Cutting It Fine
Here’s what the end users look at while selecting their perfect cutting tool
Principal categories of cutting tools include single point lathe tools, multi-point milling tools, drills, reamers, and taps. All of these tools may be standard catalogue items or tooling designed and custom-built for a specific manufacturing need. The important properties of cutting tool materials are hot hardness, wear resistance, high thermal conductivity, resistance to thermal shock, easy to grind and sharpen, low mechanical and chemical affinity for the work material. Carbon tool steel, high speed steel, cemented carbides and ceramics and diamonds are the different types of carbide and non carbide tool materials. Carbide is used in solid round tools or in the form of replaceable inserts and every manufacturer of carbide tools offer a variety for specific applications.
With carbide, the machining time can be reduced substantially and hence the cost of the component. Also, costs towards rework and rejections are almost zero.
“The proper choice can double tool life or double the cutting speed of the same tool. Shock-resistant types are used for interrupted cutting. Harder, chemically-stable types are required for high speed finishing of steel. More heat-resistant tools are needed for machining super alloys, like Inconel and Hastelloy,” says Ramchandra D Mahind, vice president and head,Kondhapuri plant and marketing, Kirloskar Brothers. When it comes to machining with carbide or noncarbide tools, usually parameters like “material to be cut, selection of cutting tool material and tool geometry, tool life/cost of cutting tool, type of chip generated have to be considered,” asserts Pradeep Nisal, manager, production, Bosch Chassis Systems India.
“The proper choice of a cutting tool can double tool life or doublethe cutting speed of the same tool."– Ramchandra D Mahind, VP and head, Kondhapuri plant & marketing, Kirloskar Brothers.
HOWEVER, IT IS also the cost of the final product that plays a role in the selection of a carbide or noncarbide tool. “Cost of a machined component largely depends on the machine hour cost. With carbide, the machining time can be reduced substantially and thus the cost of the component. Other than this, costs towards rework and rejections too matter which are almost zero with carbide,” mentions D N Narveker, head, manufacturing, commercial vehicle division, Bajaj Auto. At the Kirloskar Brothers, Kondhapuri plant, different types of valves are manufactured. For processingthe component of a valve, variety of machines like vertical turret lathe, horizontal boring and radial drilling are used. They machine the maximum quantum of material grade like cast iron, steel and stainless steel on the above mentioned machines.
“In this process, cost cutting tool plays a major role. If we would have used a non carbide tool for turning operation then we would not have got the optimum cutting speed which limits the 15-40 m/min with the depth of cut 1 mm. Whereas by using a carbide insert that is CVD/ PVD coated we get two to three times more cutting speed i.e. 80 m/min to 200 m/min with the depth cut of 2-8 mm for cast iron machining. Ultimately, it results in cycle time reduction and getting the maximum output from a machine. It also helps in reducing the process cost of the product,” explains Mahind. When the same material has to be machined on a radial drilling machine, taking into consideration the cutting tool selection parameter i.e. machine capacity and rigidity, machining process, using carbide cutting tools for the drilling/tapping operation is difficult. This is because it has the ability of higher cutting parameter for which the machine is not suitable. Also, it increases the process/tool cost.
“Instead of using the carbide here high speed steel tool grades are used to reduce the tool and process cost. It’s cutting parameters range for tap-Vc:- 8-20m/min, HSS Drill- Vc:-5-12 m/min with feed rate of 0.2 mm maximum, which are suitable for the conventional radial drilling machine. Overall benefit of the product with proper cutting tool selection, which includes cycle time, tool cost reduction and surface finish as per quality norms, dimensional accuracy and tool indexing frequency, is less in carbide,” emphasises Mahind.
If That is the kind of thought process that goes behind selecting the tool, imagine when it comes to selecting the tooling provider. “While selecting my provider, I would primarily look at consistency in performance, response time, lead time for development, optimum cost of cutting tool and the service backup,” states Narveker. It also makes a huge difference to the users knowing their tool providers manufacturing process. Seconding Mahind adds, “One of our solution providers, ISCAR Tooling, has a variety of tools for the internal grooving operation which helped us change the process at our end. Also, because we knew they do not compromise on quality in their manufacturing process it was easier for us to decide on using their solution.”
“While selecting my provider, I would look at consistency, response & lead time, cost and service backup.”– D N Narveker, head, manufacturing, commercial vehicle division, Bajaj Auto
He further elucidates, “On a horizontal boring machine we used to use the conventional method that is grooving tool holder with bar, which is mounted on the face plate of machine, giving the manual feed control and set up for internal grooving operation. After conversion of the horizontal boring machine with CNC control we implemented their grooving cutter with interpolation grooving operation which has resulted incycle time reduction.” Summing up, the key parameters for choosing the perfect tool and solution provider, according to Nisal is to “think out of the box and do a micro analysis at the start of project. This will give one a lot of ideas. I believe, one should try to use a combination of special tools instead of standard catalogue items. I would like to suggest to both users and solution providers to give all the information to the service provider as this would benefit both the parties. I have often observed that in case of any tool failure the user tries to put the blame on the service provider but if he is successful the credit lies only with him. Finally, for a service provider commitment has to be very important.”