Friction Coefficient - steel on hardened steel

[Tmoore]

I was wondering if someone could give me an approximate value for the coefficient of friction between two steel parts rubbing against each other. The first steel part is made of SAE 4140 and is not treated. The second steel part is made of hardened steel. If anyone has a value or knows where I could find it, it would be most appreciated.
Thanks
Tom

 

[CoryPad]

Is there any lubrication or contamination on the mating surfaces? If so, then the friction coefficient can be as low as ~ 0.1. If not, then it can be as high as ~ 0.3. Friction coefficient has large variability, so it needs to be classified with a range, not a single value.


Regards,

Cory

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[Tmoore]

Where did you find this value? The Marks handbook lists hard steel on hard steel as .78 and mild steel on mild steel as 0.74.

 

[CoryPad]

Most of my experience with friction comes from engineering fastened joints. Friction is important to calculate torque/preload behavior, and transverse slip of the joint at the mating surfaces. The friction coefficients I listed have been from personal testing and published sources, such as VDI 2230 Systematic Calculation of High Duty Bolted Joints, Handbook of Bolts and Bolted Joints, and Guide to Design Criteria for Bolted and Riveted Joints. Anything higher than ~ 0.4 that I have seen usually involves vacuum conditions (no oxide layers to allow sliding). I have no comments regarding Marks data.


Regards,

Cory

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[CoryPad]

Tmoore,

I looked in Marks' Standard Handbook for Mechanical Engineers 10th edition for their friction data. Table 3.2.4 shows the data you referenced: hard steel on hard steel is 0.78, while mild steel on mild steel is 0.74. These data are attributed to Campbell, Trans. ASME, 1939. Two pages before Table 3.2.4 is Table 3.2.1. It shows static friction coefficients for steel on steel. In the "Grease-free in vacuum" condition, it lists a value of 0.78. In the "Grease-free in air" condition, it lists 0.39. These data are attributed to the same source as before: Campbell, Trans. ASME, 1939.

Friction is a complex subject, with huge variability. One must be careful when relying upon it to perform a function. Calculations cannot use a single value from a source that did not have the same conditions. In fact, it is difficult to obtain the same conditions, so each case should be tested to have confidence in the values.


Regards,

Cory

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[skills]

Ditto on the angle tan begin to slip method for static friction!

 

[aviteri]

Tmoore, dinamics coeficient friction is fewer than statics, better try the inclined plane i guess that will satisfy your question and you'll be absolutely sure of the real conditions

 

[f100]

I suggest:
Rothbart: Mechanical Design and Systems Handbook
1964 McGRAW-HILL
Section 11: FRICTION. LUBRICATION AND WEAR
(f) Kinetic Friction of Metals.
Also see: Dubbel's Handbook (Originally German, but also in English.)
Dubbel (1966)indicates all over much lower values.
Or has there been a development towards more agreement later?