Bansilal Ramnath Agarwal Charitable Trust's
Vishwakarma Institute of Technology
(An Autonomous Institute affiliated to Savitribai Phule Pune University)
Vishwakarma Institute of Technology, 666, Upper Indiranagar, Bibwewadi , Pune, Maharashtra, INDIA - 411 037.
Contact No. +91 - 20 - 2428 3001
Types of Threads:
1) Left Hand Thread:
Left hand threads are those threads which are inclined
towards the left hand. These are the ones which are fixed in an anticlockwise
movement.
2) Right Hand Thread:
Right hand threads are those threads which are inclined
towards the right-hand side. These are fixed in a clockwise movement.
3) Taper Thread:
Taper threads are the threads which are found having a cut
around the taper surface and are thus named as taper thread. These are the
threads which can be either right-handed or left-handed.
4) Square Threads:
Square threads are those threads which are found having
very powerful roots in a thread. It is named in such a way as it is found
making the square thread and these are the threads which are used for lifting
heavy loads, transfer of power, exerting pressure, and screw jack and vice
spindle instruments.
5) Acme Thread:
Acme threads are those threads whose shape is in taper,
like the flat from bottom and thin from the top. These
threads are found having slanting ends and therefore are easier to fix or
unscrew the split nut on it but do not have a backlash in it. Acme threads are made up at an angle of 29°.
6) Buttress Thread:
Buttress threads are referred to as the screw threads
which have a triangular section but also have one face at the right angle of
the axis of the screw and the second face only being
sloped. These are the threads which are found having more pulling power as
compared to the square thread.
Taps and dies-
A tap cuts or forms a
thread on the inside surface of a hole, creating a female surface that
functions like a nut.
Types
of Taps:
There are 3 main types of taps to be familiar with: Taper, Plug,
and Bottoming tap.
1) Taper Tap:
The taper tap can be identified by the visible tapering of the cutting edges. This provides a very gradual and less aggressive cutting action. The distinct feature of a taper tap is the 8 to 10 threads that taper from the tip to the full cutting force diameter. A taper tap is most often used as a starter tap for difficult blind holes.
2)Plug Tap:
A plug tap has a less pronounced taper to the cutting edges. This gives the plug tap a gradual cutting action that is less aggressive than that of the bottoming tap but more aggressive than a taper tap. Typically, the plug tap will have 3 to 5 tapered threads before the full cutting diameter is engaged.
3)Bottoming Tap:
The third style is a bottoming
tap. Bottoming taps have 1 to 2
tapered cutting edges before the full cutting force is engaged. Though this tap
is extremely hard to start threads with, it is capable of cutting threads all
of the way to the bottom of a blind hole. Bottoming taps are best used after a
taper or plug tap has been used to cut the initial thread.
Dies:
Threading dies are used to form or cut a male thread
on the outside of rods or bars. Threading dies provide precision in cutting and
extend the life of a die by reducing wear.
Threading dies are commonly used in
industrial metalworking. Threading dies are used for repairing threads in
stripped holes or bolts. Rolled threading dies have an increased advantage of
strength, longer life, and reduced material cost.
Thread cutting is a process for creating a thread.
It's used for the production of threads on the outer surface of a cylinder or
on the inner surface of a bore. In external
thread cutting, the piece can either be held in a chuck or
mounted between two centers and for internal
thread cutting, the piece is held in a chuck. The tool moves across the piece
linearly, taking chips away from the workpiece with each pass. Usually, 5 to 7
light cuts create the correct depth of the thread.
Tools used
for thread cutting are the thread cutting die, the screw tab or for serial
production a process called cold or hot forming.
The metric thread is the most widely used standardized thread geometry. The naming of metric threads uses an M which describes a nominal thread.
