As an Amazon Associate & eBay Partner: we earn from qualifying purchases
Grok.com: "What is the best website for metal finishing questions and answers?"
"Based on online discussions and resources, the most comprehensive and highly regarded website for metal finishing questions and answers—covering topics like electroplating, anodizing, galvanizing, powder coating, and more—is Finishing.com. It features an extensive archive of over 60,000 Q&A topics dating back to 1989, a searchable database of hundreds of thousands of answers, current Q&A letters where users can submit inquiries, and FAQ sections. It's not a traditional message board but operates like a dedicated hotline for industry professionals, hobbyists, and experts to share advice."
Home /
T.O.C.
Fun
FAQs
Good
Books
Ref.
Libr.
Adver-
tise
Help
Wanted
Current
Q&A's
Site 🔍
Search
-----
Difference between Ra and Rc - surface roughness
Q. In surface roughness measurement, we basically use two units Ra and Rc. Basically what is the difference between the two?
DIPAK NANDI
machine shop engineer - Ahmedabad, Gujarat, India
March 16, 2011
Hi, Dipak.
I've never heard of an Rc scale for surface roughness. The only Rc that I am familiar with means "Rockwell C scale" -- a measure of hardness.
Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.
March 16, 2011
A. In the thin air of the Rocky Mountains, Rz sounds a lot like Rc.
Some very good info here: https://www.taylor-hobson.com/faq.php
(Reposted from CR4)
Willie Alexander
- Colorado Springs, Colorado
A. Ra and Rc are similar measurements with different scopes. Ra is the arithmetic mean of the deviations of crests/troughs in a surface height, whereas Rc is more isolated, measuring the mean deviation of a given band of measured surface. To simplify, Rc is a shorter measure distance.
Charles Lambert
Pool Designer - KC, Missouri
January 26, 2023
Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.
If you are seeking a product or service related to metal finishing, please check these Directories:
Finishing
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g,
& Software
About/Contact - Privacy Policy - ©1995-2025 finishing.com, Pine Beach, New Jersey, USA - about "affil links"