Choosing parts for a diy milling head


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    Default Choosing parts for a diy milling head

    I want to have a go at assembling my own (small) milling head from off-the-shelf parts. I am going to use this project mainly as a learning experience to get familiar with the process before attempting to build something with more expensive components. I will fill in some of the gaps as I go but I wanted to make sure I am buying the right parts. I know that some of you guys have done this before so I was hoping you could set me straight if I am missing something.




    I plan to start with a cheap R8 spindle cartridge like this (as it's just for education):


    https://littlemachineshop.com/produc...3751&category=


    It is my understanding that when they call it a "cartridge" it means that it includes the spindle shaft, all the bearings and the housing / quill / flange. I.e. Everything except the motor and pulleys. Is this assumption correct?


    The plan is to buy a pair of metal pulleys with a 1:1 ratio and driving the spindle via a rubber timing belt with a brushless DC spindle motor like this one:


    https://www.automationtechnologiesin...or-and-driver/


    I am aware that the spindle is rated for 1000w and 5000rpm while the motor is 1100w and 6000rpm max. My thought was that if I limited the motor to 5000rpm then it wouldn't exceed 1000w. Or, I'm sure I can find a cheap 1000w max motor on ebay.


    To connect the motor / belt and spindle, I would buy or make a casting. Little machine shop sells some inexpensive cast iron ones that could probably be adapted (if they don't fit out the box).


    Would this motor, cartridge and casting make up a complete milling head or am I missing some key components? (Aside from the drawbar and toolholder)?


    For example, how does cooling work on these smaller milling heads? On high speed air cooled spindles, there would be a shaft fan or a separate electric fan but I can't see how cooling works on mini mill spindles. I know that some electric motors have built in fans but my understanding with spindles is that it is the bearings that need to be kept cool. Would I need to buy a separate electric cooling fan?


    I looked through the write-ups for some other diy mill and CNC projects and I couldn't see any other components but I am having those "surely it can't be that easy" thoughts.



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    Community Moderator Jim Dawson's Avatar
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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by Goemon View Post
    .................I plan to start with a cheap R8 spindle cartridge like this (as it's just for education):

    https://littlemachineshop.com/produc...3751&category=

    It is my understanding that when they call it a "cartridge" it means that it includes the spindle shaft, all the bearings and the housing / quill / flange. I.e. Everything except the motor and pulleys. Is this assumption correct?
    The cartridge goes inside of the quill which is not included in the link provided. You get what you see in the picture.

    Jim Dawson
    Sandy, Oregon, USA


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    Quote Originally Posted by Goemon View Post
    I want to have a go at assembling my own (small) milling head from off-the-shelf parts. I am going to use this project mainly as a learning experience to get familiar with the process before attempting to build something with more expensive components. I will fill in some of the gaps as I go but I wanted to make sure I am buying the right parts. I know that some of you guys have done this before so I was hoping you could set me straight if I am missing something.




    I plan to start with a cheap R8 spindle cartridge like this (as it's just for education):


    https://littlemachineshop.com/produc...3751&category=


    It is my understanding that when they call it a "cartridge" it means that it includes the spindle shaft, all the bearings and the housing / quill / flange. I.e. Everything except the motor and pulleys. Is this assumption correct?


    The plan is to buy a pair of metal pulleys with a 1:1 ratio and driving the spindle via a rubber timing belt with a brushless DC spindle motor like this one:


    https://www.automationtechnologiesin...or-and-driver/


    I am aware that the spindle is rated for 1000w and 5000rpm while the motor is 1100w and 6000rpm max. My thought was that if I limited the motor to 5000rpm then it wouldn't exceed 1000w. Or, I'm sure I can find a cheap 1000w max motor on ebay.


    To connect the motor / belt and spindle, I would buy or make a casting. Little machine shop sells some inexpensive cast iron ones that could probably be adapted (if they don't fit out the box).


    Would this motor, cartridge and casting make up a complete milling head or am I missing some key components? (Aside from the drawbar and toolholder)?


    For example, how does cooling work on these smaller milling heads? On high speed air cooled spindles, there would be a shaft fan or a separate electric fan but I can't see how cooling works on mini mill spindles. I know that some electric motors have built in fans but my understanding with spindles is that it is the bearings that need to be kept cool. Would I need to buy a separate electric cooling fan?


