What is "100%" machinable?

I get most of my plain and alloy steel from Pacific Machinery and Tool
All of the different alloys have a "machinability" rating. 1018, 4140, 303,
4152 etc. are 50% to 75% or so. 12L14 is over 100%. So what is 100%?
What is the baseline material that all others are compared to?
Reply to
Bill Marrs
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Don't remember where I got this. Pulled it from my Palm PDA.
Relative Machinability Carbon Steels 1015 72% 1018 78% 1020 72% 1022 78% 1030 70% 1040 64% 1042 64% 1050 54% 1095 42% 1117 91% 1137 72% 1141 70% 1141 Annealed 81% 1144 76% 1144 Annealed 85% 1144 Stressproof 83% 1212 100% 1213 136% 12L14 170% 1215 136% Alloy Steels 2355 Annealed 70% 4130 Annealed 72% 4140 Annealed 66% 4142 Annealed 66% 41L42 Annealed 77% 4150 Annealed 60% 4340 Annealed 57% 4620 66% 4820 Annealed 49% 52100 Annealed 40% 6150 Annealed 60% 8620 66% 86L20 77% 9310 Annealed 51% Stainless Steels and Super Alloys 302 Annealed 45% 303 Annealed 78% 304 Annealed 45% 316 Annealed 45% 321 Annealed 36% 347 Annealed 36% 410 Annealed 54% 416 Annealed 110% 420 Annealed 45% 430 Annealed 54% 431 Annealed 45% 440A 45% 15-5PH Condition A 48% 17-4PH Condition A 48% A286 Aged 33% Hastelloy X 19% Tool Steels A-2 42% A-6 33% D-2 27% D-3 27% M-2 39% O-1 42% O-2 42% Gray Cast Iron ASTM Class 20 Annealed 73% ASTM Class 25 55% ASTM Class 30 48% ASTM Class 35 48% ASTM Class 40 48% ASTM Class 45 36% ASTM Class 50 36% Nodular Iron 60-40-18 Annealed 61% 65-45-12 Annealed 61% 80-55-06 39% Aluminum and Magnesium Alloys Aluminum, Cold Drawn 360% Aluminum, Cast 450% Aluminum, Die Cast 76% Magnesium, Cold Drawn 480% Magnesium, Cast 480%
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Cold-rolled SAE 1212. Sometimes SAE 1112. It's based on a percentage of the cutting speed obtainable in 1212 for 20 minutes of tool life.
That leads to some strange numbers. For example, high-silicon aluminum is fairly easy to machine, but it tears heck out of tools. For an idea of the range in typical materials, 304 stainless is somewhere around 25 (I'm doing this from memory, so look it up if you need a useable number), and magnesium alloys can range up to 2000.
-- Ed Huntress
Reply to
Ed Huntress
"Bill Marrs" fired this volley in news:uIf4l.789$ snipped-for-privacy@nwrddc02.gnilink.net:
100% machinable alloys are those that will self-correct mis- measurements, surface speed errors, lost motion chatter and hogging, and tool angle and rake errors without causing you to scrap a piece of work.
I have some 100% machinable wax. If you goof, you melt it, and try again. No waste! (well... almost)
I'd say the baseline is "machinable wax".
Reply to
Lloyd E. Sponenburgh
Machinable vs machinability... Everything is 100% machinable, but as was pointed out, not everything has 100% machinability compared to the the baseline material. Who said that grammar was not important?
Merry Christmas to all contributors (even the OT) of this enjoyable discussion group.
Reply to
SAE 12L14 is leaded free machining steel. it cuts like butter.
back in George Thomas's time he produced a number of beautiful functional machining projects for model engineers. while most of us buy scrap steel and bear with the surfaces showing a little tearing George's projects were flawlessly finished. the question 'how do you get the finishes?' was posed in Model Engineer at the time. the answer was in the use of 12L14 which most model engineers hadnt heard of.
if you cant get SAE12L14 you will often be able to get SAE1214 which lacks the lead but is almost as easy to achieve the finishes on. it is well worth hunting out a supply of these alloys for model engineer use. they will turn good workmanship into superb workmanship.
(others have answered your actual question about the comparison basis) Stealth Pilot
Reply to
Stealth Pilot
Thanks for the table. Kinda looks like the inverse of cutting speed.
The only one I don't understand is the "Aluminum, Die Cast 76%". ----Must be the chilling of the mold?
Anyway, it's a keeper. Pete Stanaitis -----------------------
Reply to
Which points out how the machineability ratings can be misunderstood. High-silicon aluminum actually cuts pretty easily, but it tears the heck out of tools. Much production machining of those grades is done with diamond tools for that reason.
But it's no harder to cut than many other aluminum alloys, until your tool wears out. The machineability rating is based on tool life, not on horsepower required to cut the material. The implication of the rating is that tool life will be related to the tendency of the material to heat the tools, which is a reasonable assumption with homogeneous materials. But high-silicon aluminum is more like an abrasive composite.
-- Ed Huntress
Reply to
Ed Huntress
AISI arbitrarily chose 160 Brinell B1112 as a value of 100%. Anything lower that 100% is more difficult to machine, over 100% would be easier.
There is a newer Ito-Bessyo Carbon Equivalency test using 1045 as a standard and employing a formula for computing machinability. I don't know much about the new one, but it sounds handy.
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