums A, B, and C. The measured center location deviates 0.004 in in X and 0.003 in in Y from true position. Does the hole pass the positional tolerance?
  1. Calculate the actual positional deviation using the distance formula: deviation = 2 × √(ΔX² + ΔY²)
  2. ΔX = 0.004 in, ΔY = 0.003 in
  3. ΔX² = 0.000016, ΔY² = 0.000009
  4. Sum = 0.000025; √0.000025 = 0.005 in
  5. Multiply by 2 to get the diameter of the positional error zone: 2 × 0.005 = 0.010 in
  6. Compare to the tolerance: 0.010 in ≤ 0.010 in (at MMC, no bonus tolerance applied here for simplicity).
Answer: The positional error diameter is exactly 0.010 in, which equals the tolerance zone diameter; the hole is at the boundary and passes the true position callout.

The math in this lesson3

Learners compare micrometer readings with ±0.002 in tolerance limits.
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Brush up in the math halls at newSchoolWorks.com:
In class: Rotate through six NIMS domain stations (measurement and quality control; print reading and GD&T; milling operations; turning operations; CNC operations; workplace safety and material properties), spending approximately 40 minutes per station completing 20 timed practice items per station drawn from the NIMS item bank, then discussing missed items with a peer reviewer using the NIMS domain explanations. · Perform two NIMS-style performance skill tasks on the manual mill and CNC lathe—each task specifies a drawing with tolerances of ±0.002 in or finer, requires selection of speeds and feeds from a machining handbook, and culminates in full first-article inspection with a coordinate measuring tool or micrometer; record all measurements on a NIMS performance task sheet and self-assess against the NIMS tolerance criteria. · Complete a 45-minute written timed practice exam of 80 NIMS-format questions under test conditions (no notes, instructor proctored), score immediately, enter results into the remediation log, and spend the remaining time in directed remediation using NIMS study guide sections matched to missed items.
Materials: NIMS Machining Level 1 and Level 2 study guides; NIMS practice item banks (school NIMS Center or NIMS-provided materials); manual mill, CNC lathe, and associated tooling; 6-inch digital calipers, 0–1 in micrometer, depth micrometer, dial test indicator; machining handbooks (Machinery's Handbook); part drawings with GD&T callouts; personal remediation logs.
Check: Students must score at or above the published NIMS passing threshold (currently 70% or higher per NIMS policy—confirm with current NIMS guidelines) on the timed 80-question written practice exam AND meet all dimensional tolerances on both performance skill tasks before this lesson is marked complete; students below threshold receive one structured remediation session and one retest attempt within the lesson block.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Measurement and Quality Control
1. During a NIMS performance skill task, you measure a turned diameter as 0.9985 in. The drawing specifies 1.000 in ±0.002 in. What is the correct conclusion?
Workplace Safety and Material Properties
2. Which OSHA-required procedure must be completed before clearing a chip jam inside a CNC lathe chuck area with the power on?
Print Reading and GD&T
3. A feature control frame reads: [⏤ | 0.005 | A]. What does this symbol and tolerance specify?
Milling Operations
4. You are milling 1018 low-carbon steel with a 0.750-inch-diameter HSS end mill at a recommended cutting speed of 100 SFM. What is the correct spindle speed?
CNC Operations
5. On a CNC machining center, G54 is used to:
Workplace Safety and Material Properties
6. When turning 304 stainless steel compared to 6061 aluminum, a machinist should generally expect:
Measurement and Quality Control
7. A NIMS-style performance task drawing calls for a bored hole diameter of 1.5000 in +0.0010/−0.0000 in. Which of the following measured values would cause the part to FAIL?
Measurement and Quality Control
8. During the 80-question NIMS timed practice exam, a student scores 64 correct answers. What is the percentage score, and does it meet the NIMS passing threshold?
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