    I looked through the write-ups for some other diy mill and CNC projects and I couldn't see any other components but I am having those "surely it can't be that easy" thoughts.

    Have you tried places that sell benchtop machines I can get a replacement spindle for a Craftex mill for $125.00 from Busy Bee here in Calgary Alberta.



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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by tom o View Post
    Have you tried places that sell benchtop machines I can get a replacement spindle for a Craftex mill for $125.00 from Busy Bee here in Calgary Alberta.
    it's not what I asked. My question is about listing the components of a complete milling head so I can teach myself to build one.



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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by Jim Dawson View Post
    The cartridge goes inside of the quill which is not included in the link provided. You get what you see in the picture.
    Thanks. I misunderstood what the quill is used for. I thought it was the part that the spindle was housed in behind the flange to make up a cartridge (together with bearings).... I haven't used R8 spindles before so I obviously need to read up on what the quill does.

    Is the quill the only other piece I am missing?



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    Community Moderator Jim Dawson's Avatar
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    Default Re: Choosing parts for a diy milling head

    The quill is the ''can'' that the cartridge slips inside of. The quill moves up and down inside of the head bore.

    Google R8 Quill and look at the images to understand how it all works.

    To answer your question about cooling, at 5000 RPM it's not needed. The fan in the air cooled spindles is primarily for the motor cooling, those spindles turn 20,000 + RPM.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by Jim Dawson View Post
    The quill is the ''can'' that the cartridge slips inside of. The quill moves up and down inside of the head bore.

    Google R8 Quill and look at the images to understand how it all works.

    To answer your question about cooling, at 5000 RPM it's not needed. The fan in the air cooled spindles is primarily for the motor cooling, those spindles turn 20,000 + RPM.

    That's interesting on the cooling thing. When I bought my high speed CNC spindle, the sales guy convinced me that I needed to spend an extra $1,000 to buy the upgraded electric fan cooled model because I wanted to use it for lower speeds (2000-8000rpm) when milling aluminum with larger end mills. He said that the cheaper shaft fan cooled option only cooled well at higher speeds and was therefore not suitable for extended use at low rpm... Maybe it's different when you use motors with a lower base speed like those found in milling heads.

    Is it possible that another component could be used instead of the quill on a CNC mill or is there another name used for it sometimes? There doesn't seem to be any quills for that R8 cartridge on the LMS site. It looks like that cartridge is meant to attach to this mounting bracket:


    https://littlemachineshop.com/produc...ory=1963256904


    Thank you for taking the time to help me.





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    Default Re: Choosing parts for a diy milling head

    In a typical large milling machine, the head doesn't move up and down, like the head of a router. Instead, the quill does that, and the spindle cartridge rides inside it. It's often driven with a splined shaft to accommodate that motion. You could mount the cartridge router-style in a bracket like that one instead, but the other components, like the pulleys and motors, would either have to move up and down along with it or be driven with a spline or something.

    I'm not sure that simply providing an electric fan on a high-speed spindle will make it perform well at low speeds, although it may prevent it from burning up. Usually spindles like that have very little torque at speeds less than half the maximum. It's better to use pulley and/or gear reduction to run at low speeds, since they multiply the torque as they divide the RPMs.

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    Default Re: Choosing parts for a diy milling head

    Large machines move the table up and down. One reason the big machines have a quill is because you can tilt the head every which way where raising the table doesn't get you the feed direction needed at an angle. Also handy for manual operations.

    Choosing parts for a diy milling head-topwell_tw-head-bp-gif

    The little machines, you have a course travel/fine travel which moves the whole head (table is fixed in Z).

    Choosing parts for a diy milling head-8_head-right-view-jpg

    If you're cncing it, no need for anything other than the leadscrew, certainly not for the added complexity. Well, maybe if you wanted a manual feed,but then you'd still be moving the head with the screw for the rough adjustment.


    Checkout this thread, maybe of interest
    http://www.cnczone.com/forums/open-s...y-granite.html



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    Default Re: Choosing parts for a diy milling head

    On smaller mills, the spindle usually mounts in a casting, like this:
    https://littlemachineshop.com/produc...ory=1963256904

    But you really need to find a parts diagram to see exactly whats required.

