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    Default Feed Rate & Chip Load

    Hi,

    Does anyone have a formula for calculating, or a chart for referencing Chip Load / Feed per Tooth when cutting mild steel? Ideally for a range of end mill HSS cutter diameters.

    I am trying to calculate my estimated feed rate (IPM) using RPM x Chip load x # of flutes. But I have no chip loading charts or formula to work from, and I have no idea who manufactured my collection of HSS end mills (so cannot go to them).

    Another question, how do I incorporate different cutting depths into the feed rate formula? Obviously, with increased depth I have to reduce feed rate?

    I except these formulas produce only rough guide values, and many other factors such as HP, rigidity, tool sharpness and cutting conditions come into play. As long as I have rough figures to work from I can then adjust accordingly.

    Please forgive my in-experience with this!

    Thanks,
    Jim

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    Google is your friend, friend. You may also try to find a slightly older textbook. A lot of times, these things scale, until you get into particularly small (less than 1/8", say) end mills...

    Off the top of my head, perhaps a decent guesstimate would be .001" per tooth for every 1/4" of diameter. .001/tooth for a 1/4", .002/tooth for a 1/2", etc.. .0005/tooth for an 1/8". Less than that, and you basically get into .0002" to .0001"/tooth territory. For 1/8" and above, say +/- 30% chipload.

    Typically you'll see 80 to 100 SFM on an HSS tool in plain carbon steel. Quite higher if it's leaded steel. Less if medium or higher carbon. Slightly higher SFM if an HSS-cobalt tool.

    You'd want to lower your RPM and increase your chipload for heavier cuts, and the opposite for finishing. A lot of times you can use the same feedrate in IPM, and simply increase RPM somewhat for light finish cuts.

    My take on it? If you're doing heavy cutting - slots at 1/4 the depth of the end mill diameter at a time, or side milling say 1xD deep and 10% wide, start in the middle for FPT and low end for RPM. Increase from there. Lighter cutting? Start at the high end for RPM and middle for FPT.

    These are just values that I've found that work, so - your results may vary.

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    Machinery's Handbook comes to mind.. You do have at least one.. Don'cha?? If you don't, just pick a cheapy up
    on e-bay, anything over 14th edition or so is fine, they never change the actual info in them, just the order and
    the color of the cover.

    There are quite a few feed/speed calcs made and sold by members of this here board..

    There is a sort of a lot involved in dialing it all in based on WOC, DOC, and all the other stuff you mentioned.. A lot
    of it comes with experience, and I don't mean "you'll know it when you see it".. I mean that you will know what #'s to use
    for what conditions, what fudge factors to use based on what you are seeing and the conditions you have to deal with..

    For a HSS endmill... Feeds and speeds wise, I would start by throwing the damn things in the trash and buying a handful
    of variflute/helix carbide endmills..

    If I was desperate, if I can remember that far back.. 80sfm on the LOW end. 130sfm on the high end... Figure .002 per flute
    on a half inch. .003 to .0035 on a 3/4.. That is where I would start.. Not knowing anything about what you are doing or
    what machine you are doing it on. Jump those feeds up 50-100% if running corncobs.

    Manufacturer of the endmill doesn't matter so much.. Just start googling...

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    Go download a trial of G-Wizard Feeds and Speeds Calculator. It's an excellent tool that I use all the time. http://www.cnccookbook.com/GWizard/G...nstall1SC.html

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    Quote Originally Posted by jim_cliff11 View Post
    Hi,

    Does anyone have a formula for calculating, or a chart for referencing Chip Load / Feed per Tooth when cutting mild steel? Ideally for a range of end mill HSS cutter diameters.

    I am trying to calculate my estimated feed rate (IPM) using RPM x Chip load x # of flutes. But I have no chip loading charts or formula to work from, and I have no idea who manufactured my collection of HSS end mills (so cannot go to them).

    Another question, how do I incorporate different cutting depths into the feed rate formula? Obviously, with increased depth I have to reduce feed rate?

    I except these formulas produce only rough guide values, and many other factors such as HP, rigidity, tool sharpness and cutting conditions come into play. As long as I have rough figures to work from I can then adjust accordingly.

