Selection of cutting oil for gear hobbing

5 min read

Introduction

Dr. Castle our expert on Metal Working oils is going to brief you on the process of Gear manufacturing and selection of cutting oils for Gear Hobbing operation.

Gear Manufacturing

Gear manufacturing is a fairly complex metal cutting process and forms an integral part of many industrial products. Gears and Gear drives are one of the key components of all kinds of vehicles, machine tools, aircrafts, and household appliances as well as a broad variety of industrial equipment's. Proper understanding about the various Gear manufacturing processes and controlling parameters is essential in order to meet the growing demands for better productivity and quality of gears.

Gear Manufacturing Process

There are a number of processes related to gear manufacturing.

Gear manufacturing can involve several applications to create splines or the teeth of a gear. Gear hobbing is the most common method for modern gear manufacturing while gear shaping still finds some use.

Gear hobbing is a multipoint machining process in which gear teeth are progressively generated by a series of cuts with a cutting tool known as hob. Both the hob and the workpiece revolve constantly as the hob is fed across the face width of the gear blank.

Types of Gears

Spur Gears

Helical Gears

Rack and Pinion

Bevel Gears

Miter Gears

Worm and Worm Gear

Screw Gears

Internal Gears

Selection of cutting fluid for Gear Hobbing

Factors influencing Gear Hobbing process.

The cutting tool used for tooth generation is called hob, which is very expensive and ensuring the extended tool life to increase the productivity and better quality gear is very essential requirement.

In the age of economic war of survival it has become essential to consider and evaluate new cutting fluids which can offer better tool life and improve productivity and lowering overall cost

While deciding the type of cutting oil to choose between water miscible (Soluble types) or neat type for various applications one must consider following factors

Severity of machining operation
Type of material
Size of components
Speed of machining operation
Feed Rate

In summary, as a general guideline it is accepted that low speed and heavy cuts involving considerable force are best served by neat oils with selective EP additives however light cut and high speed operation calls for efficient cooling and hence soluble type oils are selected.

For Gear Hobbing which is considered as severe operation where depth of cut or metal removal is relatively large and operating speed is comparatively slow wherein more lubrication rather than cooling is required, as a general guidelines following table helps in selecting suitable coolant as per the machining operation.

Module Victory Range Types of Base oil
Bigger Gears > M8 Above 35 Cst Ester Based
Medium to Bigger Diameter
Gears - M4 to M 8type
30 Cst Ester Based/ Mineral Base
Smaller Gears - Ml to M3 @15 -20 est GTL / Ester blended / Mineral Base

Most of the gears are of MS and HSS material which are more difficult to machine. Hence to achieve desired tool life and good surface finish and higher productivity neat oil with high level of sulphurised and /or chlorinated EP additive type cutting oils are recommended with the different viscosity levels. Different additive and operating temperatures are highlighted below.

Different TypeOf Additives

Friction Coefficient For Different additives

One of the major issue faced during Gear Hobbing operation is heavy smoke/fume generation due to very severe cutting operation which is not operator friendly. This is mainly due to poor lubricity and selection of low flash base oils and in-sufficient EP additive package.

It is also observed that in few older machines there is always uncontrolled leakage of hydraulic oils which affects the performance of cutting oil thereby reducing the tool life and desired finish. This leads to increase in operating cost therefore such machines it is advisable to offer a Dual Purpose oil .i.e cutting oil cum Hydraulic oil to avoid cross contamination and reduce the oil consumption.

Dr. Castle Solution on Gear Machining

  • Ester Base oil Products - lsocut E Series
  • Low & High Viscous - Mineral oil with EP additives: HICUT N VG Series HICUT DP Series
  • GTL Based products : lsocut LG Series
  • Multipurpose oil - Machining & Circulating fluids: Megacut Series