©JASONMcCONNELL 2024/2025 ALL RIGHTS RESERVED 1/28/2025.
DML Final Exam Questions With Correct
Answers 100% Verified.
Pitch Diameter - Answer✔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. - Answer✔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? - Answer✔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. - Answer✔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.
Describe UNC and UNF. - Answer✔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? - Answer✔The formula is
D=number of the machine screw x.013in. + .060in.; D=8 x .013in. + .060in. = .164in.
What are setscrews used for? - Answer✔Used to secure gears or pulleys to shafts.
When are stud bolts used? - Answer✔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. - Answer✔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. - Answer✔Flat washers provide a larger contact
area than nuts and screw heads to distribute the clamping pressure over a larger area.
1|Page
, ©JASONMcCONNELL 2024/2025 ALL RIGHTS RESERVED 1/28/2025.
What is the purpose of a helical spring lock washer? - Answer✔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? - Answer✔Are used on oversized holes or
to provide a large bearing surface.
When are dowel pins used? - Answer✔Are used to achieve accurate alignment between two or
more parts.
When are taper pins used? - Answer✔Accurately align parts that have to be disassembled
frequently.
When are roll pins used? - Answer✔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? - Answer✔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? - Answer✔To transmit the driving force between a shaft and
pulley.
When is a woodruff key used? - Answer✔Are used where only light loads are transmitted.
When is a gib-head key used? - Answer✔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. - Answer✔Speeds, feeds, and
coolants.
What are some results of excessive drilling speed? - Answer✔Worn margins and outer corners
broken down.
Explain what can happen to small-diameter drills when the cutting speed is too slow. -
Answer✔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? - Answer✔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? - Answer✔Feeds are designated by a small, measured
advance movement of the drill for each revolution.
Name two different cutting fluid types. - Answer✔The water-solubable oil types and the cutting
oils, both organic and mineral.
2|Page
, ©JASONMcCONNELL 2024/2025 ALL RIGHTS RESERVED 1/28/2025.
How can jamming of a drill be avoided when drilling deep holes? - Answer✔Drill jamming can
be avoided by a "pecking" procedure. The operator drills a small amount and pulls out the drill
to remove the chips. This is repeated until the hole is finished.
Name three uses for the depth stop on a drill press. - Answer✔The depth stop is used to limit
the travel of the drill so that it will not go into the table or vise. The depth of blind holes is
preset and drilled. Countersink and counterbore depths are set so that several can be easily
made the same.
What is the main purpose for using work-holding devices on drilling machines? - Answer✔The
purpose of using work-holding devices is to keep the workpiece rigid, to prevent it from turning
with the drill, and for operator safety.
Why should the support on a narrow or thin workpiece be as close to the drill as possible? -
Answer✔Thin minerals tend to be sprung downward from the drilling force until drill break-
through begins. The drill then "grabs" as the material springs upward, and broken drill is often
the result. This can be avoided by placing the support or parallels as near the drill as possible.
Describe 2 methods for angle drilling. How would this be done if no angular measuring devices
were mounted on the equipment? - Answer✔Angle drilling is done by tilting a drill press table
or by using an angular vise. If no means of setting the exact angle is provided, a protractor head
with level may be used.
What is the purpose of a wiggler? - Answer✔Is used for locating a center punch mark under the
center of the axis of a drill spindle.
Why would you ever need an angle plate? - Answer✔Some odd-shaped workpieces, such as
gears with extending hubs that need holes drilled for setscrews, might be difficult to set up
without an angle plate.
What is the purpose of starting a tap in the drill press? - Answer✔One of the difficulties with
hand tapping is the tendency for taps to start crooked or misaligned with the tap-drilled hole.
Starting a tap by hand in a drill press with the same setup as used for the tap drilling ensures a
perfect alignment.
When is a countersink used? - Answer✔Countersinks are used to chamfer holes and to provide
tapered holes for flat head fasteners such as screws and rivets.
Why are countersinks made with varying angles? - Answer✔Countersink angles vary to match
the angles of different flat head fasteners or different taper hole requirements.
What is a center drill? - Answer✔A center drill is used to make a 60-degree countersink hole in
workpieces for lathes and grinders.
When is a counterbore used? - Answer✔A counterbore makes a cylindrical recess concentric
with a smaller hole so that a hex head bolt or socket head cap screw can be flush mounted with
the surface of a workpiece.
