DML Final Exam Questions and Answers
100% Solved | Graded A+
Pitch Diameter - ✔✔Sometimes called "mean diameter" is the diameter in
between the major and minor diameter. It is the theoretical diameter at which
each pitch is equally divided between threads. Pitch diameter can be thought of
as the diameter at which the male and female thread should meet. It could be
thought of as the working diameter.
Name two ways to measure a thread. - ✔✔Thread micrometer or three-wire
thread measurement method.
What is the rule of thumb for the length of internal thread to maximize the
strength of the bolt? - ✔✔The minimum recommended thread engagement for
a screw in an assembly is as much as the screw diameter; a better assembly will
result when 1 1/2 times the screw diameter is used.
Describe when class two fits are used. - ✔✔Class 2 threads are found on most
screws, nuts, and bolts used in the manufacturing industry. Studs used on many
types of machines are examples of class 3 fits.
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,Describe UNC and UNF. - ✔✔UNC stands for Unified National Coarse thread
series and UNF stands for Unified National Fine thread series. Each has its own
strengths. Fine is generally stronger in hard materials and coarse is generally
stronger in soft materials.
What is the formula for calculating the OD of a machine screw? - ✔✔The
formula is D=number of the machine screw x.013in. + .060in.; D=8 x .013in. +
.060in. = .164in.
What are setscrews used for? - ✔✔Used to secure gears or pulleys to shafts.
When are stud bolts used? - ✔✔Can be used instead of long bolts. Often used to
aid in the assembly of heavy parts by acting as guide pins.
Describe the strength classification system and marking for bolts. - ✔✔The
strength grades of bolts are identified by the markings on the heads. The grade
indicates the strength of the fastener. A manufacturer's chart may be used as a
guide for proper torque of fasteners.
Explain two reasons why flat washers are used. - ✔✔Flat washers provide a
larger contact area than nuts and screw heads to distribute the clamping
pressure over a larger area.
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,What is the purpose of a helical spring lock washer? - ✔✔A helical spring lock
washer prevents the unplanned loosening of nut and bolt or screw assemblies.
Spring lock washers will also provide for a limited amount of take-up when
expansion or contraction takes place.
When is an internal-external tooth lock washer used? - ✔✔Are used on
oversized holes or to provide a large bearing surface.
When are dowel pins used? - ✔✔Are used to achieve accurate alignment
between two or more parts.
When are taper pins used? - ✔✔Accurately align parts that have to be
disassembled frequently.
When are roll pins used? - ✔✔Are used to align parts. Holes to receive roll pins
do not have to be reamed, which is necessary for dowel pins and taper pins.
What are retaining rings? - ✔✔Retaining rings are used to hold bearings or seals
in bearing housings or on shafts. Retaining rings have a spring action and are
usually seated in grooves.
What is the purpose of a key? - ✔✔To transmit the driving force between a
shaft and pulley.
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©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
, When is a woodruff key used? - ✔✔Are used where only light loads are
transmitted.
When is a gib-head key used? - ✔✔Are used to transmit heavy loads. These keys
are installed and removed from the same side of a hub and shaft assembly.
Name 3 important things to keep in mind when using a drill press. - ✔✔Speeds,
feeds, and coolants.
What are some results of excessive drilling speed? - ✔✔Worn margins and outer
corners broken down.
Explain what can happen to small-diameter drills when the cutting speed is too
slow. - ✔✔The operator will increase the feed to produce a chip. This increased
feed is often greater than the drill can stand without breaking.
How can an operator tell by observing the chip if the feed is about right? -
✔✔The feed is about right when the chip rolls into a close helix. Long, stringy
chips can indicate too much feed.
In what way are power feeds designated? - ✔✔Feeds are designated by a small,
measured advance movement of the drill for each revolution.
Name two different cutting fluid types. - ✔✔The water-solubable oil types and
the cutting oils, both organic and mineral.