    And these spindles don't use any methods for cooling the spindle. Router spindles have cooling fans to cool the motor. With these milling spindles, the motor is separate, so no cooling is required.

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    Default Re: Choosing parts for a diy milling head

    I just clicked the link to the $600 motor/controller.

    Treadmill motor on a minimill
    7x treadmill motor and speed controller conversion





    I routinely see treadmills for $30 at thriftstores and on 1/2 off days, don't get in front of me....



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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by awerby View Post
    In a typical large milling machine, the head doesn't move up and down, like the head of a router. Instead, the quill does that, and the spindle cartridge rides inside it. It's often driven with a splined shaft to accommodate that motion. You could mount the cartridge router-style in a bracket like that one instead, but the other components, like the pulleys and motors, would either have to move up and down along with it or be driven with a spline or something.

    I'm not sure that simply providing an electric fan on a high-speed spindle will make it perform well at low speeds, although it may prevent it from burning up. Usually spindles like that have very little torque at speeds less than half the maximum. It's better to use pulley and/or gear reduction to run at low speeds, since they multiply the torque as they divide the RPMs.
    Their point about the shaft fan spindles is that the fan blades don't turn fast enough to generate sufficient cooling for continuous use which is why they are only rated for 10,000 - 24,000 rpm and I wanted to work from 4000 - 16,000 rpm for aluminum. Their electric fan models can offer max cooling regardless of speed. The model I got is rated for 2,000 to 24,000 rpm.

    The vast majority of high speed CNC spindles are constant torque from 0 up to their base speed. It's just that they have very high base speeds so they have less torque than low speed milling heads. They have less torque at their top speed than their lowest speed though.


    My spindle is around 3nm from 0 to 18,000rpm. It's not much but not that much less than what you find on smaller benchtop CNC mills. High speed precision milling doesn't seem to need much torque. Those Datron machines happily cut through steel at 50,000rpm with 1.5nm or less.


    It would be awesome if someone offered an affordable (for home use) belt drive or even direct drive milling spindle capable of handling both high speed and high torque but I haven't seen anything like that until you get to the Haas price point. Their 20-40hp 24,000 and 30,000 rpm heads can literally handle anything. I doubt I could run one on my 230v 50amp 1ph outlet though.


    I wondered why they didn't use gears and pulleys on industrial high speed routers (like they did on the old pin routers) for a while. It seemed like a good way of achieving both high speed and high torque at low speeds while using less power. Then I saw the size and weight of your average 7.5hp 3000rpm spindle motor and I had my answer.


    Based on what you said, I wonder if that means that smaller R8 CNC mills don't use a quill because they have smaller milling heads that do travel up and down the Z axis. The Tormach machines and the "high torque bench mills" sold by LMS have moving spindle heads anyway.



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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by rocketflier View Post
    I just clicked the link to the $600 motor/controller.

    Treadmill motor on a minimill
    7x treadmill motor and speed controller conversion





    I routinely see treadmills for $30 at thriftstores and on 1/2 off days, don't get in front of me....

    This is the primary motivation for teaching myself how to assemble my own machines. CNC vendors hate us all and they've created a truly awful shopping experience.


    It doesn't matter what it is, the price goes up 10x when it's sold as a milling or CNC part. Regular stepper motor $30. Same motor for CNC $300. Add the word "precision" and it's $3,000 with no design improvements required.


    I am currently making a killing and have a long waiting list for my $20,000 precision CNC T-shirts and my $15,000 dynamically balanced ceramic CNC pens.


    It seems like there is a far wider choice for high end components at bargain prices for people who are able to do some basic assembly. It also allows you to get around some of the issues of unrealistic power requirements (for home shops) with industrial equipment as you can choose whatever spindle motor you want.


    I also I like things that are modular and upgradable so I can invest at my own pace.


    Anyway... I plan to practice with cheap components while I acquire the knowledge but eventually.... I want to build a high end set-up I can work on over time. I enjoy projects like this more than I enjoy using them when they are done.



