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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by mactec54 View Post
    Not out of context, it's a very good example of what happens with these HS Spindles, it's how they are Designed

    The spindle the OP was looking at was one with a ATC
    I apologise Mac for misinterpreting your explanation as I overlooked the point that the spindle in question was ATC and not just an ordinary plain 24,000 water cooled job...….and I advocated using the said ATC spindle as a motor per se to drive a plain spindle, the ATC model, being a complete entity, would not be practical or at all possible.

    I'm astounded that the spindle shaft or bearing can move out of the housing when it ejects the tool......watching the video explains this phenomena totally......surely the spindle has bearings that are opposed to one another and therefore are held in the housing like a normal mill spindle....it must be a design function then.

    But I expect it is the design of this particular type of (cheap?) high speed spindle, with the ATC function, that dictates how it is designed and constructed to give the tool ejection function as it has the motor on top and therefore probably no way to have a conventional power draw bar design......unless the motor had a hollow spindle too.....and a big escalation in price.

    Perhaps by some cunningly devious design the motor part could be made to raise up and down to act as the draw bar in itself without making the bearings in the milling spindle part prone to movement.....2 separate spindle shafts etc......no doubt a more expensive design "could" work like that.

    For those that like to think outside of the box, supposing a conventional mill spindle had a high speed water cooled spindle mounted on top of it and a solenoid thingy....whatever..... between the two to make the motor rise and fall and would be attached to the draw bar so that you have an ATC model on the cheap without the problems of bearing moves...….but for milling steel you wouldn't want to have a high speed motor without the reduction I mentioned, so it would be a none starter for the pure milling of metals.

    What it would be useful for is to act as an ATC motor on a gantry router for highspeed milling and carving without the bearing problems.

    I imagine that a 6040 gantry router fitted with a cheap ATC spindle to that design would be highly sought after......just thinking......if the Chinese are listening ….go for it......cheap CNC gantry type routers will never be the same again.
    Ian.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by handlewanker View Post
    I apologise Mac for misinterpreting your explanation as I overlooked the point that the spindle in question was ATC and not just an ordinary plain 24,000 water cooled job...….and I advocated using the said ATC spindle as a motor per se to drive a plain spindle, the ATC model, being a complete entity, would not be practical or at all possible.

    I'm astounded that the spindle shaft or bearing can move out of the housing when it ejects the tool......watching the video explains this phenomena totally......surely the spindle has bearings that are opposed to one another and therefore are held in the housing like a normal mill spindle....it must be a design function then.

    But I expect it is the design of this particular type of (cheap?) high speed spindle, with the ATC function, that dictates how it is designed and constructed to give the tool ejection function as it has the motor on top and therefore probably no way to have a conventional power draw bar design......unless the motor had a hollow spindle too.....and a big escalation in price.

    Perhaps by some cunningly devious design the motor part could be made to raise up and down to act as the draw bar in itself without making the bearings in the milling spindle part prone to movement.....2 separate spindle shafts etc......no doubt a more expensive design "could" work like that.

    For those that like to think outside of the box, supposing a conventional mill spindle had a high speed water cooled spindle mounted on top of it and a solenoid thingy....whatever..... between the two to make the motor rise and fall and would be attached to the draw bar so that you have an ATC model on the cheap without the problems of bearing moves...….but for milling steel you wouldn't want to have a high speed motor without the reduction I mentioned, so it would be a none starter for the pure milling of metals.

    What it would be useful for is to act as an ATC motor on a gantry router for highspeed milling and carving without the bearing problems.

    I imagine that a 6040 gantry router fitted with a cheap ATC spindle to that design would be highly sought after......just thinking......if the Chinese are listening ….go for it......cheap CNC gantry type routers will never be the same again.
    Ian.
    Your High Speed Spindle is made the same way, is non adjustable, unless you know what you are doing with Bearing Preloading, this is how these spindles have to be made No the Bearings are not apposed the Front Bearings by Design for High Speed are mounted this way with cups facing out, now the rear Bearings at the top of the spindle are the opposite way giving you a Back to Back Bearing arrangement, the difference here is that they are spring loaded to keep a constant preload on the front Bearings, this is the only way to get a high speed spindle like this to last

    The spring loading at the top Bearings can be adjusted down to a small number, only on these ATC spindles, the Video is showing the extreme with a spindle that needs adjusting which is easy to do by removing the top cap and adjust the preload

    If the tool changer was designed and working correctly it would not be putting any load on the spindle to push it forward like this also


    This is why I posted this to show that these HS spindles are not suitable for milling steel with Endmills, there are some of these Spindles that have different Bearing arrangements that can be used for steel, normally don't go up to 24,000 RPM and Bearing life is low

    Mactec54


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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    I am suitably impressed and enlightened....ta.

    I have to wonder just how much pressure is exerted by the drawbar....or whatever....in one of these self contained ATC spindles to hold the ISO 30 tooling in.....would it be a pneumatic type?.....it would be interesting to see a cut away sectional drawing of the insides of the spindle.
    Ian.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by handlewanker View Post
    I am suitably impressed and enlightened....ta.

