Drilling and Reaming MCQ Quiz - Objective Question with Answer for Drilling and Reaming - Download Free PDF

• A reamer is a cutting tool used to enlarge or finish existing holes to precise diameters and shapes.
• It is often used in metalworking and carpentry to create smooth, accurate holes for things like bolts, dowels, and bearings.

Here are the reasons why the other options are not the answer:

• Let L: This is not a tool, but rather a mathematical expression.
• Metal: Metal is a material, not a tool. While a reamer can be made of metal, this is not specific enough to be the correct answer.
• TTTL: This is not a commonly used abbreviation for any tool that I am aware of.

Explanation:

Important Points

Punching/Blanking

• Punching or blanking is a process in which the punch removes a portion of material from the larger piece or a strip of sheet metal.
• If the small removed piece is discarded, the operation is called punching, whereas if the small removed piece is the useful part and the rest is scrap, the operation is called blanking.

Concept:

• Usually, all the drilling tools have straight or tapered shanks.
• This shank must be held in a machine spindle when machining is to be carried out.
• To hold the drill in the spindle, proper drill heads are required.
• Some of the tool-holding devices commonly used in a drilling machine are:
  1. Sleeve 
  2. Socket
  3. Drill chucks

Sleeve

• When the drill shank size is smaller than the spindle of the machine, then the device used to hold the small shank drill is called Sleeve.
• The drilling tool required to hold in the spindle is first fitted into the inner taper of the sleeve.
• Then the sleeve along with the tool is fitted into the machine spindle.
• This outer taper of the sleeve always matches the spindle taper.
• The availability of different types of sleeves facilitates the use of a drilling tool with any taper corresponding to a sleeve that fits in the spindle.

Socket

• The device used to hold the drill, when the tapered shank of the tool is larger than the spindle taper, is called a Socket.
• The generally used socket is shown in Figure. In which, the socket taper matches the spindle taper, and the inside taper of the socket matches the spindle taper.

Drill chuck

• For fixing and removing drills, the chucks are provided either with a pinion and key or a knurled ring.
• Drill chucks are held on the machine spindle by means of an arbor fitted on the drill chuck.

Explanation:

Cutting speed:

• Cutting speed is the speed at which the cutting edge passes over the material while cutting, and is expressed in meters per minute.
• It is given by:

V = \(\frac{\pi~\times~D~\times~N}{1000}\)

Where, D = Diameter of drill (mm), N = rpm, V = Cutting speed in m/min

• At a particular drill diameter, if rpm is increased, the cutting speed increases.
• Cutting speed is also sometimes stated as surface speed or peripheral speed.
• The selection of the recommended cutting speed for drilling or turning etc. depends on the materials to be machined, and the tool material.

Explanation:

Spot facing removes sufficient metal from the surface around a drilled hole to form a true seat for a bolt head or nut.

Additional Information

Cutting speed is the speed at which the cutting edge passes over the material while cutting and is expressed in meters per minute.

\(v = \frac{{\pi dN}}{{1000}}\)

Where v is cutting speed (m/min), d is diameter (mm) and N is in rpm

Calculation:

Given:

v = 35 m/min, d = 24 mm

\(v = \frac{{\pi dN}}{{1000}} \Rightarrow 35 = \frac{{\pi \times 24 \times N}}{{1000}} \Rightarrow N = 464\;rpm\)

Explanation:

Centre Lathe → Knurling

Milling → Slotting

Grinding → Dressing

Drilling → Counter-boring

Knurling

Knurling is the operation of producing a straight-lined, diamond-shaped pattern or cross lined pattern on a cylindrical external surface by pressing a tool called knurling tool. Knurling is not a cutting operation but it is a forming operation.

A lathe is used for many operations such as turning, threading, facing, grooving, Knurling, Chamfering, centre drilling

Counter - boring

Counter - boring is an operation of enlarging a hole to a given depth, to house heads of socket heads or cap screws with the help of a counterbore tool.

