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Activity 002: Workholding Setup and Indicator Practice

Activity ID: U8M1-ACT-002 Duration: 40 minutes Objective: Set up workholding on the lathe and mill, and practice using a dial indicator for alignment verification.

Overview

Students practice mounting workpieces in a lathe chuck, setting up a milling vise, and using a dial test indicator to verify alignment. These are prerequisite skills for all machining operations.

Materials & Equipment Needed

  • Metal lathe with three-jaw and four-jaw chucks
  • Milling machine with Kurt-style vise
  • Dial test indicator (0.001" resolution) with magnetic base
  • Precision ground test bar (1" diameter)
  • Assorted round stock (3/4", 1", 1-1/2" diameter aluminum)
  • Parallels set
  • Brass hammer (soft mallet)
  • T-slot bolts, step blocks, strap clamps
  • Safety glasses

Instructions & Procedure

Phase 1: Three-Jaw Chuck Setup (10 minutes)

  1. Open the three-jaw chuck using the chuck key.
  2. Insert a 1" diameter aluminum rod, extending approximately 2" from the jaws.
  3. Tighten the chuck firmly using the chuck key. Remove the chuck key immediately.
  4. Mount the dial indicator on the carriage or tool post with the magnetic base.
  5. Touch the indicator tip to the workpiece surface. Zero the indicator.
  6. Slowly rotate the chuck by hand (one full revolution). Read the Total Indicator Runout (TIR).
  7. Record the TIR. Typical for a three-jaw: 0.003-0.005".
  8. Repeat with a different diameter rod (3/4" or 1-1/2").

Phase 2: Four-Jaw Chuck Centering (15 minutes)

  1. Switch to the four-jaw independent chuck (instructor assists with chuck change).
  2. Roughly center the 1" aluminum rod using the jaw markings as guides.
  3. Mount the dial indicator to contact the rod surface.
  4. Rotate the chuck by hand. Note the high and low points on the indicator.
  5. Centering process:
  6. Identify the jaw nearest the high point (maximum indicator reading)
  7. Loosen that jaw slightly and tighten the opposing jaw to move the workpiece toward center
  8. Rotate again and repeat for the perpendicular jaw pair
  9. Iterate until TIR is 0.002" or less
  10. Record the final TIR. Note how many iterations were required.

Phase 3: Mill Vise Setup (10 minutes)

  1. Clean the mill table and vise base thoroughly—any debris causes misalignment.
  2. Bolt the vise to the mill table using T-slot bolts. Snug but not fully tight.
  3. Mount the dial indicator in the mill spindle using a magnetic base on the quill.
  4. Touch the indicator to the fixed jaw face.
  5. Move the table in the X-axis using the handwheel. The indicator should read consistently along the jaw face.
  6. If the jaw is not parallel to X travel, tap the vise body with a brass hammer to adjust. Re-check with the indicator.
  7. Once the jaw is within 0.001" over its full length, fully tighten the mounting bolts.
  8. Re-verify alignment after tightening (tightening can shift the vise).

Phase 4: Workpiece in Vise (5 minutes)

  1. Place parallels in the vise (appropriate height to elevate the workpiece above the jaw tops).
  2. Place an aluminum block on the parallels.
  3. Tighten the vise handle firmly.
  4. Tap the workpiece down onto the parallels with a brass hammer. Check that both parallels are captive (cannot slide out).
  5. If a parallel is loose, the workpiece is not seated—loosen, reposition, and retighten.

Discussion Points

  • Why is removing the chuck key the most critical habit in machining?
  • What TIR would be acceptable for roughing vs. finishing operations?
  • Why must the mill vise be indicated every time it is mounted?
  • What happens if parallels are not fully seated?

Expected Outcomes

  • Students can mount workpieces in three-jaw and four-jaw chucks
  • Students can center a workpiece in a four-jaw chuck to within 0.002" TIR
  • Students can indicate a mill vise to within 0.001" over its jaw length
  • Students demonstrate chuck key discipline (immediate removal after use)

Assessment Rubric

Criteria Excellent (4) Proficient (3) Developing (2) Beginning (1)
Three-Jaw Setup Clean setup, key removed immediately, TIR recorded Minor prompting on key removal Needed guidance on indicator setup Cannot operate chuck
Four-Jaw Centering Achieved <0.002" TIR in <5 iterations Achieved <0.002" in 5-8 iterations Achieved <0.005" Cannot center workpiece
Vise Indication <0.001" alignment, maintained after tightening <0.002" alignment Aligned but shifted on tightening Cannot use indicator
Chuck Key Discipline Never left key in chuck Left key once, self-corrected Required prompting twice Repeatedly left key

Safety Considerations

  • NEVER leave the chuck key in the chuck—it becomes a lethal projectile when the lathe starts
  • Always stand clear of the chuck when another person is near the lathe controls
  • Use only a brass or soft mallet for tapping workpieces—never a steel hammer on aluminum
  • Keep the indicator away from moving parts when spinning the chuck
  • Safety glasses required throughout

Last Updated: 2026-03-19