What is the practical low end on 3/8 router bits
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    Default What is the practical low end on 3/8 router bits

    I am designing CNC machine , I want it to cut steel and wood , so I have the classic problem of "fast enough for wood but slow enough for steel" So far what I have will hold up to 10mm 3/8" and top out at 12,000 Rpm at a maximum speed of 105 or 150 inches per minute depending on if I decide to build it for speed or precision , AND still slow down enough to be useful on steel AND be something I can make. I don't mind using 3 or 4 flute routers exclusively if necessary. I will be mostly cutting hard wood plywood . do these numbers sound reasonable ?

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    My pin router is 5.000/10,000 rpms (2 speed)
    I have run 1/4" cutters in plywood at 10,000. Faster rpms would be better. Suppose in my case i could put a VFD on it.

    I routinely run 3/8" & 1/2" 2 fl carbide bits, and its fine. 15K would be nice, but again, not so's you notice much with most set ups.

    For your app, the question is would feed speed be chip limited.

    smt

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    Thank you , that really helps , I think I have found a good compromise speed range.
    As to the feed question if I go with the faster feed limit option "A" 150 Inches per minute I limit my precision to +- .002" or option "B" if I go with the slower 105 inches per minute I limit my precision to .0015". I really have no clue on this one .
    Can I ask for a vote on here ?
    option A 150 Inches per minute And +- .002"
    option B 105 Inches per minute And +- .0015"

    By the way I plan to incorporate a "Feedback" system so I feel I will actually achieve that precision in time.

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    CNC Routers use a low torque high RPM Spindle to cut non ferrous metals (with a cooling mister), wood and plastics. Cutting Steel requires a High torque low RPM spindle with flood coolant. A router spindle dosent have enough torque on low RPM to cut steel.

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    Quote Originally Posted by southerncncguy View Post
    CNC Routers use a low torque high RPM Spindle to cut non ferrous metals (with a cooling mister), wood and plastics. Cutting Steel requires a High torque low RPM spindle with flood coolant. A router spindle dosent have enough torque on low RPM to cut steel.
    That is the whole point of what I am doing , I'm changing the game.

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    Are you changing the game? Or dreaming? Any machine you build will cut any material with any tooling, almost. But for how long before tool failure? Spindle failure? Frame flex making seriously crappy parts?
    You are asking about low end router bits? You cannot change "the game" unless you know what "the game" is.

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    I think you miss understood "low end" refers to the RPM ie. "the low end of the RPM range". The spindle I am making has several speed ranges provided by changing the belts , I don't understand how you have concluded that the hundreds of Kilos of polymer concrete are going flex so much as to result in "seriously crappy parts" without knowing anything about how the base will be constructed.I think you are criticizing something you know nothing about. I am essentially building a small milling machine that can be sped up enough to work as a wood router , this is not easy as I am asking a heavy machine to move fast but I believe it is entirely possible.I came here with a simple question and I got one good answer which I appreciate , but I can do without the trolling .

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    "Low end" almost always refers to low price, not low rpm. 3/8 router bits are run at 18,000 rpm in wood BECAUSE THEY CAN. I run my .750" and even 1.000" bits at 18,000 in wood all the time. But that is a 25,000 pound machine. And often will run wood router bits in my VMC at 6-7,000 rpm or less. Higher rpm of a router allows faster feeds in wood products, but slower rpm and feeds work just as well. And if any machinist on this site could get great tolerances/finish with a .750 endmill running wood rpms and feeds, they would. Their shop would be very loud with a lot of sparks flying.
    I witnessed an 18" carbide tipped saw blade cut 3 steel bars, each about 1" x 2". 4000 rpm at 40 meters a minute. 25 HP motor. It cut the first 2 clean and almost made it through the third one. Lack of teeth forced a feed overload. That was the installation of my wood panel saw. Tech was white as a sheet. Not his fault though. EPROM program error.

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    Quote Originally Posted by Robertsolo View Post
    I think you miss understood "low end" refers to the RPM ie. "the low end of the RPM range". The spindle I am making has several speed ranges provided by changing the belts , I don't understand how you have concluded that the hundreds of Kilos of polymer concrete are going flex so much as to result in "seriously crappy parts" without knowing anything about how the base will be constructed.I think you are criticizing something you know nothing about. I am essentially building a small milling machine that can be sped up enough to work as a wood router , this is not easy as I am asking a heavy machine to move fast but I believe it is entirely possible.I came here with a simple question and I got one good answer which I appreciate , but I can do without the trolling .
    this site is an incredible resource, but it can be a tough neighborhood, especially if you are trying something new, don't do your homework before showing up here, or are unwilling to listen and learn. not saying that's you, but you gotta understand a lot of us here have tried all kinds of stupid shit, and have listened to and put up with others trying to get us to help them do all kinds of stupid shit also. toughen up a little there!

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    Quote Originally Posted by cyanidekid View Post
    this site is an incredible resource, but it can be a tough neighborhood, especially if you are trying something new, don't do your homework before showing up here, or are unwilling to listen and learn. not saying that's you, but you gotta understand a lot of us here have tried all kinds of stupid shit, and have listened to and put up with others trying to get us to help them do all kinds of stupid shit also. toughen up a little there!
    I will do that.

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    Robertsolo, I'm curious about the design of your machine, as I'm thinking of building a router myself. What is the work envelope of your cnc? Moving gantry or table? What will be the low speed of your spindle? Have any drawings?

    In regard to your question about speeds for wood, I have cut a lot of hardwoods on my Bridgeport and the mass and rigidity compensates for the slow spindle speed. Have to move very slow, but the cuts are good, and the precision is great.

