what are main factors that drive speed/feed even two materials have similar hardness

god_paul · Mar 11, 2015

i just came across nachi speed/feed calculator

AQUA EX Flat Drill Calculator
Feed/Speed Calculator | Nachi America

i select mold steel (20-30HRC) and alloy steel (20-30HRC)

the calculator gives higher speed for alloy steel but lower one for mold steel

so, apart from material, are other factors drive this speed? like material structure, grain size, grain shape, other impurity metal involved in the material?

Diezel · Mar 11, 2015

I think it mostly has to do with carbon content but other additives to the steel itself such as selenium etc are other factors as well. Abrasive materials call for different cutting speeds, also heat conductivity as well. For instance in titanium speed matters the most as it doesn't take heat nicely, however chip load can vary as much as .015 without creating much more heat.. A difference of about 200-300 degrees I believe.

CalG · Mar 11, 2015

Simplified

god_paul said:
i just came across nachi speed/feed calculator

AQUA EX Flat Drill Calculator
Feed/Speed Calculator | Nachi America

i select mold steel (20-30HRC) and alloy steel (20-30HRC)

the calculator gives higher speed for alloy steel but lower one for mold steel

so, apart from material, are other factors drive this speed? like material structure, grain size, grain shape, other impurity metal involved in the material?

Machinability

DMF_TomB · Mar 11, 2015

feed speed

god_paul said:
i just came across nachi speed/feed calculator

AQUA EX Flat Drill Calculator
Feed/Speed Calculator | Nachi America

i select mold steel (20-30HRC) and alloy steel (20-30HRC)

the calculator gives higher speed for alloy steel but lower one for mold steel

so, apart from material, are other factors drive this speed? like material structure, grain size, grain shape, other impurity metal involved in the material?

.
it is not a exact science. i do know some materials like cast iron even if on the soft side the sfpm recommended is slower but a higher ipt feed is recommended. probably because heat can affect it plus it can have abrasive particles mixed in with it.
.......... annealed hss steel is relatively soft but abrasive. cutting tools will get abrasive wear 3x faster than 1018 steel. usually a lower ipt feed is recommended to raise tool life to reasonable values. often sfpm and feed is adjusted to get a 30 to 120 minute tool life. easy to adjust settings 30% and double or cut in half tool life
.
i remember trying what a "expert" recommended with annealed hss milling. in 5 minutes the end mill was throwing sparks and in 10 minutes at a white hot glow it finally melted

Terrible Juan · Mar 11, 2015

god_paul said:
i just came across nachi speed/feed calculator

i select mold steel (20-30HRC) and alloy steel (20-30HRC)

the calculator gives higher speed for alloy steel but lower one for mold steel

so, apart from material, are other factors drive this speed? like material structure, grain size, grain shape, other impurity metal involved in the material?

It is pretty much based on all the alloying elements. Some are more abrasive than others, so they have to be treated differently. When you cut a metal, you are actually "plasticizing" or melting it at the point of contact. You aren't necessarily "cutting" it in the sense most people think of. Watch the high speed video of this tool bit in action:
https://www.youtube.com/watch?v=mRuSYQ5Npek

You will see that the amount of heat/friction generated at the cutting edge causes an extremely high temperature which is just enough to melt the material and allow it to peel away. Material like titanium is a HEAT RESISTANT ALLOY which is what makes it harder to cut if you compare it to another material with the same hardness. If the material resists heat, it resists you cutting it as well.

god_paul · Mar 11, 2015

thank you all,

so can i say it's a little unsafe to rely on feed/speed table as those tables are only for starting the process but to get the optimize condition, the speed/feed are adjusted by experiment..

Terrible Juan · Mar 11, 2015

god_paul said:
thank you all,

so can i say it's a little unsafe to rely on feed/speed table as those tables are only for starting the process but to get the optimize condition, the speed/feed are adjusted by experiment..

Those parameters are almost ALWAYS based on a rigid setup, rigid machine, spindle that is in good condition, rigid part (not machining something paper thin), etc. If you see a recommendation for 500SFM-900SFM and you think to yourself "Oh come on, that is a huge range!" it generally means that if you are taking light cuts, go with the higher end. If you are burying the tool and taking a hard cut, go on the lower end. Then adjust from there.

You have to remember that every single machine is different. Some people run BT30, some people run HSK100. It is impossible to put all those variables in a feed/speed table. That is why it is important to get in contact with the local tooling rep who supports that particular product/brand.

DMF_TomB · Mar 11, 2015

cutting parameters

god_paul said:
thank you all,

so can i say it's a little unsafe to rely on feed/speed table as those tables are only for starting the process but to get the optimize condition, the speed/feed are adjusted by experiment..

.
many things like cutting tool length and tool holder length can effect things 1000% easily yes thats by a factor of 10........ i would laugh big time anybody using "recommended settings" with a 24" long tool.
.
horsepower and rigidity of machine and rigidity of part can effect things by a factor of 10 too or more
.
even material. some metal like 304 stainless in the work hardened condition is at least 2 times harder to machine than annealed stainless.
.
i keep a excel file of all tools in tool holders used in many hundreds of programs with a record of all sudden tool failures. there is a wide variation in sfpm and feed and depth and width of cut usually on the order of 300% ........ recommended maximum speeds and feeds are just a rough guess on average settings........ they certainly are not anything ultra precise one setting good for everything

god_paul · Mar 13, 2015

DMF_TomB said:
.
many things like cutting tool length and tool holder length can effect things 1000% easily yes thats by a factor of 10........ i would laugh big time anybody using "recommended settings" with a 24" long tool.
.
horsepower and rigidity of machine and rigidity of part can effect things by a factor of 10 too or more
.
even material. some metal like 304 stainless in the work hardened condition is at least 2 times harder to machine than annealed stainless.
.
i keep a excel file of all tools in tool holders used in many hundreds of programs with a record of all sudden tool failures. there is a wide variation in sfpm and feed and depth and width of cut usually on the order of 300% ........ recommended maximum speeds and feeds are just a rough guess on average settings........ they certainly are not anything ultra precise one setting good for everything

thank you for your experience

another question to ask is:
before people put a new tool to production, they want to test it to make sure it works...
however, the testing tool is usually put on a lab machine to be tested; if it's good, then, people will put it into production; otherwise, just tell tool supplier this tool is not good...

we know machine is different and is this kind of test legitimate ? partial reason why people doing this is they dont want to stop production machine for you to perform test.....

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what are main factors that drive speed/feed even two materials have similar hardness

god_paul

Aluminum

Diezel

Aluminum

CalG

Diamond

DMF_TomB

Diamond

Terrible Juan

Cast Iron

god_paul

Aluminum

Terrible Juan

Cast Iron

DMF_TomB

Diamond

god_paul

Aluminum

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