Dressing:

When the sharpness of grinding wheel becomes dull because of glazing and loading, dulled grains and chips are removed (crushed or fallen) with a proper dressing tool to make sharp cutting edges.

The dressing is the operation of cleaning and restoring the sharpness of the wheel face that has become dull or has lost some of its cutting ability because of loading and glazing.

Slot Milling:

Slot milling is an operation of producing slots like T - slots, plain slots, dovetail slots etc.

Concept:

Tapping is the operation done for forming internal threads by means of the tool called tap.

Before a tap is used for cutting internal threads, a hole is to be drilled. The diameter of the hole should be such that it should have sufficient material in the hole for the tap to cut the thread.

Tap drill size is given by:

Tap drill size = Major diameter - Pitch

Common metric tap drill size:

Concept:

Drill chucks are held on the machine spindle by means of an arbor fitted on the drill chuck.

Drift: 

• Taper shank drills are held on the machine spindle with the help of a sleeve, morse taper, and socket.
• Drift is used to remove the socket from the machine's spindle.

For fixing and removing drills, the chucks are provided either with a pinion and key or a knurled ring.

Concept:

Boring: Boring is an operation to enlarging of an existing hole, which may have been made by a drill or maybe the result of a core in a casting. 

Reaming

• Reaming is a sizing operation that removes a small amount of metal from a hole already drilled.
• It is done for two purposes:

1. To bring holes to a more exact size
2. To improve the finish of an existing hole

Drilling: Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of circular cross-section in solid materials. The drill bit is a rotary cutting tool.

Counter sinking: It is the process of making the holes slightly tapered in the beginning. It is a seating place for screws.

Concept:

A reamer is a multipoint cutting tool used for enlarging by finishing previously drilled holes to accurate sizes.

For reaming with a hand or a machine reamer, the hole drilled should be smaller than the reamer size.

Calculating drill size for reamer

A method generally practised in workshop is by applying the following formula:

Drill size = Reamed size - (Undersize + Oversize)

• Finished size is the diameter of the reamer.
• Undersize is the recommended reduction in size for different ranges of drill diameter.

• Oversize is generally considered that a twist drill will make a hole larger than its diameter. The oversize for calculation purposes is taken as 0.05 mm - for all diameters of drills.

Given: Ø 6H7 hole

Calculation:

Finished size = 6 mm

Under size as per table = 0.2 mm

Over size = 0.05 mm

Explanation:

Portable hand drills

Portable hand drills of different types are used for certain jobs which cannot be handled on stationary drilling machines.

The electric hand drill has a small electric motor for driving the drill. At the end of the spindle, a drill chuck is mounted. 

It is very commonly used for drilling holes in such components that cannot be transported to the shop due to their size or weight.

It is used for light duty with a usually single speed.

Radial drilling machine

The radial drilling machine has a radial arm on which the spindle head is mounted, The spindle head can be moved along the radial arm and can be locked in any position.

The arm is supported by a pillar (column). It can be rotated about with the pillar as a centre.

Therefore, the drill spindle can cover the entire working surface of the table. The arm can be lifted or lowered.

Radial drilling machines are used to drill

• large diameter holes
• multiple holes in one setting of the work
• heavy and large work-pieces

Explanation:

The common defects in drilling are listed below:

Radial drilling machine

The radial drilling machine has a radial arm on which the spindle head is mounted, The spindle head can be moved along the radial arm and can be locked in any position.

The arm is supported by a pillar (column). It can be rotated about with the pillar as a centre.

Therefore, the drill spindle can cover the entire working surface of the table. The arm can be lifted or lowered.

Radial drilling machines are used to drill

• large diameter holes
• multiple holes in one setting of the work
• heavy and large work-pieces

Pillar drilling machine 

Pillar drilling machine is an enlarged version of the sensitive bench drilling machine. These drilling machines are mounted on the floor and driven by more powerful electric motors.

These machines are provided with a rack and pinion mechanism to raise the table for setting the work. Parts of pillar drilling machines are shown here: