Frequently Asked Questions

Grease fittings, grease nipples or Zerks are small mechanical components used to deliver lubricating grease to specific points on machinery or equipment that require regular lubrication. The primary purpose of grease fittings is to ensure that moving parts, such as bearings, joints, and pivot points, remain properly lubricated to reduce friction, wear, and heat generation.

Grease fittings come in various different shapes and specifications, and are used in several applications. View our full range of fittings here.

A grease fitting usually has a ball check. This is where a ball bearing is present at the surface of the fitting. This is to prevent containments entering the fitting, which could cause damage to the shaft/bearing. The ball must always return to the surface after greasing.
The ball check is not a mechanism to seal against back pressure. It must not be relied upon to be a leak proof seal. This is dangerous.
If the greasing system is to retain any pressure, then a special fitting or non return valve must be used. High pressure grease can be extremely dangerous.

Samples of a competitors fittings after high pressure greasing

Because this will happen if you don’t!!

If the spring is not stress relieved, it will deform or collapse when greased. The ball will not return to the surface and contaminants will be allowed to enter the fitting. This dirt will get into the lubricated joint/bearing causing expensive damage and downtime.

Kingfisher stress relieves all springs after they are coiled to ensure the ball returns to the surface every time, even after high-pressure grease has passed through the fitting. A couple of pennies saved on a cheap fitting could cost thousands.


The ball and spring prevent the ingress of dirt and other debris into the fitting.  There are low pressure applications when this is not a factor. Particularly if oil is used.

Resin, concrete repairs and wood preservative application can demand a different configuration. Resins set quite quickly and often require that the flow is merely slowed down to reduce the seepage after injection to reduce cavitation before setting.

Kingfisher produce special fittings with no balls and springs, but if a standard thread is required an unassembled body may be offered which has an un-peened lip.

Kingfisher steel hydraulic grease fittings are carbo nitride case hardened to meet the relevant grease fitting standards. Hydraulic grease fittings are case hardened to withstand the hardened steel jaws of the grease coupler which can exert large forces under high pressure. It also gives some protection against any abrasion the fitting maybe subject to in the field.
For self forming thread fittings, the case hardening allows the grease fitting to form a thread in an un-tapped hole.

Kingfisher steel hydraulic grease fittings are carbo nitride case hardened to meet the relevant grease fitting standards.

Surface hardness is measured using the appropriate hardness tester and is taken perpendicular to the surface of the fitting in the absence of any zinc plating.

Case depth is the measurement of TOTAL CASE DEPTH. This is the measurement from the surface to a depth where the material becomes indistinguishable from the core material. Across this layer the micro hardness will reduce and visible structure will change to a point where it becomes the same as the core material.

Effective case depth is not a suitable measurement for thin case carbo nitriding


A BP1 is the standard box used by Kingfisher.  It contains grease fittings and is sealed and clearly labelled with the part number, quantity and a unique trace number. They are manufactured from high quality carboard and are recyclable.

Stainless steel is the alloy result of adding nickel, chromium and other elements to iron. These elements inhibit corrosion from occurring to the metal, and make stainless steel a useful material.

The 300 stainless steels have approximately 18 percent chromium and 8 percent nickel added. This makes it also known as 18-8 stainless steel. The 300 series has the best corrosion resistance of the different stainless steel grades. These different alloy variations affect corrosion resistance and ability to manufacture. This allows use of the 300 series for a variety of commercial applications.

Type 303 is similar to both 304 and 316 grades of stainless steel. Its corrosion resistance is similar to 304 but not as resistant as type 316. Mechanical properties are similar, but the higher sulphur content in the 303 alloy allows easier machining of this grade than both 304 and 316.

Product that requires volume machining of large quantities to be produced at high quality and most  efficiently make type 303 a good choice.

303 is used in the manufacture of grease fittings, shafts, gears, threaded uses, aircraft fittings and bushings.

View our full range of 303 Stainless fittings here.


This type of stainless steel has 16 to 18 percent chromium and 11 to 14 percent nickel and a minimum of 2 percent molybdenum. Molybdenum gives 316 additional resistance to corrosion making it useful in chemically hostile conditions. Uses for this grade of stainless steel in the more corrosive conditions such as food processing, chemical processing, agricultural uses and the pulp and paper industry.

View our full range of 316 Stainless Grease Fittings here.

