Danfoss Lubrication of Spline Shafts Data sheet

Data Sheet

Lubrication of Spline Shafts

Technical Specifications

A high percentage of transmitted power in the mobile
market is through splined pump and motor shafts and
couplings. Most of the Danfoss transmissions are
produced with splined shafts. It is necessary to use
proper installation and maintenance procedure to
expect normal life.

The life expectancy of any splined drive is dependent
on many factors. Length of the spline engagement,
alignment, transmitted torque, duty cycle, material
hardness, class of fit, and lubrication are a few of
these factors.

Let’s give some consideration to the
lubrication needs. Good lubrication is
readily achieved if the spline is submerged
in oil or if it has “splash” lubrication, as in
most gear boxes. Pump input and motor
output spline wear can usually be
controlled with proper care. These splines
are often exposed to the elements and
maintaining proper lubrication is often a
problem. Spline wear caused by fretting
corrosion is usually due to inadequate
lubrication and is characterized by a red
dust like deposit in the splined joint.
Conditions that lead to this type of wear
are: small relative motion between the
mating splines, localized loading,
insufficient lubrication and oxygen present
at the joint.

Controlling fretting corrosion by stopping
relative motion is usually not practical.
Contact stresses below 35 N/mm2, when
poorly lubricated, help reduce wear, but
most drives would typically have higher
contact stresses than 35 N/mm2. Danfoss
customer end splines are generally alloy
carbon steels surface hardened. Mating
couplings should have a suitable surface
hardness to minimize wear.

Applying a lubricant to the splined joint,
when not running in flooded oil or if
splashed oil is not possible, reduces friction

and restricts the presence of oxygen. A
recommended spline lubricant is a 50/50
compound of a high temperature grease
and a molybdenum disulphide powder.
When applied initially and re-applied at
proper intervals, it will help prevent
fretting corrosion and premature wear.
This lubricant is not soluble in oil and
should be used accordingly. Further
products which may be recommended are
Molycote, Metaflux, Never Seeze, Optimol
and similar.

Another method of stopping fretting
corrosion is to use a clamped coupling.
With a clamped coupling it is possible to
vary the fit from sliding to solid.

A tight fit can also be achieved by the use
of adhesives. Through careful application a
durable connection of splined joints is
achievable. During application special
attention should be given to thorough
cleaning and degreasing of the splines, to
keeping to the permitted clearances and to
even wetting of the joints with adhesive.
As adhesive such as Delo ML 115 is
recommended.

Spline drives are each unique and
generalizing on solutions is difficult. Proper
attention to the factors influencing
acceptable spline life such as alignment,

torque limits and lubrication with regular
maintenance will pay dividends in
providing a longer application life.

For applications where problems with
fretting corrosion are foreseeable tapered
shafts should be used. For most of Danfoss
products such shafts are in production.

Comprehensive technical literature online
at powersolutions.danfoss.com

©

Danfoss | May 2019

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