    Please forgive my in-experience with this!

    Thanks,
    Jim
    HSM Advisor.
    Best there is.
    Advanced CNC Speed And Feed Machinist Calculator - HSMAdvisor

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    Quote Originally Posted by jim_cliff11 View Post
    Hi,

    Does anyone have a formula for calculating, or a chart for referencing Chip Load / Feed per Tooth when cutting mild steel? Ideally for a range of end mill HSS cutter diameters.

    I am trying to calculate my estimated feed rate (IPM) using RPM x Chip load x # of flutes. But I have no chip loading charts or formula to work from, and I have no idea who manufactured my collection of HSS end mills (so cannot go to them).

    Another question, how do I incorporate different cutting depths into the feed rate formula? Obviously, with increased depth I have to reduce feed rate?

    I except these formulas produce only rough guide values, and many other factors such as HP, rigidity, tool sharpness and cutting conditions come into play. As long as I have rough figures to work from I can then adjust accordingly.

    Please forgive my in-experience with this!

    Thanks,
    Jim
    .
    there are many many end mill manufacturers that list recommendations on their web sites or in their catalogs. most end mills are similar and behave the same. math formulas are also usually found on the web sites and or catalogs all free with only a little effort looking

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    Quote Originally Posted by Mtndew View Post
    I agree with this. CNC cookbook is good too.

    Also depending on the tool manufacturer some of them have some tailored speeds/feeds.

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    Sandvik has a good chart you could print with formulas. Formulas

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    Good lord what would you guys do without the internet? And Bob promoting that book tsk, tsk.

    The answer is feed per minute\RPM\Flutes=cl, and the opposite-chip load per flute*RPM=feed per minute.

    R

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    Quote Originally Posted by litlerob1 View Post
    Good lord what would you guys do without the internet?
    In short litlerob1...I'd be screwed.

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    Quote Originally Posted by litlerob1 View Post
    Good lord what would you guys do without the internet?

    I wondered how my parents avoided boredom before there was an internet. I asked my 19 brothers and sisters, and they don't know, either.

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    Quote Originally Posted by litlerob1 View Post
    Good lord what would you guys do without the internet? And Bob promoting that book tsk, tsk.

    The answer is feed per minute\RPM\Flutes=cl, and the opposite-chip load per flute*RPM=feed per minute.

    R
    Double edged sword. Of course on the plus side, I would not be here *wasting time, but then again, I could not come here (PM and the net in general) and find information that I otherwise don't have (or even know I need!).

    *I'm sure the boss sees it as a time sink, but I have found lots of good stuff here, not to mention I can Google part numbers and workholding, watch videos on the latest greatest machine tools and so on...

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    as already stated, FSWiz (HSMAdvisor online).

    Nobody should be using a computer AND machine tools without knowing this exists and applying it regularly.

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    i keep copy from catalogs on different tools like endmills for reference but in general most programmers keep a list of standardized setup tools that is tool in tool holder combination with tight tolerances on length, dia, stickout, etc and after testing different feed and speed settings they record what works best and usually just look up tool number and feed and speed and other recommended cutting parameters are listed.
    .
    after you record sudden tool failures and amounts you get a range of setting that work as often "recommended settings" usually do not work that well. it can start with pencil and paper recording things but i use a excel spreadsheet as it can autocalculate thousands of math formulas in a second
    .
    excel can calculate where rework cause of a sudden tool failure caused 20 minutes more time per 50 parts in 6 months in a millisecond and prove where often going slower is faster. that is total time to manufacture a part including rework or remaking part.
    .
    excel is a very powerful math tool and libreoffice has a free version that does 99% of same thing. i even have used a excel type program from google that is free and can be downloaded to cell phone and used offline.
    .
    many things out there that cost nothing but some little effort in looking
    Attached Thumbnails Attached Thumbnails toolrack.jpg   longmill.jpg  

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    Thanks for the replies guys, and sorry for the massively delayed reply!

    I'm still trying to get my head around this. I'm going to give CNC cook book a try but I would like to understand the theory behind it.

    The main cause of my headache is how can chip load be calculated without taking axial and radial cut depths into account? Surely without these factors it's impossible to calculate it accurately?

