Thread cutting is an essential process in manufacturing components that need threaded holes or fittings, such as screws, bolts, pipes, and valves. As the cutting tool rubs against the workpiece to create the threads, a tremendous amount of heat is generated due to friction. This heat can negatively impact the cutting process in a variety of ways.
That’s where cutting fluids – coolants and lubricants help. They provide critical cooling and lubricating functions that can greatly improve various aspects of the thread-cutting operation.
The major benefits include:
- Reduced cutting temperatures
- Improved tool life
- Enhanced surface finish
- Effective chip control
- Corrosion prevention
- Cost savings
In this article, we’ll discuss these advantages in detail. We’ll also look at proper selection and application methods for these indispensable fluids to reap the full rewards in your thread-cutting applications.
Friction and heat generation in thread cutting
During thread-cutting processes like tapping or thread milling, there is intense friction as the cutting edges of the tool slide against the workpiece. The rotational movement combined with major resistance as the material is sheared off generates extreme heat.
Temperatures can easily exceed 1000°C at the cutting interface point. For tough materials like steel alloys that already require high energy input, the problem is further amplified.
All this generated heat can have damaging consequences by increasing wear rates on the cutting tool or inducing dimensional errors and poor tolerances due to thermal expansion on the machine, tool, and part. For example, in thread tapping of pipe taps, binding and breakage in the tap are more likely to occur.
Improving cutting tool life
One of the biggest benefits of cutting fluids is the dramatic improvement in the lifespan and durability of cutting tools used for thread production.
They directly cool and lubricate the cutting edges- the exact spot subject to the most extreme conditions. Lower temperatures significantly reduce abrasive wear, cratering, deformation, and eventual blunting under high loads that would otherwise debilitate the cutting tool prematurely.
Cutting tools stay sharper for much longer, allowing higher productivity through faster feeds, speeds, or deeper cut depths.
Enhancing surface finish
As heat becomes excessive during dry machining, it can lead to tears, chatter marks, smearing, and a poor finish on the workpiece.
Appropriate cutting fluids minimize such thermal damage via lower friction and temperatures. This is vital in industries like medicine and aerospace, where high-quality thread finishes are needed for mating with other precise components, fasteners, or sealing with gaskets.
Effective chip removal
As the cutting tool shears away material to form the thread profile, hot metal chips are generated, which can easily be re-welded and embedded back onto the workpiece or machine tool without proper chip evacuation.
Coolant flows across the cutting zone, rapidly flushing away hot chips through liquid curling, turbulence, and internal pressures. This is critical in confined thread-cutting operations like deep hole tapping, where chip clearance space is extremely limited.
Corrosion protection
Many common materials that need threading, like aluminum and magnesium alloys, can experience heavy oxidation or galvanic corrosion damage without sufficient protection. Steel components are susceptible during interim periods before secondary surface finishing or treatments.
Quality coolants and lubricants contain rust inhibitors and surfactant additives that form a temporary water-repellent film layer over exposed metal surfaces. This guards against chemical reactions right after machining, so parts aren’t degraded while they await subsequent processing, cleaning, or shipment.
Cost savings benefits
Cutting fluids entails higher upfront purchase, maintenance, and disposal costs than dry machining. However, if we factor in the total operational costs, it exposes the significant economic benefits over the long run. Such as:
- Prolonged tool life lowers cutting tool costs
- Lower scrap rates as quality is enhanced
- Allows more holes per tool, so fewer tool changes.
- Limits machine damage or abrasion from chips
Environmental considerations
While conventional mineral oil-based fluids have come under environmental scrutiny, the latest generation of cutting fluids use much safer, sustainable options:
-Semi-synthetic fluids balance performance and ecological profile with around 50% plant-based or organic base oils.
-Vegetable oil microemulsions derived from renewable triglyceride plant stocks provide biodegradable lubrication.
Gas-based coolants, like liquid nitrogen or CO2, aren’t toxic and don’t leave any residues.
Whichever fluid is selected, responsible disposal methods like capturing, filtering, treating, and reusing spent coolants are vital for minimizing environmental impact.
Conclusion
There is no denying cutting fluids provide indispensable cooling, lubricating, chip removal, and protective properties that enable and enhance thread production processes. They curb destructive friction and heat generation that is inherently magnified during thread cutting.
While cutting fluid selection, methods, and maintenance entail further complexity and cost, this is offset multiple times over by the performance boost, savings, and part quality improvement they unlock.