    I use my current tiny cnc for pearl inlay work and slotting fretboards for banjos. Max speed is 24K, but for the tiny cutters used (3mm down to .4mm) would be nice to have 50K or 60K. I'm thinking of adding a pneumatic pencil grinder piggy-back onto the spindle mount. Did this on the Bridgeport for cutting .75mm grooves in wood, worked great.

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    Also, about the culture of PM - as cyanidekid mentioned, there are some pretty direct and crusty members here, but it's just a great resource. I'd much rather get good advice, even it it's not what I want to hear, than be part of a club and get stroked and encouraged.

    The woodworking forum is about as tolerant as it gets, and to be honest we get an awful lot of amateur and bonehead posts, but none get locked, and most get good feedback, so long as they don't act like assholes.

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    Quote Originally Posted by Robertsolo View Post
    ...I'm changing the game...
    Sadly, I don't think you are. CNC routers are not "new" technology; they've been around for a long time.
    If it were possible to design a machine capable of accurately and consistently cutting steel day in and day
    out someone would already have done it. Going from wood to steel requires a huge increase in machine
    rigidity; that's why CNC milling machines have as much mass as they do. And even then a decent sized
    machine will have a "relatively" small work envelope. When you say "CNC router" I think of a machine with
    perhaps a 5 ft. x 10 ft. table and cutting steel in a work envelope that size is going to require something
    equivalent to a very large and heavy gantry mill...

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    Quote Originally Posted by richard newman View Post
    Robertsolo, I'm curious about the design of your machine, as I'm thinking of building a router myself. What is the work envelope of your cnc? Moving gantry or table? What will be the low speed of your spindle? Have any drawings?

    In regard to your question about speeds for wood, I have cut a lot of hardwoods on my Bridgeport and the mass and rigidity compensates for the slow spindle speed. Have to move very slow, but the cuts are good, and the precision is great.

    I use my current tiny cnc for pearl inlay work and slotting fretboards for banjos. Max speed is 24K, but for the tiny cutters used (3mm down to .4mm) would be nice to have 50K or 60K. I'm thinking of adding a pneumatic pencil grinder piggy-back onto the spindle mount. Did this on the Bridgeport for cutting .75mm grooves in wood, worked great.
    I only change the design about 3 times a day I am working on a drawing right now , I should have something in a week or two . but basically it looks like a box that bolts to a wall or bulkhead (if you mount it on a ship) the spindle , laser , sealant/adhesive dispenser are horizontal and mounted about in the middle (fore and aft) and move side to side and up and down on BWC "V" rollers by Sanyo Denki 5 phase NEMA23 steppers with 1-7.2 anti backlash gearboxes pulling Gates "carbon" poly chains. The fore and aft axis is the work table a Jergens 15x10 Bridgeport style ball lock sub plate , the 4th axis is a 105mm Nikken rotary table mounted to a 15x10 fixture plate , it can be used or not , the sub plate is moved the same way as the spindle plate. The envelope is 16"x 11"x 6.45". The biggest design problem now is I need the machine to do precision sheet metal bending (I make small solder nozzles) the sections are photo chemically cut out , but bending to less than a degree tolerances is hell by hand and is a huge bottleneck, that function alone will pay for the machine 10 times over. Oh one other cleaver detail the "box" has gloves and can be purged for laser welding under a inert gas. One question you said 50K-60K would be nice , how do you know ? what are the signs ?

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    Quote Originally Posted by Robertsolo View Post
    One question you said 50K-60K would be nice , how do you know ? what are the signs ?
    Cutting at 24K works fine, but I'd like to speed up the process. I should be able to feed twice as fast at 50K and maintain the same chipload. Too high chipload and the bits break.

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    Quote Originally Posted by richard newman View Post
    Cutting at 24K works fine, but I'd like to speed up the process. I should be able to feed twice as fast at 50K and maintain the same chipload. Too high chipload and the bits break.
    Good sign , that one !

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    I guess it is a game changer. High speed wood and metal machining, precision metal bending, laser welding, sealant dispensing, glove hand holes, laser blocking glass?
    How many axis? What kind of control/drives are you using?
    And it bolts to a wall of a ship? And hundreds of kilos of polymer concrete?
    Not funning on you, just the descriptions makes an entertaining good read. I do have plenty of experience casting polymer concrete. But you need to brush up on speeds and feeds, chip load per tooth.

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    I am not anti stepper. A nema 23 stepper is not going to push hundreds of kilos of concrete or Styrofoam at game changing speeds.


    wait, what is the game?

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    Quote Originally Posted by Scruffy887 View Post
    I guess it is a game changer. High speed wood and metal machining, precision metal bending, laser welding, sealant dispensing, glove hand holes, laser blocking glass?
    How many axis? What kind of control/drives are you using?
    And it bolts to a wall of a ship? And hundreds of kilos of polymer concrete?
    Not funning on you, just the descriptions makes an entertaining good read. I do have plenty of experience casting polymer concrete. But you need to brush up on speeds and feeds, chip load per tooth.
    F**k I need to brush up on everything! I just read a 240 page book on spindle bearings.

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    3 or 4 axis's depending what you need for the job , Not "glass" but laser blocking yes (another thing I need to research (unbreakable laser blocking "something") the concrete is not moving and the steppers have gearboxes on them , 105 or 150 IPM and the machine has space to switch to larger steppers (never said "game changing speed") , Sanyo has their own drives , It's 5 phase. The machine is what I need , and is also set up for the "bolt it to a bulkhead of your boat and it won't rust up or get loos and kill some one market" YouTube
    Last edited by Robertsolo; 02-07-2020 at 02:47 AM.


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