4|Page
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
100% Solved | Graded A+
Pitch Diameter - ✔✔Sometimes called "mean diameter" is the diameter in
between the major and minor diameter. It is the theoretical diameter at which
each pitch is equally divided between threads. Pitch diameter can be thought of
as the diameter at which the male and female thread should meet. It could be
thought of as the working diameter.
Name two ways to measure a thread. - ✔✔Thread micrometer or three-wire
thread measurement method.
What is the rule of thumb for the length of internal thread to maximize the
strength of the bolt? - ✔✔The minimum recommended thread engagement for
a screw in an assembly is as much as the screw diameter; a better assembly will
result when 1 1/2 times the screw diameter is used.
Describe when class two fits are used. - ✔✔Class 2 threads are found on most
screws, nuts, and bolts used in the manufacturing industry. Studs used on many
types of machines are examples of class 3 fits.
1|Page
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
,Describe UNC and UNF. - ✔✔UNC stands for Unified National Coarse thread
series and UNF stands for Unified National Fine thread series. Each has its own
strengths. Fine is generally stronger in hard materials and coarse is generally
stronger in soft materials.
What is the formula for calculating the OD of a machine screw? - ✔✔The
formula is D=number of the machine screw x.013in. + .060in.; D=8 x .013in. +
.060in. = .164in.
What are setscrews used for? - ✔✔Used to secure gears or pulleys to shafts.
When are stud bolts used? - ✔✔Can be used instead of long bolts. Often used to
aid in the assembly of heavy parts by acting as guide pins.
Describe the strength classification system and marking for bolts. - ✔✔The
strength grades of bolts are identified by the markings on the heads. The grade
indicates the strength of the fastener. A manufacturer's chart may be used as a
guide for proper torque of fasteners.
Explain two reasons why flat washers are used. - ✔✔Flat washers provide a
larger contact area than nuts and screw heads to distribute the clamping
pressure over a larger area.
2|Page
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
,What is the purpose of a helical spring lock washer? - ✔✔A helical spring lock
washer prevents the unplanned loosening of nut and bolt or screw assemblies.
Spring lock washers will also provide for a limited amount of take-up when
expansion or contraction takes place.
When is an internal-external tooth lock washer used? - ✔✔Are used on
oversized holes or to provide a large bearing surface.
When are dowel pins used? - ✔✔Are used to achieve accurate alignment
between two or more parts.
When are taper pins used? - ✔✔Accurately align parts that have to be
disassembled frequently.
When are roll pins used? - ✔✔Are used to align parts. Holes to receive roll pins
do not have to be reamed, which is necessary for dowel pins and taper pins.
What are retaining rings? - ✔✔Retaining rings are used to hold bearings or seals
in bearing housings or on shafts. Retaining rings have a spring action and are
usually seated in grooves.
What is the purpose of a key? - ✔✔To transmit the driving force between a
shaft and pulley.
3|Page
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
, When is a woodruff key used? - ✔✔Are used where only light loads are
transmitted.
When is a gib-head key used? - ✔✔Are used to transmit heavy loads. These keys
are installed and removed from the same side of a hub and shaft assembly.
Name 3 important things to keep in mind when using a drill press. - ✔✔Speeds,
feeds, and coolants.
What are some results of excessive drilling speed? - ✔✔Worn margins and outer
corners broken down.
Explain what can happen to small-diameter drills when the cutting speed is too
slow. - ✔✔The operator will increase the feed to produce a chip. This increased
feed is often greater than the drill can stand without breaking.
How can an operator tell by observing the chip if the feed is about right? -
✔✔The feed is about right when the chip rolls into a close helix. Long, stringy
chips can indicate too much feed.
In what way are power feeds designated? - ✔✔Feeds are designated by a small,
measured advance movement of the drill for each revolution.
Name two different cutting fluid types. - ✔✔The water-solubable oil types and
the cutting oils, both organic and mineral.
4|Page
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
