The main functions of thread are:
- achieve mechanical coupling
- transfer motion by converting rotation/linear motion to linear/rotational motion
- to achieve mechanical benefits;Use a small force to produce a large force.
Thread type:
Thread profile defines the geometry of the thread, including part diameter (large diameter, medium diameter, and small diameter), thread profile Angle, pitch, radius, and helical raising Angle.
Most common thread type:
Thread working:
There are a variety of thread processing methods and tools suitable for different parts, thread types and pitch.Each thread processing method and tool has its own advantages in specific situations.
Initial considerations for thread machining:
These initial considerations will influence the selection of thread processing methods, thread processing tools and their applications.
Thread:
Consider the following dimensions and quality requirements for threads to be machined:
Male or female?
Thread type (e.g. metric, UN)
pitch
Right or left?
thread
Tolerance (tooth type, position)
Spare parts:
After considering the features, observe the parts:
Is the workpiece securely clamped?
Is chip removal or chip control a key issue?
Does the material have good chip breaking properties?
Parts are produced in batches.
Single or multiple thread
Machine tools:
Machine tool considerations include:
Stability, power and torque, especially for larger diameters
Cutting fluid and coolant supply
Is a high pressure coolant required to break long chip material?
The number of tool bits available for the selected thread processing method
Speed limit, especially for bar feeder and small diameter
Clamping possibilities, is there a subspindle or tailstock?
Are threaded cycles provided?
Thread processing method:
Each thread processing method has its own advantages in specific situations.
The thread turning
High productivity thread processing method
Machining threads for parts rotating around the center of rotation
Covers the largest number of thread types
A simple and well - known screw thread machining process
Provide good surface quality and thread quality
Thread milling
For non-rotating parts, machining threads outside the rotating center of the rotating parts
Intermittent cutting ensures good chip breaking performance in all materials
The low cutting force enables the machining of threads in long overhangs and thin wall parts
Can be machined close to the shoulder or bottom of the table without the use of a backing groove
It can process large workpieces that are not easily mounted on lathes
Able to process large diameter threads with low power and torque requirements
tapping
A well-known simple thread machining process
High productivity and economic thread processing method, especially suitable for processing smaller threads
Covers most common thread types
Suitable for all kinds of machine tools, can process not only rotating parts, but also non-rotating parts
A wide variety of material specific products ensure good chip control
Easy to process deep hole threads
Formed threads can be machined
High quality thread available
Spiral thread milling
Suitable for slender parts, such as screws
Able to produce high quality threads without bending
All margins can be removed in a single pass, thus shortening the production cycle
Precise threads are machined by tilting the cyclone cutter head to the helical raising Angle
Good chip control enables more continuous high productivity machining
A machine tool with screw thread milling capability is required
Some key factors to consider in thread turning:
• check the workpiece diameter for correct machining allowance before thread turning. Add 0.14mm as top margin.
• accurately position the tool in the machine.
• check the setting of the cutting edge relative to the center diameter.
• make sure to use the correct blade groove (A, F or C).
• ensure adequate and even clearance (blade-blade inclination) by selecting the right knife pad to obtain the correct side clearance.
• if the thread is not qualified, check the entire clamping including the machine tool.
• check the nc program available for thread turning.
• optimize the feeding method, the number of times and the size of the tool.
• ensure correct cutting speed to meet application requirements.
• if the thread pitch of the workpiece is wrong, check whether the machine pitch is correct.
• before cutting into the workpiece, it is recommended that the cutter should start with a minimum distance of 3 pitch.
• high precision coolant prolongs tool life and improves chip control.
• quick change system ensures easy and fast clamping.
• for optimal productivity and tool life, multi-tooth blades are preferred, followed by full-tooth single-blade blades and v-tooth blades.
Tapping hole dimensions and tolerances:
Basic calculation of cutting tap bottom hole size:
D i= TD-TP
D = diameter
TD = nominal thread diameter
TP = pitch
M10 x 1.5 cutting tap hole size:
10-1.5 = 8.5 mm
Basic calculation of the size of the bottom hole of the extruded tap:
D = TD -(TP/2)
D = diameter
TD = nominal thread diameter
TP = pitch
M10 x 1.5 drill size for extruded taps:
10 - (1.5/2) = 9.3