Read the following paragraph and answer the questions given below: Grub screw, also known as set screw, is a type of fixing screw that is most often used to join one component or part securely to another. Grub screws are used to hold parts like sleeve, collar, gear etc. on a shaft to prevent relative motion. It is represented by thread size such as M8, M10 etc. Where M stands for metric thread and the numeral represents the diameter of screw in millimeter.
Question: 1
The front view of a vertical grub screw is represented by which of the following views?
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Grub screws are headless and are recognized in drawings by their internal drive (like hex socket) and cylindrical body.
A grub screw, also known as a set screw, is typically a small, headless screw that is threaded along its entire length.
It is inserted into a threaded hole and tightened against another part to prevent relative motion.
Since it does not have a conventional hexagonal or slotted head like other screws, it is embedded completely within the part.
In front view, the grub screw appears as a simple cylindrical form with an internal feature, often a socket or hexagonal drive, for tightening.
Let's analyze the options:
- Option (i): Shows a cylindrical body with a hexagonal recess visible from the top (front view), and an internal dashed line representing internal threading. This is the correct depiction of a grub screw.
- Option (ii): Shows a head like a countersunk screw — this is not a grub screw.
- Option (iii): Depicts a flange, which is again inconsistent with a grub screw.
- Option (iv): Depicts a headed screw with visible contours, not matching the set screw's typical structure.
Hence, Option (i) accurately represents the front view of a vertical grub screw.
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Question: 2
The complete circle of $\phi d$ and the incomplete circle of $\phi 0.8d$ in the top view of a vertical grub screw with diameter ‘d’ are drawn to __________
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Use full and partial circles to represent internal threads in top view; major diameter = $d$, minor = $0.8d$.
In engineering drawings, thread representation uses standard conventions.
When drawing a top view of a threaded object such as a grub screw (which typically contains internal threads), two circles are used:
- One full circle with diameter $\phi d$ (major diameter)
- One partial (dashed or broken) circle with diameter $\phi 0.8d$ (minor diameter)
This symbolic representation indicates internal V-threads that follow standard metric thread design.
The use of $\phi 0.8d$ represents the root of the internal thread, while $\phi d$ is the crest.
This system helps engineers interpret internal threads at a glance without unnecessary complexity.
Hence, the correct answer is Option (C).
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Question: 3
Grub screws are also known as
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Grub screw = set screw = headless screw. All three mean the same thing in mechanical design.
A grub screw, or set screw, is a threaded fastener without a head.
It is fully threaded and is driven by an internal socket (such as a hex drive).
Because it is tightened completely inside the threaded hole, it does not have any external head that protrudes.
This makes it ideal for use where space is limited, or a smooth finish is needed on the outer surface.
Therefore, it is commonly known as a headless screw.
Other screw types like countersunk or pan head screws have visible heads, which grub screws lack.
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Question: 4
Why grub screws are used to hold sleeve on a shaft?
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Grub screws are excellent for securing components on rotating shafts without needing complex locking mechanisms.
Grub screws are primarily used to hold one part tightly against another to avoid any sliding or rotational movement.
In the case of a sleeve mounted on a shaft, if the sleeve is not fixed, it may rotate or slide, disrupting the mechanical function.
By driving a grub screw into the sleeve and tightening it against the shaft, any relative motion is restricted.
This secure contact ensures that the sleeve remains fixed in its intended position during operation.
Thus, the main reason for using a grub screw here is to prevent relative motion between parts.
