Most people think cast iron is easy to machine, especially when considering its theoretical values for machining like chip type, cutting forces and hardness. While it may look that way, out on the machine shop floor, graphite and sand inclusions as well as the outer skin of the casting tend to degrade edge life quickly. As edge life degrades, so does surface finish quality from batch to batch. Using cost effective tooling for a single component starts with selecting the proper machining grade for that component material.
This guide focuses on the grade of material called LF3018, which is perfect for this machining application.
Why Cast Iron Punishes the Wrong Insert
India is second in the world in total casting production, behind only the US. Grey iron, ductile iron, and steel castings account for a majority of total casting production in India. All ferrous metals. The automotive industry, including component production like valves and compressors, as well as machining centers and lathe beds, accounts for the majority of the production of metal castings. The manufacturing sector in India is dominated by casting of metals. The combination of volume and variability means consistent insert life and surface finish become more valuable and difficult to achieve. A steady cast iron machining process results in savings in machine, rework, and tool downtime and replacement. themachinemaker
The material creates its own challenges. Graphite flakes in grey iron lubricate the cut and help chips break cleanly, but the surrounding matrix is abrasive and wears the flank of the edge steadily. Interrupted cuts across the casting skin add impact on top of that wear, and any residual sand or scale speeds it up. The result is typically flank wear and small chipping rather than the crater wear common in steel. Effective carbide inserts for cast iron machining must therefore balance wear resistance with enough toughness to survive the first pass through the skin.
Understanding the LF3018 Grade
Within Deskar’s range as listed on Jaibros, LF3018 is the grade intended for cast iron, while other grades in the range are aimed at steel and stainless steel. The LF3018 carbide insert is available in two formats, TNMA and WNMA, which cover most general turning needs on castings. Grade selection matters because the substrate and coating are tuned to a specific wear mechanism, and a grade built for one material rarely performs as well on another. Before fixing a process, confirm coating details and recommended cutting data on the manufacturer’s datasheet or with the Jaibros team, since product pages seldom show every parameter.
Deskar Insert for Cast Iron: TNMA and WNMA Formats
The first four letters provide a good idea of what's inside. The letters describe shape (T), clearance angle (N, which is negative), insert tolerance (M), and chipbreaker (A). Size and thickness along with nose radius are given as a series of three numbers. A top surface that has no chipbreaker and is flat can work for machining cast iron due to its natural ability to create shorter chips and break more easily without assistance. Also, negative inserts allow double-sided use of the insert, which is economically favorable for machining lots of parts.
Similarly, WNMA is designed for an insert with a trigon shape, an 80° clearance angle and four negative inserts. Having a clearance angle of 80° is more beneficial than a smaller clearance angle (such as the 60° on a triangle insert) when working with parts that have casting surface irregularities and parts with larger interrupted cuts. Triangles have better edge reach when facing. However, trigons offer better edge strength. You must consider both geometry and grade, not just shape. The pack size and availability are listed on the collection page.
Where LF3018 Fits Best
Automotive and Transport Components
Automotive work is the clearest fit. Brake drums, brake discs, flywheels, hubs and housings are commonly grey or ductile iron castings that need facing, boring and outside turning in repeat batches. Consider a shop running brake drums every week: the first pass breaks through the skin, the second finishes the friction surface, and both are interrupted by casting variation. In that environment, the Deskar insert for cast iron range, used in TNMA or WNMA format, gives predictable wear, so operators can plan edge changes on a schedule rather than reacting to unexpected breakdowns.
Pumps, Valves and General Engineering
Pump casings, valve bodies, pulleys, flanges and machine beds form the second large group. These parts come in lower volumes but wider variety, so shops often move between roughing and finishing within a single job. LF3018 suits this work when the material is clearly cast iron and the machine has enough rigidity for a negative insert. If the setup is light or the part is slender, discuss geometry options with your supplier before ordering. Matching grade to metal and shape to machine is what turns a good insert into consistent production.
Where a Different Grade Is the Better Choice
No grade covers every material. Steel, stainless steel and aluminium each need a different edge, and the steel and stainless grades in the same range are the right choice for those jobs. Ductile or SG iron is tougher than grey iron and can behave differently at the edge, so trial a small quantity and compare wear before committing a full batch. Using a cast iron grade on steel usually shortens tool life, because heat and crater wear replace abrasion as the dominant mechanism. Recording the correct grade on the job card is a simple habit that protects both tools and parts.