    I've found an old text book from MSC (see attached). It shows chip load, rpm and feed rate for multiple cutter diameters using the following factors : cut depth = 1/2 diameter. Cut width = diameter.

    From this, Would I be right in thinking for example......

    A 10mm diameter slot drill @ 5mm depth @ 10mm width = 0.048mm / tooth (chip load) on mild steel. So to calculat e the chip load for a 1mm depth and 10mm cut I would divide 0.048 by 5 = 0.0096 chip load. I can then go and calculate my feed rate for the 1mm cut?chart.jpg

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    The main cause of my headache is how can chip load be calculated without taking axial and radial cut depths into account? Surely without these factors it's impossible to calculate it accurately?
    Usually speeds and feeds are given for shouldering medium roughing cuts.
    How medium and what WOC DOC to use? Well there are various rules of thumb that would guide to starting numbers.

    The problem begins when you realize that there is not only different speed and feed for every Tool_Type/Tool and Work Material combination, but also a different WOC and DOC combination.

    Eventually the number of parameters is becoming overwhelming and experienced machinists, instead of trying to calculate speeds, feeds and DOC/WOC resort to "number that work".

    Simply put. It is easier to remember that, for example, "a 4 flute coated carbide can slot D2 at 2500RPM and 25ipm feed at .25" DOC" rather than try to calculate the same number every time. It is called "experience".

    For simple formulas check here: HSM Machining > General Speeds and Feeds Formulas

    I developed my own calculator (mentioned here HSMAdvisor) that calculates not only Speed and Feed for various combinations of Tool and Work material, but also suggests DOC and WOC.
    It will warn you if Depth of cut you are planning to take is too much for your machine or the tool.
    Unlike any other tool it considers tool anf flute length, that play major role in determining how much of a bite your tool can handle.

    Then there is also the free online FSWizard that i made and introduced on this very forum(OMG it was 5 years ago!). It is pretty popular among hobbyists and beginners: FSWizard - Advanced Online CNC Speed and Feed Calculator
    Though I no longer update it, I keep it there for anyone who might find it useful. Because i know how hard it may be to try to figure this stuff out on your own.

    Good luck!

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    Pull out your smart phone.
    Do an app search under CNC machinist applications.
    Do this in the evening, its like porn, tons of this stuff to look at and play with.

    I use a lot of Iscar tooling so I use theirs IbaQus

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    I would just buy Eldar/zero divide program i have it on 2 computers and my iphone i have enough to figure out his program makes it easy to figure speeds and feeds!!! Also if you need any help he is their for support [i needed his help one time]

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    hy jim i am not the voice of experience ...

    Hi,Does anyone have a formula for calculating, or a chart for referencing Chip Load / Feed per Tooth when cutting mild steel?
    cutting specs references are wide, they may vary between a lower and upper = 6 * lower

    same cutting spec, on same tool, differ from one cnc / machine to another, relative to machine / spindle rigidity

    stay near the machine, hear it, feel it, and inspect tool and part each time a machinist does not need charts : it hears the machine and also it analyses chips

    learning on HSS tools may be harder, because they reach wear fast, thus your learning may be influenced by accelerated wear, and this may spoil your data / try to ask for local help or to somewhere where a stable setup runs for days ... you must be 1st an operator and train your ears

    get some parts and start playing


    I am trying to calculate my estimated feed rate (IPM) using RPM x Chip load x # of flutes.
    there is not only cutting spec, so if you wish for a good / relevant sugestion, than :
    ... upload drawing
    ... fixture
    ... tool
    ... toolholder
    ... machine

    i never use chip load into calculations ; also, try to hit less then 5% with tools cost

    I have no idea who manufactured my collection of HSS end mills (so cannot go to them).
    you don't need to know the producer; imagine that you would be on a lonely planet with your machine and your tools

    leart your tools, and in time you will use them wise ... i respect tools

    how do I incorporate different cutting depths into the feed rate formula? Obviously, with increased depth I have to reduce feed rate?
    generally yes, 4 deeper you must go safer ; another issue for holes is cilindricity, and from this point of view, a 7D hole may be harder to achieve than a 10D

    these formulas produce only rough guide values
    again, recomended cutting specs are in a wide range : right ones depend on setup : machine, fixture, hoder

    how can chip load be calculated without taking axial and radial cut depths into account?
    why do you care about chip load ? just let the tool spin ...