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    Default Re: Choosing parts for a diy milling head

    Building a spindle that uses a quill is the wrong place to start learning how to do one in the 21st century.
    Quills are pretty old designs in general. Multi-purpose uses as well and generally fair much better under manual control. I have a hard time putting the word precision and quill in the same sentence. They generally work great for axial loads much like a drill press. Not as good at radial loads needed for machining.
    I had a mill that was quill type sitting here for about 10 years taking up space because of these limitations.
    It was new when I bought it and I sold it for 1/4 price of new, but half of what I paid for it.
    Don't get me wrong, for the right uses, they can be a work horse.
    I just find that our smaller drill presses are far easier to use.

    If you are looking to further your skills, why not work on a true cartridge type? Though I do see your point about not being able to put one together from off the shelf parts, you can certainly buy them in parts and assemble and or upgrade bearings etc.

    Lee


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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by LeeWay View Post
    Building a spindle that uses a quill is the wrong place to start learning how to do one in the 21st century.
    Quills are pretty old designs in general. Multi-purpose uses as well and generally fair much better under manual control. I have a hard time putting the word precision and quill in the same sentence. They generally work great for axial loads much like a drill press. Not as good at radial loads needed for machining.
    I had a mill that was quill type sitting here for about 10 years taking up space because of these limitations.
    It was new when I bought it and I sold it for 1/4 price of new, but half of what I paid for it.
    Don't get me wrong, for the right uses, they can be a work horse.
    I just find that our smaller drill presses are far easier to use.

    If you are looking to further your skills, why not work on a true cartridge type? Though I do see your point about not being able to put one together from off the shelf parts, you can certainly buy them in parts and assemble and or upgrade bearings etc.



    It looks like the cheap R8 cartridge I am looking to start with doesn't use a quill as it goes directly into a casting / bracket which connects to a Z-axis on the CNC machine it was built for so it shouldn't be an issue.

    What do you mean by a "proper" cartridge? That R8 cartridge looks to be the same (or similar) design to the Tormach cartridges.


    If proper means a high quality one, that is the eventual goal. I just want to practice with cheap throw-away components so I'll know what I am doing when I invest in the 12,000 rpm 40 taper direct drive Hass spindle cartridge I have been eying up.


    I don't expect this cheap R8 cartridge to do any precision milling or any commercial work or anything like that. It's more like buying one of those old RadioShack electronics kits to teach yourself how to wire a motor before investing in a 200hp electric motor to build an electric car.


    It is important that I start with the same type of components I would be buying when i'm ready to invest in the good stuff. Buying a complete head, taking it apart and reassembling it doesn't teach me anything.



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    Default Re: Choosing parts for a diy milling head

    [QUOTE=Jim Dawson;2121094]The cartridge goes inside of the quill which is not included in the link provided. You get what you see in the picture.[/


    As an update / FYI for others on this spindle cartridge: this cartridge does not come with a sleeve and LMS does not sell the casting or sleeve for the KX3 (3503) CNC mills. Unlike other cartridges, this one can not be used without the sleeve because it has exposed bearings (which are meant to fit into the sleeve). You can't see the bearings on "complete" cartridges.

    In other words, that $250 for an R8 spindle cartridge is not such a good deal for a diy milling head (unless you are capable of milling your own sleeve). I couldn't find this part available anywhere else either.


    LMS does sell the spindle and sleeve with casting for the KX1 CNC mill but it is a 2MT one that is only rated for a 500watt motor....


    Now I am thinking that the Tormach spindle cartridges might be a better choice as they come ready to mount. You just need to buy the pulley and drawbar (which are cheap and available to buy). Their BT30 and R8 cartridges for the 1100 look to be good deals compared to any other option.


    There are Chinese BT30 spindle cartridges available for less on eBay but by the time you pay for shipping from China, they end up the same price.


    The R8 cartridge for the 770 is a little more expensive but it comes with the pulley and it is rated for 10,000 rpm. I haven't seen any 10,000rpm spindle cartridges available for anything close to the same price anywhere else, not even used ones.


    Any deals on used cartridges on eBay are usually for 40 taper spindles and my assumption is that these are too big for your average small homemade mill....


    A Tormach BT30 cartridge plus a used 1.5hp spindle motor with a diy cast iron mount sounds like a nice affordable and achievable diy milling head project.