3|Page
DML Final Exam Questions With Correct
Answers 100% Verified.
Pitch Diameter - Answer✔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. - Answer✔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? - Answer✔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. - Answer✔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.
Describe UNC and UNF. - Answer✔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? - Answer✔The formula is
D=number of the machine screw x.013in. + .060in.; D=8 x .013in. + .060in. = .164in.
What are setscrews used for? - Answer✔Used to secure gears or pulleys to shafts.
When are stud bolts used? - Answer✔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. - Answer✔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. - Answer✔Flat washers provide a larger contact
area than nuts and screw heads to distribute the clamping pressure over a larger area.
1|Page
, ©JASONMcCONNELL 2024/2025 ALL RIGHTS RESERVED 1/28/2025.
What is the purpose of a helical spring lock washer? - Answer✔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? - Answer✔Are used on oversized holes or
to provide a large bearing surface.
When are dowel pins used? - Answer✔Are used to achieve accurate alignment between two or
more parts.
When are taper pins used? - Answer✔Accurately align parts that have to be disassembled
frequently.
When are roll pins used? - Answer✔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? - Answer✔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? - Answer✔To transmit the driving force between a shaft and
pulley.
When is a woodruff key used? - Answer✔Are used where only light loads are transmitted.
When is a gib-head key used? - Answer✔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. - Answer✔Speeds, feeds, and
coolants.
What are some results of excessive drilling speed? - Answer✔Worn margins and outer corners
broken down.
Explain what can happen to small-diameter drills when the cutting speed is too slow. -
Answer✔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? - Answer✔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? - Answer✔Feeds are designated by a small, measured
advance movement of the drill for each revolution.
Name two different cutting fluid types. - Answer✔The water-solubable oil types and the cutting
oils, both organic and mineral.
2|Page
, ©JASONMcCONNELL 2024/2025 ALL RIGHTS RESERVED 1/28/2025.
How can jamming of a drill be avoided when drilling deep holes? - Answer✔Drill jamming can
be avoided by a "pecking" procedure. The operator drills a small amount and pulls out the drill
to remove the chips. This is repeated until the hole is finished.
Name three uses for the depth stop on a drill press. - Answer✔The depth stop is used to limit
the travel of the drill so that it will not go into the table or vise. The depth of blind holes is
preset and drilled. Countersink and counterbore depths are set so that several can be easily
made the same.
What is the main purpose for using work-holding devices on drilling machines? - Answer✔The
purpose of using work-holding devices is to keep the workpiece rigid, to prevent it from turning
with the drill, and for operator safety.
Why should the support on a narrow or thin workpiece be as close to the drill as possible? -
Answer✔Thin minerals tend to be sprung downward from the drilling force until drill break-
through begins. The drill then "grabs" as the material springs upward, and broken drill is often
the result. This can be avoided by placing the support or parallels as near the drill as possible.
Describe 2 methods for angle drilling. How would this be done if no angular measuring devices
were mounted on the equipment? - Answer✔Angle drilling is done by tilting a drill press table
or by using an angular vise. If no means of setting the exact angle is provided, a protractor head
with level may be used.
What is the purpose of a wiggler? - Answer✔Is used for locating a center punch mark under the
center of the axis of a drill spindle.
Why would you ever need an angle plate? - Answer✔Some odd-shaped workpieces, such as
gears with extending hubs that need holes drilled for setscrews, might be difficult to set up
without an angle plate.
What is the purpose of starting a tap in the drill press? - Answer✔One of the difficulties with
hand tapping is the tendency for taps to start crooked or misaligned with the tap-drilled hole.
Starting a tap by hand in a drill press with the same setup as used for the tap drilling ensures a
perfect alignment.
When is a countersink used? - Answer✔Countersinks are used to chamfer holes and to provide
tapered holes for flat head fasteners such as screws and rivets.
Why are countersinks made with varying angles? - Answer✔Countersink angles vary to match
the angles of different flat head fasteners or different taper hole requirements.
What is a center drill? - Answer✔A center drill is used to make a 60-degree countersink hole in
workpieces for lathes and grinders.
When is a counterbore used? - Answer✔A counterbore makes a cylindrical recess concentric
with a smaller hole so that a hex head bolt or socket head cap screw can be flush mounted with
the surface of a workpiece.
3|Page