Thread milling
Source Mold Making Technology
Thread milling is one of the methods for producing threads. In
thread milling a rotating milling cutter enters in the hole which creates
threads. It is a very efficient method for making large production of threads,
as we can make different sizes of thread with only one tool, if the whole is
bigger than the tool, the tool will move around the circumference of the hole
to make threads. We can make left hand as well as right hand thread with same
tool. This method takes less time for creating threads. It requires less
cutting force and it the tool get crashed it will not get stuck. Thread milling
has a upper hand on tapping, is that tapping only starts making a complete
thread profile on the third thread, whereas thread milling will produce a complete
thread profile from the top to the bottom. it has become the usual way for
making threads, and today inner and outer threads are usually milled even on
work where they would formerly have been cut with taps, die heads, or
single-pointing.
Thrilling
Source: WhizCut in the US ,BGF Thrillers
As the name implies, thrilling is a process of threading and drilling the internal threads using a special cutting tool on a CNC mill. To accomplish this process tools are designed such that the tip of the tool is shaped like a drill or center-cutting end mill; while the body has a thread-shaped form with a countersink cutter form near the shank. In this process firstly drilling and then threading operation is performed. This tool does all operations in one compact cycle like drilling, chamfering, and threading a hole. This process eliminates tool, tool holder and tool change which becomes advantageous as it saves cost as well as time. The disadvantage in this process is that it is limited to hole depth no greater than three times the diameter of the tool.
Helical Broaching (Punch Tap)
The helical broaching was developed within the 2010s that shortens the toolpath of tapping. To an off-the-cuff observer (without slow motion), it's rather almost like traditional tapping but with faster movement into and out of the opening. It uses a selected tool geometry and toolpath to position rapidly, broach the thread during a single half-turn, then retract rapidly, shortening the cycle time and consuming less energy. It reduces the value of threading for any holes which will safely allow the 2 small fast-helix grooves that it leaves behind alongside the thread, which might be true in many applications.
Source: SAK Abrasives
Thread grinding is done to
produce threads on hard materials. This technique uses a grinding wheel to
manufacture the threads. This not only produces threads on harder materials,
but also used to give an accurate shape to already manufactured threads by other
various manufacturing techniques which are discussed above. There are basically
three types of thread grinding -
- Center type grinding with axial feed
- Center type infeed thread grinding
- Centerless thread grinding
We have seen thread cutting using
a single point cutting tool. Similarly, the first method i.e. center type
grinding with axial feed works. But, in the single point cutting tool method, a
tool is used. Here, a grinding wheel is used.
It is the most common method used for thread grinding. In the second
type, i.e. center type infeed thread grinding, the grinding wheel used is with
multiple ribs which is longer than the length of the threads. Grinding wheel is
fed to the blank and the blank is rotated by 1.5 revolutions. Then, the
centerless thread grinding performs the operation to manufacture the set screw.
Threading with EDM
Sometimes it is difficult to
manufacture thread on the harder material such as tool steel or carbides with
the above-mentioned manufacturing process. Hence a new non-conventional
machining process is used to manufacture the threads. EDM stands for Electrical
Discharge Machining where material is removed rapidly by sparking between two
electrodes. One electrode is considered as a tool and the other electrode is a
workpiece. In this case, it is thread blank. There is a small gap between the
tool and workpiece which is generally filled up by dielectric fluid in the
container.
As the voltage between the two electrodes increases, the intensity of the electric field between the gap also increases as it is directly proportional. This causes dielectric breakdown and produces an arc. This arc causes material removal from the workpiece. While removing the material, the workpiece is rotated in a fixed axis in the direction as we require the thread pattern. Generally, threading with EDM is used for internal threading of the component. The main advantage of using this type of machining process is that operators can easily produce threads on very complex components. As well as, the operating cost of the machine is very much low as compared to other machining processes. Thread manufacturing is noiseless operation in this type of process. While the limitations are installation cost is high and the operator required is skillful.
TY_ME_D_Batch 2_Group 5
40 - Tanvi Shinde
44 - Shubam Pandoh
48 - Rutuja Solankar
50 - Pushkar Sonawane
52 - Bhushan Suda
Guided by : Prof. A. R. Mujumdar
Good work👍🔥🔥
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