Module 3: Assessment Quiz

Module: U8M3 - Milling Machine Operations Duration: 20-30 minutes Passing Score: 70%

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What is the primary difference between a vertical mill and a horizontal mill?

Vertical mills are larger than horizontal mills

A vertical mill has a vertically oriented spindle; a horizontal mill has a horizontally oriented spindle with an arbor for mounting cutters

Vertical mills can only drill holes

Horizontal mills are faster

Submit

Explanation: The spindle orientation defines the mill type. Vertical mills (like the Bridgeport) hold end mills and face mills in a vertical spindle—the cutter points downward. Horizontal mills mount cutters on a horizontal arbor for slab milling, gang milling, and other operations. Vertical mills are more common in makerspaces.

What is an R8 collet used for on a vertical milling machine?

To hold the workpiece in the vise

To hold cutting tools (end mills, drills) in the mill spindle

To measure the depth of cut

To lock the quill in position

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Explanation: R8 collets are the standard toolholding system for Bridgeport-style vertical mills. The collet grips the tool shank and is pulled into the spindle taper by the drawbar. Each collet size fits one specific shank diameter (3/8", 1/2", 3/4", etc.).

What is "tramming" a milling machine head?

Adjusting the table level

Aligning the spindle perpendicular to the table surface so that face mills cut flat surfaces

Setting the spindle speed

Indicating the vise

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Explanation: Tramming adjusts the mill head so the spindle axis is exactly perpendicular to the table in both the X and Y planes. If the head is not trammed, face mills will leave a concave or convex pattern and end mills will cut at an angle. A dial indicator in the spindle, swept in a circle on the table surface, is used to check and adjust tram.

What is the difference between an end mill and a drill bit?

They are the same tool

End mills can cut laterally (on their sides) as well as axially; most drill bits can only cut axially (straight down)

Drill bits are always larger

End mills are made of softer material

Submit

Explanation: End mills have cutting edges on their sides (periphery) and often on their bottom face, allowing them to plunge and then feed sideways. Standard drill bits only cut on their pointed tip and are designed for axial plunging only. Center-cutting end mills can plunge like drills, but non-center-cutting end mills cannot.

When setting up a workpiece in a milling vise, what is the purpose of parallels?

To clamp the workpiece from the sides

To measure the workpiece height

To elevate the workpiece above the vise jaws so the cutter can machine the top surface without hitting the jaws

To protect the vise from damage

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Explanation: Parallels are precision-ground steel blocks placed under the workpiece. They raise the workpiece so the machining surface is above the jaw tops, preventing the cutter from contacting the hardened vise jaws (which would destroy the cutter). Parallels must be seated firmly under the workpiece.

What does "climb milling" mean and when should it be avoided?

Milling while climbing a ladder

The cutter rotates in the same direction as the table feed; it should be avoided on machines with significant backlash in the lead screws

Milling at maximum speed

Milling upward against gravity

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Explanation: In climb (down) milling, the cutter teeth bite into the thickest part of the chip first. This produces a better surface finish and less heat but can pull the workpiece into the cutter if there is backlash in the table lead screw. Conventional (up) milling is safer on manual mills with worn lead screws.

What is the correct procedure for touching off (finding the edge of) a workpiece on the mill?

Eyeball the cutter position

Use a ruler to estimate

Use an edge finder, wiggler, or dial indicator to precisely locate the workpiece edge, then offset by the tool radius

Lower the cutter until it scratches the surface

Submit

Explanation: An edge finder (wobble finder) spins in the spindle and kicks when it contacts the workpiece edge. At the kick point, the edge finder center is exactly one radius (typically 0.100") from the workpiece edge. The operator then zeros the dial collar or DRO and adds the offset to establish the exact edge position.

What is a face mill used for?

Cutting deep slots

Drilling holes

Machining large flat surfaces on the top of a workpiece

Cutting external threads

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Explanation: A face mill is a multi-tooth cutter (typically 3-6 inserts) with a large diameter (2"-6") that machines broad, flat surfaces quickly. The inserts cut on their bottom face and slightly on their periphery. Face mills are the most efficient way to produce flat surfaces on the mill.

What is the purpose of a DRO (Digital Readout) on a milling machine?

To control the spindle speed digitally

To program automated tool paths

To display the exact table position on each axis in real time, replacing reliance on dial collar counting

To measure the workpiece temperature

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Explanation: A DRO uses linear scales mounted on each axis to display position to 0.0005" or better. It eliminates the need to count handwheel turns and dial graduations, reduces errors from backlash, and allows absolute or incremental positioning. DROs dramatically improve accuracy and productivity on manual mills.

When milling a slot with an end mill, why should you avoid plunging a non-center-cutting end mill straight down?

It will damage the vise

It is too slow

Non-center-cutting end mills have no cutting edges at the very center of their bottom face, so they cannot cut axially and will break or burn

The slot will be too wide

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Explanation: Non-center-cutting end mills have a gap at the center bottom where no cutting edge exists. Plunging straight down forces the center of the tool against the material without cutting, generating extreme heat and typically breaking the end mill. Use a center-cutting end mill for plunge cuts, or pre-drill and then feed laterally.

What is the correct order for locking the mill table axes when not in use?

X first, then Y, then Z

Lock all simultaneously

Lock any axis not being fed during the current cut to prevent unwanted movement from cutting forces

Never lock the axes

Submit

Explanation: Locking unused axes prevents the table from shifting due to cutting forces, which would ruin the cut and potentially cause a crash. For example, when feeding in the X-axis, lock Y and Z. When plunge cutting in Z, lock X and Y. This is a fundamental milling discipline.