Your Answer : (Not Answered)

Correct Answer : C

A point to point system suits Drilling.

In point to point (positioning) control, the machine moves the tool or table to a programmed position, stops, and then performs an operation there. The path taken between points does not matter, because no cutting happens during the move. Drilling, reaming, tapping and punching patterns of holes are exactly this kind of work.

Milling and turning cut while the tool is moving, so the path and feed rate along it must be controlled continuously; they need straight-cut or contouring systems.

Your Answer : (Not Answered)

Correct Answer : D

The answer is none of these: every method listed is used for taper turning.

A form tool turns short tapers by plunging a tool ground to the taper angle. Swivelling the compound rest turns short, steep tapers by hand feed. Combining longitudinal and cross feed moves the tool along a sloping line, which is how the taper turning attachment and CNC lathes produce tapers.

Since each of the first three is a recognised taper-turning method, none of them is the one 'not used'.

Your Answer : (Not Answered)

Correct Answer : A

The keyed material removal rate is 7538.4 mm³/min.

The key uses the standard approximation MRR = cutting speed × feed × depth of cut, with the cutting speed taken at the original diameter. Feed per revolution is the axial speed divided by rpm, and depth of cut is half the reduction in diameter:

\[ \begin{aligned} f &= \frac{200}{500} = 0.4\ \text{mm/rev}, \quad d = 1\ \text{mm} \\ v &= \pi \times 12 \times 500 = 18850\ \text{mm/min} \\ \text{MRR} &= v f d \approx 7540\ \text{mm}^{3}/\text{min} \end{aligned} \]

With \(\pi\) taken as 3.141 this is 7538.4. Measured exactly, as the annulus removed per minute, \(\frac{\pi}{4}(12^2 - 10^2) \times 200\), the rate is lower, about 6910, because the cutting speed falls across the depth of cut; that value is not offered, so the paper follows the textbook formula.

Your Answer : (Not Answered)

Correct Answer : D

The spindle speed is 50 rpm.

Cutting speed is the surface speed of the work, \(v = \pi D N / 1000\) with \(v\) in m/min and \(D\) in mm. Rearranging:

\[ \begin{aligned} N &= \frac{1000\,v}{\pi D} = \frac{1000 \times 31.4}{3.14 \times 200} \\ &= \frac{31400}{628} = 50 \end{aligned} \]

Forgetting the factor 1000 that converts metres to millimetres, or using the radius instead of the diameter, produces the other answers: with the radius of 100 mm the result is 100 rpm.

Your Answer : (Not Answered)

Correct Answer : C

The accessory that supports a long, slender job is the steady rest.

A long thin job held between centres or in a chuck sags and springs away from the tool. A steady rest, clamped to the bed, carries three adjustable jaws that bear on the job part-way along its length and stop it deflecting, so it can be turned, drilled or bored at the end.

A dead centre supports the job only at its end, in the tailstock. A lathe dog and a lathe carrier are the same device: a clamp that transmits the drive from the driving plate to the job; neither gives any support.

Your Answer : (Not Answered)

Correct Answer : B

Lathe beds are usually made of cast iron.

Grey cast iron suits a machine bed: it absorbs vibration well, which reduces chatter; it is stable and keeps its shape; it can be cast into the complex box sections a bed needs; and the graphite in it gives the guideways good wearing and sliding properties. It is also cheap.

Mild steel and stainless steel damp vibration poorly and are expensive to form into a bed, and an aluminium alloy is too flexible and wears too quickly for the ways of a machine tool.

Your Answer : (Not Answered)

Correct Answer : A

The drill size is 9.75 mm.

Before reaming, the hole is drilled smaller than the finished size to leave a reaming allowance. Using the workshop formula

\[ \begin{aligned} \text{drill size} &= \text{reamed size} - (\text{undersize} + \text{oversize}) \\ &= 10 - (0.2 + 0.05) = 9.75\ \text{mm} \end{aligned} \]

9.8 mm subtracts only the undersize and leaves out the oversize a drill tends to cut. 10.25 mm is larger than the reamer, which would leave nothing to ream, and 9.85 mm subtracts the difference of the two allowances (0.2 − 0.05) instead of their sum.

Your Answer : (Not Answered)

Correct Answer : D

The answer is None of the above, because all three statements are true.

Gang milling uses two or more cutters mounted together on the same arbor of a horizontal milling machine, so that several surfaces are machined in one pass. The cutters may be of the same or different diameters and widths, depending on the profile and the heights of the surfaces to be cut, and each cutter is mounted on the arbor.

Since none of the first three statements is false, none of them can be 'not true', which leaves 'None of the above'. Straddle milling is the special case of two side-and-face cutters spaced apart to machine two parallel faces at once.

Your Answer : (Not Answered)

Correct Answer : B

They should remain parallel to each other.

A plate cam is milled on a vertical milling machine with the cam blank on a dividing head. The dividing head spindle and the vertical head spindle are tilted to the same angle, keeping the axis of the blank parallel to the axis of the end mill. As the blank is rotated and fed, the end mill then cuts the cam profile square across the blank's face, and the angle of tilt sets the lead (rise) of the cam.

If the axes were inclined to each other the cutter would cut the profile at a slant. 'Opposite' and 'vertical and inclined' do not describe a fixed geometric relationship at all.

Your Answer : (Not Answered)

Correct Answer : D

The answer is All of the above.

Each of these removes metal with hard abrasive grains rather than a defined cutting edge. Grinding uses a rotating bonded abrasive wheel. Honing uses bonded abrasive stones that rotate and reciprocate in a bore to correct its geometry and finish. Lapping uses loose fine abrasive in a paste between the work and a lap to produce very flat or very fine surfaces.