    Surely without these factors it's impossible to calculate it accurately?
    of course, you need axial and radial depth for an accurate calculation, but still, why do you need it ?

    you should learn to hear the machine ; only case where i would the math, would be for constructions, chasis, not machining ... in other words just clamp the tool and be sure that nothing flies out of the machine

    cut depth = 1/2 diameter. Cut width = diameter
    area = d/2 * d; chip volume is = area * feed ; but do you need this ?

    some tools work more on frontal, other on lateral, thus d/2*d may or may not be hit

    even if you hit such a cutting spec, do you think you need the math ?

    A 10mm diameter slot drill @ 5mm depth @ 10mm width = 0.048mm / tooth (chip load) on mild steel. So to calculat e the chip load for a 1mm depth and 10mm cut I would divide 0.048 by 5 = 0.0096 chip load. I can then go and calculate my feed rate for the 1mm cut?
    finally, a real example ... i will do my thing on it i would take a mill o10, z4, and if on lathe i would go 1200..1500x0.08 ..0.10, depth 15, side 0.7 ... broach for live tools is not so rigid

    on a mill, i would clamp it in a hydra holder, deep for 10..12, width=10, rpm 2500..3000, and feed : i will start with 0.10


    ps : in my opininon, you focus 2 much on chip load, and i don;t think is not necessary; is good to know, but is not critical ... you ust try to learn 2 hear, and not to be the slave of charts .... use charts as a start point, and after try to adjust how you think ... break some tools, learn

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    chip thinning math formulas taking into account radial width of cut i have in excel and like i said it easily can recalculate in a millisecond thousands of formulas. obviously a row of calculation with dozens of formulas can be copied and pasted in a second to record a different feed and speed or tool or what ever you want
    .
    excel is free or free version like from libreoffice are available and entering math formulas is basic excel and most can do it after less than 2 minutes with excel help.
    .
    like i said standardized tools in standard tool holders and you can easily record feeds and speeds that work and sudden tool failures indicate extreme settings not working that good recorded in excel. and obviously extremely basic you can note different materials being machined only takes a second.
    .
    most programmers just put a ****cast iron**** in the tool description cell to note it is average setting to best try to use first. chip thinning obviously is easy to have excel auto calculate after you enter width of cut. but longer tools do not tolerate extreme side load forces with severe vibration. obviously any and all settings tried you can make a note on what works poorly, fair, good, best.
    .
    of course some machinist do not write stuff down or make operator notes and they are always retrying things. obviously in a program hardcopy printout i will make notes like increased feed F20. to F30. and sudden tool failure occurred on 10/1/2016, 10/3/2016 so reduced back to F25. on 10/3/2016 which worked ok 27 times
    .
    obviously if you record what did not work that good you are most likely not to repeat that mistake. machinist who record nothing often make same mistakes again and again and again and they often will say waste of time to write stuff down. quite often you have to adjust feeds and speeds for particular parts as one part shape can vibrate severely where another can easily take the feeds and speeds. nobody can accurately predict how a particular tool and tool holder AND part shape will react in combination. you often have to try different settings and record what works best
    .
    excel i show does a lot including cells going automatically yellow (near limits) and red (exceeding limits) if they exceed normal parameters if i change a feed and hit enter it all auto calculates in blink of a eye. particular one shown has tens of thousands of formals from over 1000 tool and feed and speeds and will auto calculate many things including horsepower, cutting forces, chip thinning, etc. it all starts with enter one math formula into excel. like i said you can copy and paste a row with many many formulas in a second. you can make it as simple or as complicated as you want that is do one calculation or do tens of thousands of calculations
    .
    only limit i have seen if after over 2000 different tool settings rows and tens of thousands of formulas you might hit a memory limit. i had excel file with dozens of similar worksheets as big and had to move them to 2 separate excel files. my guess is over a million cells you reach some sort of memory limit. about 10 megabyte file is limit i have come across
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