Drilling 316 Stainless Steel Speeds And Feeds
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    Default Drilling 316 Stainless Steel Speeds And Feeds

    I have read the many threads here on the fact that 316 Stainless is special to work with and I have a special situation that needs some old school help.

    I'm trying to drill into 4mm of 316 Bohler stainless steel plate with a Gurhing Step 1.2mm (.0472inch) drill bits. I am using a multiple drill system or gang drill to make multiple holes at the same time.

    I'm breaking bits because I know my feed and speed are not right and I admit that I am new at doing this. PLUS

    The machine is limited to 2500 rpm or slower
    It's feed is controlled by a dial that looks like a dimmer switch so has to be done by watching it go down and timing it.

    Any old school suggestions would be great.

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    Quote Originally Posted by Oldandcrazy View Post
    I have read the many threads here on the fact that 316 Stainless is special to work with and I have a special situation that needs some old school help.

    I'm trying to drill into 4mm of 316 Bohler stainless steel plate with a Gurhing Step 1.2mm (.0472inch) drill bits. I am using a multiple drill system or gang drill to make multiple holes at the same time.

    I'm breaking bits because I know my feed and speed are not right and I admit that I am new at doing this. PLUS

    The machine is limited to 2500 rpm or slower
    It's feed is controlled by a dial that looks like a dimmer switch so has to be done by watching it go down and timing it.

    Any old school suggestions would be great.
    is it a cobalt drill ?
    are you using coolant or cutting fluid ?
    are you pecking ?
    when drill is dull are you stopping to replace with sharp one or are you continuing to use til it breaks ?
    most do not use max recommended rpm. max rpm recommendations are from salesman to sell you more drill bits

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    is it a cobalt drill ?

    High Speed Steel with Tin coating

    are you using coolant or cutting fluid ?

    I am using 11% HOCUT coolant

    are you pecking ?

    I cannot peck

    when drill is dull are you stopping to replace with sharp one or are you continuing to use til it breaks ?

    I continue until the drill bit breaks. I have no choice I have to watch up to 88 of them at the same time.

    most do not use max recommended rpm. max rpm recommendations are from salesman to sell you more drill bits

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    cobalt drill usually last longer the hss drilling stainless
    .
    if no peck you can program same hole at 2 different depths. that is 1/2 way drill pulls up cause it was programmed to only go that far of 1st drill op. 2nd drill op at same location but deeper depth will finish hole.
    .
    drill gets hot deeper it goes and more chips in flutes. by stopping it gives it a chance to cool off.
    .
    usually tool life is based on reasonable expectations. if drill dont last 10 minutes 99.9% of the time than you replace every 10 minutes. any machine if drill makes noise you can feed hold and stop machine and pull out of hole. small drill hard to hear. often you just go by reasonable tool life. if that means you change drill after a few holes than thats what you got to do.
    .
    stainless often is cold worked or cold rolled and about 200% harder to drill. many will get it stress relieved or annealed so its easier to machine and it warps less. sure it cost more but so does replacing broken tooling and taking extra time.

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    You're in a multi-spindle head drill press?

    I guess I'd say to move up to cobalt drills

    Set rpm well on the slow side so that you don't burn up 88 tools at once

    I'm guessing that getting fresh coolant to those tips in the middle aint easy either?
    Another reason to run slow.


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    You're in a multi-spindle head drill press?

    Yes

    I guess I'd say to move up to cobalt drills


    they want me to use the HSS bits for now as the only ones to use.

    Set rpm well on the slow side

    How slow are we talking?? I need to go though Stainless at 162 Brinell hardness

    so that you don't burn up 88 tools at once

    I'm guessing that getting fresh coolant to those tips in the middle aint easy either?
    Another reason to run slow.

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    What brand of "CNC Machinery" do you have ?

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    Ballparking 35 SFM, 1/2D pecks 1/64 drill diameter FPR

    That's 3000 rpm and 2.2 IPM so back it off as a percentage for what you have available. Split point cobalt drills.
    You should be able to drill 4xD deep without pecking.