Setup Practices That Protect Tool Life
Start from the manufacturer’s recommended parameters and refine them using actual wear data from your own machine. Make the first pass deep enough to cut beneath the casting skin so the edge does not rub on hard crust. Keep the insert seat clean, the clamp secure and the tool overhang as short as the job allows, because small setup errors show up as chipped corners. Whether you run a Deskar insert or any other brand, rigidity and clean seating matter as much as the grade itself.
Coolant deserves a deliberate decision. Cast iron is frequently machined dry because graphite already lubricates the cut, and a sudden splash of coolant on a hot carbide edge can cause thermal cracking. If you need coolant for size control or chip evacuation, apply it as a steady flood rather than an intermittent spray. Dry cutting produces fine abrasive dust, so use proper extraction to protect slideways and operators. Finally, index edges on a planned schedule and log how many parts each edge produces. That record is your most reliable guide when planning future purchases.
Industry Trends: Consistency Over Raw Speed
Workshops across India are steadily moving from conventional lathes toward CNC turning centres, and with that shift comes closer tracking of cost per component. Buyers increasingly judge tooling by how many good parts each edge delivers rather than by the price of the box. This is why CNC inserts for cast iron are being specified by grade and application instead of shape alone, and why dependable batch quality matters to purchasing teams. The shops that benefit most treat CNC tools as a controllable part of the process, not as a consumable line item.
How to Choose the Right Insert for Cast Iron
Before ordering cutting inserts for cast iron, work through a short checklist. Confirm whether the workpiece is grey, ductile or malleable iron, and whether you are cutting clean stock or a rough casting skin. Match the shape to the operation: a triangle for reach, a trigon for edge strength. Check that the machine has the power and rigidity to support a negative insert, and plan batch size so that you can compare tool cost per component over time. A few minutes spent on these questions prevents most wrong purchases and keeps the tool crib simple.
Common Mistakes to Avoid
There are three common blunders. The first error is the use of an overly simple steel grade that was immediately available for use. This leads the user to complain about early edge degradation of their tool, however, it is in fact the user’s fault as the user chose the wrong tool. The second mistake is that the first cut is too light to go beneath the scale, which instead rubs the edge on the scale. Lastly, if a user uses an edge for too long past a reasonable level of degradation, they end up with broken tools and useless materials. There is no replacement for proper planning and execution when it comes to tools of any sort, and insert choice is only as good as the conditions and use, and there are many such basic rules which must be followed, even if the choice is a good one, for example, a Deskar insert.
Conclusion
Cast iron may look forgiving, but its abrasive structure and rough skin punish an unsuitable edge quickly. LF3018 gives workshops a grade built for that environment, available in TNMA and WNMA formats. Combine it with a first cut that clears the skin, sound setup, a sensible approach to coolant, and a simple wear log, and tool life becomes far more predictable. Dependable carbide inserts for cast iron machining come down to matching grade, shape, and process. If you are comparing options, the Deskar insert range is a practical place to start, and a trial batch of the LF3018 carbide insert will show how it performs on your parts.
Jaibros is a trusted manufacturer and supplier of CNC tools and carbide cutting solutions for Indian workshops, covering turning and milling inserts, holders, collets and drills. Whether you are setting up a new cast iron job or standardising tooling across a plant, the team can help you match grade, geometry and quantity to your application. Explore the full Deskar collection at jaibros.com to compare options and order with confidence.
Frequently Asked Questions
1. Which Deskar insert is best for cast iron?
For grey and similar cast irons, LF3018 is the grade listed for cast iron in Deskar’s range on Jaibros, available in TNMA and WNMA formats. Choose the triangle for reach and the trigon for edge strength.
2. What does LF3018 mean on an insert?
It is the grade code. On Jaibros, LF3018 marks the grade meant for cast iron. Ask the supplier for the coating and cutting data sheet before you finalise your process.
3. Can I use a steel insert on cast iron?
You can, but tool life is usually shorter because a steel grade is not tuned for abrasive wear and interrupted cuts. For repeat work, switch to dedicated cutting inserts for cast iron.
4. Should I use coolant when turning cast iron?
Dry cutting is common because graphite lubricates the cut and coolant can cause thermal shock. If you need coolant, apply a steady flood and keep dust extraction running.
5. What should I check before buying CNC inserts for cast iron?
Confirm the workpiece material, insert shape and size, grade and machine rigidity. If you are unsure, share your part details with the Jaibros team and they can suggest a suitable format.