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Lubrication

date2025-07-24tags:meche:

Lubricants cool tools and reduce wear during machining wrought iron and steel. They enable higher cutting speeds. Not all operations use them. Some machines lack supply equipment, and lightweight cuts often run dry. For instance, small turning operations in the lathe are usually performed dry or without a lubricant, regardless of the material being turned, especially when the cuts are light and the application of oil or a soda-water mixture to the tool would interfere with the work. When there is considerable superfluous metal to be removed and long roughing cuts must be taken, a good lubricant, while not necessary, is very desirable, as it permits higher cutting speeds and preserves the edge of the tool.

Many modern lathes, particularly the large sizes or those of the "manufacturing type," are equipped with pumps and piping to automatically supply a continuous stream of lubricant for the turning tool. Most lathes, however, are not so equipped and lubricant is generally supplied from a cam which is mounted at the rear of the carriage and travels with the tool as it feeds along the work. The objection to the use of a cam from which the lubricant flows by gravity is that the amount of lubricant is insufficient to properly cool the tool when taking heavy roughing cuts. The result is that the full benefit from the use of the lubricant is not obtained. (The different methods of supplying lubricant to turning tools and cutters on various machines is explained in Chapter II.) Cutting lubricants are more generally used on turning and milling machines of various types than on planing and slotting machines. In fact, cutting lubricants are not often used for rough planing operations, although in many cases a lubricant would be desirable. The same is true of many other operations which are ordinarily performed dry. Frequently a lubricant, such as soda-water, is used on the planer or shaper when taking light finishing cuts. The object, however, is to secure a smooth surface rather than to increase the durability of the tool or permit higher cutting speeds.

Quite a variety of cutting lubricants are used at the present time, some being compounds which are "home-made" and others commercial lubricants which have been placed on the market. Most of the following lubricants for different materials and operations are in general use and have proved satisfactory.

By operations

Lubricants for Turning Operations

Lard oil lubricates steel and wrought iron well, especially on automatic screw machines. Soda-water and commercial lubricants outperform it at high speeds.

Cheaper alternatives often used in general machining include mixtures of soda ash and water, thickened with lard oil or soft soap. A common recipe is:

Other effective mixtures include:

These alternatives offer cost savings and good performance for various machining tasks.

Lubricants for Milling

For milling operations the following compound (which is also adapted to turning) is often used. Mix together 1 pound of sal-soda, 1 quart of lard oil, 1 quart of soft soap and enough water to make 10 or 12 gallons. Boil this mixture one-half hour. For general work in milling steel, the following formula has been successfully employed: Mix 96 pounds of "Cataract" compound and 21 gallons of pure water; 'take 12 gallons of this stock mixture, add 4& gallons of water and two No. 10 jars of "Aquadag"; mix thoroughly. A mixture of equal parts of lard oil and paraffin oil is also used for milling, the paraffin being added to reduce the cost of the lubricant. For fluting, operations, paraffin oil, not mixed, has proved satisfactory.

Here's a concise summary of milling lubricants:

General purpose milling lubricant:

Equal parts. The lard/paraffin mix is economical in general milling.

Fluting milling lubricant:

Compounds for Drilling

Drilling Compounds:

Drilling Lubricants by Material:

General Drilling Tips:

Grinding Lubricant:

Lubricants for Thread Cutting

General purpose thread cutting:

High-speed, hard materials (e.g., nickel steel):

Copper:

Lubricant for Gear Cutting

The following mixture has been extensively used on gear-cutting machines: 3.5 gallons of mineral lard oil, 2.75 pounds of sal-soda, and one barrel of soft water.

Lubricants for Tapping

Tap Lubrication for steel/iron:

Tap Lubrication for cast iron:

Avoid: Machine oil (significantly increases tap breakage) Key Takeaway: Using the right lubricant drastically reduces tap breakage and power consumption during tapping.

Lubricants for Broaching Operations

General Use Broaching Steel: (Lubricant is similar to other machining operations)

For long holes, a good-quality oil is preferred for better adherence to the broach.

Lubricants for Slow Speed Saw

While the Buhler Isocut saw is supposed to be used with IsoCut Fluid, it does seem to be a micture of 2 parts kerosene to 1 part olive oil from the MSDS sheet. While unlikely to be as effective as IsoCut Fluid, it should serve in a pinch.

By materials

Lubricants for Cast Iron

Cast iron is typically machined dry, except when tapping. While applying cooling water can increase cutting speed by about 15%, many find the resulting mess from mixing cast iron shavings with lubricant outweighs this benefit.

Lubricants for Brass, Babbitt and Copper

Usually dry, but lard oil can be used for automatic screw machines.

Typically dry, but kerosene or turpentine prevents balling during boring/reaming.

Milk is best, but lard oil and turpentine mixtures also work.

Lubricants for Machining Aluminum

Aluminum Lubricants:

By lubricant type

Lard Oil as a Cutting Lubricant

Lard oil's effectiveness as a coolant degrades over time, especially when used on different materials. Contamination with brass dust, for example, can cause problems when the oil is later used on steel.

To maintain lard oil's performance: Keep it clean: Avoid cross-contamination between different machined materials. Use on the same material type: Dedicate oil to specific metals. Choose high-quality oil: Look for nearly colorless with pale yellow or greenish tinge, and a specific gravity no higher than 0.916.

By following these guidelines, lard oil can remain a highly effective cutting fluid.

Effect of Cooling- Lubricant on Cutting- Speed

F. W. Taylor tested how cooling water affects cutting speed.

8 No. 124 CUTTING LUBRICANTS

High-speed steel tools gain 35–40% cutting speed turning steel or iron with a heavy water stream. Practice gains are lower since water may miss the cutting zone. The most satisfactory results are obtained from a stream of water falling at rather slow velocity but in large volume, because a stream of this sort covers a larger area and is much freer from splash.

[image: Screenshot 2024-12-01 155900.png]
FIG. 01

The stream of lubricant should fall directly upon the chip at the point where it is being removed by the tool. The left-hand view of the accompanying illustration shows how the stream should fall upon the tool and chip. Very often the water is thrown upon the work at a point above the chip to prevent splashing, as illustrated by the right-hand view. This method, however, of applying lubricant is less effective and results in a slower cutting speed. The gain in cutting speed through the use of cooling water is prac- tically the same for all qualities of steel from the softest to the hardest. When cutting steel, the better the quality of the tool steel, the greater the percentage of gain through the use of cooling water. The gain for different types of tools when cutting steel was found to be as follows: Modern high-speed tools, 40 per cent; old-style self-hard- ening tools, 33 per cent; carbon steel tempered tools, 25 per cent.

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