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    For HSS - I'd set for 20SFM at the most - ESPECIALLY with that train wreck!
    1600 rpm

    Feeds are listed at .0007 / rev

    Oil is listed as best rec in that material.


    If you move to cobalt (highly recommended!) you could bump the speeds up a bit.


    I would NOT want to git in a hurry with that train wreck!


    I think that you have the wrong machine and wrong tools for this job, but if it's what you got ....


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    i would try feed of 2 - 3 ipm , and 1000 - 1200 rpm

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    It sounds like you will probably have to time the movement over a set distance to figure out your feed rate in inches per minute. It would probably be worthwhile to measure your feed rate after the machine has been running for some time to see if the feed rate remains constant after the machine has had a chance to warm up.

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    often very small drill bits need to be run at slower than recommended rpm and slower feed cause they are smaller than normal size and break easily
    .
    just saying if some recommendation says 30 sfpm i would run slower than that. and feed rate is often based on drill bit size. that is bigger drill bits can make thicker chips but little drills cannot and ipr feed rate is usually lower with smaller sizes. somewhat crude but
    0.1" dia drill then .001" inch per rev feed
    0.5" dia drill than .005" inch per rev feed
    1.0" dia drill than .010" inch per rev feed if you got the horsepower
    .
    just saying feed rate is usually less with smaller diameter drills. and of course longer length drills cannot handle a high feed rate without bending and breaking. so often a longer length drill needs a lower than normal feed rate to not break.

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    Quote Originally Posted by DMF_TomB View Post
    often very small drill bits need to be run at slower than recommended rpm and slower feed cause they are smaller than normal size and break easily
    .
    just saying if some recommendation says 30 sfpm i would run slower than that. and feed rate is often based on drill bit size. that is bigger drill bits can make thicker chips but little drills cannot and ipr feed rate is usually lower with smaller sizes. somewhat crude but
    0.1" dia drill then .001" inch per rev feed
    0.5" dia drill than .005" inch per rev feed
    1.0" dia drill than .010" inch per rev feed if you got the horsepower
    .
    just saying feed rate is usually less with smaller diameter drills. and of course longer length drills cannot handle a high feed rate without bending and breaking. so often a longer length drill needs a lower than normal feed rate to not break.

    Do you type this out each time, or do you have your responses stored in a spreadsheet?

    Big drill! Copy/Paste "picture of broken screen"
    Little drill! Copy/Paste "Go Conservative!"
    Anything about money! Copy/Paste "$23/hr w/ overtime = $100K/yr + no life!"
    Anything not about money! Copy/Paste "$23/hr w/ overtime = $100K/yr + something about compound interest and 401k"

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    Quote Originally Posted by TeachMePlease View Post
    Do you type this out each time, or do you have your responses stored in a spreadsheet?

    Big drill! Copy/Paste "picture of broken screen"
    Little drill! Copy/Paste "Go Conservative!"
    Anything about money! Copy/Paste "$23/hr w/ overtime = $100K/yr + no life!"
    Anything not about money! Copy/Paste "$23/hr w/ overtime = $100K/yr + something about compound interest and 401k"
    You forgot grain of rice sized hard spots in castings you need to grind out
    and you didn't use the words "sudden tool failure"

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    Please be much more specific.

    Are you breaking one drill bit at a time,
    or all / many drillbits,
    are you trying for better reliability,
    are you doing lots of parallel workpieces,
    or one piece that is very expensive with n x 80+ holes drilled for some reason ?
    Like a very long part maybe ?

    What is your *goal*.
    What is the main *problem*.

    One problem is that 3-10$ drill bits break and one is that multi-1000$ workpieces need expensive rework.
    See ?

    Drilling SS is dead easy.
    When You define the problem better solutions more appropriate can be suggested.