Since all three are abrasive processes, picking only one of them is incomplete.

Your Answer : (Not Answered)

Correct Answer : A

The rake angle for tapping cast iron is about 3 degrees.

Cast iron is brittle and breaks into short, powdery chips, so it needs little rake: a small rake angle, around 0 to 3 degrees, keeps the cutting edges strong and stops them digging in and chipping.

Larger rake angles are for ductile materials that form long chips: about 8 to 12 degrees for steels, and up to about 20 degrees for soft metals such as aluminium. Using them on cast iron would weaken the cutting edges for no gain.

Your Answer : (Not Answered)

Correct Answer : D

Chips break because of the work hardening of the work material.

As the chip forms, the metal in it is severely deformed in the shear zone and then curls against the tool face. This plastic deformation strain-hardens it, making it harder and less ductile, so the curling chip cracks and breaks into short pieces. Chip breakers on the tool increase the curl to make use of this effect.

Toughness and ductility work the other way: they let the metal deform without fracture, producing long continuous chips. Elasticity is recoverable deformation and plays no part in breaking chips.

Your Answer : (Not Answered)

Correct Answer : D

Shapers commonly use the crank and slotted link mechanism.

A bull gear carries a crank pin and sliding block that runs in a slotted link (rocker arm) pivoted at its lower end. As the bull gear turns at uniform speed, the crank sweeps a larger angle during the forward (cutting) stroke than during the return stroke, so the ram returns faster and less time is wasted on the idle stroke.

Bevel gears change the direction of a drive, a pawl and ratchet gives intermittent motion (it is used for the cross feed of a shaper), and a worm and worm wheel gives a large speed reduction. None of them produces a quick return.

Your Answer : (Not Answered)

Correct Answer : B

The prick punch used for witness marks is ground to 60 degrees.

Prick punches are made with two point angles. The fine 30 degree point makes light marks used to locate the leg of a pair of dividers. The 60 degree point makes the bolder marks punched along a scribed line as witness marks, so that the line can still be seen if the scribed mark is rubbed off.

90 degrees is the angle of a centre punch, which makes a large mark to start a drill. 20 degrees is not a standard punch angle, and the 30 degree prick punch is for divider marks, not witness marks.

Your Answer : (Not Answered)

Correct Answer : C

The cutting fluid for aluminium is kerosene.

Aluminium is soft and tends to stick to the cutting edge, forming a built-up edge. Kerosene, or paraffin, is a thin oil that wets the surface well, prevents the chips welding to the tool and gives a good finish, which is why trade practice lists it for aluminium.

Water alone does not lubricate and promotes corrosion. An air jet only clears chips and cools slightly. Ethanol is not used as a cutting fluid in workshop practice.

Your Answer : (Not Answered)

Correct Answer : C

A blind hole is reamed with a right hand spiral fluted reamer.

In a blind hole the chips have nowhere to go ahead of the tool, so they must be carried back out. A right-hand spiral on a right-hand cutting reamer lifts the chips up the flutes and out of the hole, the way a twist drill does.

A left-hand spiral does the opposite: it pushes chips ahead of the reamer, which suits a through hole, where they can fall out of the far end, and would pack them into the bottom of a blind hole. A straight fluted reamer is the general-purpose type and does not clear chips in either direction, so it is not the specific choice for blind holes.

Your Answer : (Not Answered)

Correct Answer : D

R is 0.632.

A perfectly plastic material does not strain-harden, so n = 0:

\[ R = 1 - e^{-(0 + 1)} = 1 - \frac{1}{e} = 1 - 0.368 = 0.632 \]

That is, at most about 63% reduction in area per pass. The larger values come from taking n greater than zero: n = 1 gives \(1 - e^{-2} = 0.865\), and n of about 0.75 and 0.5 give 0.826 and 0.777, reductions possible only for strain-hardening materials.

Your Answer : (Not Answered)

Correct Answer : B

A grinding ratio of 200 means the grinding wheel wears 0.005 times the volume of the material removed.

The grinding ratio (G-ratio) is the volume of work material removed divided by the volume of wheel worn away. A G-ratio of 200 means 200 units of material are removed for each unit of wheel wear, so the wheel wear is 1/200 = 0.005 of the material removed.

The first option inverts the ratio. The grinding ratio is about volumes removed and worn, not about the shape (aspect ratio) of the abrasive grains or the volume share of abrasive in the wheel.

Your Answer : (Not Answered)

Correct Answer : D

The material removal rate increases, becomes stable and then decreases as the stand-off distance grows.

Very close to the work, the jet has not yet reached full speed over its cross section and the abrasive that bounces back off the surface interferes with the incoming stream, so removal is low. As the nozzle moves back, the jet develops fully and the removal rate rises to a broad maximum over a range of stand-off distances. Further back still, the jet diverges and the particles lose velocity to air drag, so they strike a larger area with less energy and the removal rate falls.

A steady rise or a steady fall each describe only one side of this peaked curve, and 'decreases, becomes stable and then increases' is the curve turned upside down.

Your Answer : (Not Answered)

Correct Answer : B

A metalworker may prefer indirect extrusion because the billet remains stationary in it. In direct extrusion the billet slides in the container, and the friction along the container wall requires a larger force. In indirect extrusion the die moves toward the billet, so there is no relative motion with the container and the force is lower. The statement that indirect extrusion needs more force is the reverse of the truth, and the remaining options are not the reasons that favour the indirect process.