Surface Finish Correlation between Ra, Rz and Tp (bearing surface ratio)

Ron Rompen

Ron Rompen

Trusted Information Resource
#1
#1
This is a shot in the dark, but it doesn't hurt to ask. Does anyone know of any accepted studies showing a correlation between Ra, Rz and Tp (bearing surface ratio)? I am manufacturing parts which have an Ra callout of 1.0, OR Rz of 6.0, but with a Tp of 50% or better.

Anyone have any history/information to share?
 
Highly Rated Gage Tracking - Learn More
Elsmar Forum Sponsor
Miner

Miner

Forum Moderator
Leader
Admin
#4
#4
Disclaimer: I only have a small amount of experience in surface finish, so I am going from my engineering background and some theory.

Ra and Rz are measuring in the same axis, but are measuring different characteristics (Ra ~ average roughness, Rz ~ max roughness). If Ra increases, it makes sense that Rz must increase. However, Rz might increase without Ra increasing. Therefore, there should be a rough correlation between the two, but is will not be perfect. There is an article that discusses the correlation here.

Now we get to Tp. Tp is measured on an axis that is 90 degrees to the axis in which Ra and Rz are measured. This means that Tp may vary significantly with little or no impact on Ra/Rz until you get to extreme values. You could get a weak correlation, but not one that is particularly useful, or that you would want to rely upon.
 
You must log in or register to reply here.
Thread starter Similar threads Forum Replies Date
K Surface finish (Evaluation Length) Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
J Gear Surface Finish - Print with the word "calibrated" Manufacturing and Related Processes 2
8 Surface Finish - Callout as 8 - 16 Rq Manufacturing and Related Processes 1
GoKats78 Callout on Surface Finish General Measurement Device and Calibration Topics 11
S Difference between Surface Finish (Ra) and Flatness (GD&T) Inspection, Prints (Drawings), Testing, Sampling and Related Topics 6
Proud Liberal Surface finish measurement (roughness) - Rz under the ISO standard vs ANSI standard Inspection, Prints (Drawings), Testing, Sampling and Related Topics 0
Proud Liberal Measuring axial and radial surface finish (16 Rz) on a broached internal radius Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
B Surface Finish Equipment MSA (Measurement System Analysis) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
kedarg6500 Surface Finish Measurement Methods Inspection, Prints (Drawings), Testing, Sampling and Related Topics 13
P Surface Finish measurement for machined (finished) component/part Inspection, Prints (Drawings), Testing, Sampling and Related Topics 2
J Definition Standards for Dimensions and Surface Finish on a Rod Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 11
A Is it mandatory to have a profilometer to inspect >16 surface finish? General Measurement Device and Calibration Topics 8
T Interpretation of Surface Finish Specification Manufacturing and Related Processes 2
D Surface Finish Inspection Company (Laboratory) (Detroit area) needed Manufacturing and Related Processes 1
A Conducting a DOE in Minitab - Improving Surface Finish of an Impeller Using Minitab Software 10
N PCB (medical device) Surface Finish Selection. Manufacturing and Related Processes 2
S Surface Finish - Conversion factor to transform Rz Jis in Rz Inspection, Prints (Drawings), Testing, Sampling and Related Topics 6
N MSA (Measurement Systems Analysis) for Surface Finish Equipment Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
P Inner Diameter Surface Finish Ra Value vs. Surface Finish Graph Output Manufacturing and Related Processes 11
ScottK Inspecting surface finish on SS on a piece that can't be measured with current equip. Inspection, Prints (Drawings), Testing, Sampling and Related Topics 2
ScottK Surface Finish on machined brass (or other metals)- Attribute or Variable inspection? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 8
ScottK Measuring Capability on a One Sided Variable (Surface Finish) Capability, Accuracy and Stability - Processes, Machines, etc. 17
W Surface Finish parameters - Mechanical stylus based testing of a cylindrical part Manufacturing and Related Processes 2
W Surface Finish Measurement Technique Manufacturing and Related Processes 3
T Surface Finish Requirements (Ra 150) for Blasted Titanium Surfaces Manufacturing and Related Processes 12
J Surface Finish Tester Recommendations with both Ra and Rz (english and metric) scales Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
Ron Rompen Conversion of surface finish measurements Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
U How to do Gage R&Rs on Surface Finish Gages Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
Geoff Cotton Surface Finish - G5 - Where is this from and how can I measure it? Manufacturing and Related Processes 6
Marc Surface Finish Gage R&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
J The best way to define a surface finish General Measurement Device and Calibration Topics 1
J Surface Finish - What is the meaning of the term ?LAY?? Coffee Break and Water Cooler Discussions 4
D Air Gauging: Are the results affected by surface finish of the bore? General Measurement Device and Calibration Topics 1
H Regarding external surface temperature limit requirement for lab incubators. CE Marking (Conformité Européene) / CB Scheme 2
DuncanGibbons Typical Surface Roughness Requirements for Aviation AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 2
I Good Surface Plate Suppliers? General Measurement Device and Calibration Topics 1
T Capability calculation of surface profile Capability, Accuracy and Stability - Processes, Machines, etc. 20
S Alcohol based cleaner for Food Contact Surface? Food Safety - ISO 22000, HACCP (21 CFR 120) 0
V EN ISO 10993-1, Category of surface device by nature of body contact Other Medical Device Related Standards 2
W Surface Profile All-Around AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 1
T Is there a direct relation between surface roughness and gloss? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
D CED Coating in Cast iron surface Reliability Analysis - Predictions, Testing and Standards 0
S Surface roughness Rz Manufacturing and Related Processes 1
L GD&T Position for surface Inspection, Prints (Drawings), Testing, Sampling and Related Topics 9
P Surface scratch measurement General Measurement Device and Calibration Topics 1
D Surface Roughness understanding Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
D Calibration of Digital thermometer with surface probe General Measurement Device and Calibration Topics 1
R Design and Manufacture Guidelines for Surface Mount Technology Misc. Quality Assurance and Business Systems Related Topics 9
M Active Surface Disinfectant Claims - FDA vs EPA and Hands vs Objects Other Medical Device and Orthopedic Related Topics 0
P Gas Nitriding Surface Hardening of Stainless Steel 304 ISO 13485:2016 - Medical Device Quality Management Systems 4

Similar threads

Top Bottom