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    Default Re: Choosing parts for a diy milling head

    The size really depends on the design of the mill.
    Have you considered designing a horizontal mill?

    If I had the time, I would consider building something like that especially if I had a really large or heavy spindle.
    That way it becomes stationary and the machine moves around it.

    Lee


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    Default Re: Choosing parts for a diy milling head

    [QUOTE=Goemon;2135630]
    Quote Originally Posted by Jim Dawson View Post
    The cartridge goes inside of the quill which is not included in the link provided. You get what you see in the picture.[/


    As an update / FYI for others on this spindle cartridge: this cartridge does not come with a sleeve and LMS does not sell the casting or sleeve for the KX3 (3503) CNC mills. Unlike other cartridges, this one can not be used without the sleeve because it has exposed bearings (which are meant to fit into the sleeve). You can't see the bearings on "complete" cartridges.

    In other words, that $250 for an R8 spindle cartridge is not such a good deal for a diy milling head (unless you are capable of milling your own sleeve). I couldn't find this part available anywhere else either.


    LMS does sell the spindle and sleeve with casting for the KX1 CNC mill but it is a 2MT one that is only rated for a 500watt motor....


    Now I am thinking that the Tormach spindle cartridges might be a better choice as they come ready to mount. You just need to buy the pulley and drawbar (which are cheap and available to buy). Their BT30 and R8 cartridges for the 1100 look to be good deals compared to any other option.


    There are Chinese BT30 spindle cartridges available for less on eBay but by the time you pay for shipping from China, they end up the same price.


    The R8 cartridge for the 770 is a little more expensive but it comes with the pulley and it is rated for 10,000 rpm. I haven't seen any 10,000rpm spindle cartridges available for anything close to the same price anywhere else, not even used ones.


    Any deals on used cartridges on eBay are usually for 40 taper spindles and my assumption is that these are too big for your average small homemade mill....


    A Tormach BT30 cartridge plus a used 1.5hp spindle motor with a diy cast iron mount sounds like a nice affordable and achievable diy milling head project.
    Contact JT at Shopmaster- they carry a lot of spare parts for their older machines which used both R-8 and Morse#3 taper spindles. The come as a complete cartridge or as parts.



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    Default Re: Choosing parts for a diy milling head

    Quote Originally Posted by LeeWay View Post
    The size really depends on the design of the mill.
    Have you considered designing a horizontal mill?

    If I had the time, I would consider building something like that especially if I had a really large or heavy spindle.
    That way it becomes stationary and the machine moves around it.
    I understand that part. Those large higher torque / lower speed milling motors need a stronger frame to keep it stable and safe. Plus, they weigh a lot and, on my machine, they would be the second spindle.

    I have no worries about the size of motor I want for the machine it will go on because I won't go any larger than 2hp. I am less sure about the size of spindle / taper because it's so hard to judge from the pics. There have been a few occasions where I nearly bought a spindle that looked small enough to hold in my hand, only to find it was bigger than me....

    Even though deals on used 40 taper cartridges are more plentiful, I think a 30 taper or R8 is the way to go for benchtop build. I like the price and size of the Tormach cartridges.

    I don't really think it matters which way the spindle is mounted for me on a CNC machine. As I want a second (lower speed) spindle for my fixed gantry machines, it will be a vertical mount this time.



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    Default Re: Choosing parts for a diy milling head

    [QUOTE=BIGBLOCK1965;2135682][QUOTE=Goemon;2135630]

    Contact JT at Shopmaster- they carry a lot of spare parts for their older machines which used both R-8 and Morse#3 taper spindles. The come as a complete cartridge or as parts.[/QUOTE


    Thanks for the tip. I have been looking for more sources for parts.

    It's frustrating when you know what you want to buy but nobody sells it. Stores like LMS just aren't set-up to support the diy market.


    I feel like it should be easier for people to choose their own cartridge, motor and casting without having to buy a whole new milling machine every time their needs change.


    It seems like some of the Chinese vendors are starting to offer that level of flexibility but I don't have the patience or trust to deal with them. So far, Tormach is the only American vendors that stocks and sells affordable complete spindle cartridges. If there are others, I would love to know about them. I'll check out the place you recommended.





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