EN24 Rockwell Hardness EN24 Rockwell Hardness tomcannon (Mechanical) (OP) 19 Oct 10 06:29 Hi, I am soon going to be rolling some threads from EN24 bar before having them heat treated. Looking at page 10 of this pdf http://www.landisthreadingsystems.com/ThreadRolling/Library/TechnicalSupport.pdf how should I know what column I should be referring to? They refer to material hardness, which I am unsure of. EN24 is equivalent of SAE 4340. The threads will be 7/16 unf and unc. I am also getting myself confused between the difference in class 2 and class 3 shown on the same page. RE: EN24 Rockwell Hardness Wrenchbender (Mechanical) 19 Oct 10 12:08 Looks to me like one of the columns labeled "30-50C or Alloy [whatever Rockwell C hardness range you have]" would be applicable. 30-50C must be referring to the carbon content in 1/100th of a percent (customary in US).Thread Class refers to the tolerances and allowances (i.e. slop). Class 1 thru 3 get progressively tighter. Its all defined in American National Standard Institute (ANSI) B1.1, titled 'Unified Screw Threads'. There are probably online calculators, but here's an example..4375-14UNC-[what the class is]A ('A' means external.)EXTERNAL Class 2 Class 3 Major Dia 0.4360 +.0000 - 0.0103 0.4375 +.0000 - 0.0103Pitch Dia 0.3896 +.0000 - 0.0050 0.3911 +.0000 - 0.0050Minor Dia 0.3587 Max, Ref 0.3602 Max, Ref.4375-20UNF-[class]AEXTERNAL Class 2 Class 3 Major Dia 0.4361 +.0000 - 0.0081 0.4375 +.0000 - 0.0081Pitch Dia 0.4036 +.0000 - 0.0047 0.4050 +.0000 - 0.0047Minor Dia 0.3820 Max, Ref 0.3834 Max, Ref RE: EN24 Rockwell Hardness TVP (Materials) 19 Oct 10 14:03 Bestwrench is correct, the 30-50 C means 0.30-0.50 mass % carbon, which is the category for EN24. Depending on the exact processing history, it will either be "soft" or "15-25 RC". RE: EN24 Rockwell Hardness PeterCharles (Mechanical) 19 Oct 10 17:13 EN24 is a well known UK steel. It is commonly available in "condition T", meaning it has been heat treated to give a tensile strength of 55/65 T/in2Depending on ruling section and heat treatment it can achieve 100 T/in2, "condition Z".We use condition T for shafts. RE: EN24 Rockwell Hardness tomcannon (Mechanical) (OP) 20 Oct 10 03:44 Excellent thanks very much, I have been referring to http://www.westyorkssteel.com/EN24.html for information, and wondered about the carbon content but it was not on the same scale (0.4% where the thread rolling chart suggests only 30-50) but now I know. I will be heat treating the studs to V condition to finalise, as suggested by an incredibly well respected person in the industry.Can I assume that some of the information I will been and have been using is slightly complicated by the fact that the EN24 info is UK based whereas most of the thread rolling etc info is US based? RE: EN24 Rockwell Hardness TVP (Materials) 20 Oct 10 09:34 Hi Tom,I don't understand your last question, but if you want information on thread rolling that is from a European company, LMT Fette will have standard sizes, etc. for metric threads:http://www.lmtfettetools.com/catalogs/Thread%20Rolling_Turning%20Heads/2023%20Rollkopfkatalog%20deutsch%20englisch.pdf RE: EN24 Rockwell Hardness tomcannon (Mechanical) (OP) 20 Oct 10 10:00 Hi, sorry the first part was a statement, the 2nd part was just wondering if some of my confusion was because of the cross over between UK and US units and terminology, I am to be rolling imperial threads anyway so US is fine for measurements, just the hardness scales etc I wasn't sure about. Thanks for all your help. RE: EN24 Rockwell Hardness CoryPad (Materials) 20 Oct 10 10:11 Yes, units can be confusing, particularly in this field. RE: EN24 Rockwell Hardness tomcannon (Mechanical) (OP) 20 Oct 10 11:07 It's not just me then! I'm trying to remember all that I learned at college 8 years ago as since then I've been doing dirty engineering and automotive stuff! RE: EN24 Rockwell Hardness KENAT (Mechanical) 20 Oct 10 11:12 Unified threads aren't American, they are unified between US, Canada & GB as I recall.There is a BS for unified threads, I was going to say 1936 but I think that's undercuts for unified threads.www.boltplanet.com has a calculator for unified threads which can be useful to check your own calcs. Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"? RE: EN24 Rockwell Hardness PeterCharles (Mechanical) 20 Oct 10 14:20 My memory is that UNC and UNF were post-WW2 standards when the UK was still looking West to the US and Canada.However in the late 1960's the UK started looking East to Europe and metricated. RE: EN24 Rockwell Hardness KENAT (Mechanical) 20 Oct 10 14:56 Yes Britain is officially metric however, unless things have changed in the last 7 years, there are still British Standards for Unified threads and associated things such as standard undercuts etc. Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?