Monel® is a trademark of Special Metals Corporation for a series of nickel alloys, primarily composed of nickel (up to 67%) and copper, with some iron and other trace elements. Monel® was named after company president Ambrose Monell, and patented in 1906

Compared to steel, Monel® is very difficult to machine as it work-hardens very quickly. It needs to be turned and worked at slow speeds and low feed rates. It is resistant to corrosion and acids, and some alloys can withstand a fire in pure oxygen. It is commonly used in applications with highly corrosive conditions. Small additions of aluminium and titanium form an alloy (K-500) with the same corrosion resistance but with much greater strength due to gamma prime formation on aging. Monel® is typically much more expensive than stainless steel.

Monel®’s corrosion resistance makes it ideal for marine applications such as piping systems, pump shafts, seawater valves, trolling wire, and strainer baskets.

You can view a range of our Monel® Grease Fittings here.

Possible problems associated with high temperatures are;

  • Plating: Parts are zinc plated and passivated with a yellow chromate film.  Zinc has a melting point of 420° C. The yellow chromate plating provides a self healing film. At elevated temperatures, >150°C,  the film starts to dry out and cracks, reducing the corrosion resistance but this is irrelevant if the base zinc has melted.
  • The body of the fitting is steel and should be ok at elevated temperatures, although if any chemical atmosphere is present, it may be detrimental and could possibly affect the corrosion resistance and case hardness.
  • The spring is stress relieved by us at about 450°C but only for a few moments. We cannot say if prolonged changes in temperature will be detrimental to the effectiveness of the spring especially if any other chemical atmosphere is involved.

The ability of any particular grease to be handled by grease pumps, grease dispensers, and other components in a automated greasing system depends on the grease viscosity (thickness). Grease is a mixture consisting of a natural or synthetic oil base combined with thickeners and additives.

Grease viscosity depends on the amount and type of thickener(s) used as well as the viscosity of the base oil. The NLGI (National Grease Lubricating Institute) has established a scale of 000 to 6 representing very low to very high viscosity.

NLGI refers to the”“National Lubricating Grease Institute”. This US industry body is chartered to develop and maintain standards for the grease industry. Their numbers range from 6 block grease to 000 very thin runny grease. NLGI 2 is a general all prupose viscocity of grease used in many applications.

NLGI Grade     Classification   Consisitency

000                       445 – 475          Semifluid
00                        400 – 430          Semifluid
0                        355 – 385          Very Soft
1                        310 – 340          Soft
2                        265 – 295          Common Grease
3                        220 – 250          SemiHard
4                        175 – 205          Hard
5                        130 – 160          Very Hard
6                         85 – 115           Solid


The worked penetration values in the table are determined by the ASTM (American Society for Testing and Materials) testing methods. ASTM D 217 and D1403 are described as “Standard Test Methods for Cone Penetration of Lubricating Grease”. To measure penetration, a cone of given material, weight, and finish is allowed to sink into a grease for 5 seconds at a standard temperature of 25°C (77°F). The depth, in tenths of a millimeter, to which the cone sinks into the grease is the penetration.

British Standard Whitworth (BSW) is one of a number of imperial unit-based screw thread standards which use the same bolt heads and nut hexagonal sizes, the others being British Standard Fine thread (BSF) and British Standard Cycle. These three are collectively called Whitworth threads.

For more information on Whitworth, threads click wikipedia

Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. Tribology is a branch of mechanical engineering.

For more information on Tribology click wikipedia or Leeds University

The acronym ISIR is widely used and has disparate meaning. In manufacturing it stands for: Initial Sample Inspection Report

The Production Part Approval Process (PPAP) provides customers with evidence that:

  • Component suppliers have understood their requirements.
  • The product meets the customers requirements.
  • The production process is capable of consistently producing conforming product.

For more information, click wikipedia

National Pipe Taper Fuel (NPTF) also called Dryseal American National Standard Taper Pipe Thread, defined by ANSI B1.20.3, designed to provide a more leak-free seal without the use of teflon tape or another sealant compound. NPTF threads are the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.

For  more information, click wikipedia

The “R” has been adopted by the German DIN standards and is an abbreviation of Rohrgewinde which is German for external Pipe (Tube) thread and is used to define a taper thread exactly the same as BSPT. e.g. R1/8″ = 1/8″ x 28 BSPT

When “G” is used instead of “R” the threads are external parallel BSPP (was BSPF)