    E.g.
    If the machine has a variable pot, analog control, for speed,
    One option.
    1. replace it with a multi-detent switch and add suitable resistors and trimmer pots on each line.
    You could get a 40-pos switch, for example, and have very repeatable control of speed on each detent.
    The trimmer pots would give a great repeatable tuning ability.
    Cost == 30$ for 30-40 lines aka nothing, plus maybe 3 hours of fiddling.

    Add plugs !
    (Plugs of choice. DB25 would work fine, probably. So would ethernet or maybe better shielded ethernet, both cheap and dense in volume).
    So you could always use the original system, or return to it, in a few minutes.

    --
    Speed, volume, and usually but maybe/probably not here - quality (for machinists), are always the constraints.
    Let us know about the volume desired, and the key constraint(s) as You see it/them.

    Can you check for individual drill TIR ?
    Overall TIR avg. ?

    If the TIR is very bad, that might be likely, (or not,) then custom epoxy-mounted zero-tir drillbits would maybe fix 99% of your problems.

    If the drillbit wobbles in the mount, or the bit is not concentric, etc. then all sorts of cascading exponential errors tend to happen apart from the drillbit itself.

    So a very flexible HSS drill might be more forgiving initially vs a better more rigid drill, and then at random times the accumulated stress leads to bits failing be it hss, cobalt, or the more rigid modern drill options.


    My humble opinion.
    Test first with one drillbit, all other stations empty.
    Use a gage pin of drillbit size.

    Measure the gage root and tip TIR, movement linearity as the pin (simulated drill) advances.
    Compare to drill D, tool total length, drilling depth.

    Then repeat the measurements in 2-3 other stations.
    You will have actual real data .. that is comparable to cutting tool data.

    Supposition:
    If you do have a matrix of worn mounts, grabbing drillbits in worn tooling,
    at worst 3-jaw chucks well-used or very worn,

    imho - it is likely many or a lot of the drills may point wherever, and the axis of advance is sometimes very much not along the theoretical axis of advance.
    And thus replacing a drill in the same chuck will often have the drillbit pointing wherever, just due to wear and chance.

    There are endless cheap ways of making pot chucks with excellent repeatable TIR, alignment, etc. depending.

    Thus YOU need to let us know what You want to try to do in terms of volume, speed, cost, etc.

    It is very different if e.g.
    1. you want to try to do one total run of maybe 100 sets x 80 matrix and drill-bit breakage is an annoyance alone.
    2. you are trying to do 200--xx runs per week for 20 weeks.

    If you have time in hours, or some small cash in widgets, or a need for results aka plenty of cash as long as it works, the better critical paths may be very different.

    --
    Generally, on PM, the willingness to spend 8 work-hours or 1000$ in cash or a minimax of the two is assumed for an issue.

    This is an industrial site on how to do things "really well" in a competitive modern environment, either making widgets or production or "really good" or "really cool".

    So if someone wants to save say 50$ on 600$ cost in drillbits, on a one-off job, many qualified may not bother to reply, because to us(them) the right answer is "spend the money" and we usually do so every day.
    .. the extra cost in money for tooling/stuff is much more profitable than us doing it "better" via an extra 8 work hours at 150$ implied marginal *net* income loss for us.

    We actually like and help new guys.
    But they must "show willing".

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    THIS !

    Also endless ways to get old-school auto-feeds to do advanced tricks.
    Programmable relays, new cheap sub 100$PLCs, endless consumer automation devices for 60$ or less.
    Or any pc / widget + endless interfaces for it.

    Imo, ime, a PC+custom interface is the go to if *you* can make one easily.
    *Nothing* is supported or documented for custom stuff in general, so making a sw bodge loses nothing in "support" or "industrial" etc.
    Ime over 30 years.

    The 50-100-200$ in hw is a total loss anyway, imo, ime.
    So is all the work.
    The solution has functional value, that is all.


    Quote Originally Posted by DMF_TomB View Post
    .
    if no peck you can program same hole at 2 different depths. that is 1/2 way drill pulls up cause it was programmed to only go that far of 1st drill op. 2nd drill op at same location but deeper depth will finish hole.
    .
    .


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