    I have to wonder just how much pressure is exerted by the drawbar....or whatever....in one of these self contained ATC spindles to hold the ISO 30 tooling in.....would it be a pneumatic type?.....it would be interesting to see a cut away sectional drawing of the insides of the spindle.
    Ian.
    The actuator is pneumatic, and Belleville Washers as any other CNC draw tube uses

    Attached Thumbnails Attached Thumbnails Why most (non-router) milling machines don't use self-contained spindle?-spindle-design-png  
    Mactec54


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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Thanks.….I can see why you wouldn't use this spindle on a mill and only on a router.....a moving table router to compliment this would be the Bee's knees.

    At approx. 1-1/2 to 2 grand + a bit more for some tool holders, for a router of quality, this would be a must have item.

    One problem could be sourcing the ISO 25 tool holders that I believe it's designed for...….I obtained some ISO 20 tool holders for my mill when I ordered it, but sourcing them on EBAY was a none starter.
    Ian.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    I researched this topic to death when I was choosing my spindle and I have done a good bit of testing (with cutting steel and aluminum) since I finished my machine. There is a lot of regurgitated innacurate and outdated info out there.

    As a general point, you most definately can mill steel with even a basic wood router. There are a number of YouTube videos demonstrating this. E.g.





    Obviously there is a difference between milling an occasional steel pocket on a hobby CNC router and large VMCs making steel parts quickly all day every day. I wouldn't buy a Home Depot router for the latter...

    As with any other type of spindle, you need to choose tools and set feed speeds and spindle RPM etc at the appropriate level for your machine, spindle limitations and work piece.



    My personal experience has been that you run into other limitations like machine stiffness, poor spindle cooling, missed stepper steps and broken tools long before your spindle gets stuck due to a lack of torque. I have yet to see my 24,000 rpm spindle get stuck on any cuts when I use G Wizard, even in steel.


    You only have to look at how well the Datron routers cut steel with (ultra) high speed spindles (with smaller tools). They work as fast (with steel parts) as any comparably priced VMC and they do so with very little torque. Their accuracy is top notch too. Their machines are just appropriately stiff and heavy for metal milling and have great acoustics.


    It's also a myth that all mills have stronger, larger or better bearings. Obviously a $200,000 VMC spindle will have better bearings than a $300 Chinese eBay spindle. But, if you compare like with like, it's a different story. I have a 7.5hp PDS ADES 90 high speed spindle and an R8 spindle from LMS's high torque bench mill. The bearings on my PDS spindle are considerably stronger and higher quality than the cheap bench mill spindle.


    If you look at the various Chinese eBay belt drive milling spindles, they use the same cheap 7007 or even 6007 bearings as their comparably priced 24,000 rpm wood spindles.


    If you buy a high speed spindle that is cooled by water, electric fan or compressed air (instead of a shaft fan), you have the same (or a better) speed range as you would with any belt drive milling spindle. The main reason why cheap air cooled eBay spindles can not go below 12,000rpm is poor low speed cooling with shaft fans. My electric fan cooled spindle does fine from 50rpm up to 24,000rpm.


    The main advantage with belt drive spindles is that they can use gearing to increase low speed torque. It is / was a good way to take deeper cuts with smaller 1hp or 2hp motors on manual mills (where that matters). The trend has been shifting though. Newer high end VMCs are moving towards high speed direct drive spindles to take advantage of high speed machining with the newer generation of coated carbide tools. Motor sizes have increased accordingly to maintain torque. This is key as a 3hp milling head has no more torque at 12,000 rpm than a 3hp high speed 4 pole spindle at 12,000 rpm.


    Anyway, the advice I got here (and I'm glad I listened to) is to buy a spindle that is optimal for the material you will cut most often. Then, focus on building (or buying) a machine that is stiff enough to handle the work at the required level of precision. You can't put a 20hp cat 40 milling head on a cheap aluminum T slot router frame and expect good (or even safe) results.


    Even if that weren't the case, one look at the specs of your average Bridgeport milling head will shatter any illusions one might have about mounting one on a diy T-slot build. They weigh 300lb + and they are enormous. Many VMC heads are considerably larger.


    I mainly want to cut aluminum and the average RPM suggested for my 1/8", 1/4" and 3/8" carbide 2 flute end mills is between 12,000 rpm and 18,000 rpm. A low speed geared belt drive spindle would be sub-optimal for my needs.













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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    It would be nice if this was a universal assumption...…….not all EBAY routers are designed to cut more than the materials they suggest and steel is not one of them on any of them......even aluminium is a suggestion of "might do" etc......but I could be wrong on that score, just not into moving gantry routers made from aluminium extrusions, Acme threads and high speed spindles...….but don't get me wrong, pigs can fly given the right circumstances.

    As the guy in the video said.....rigidity is the key factor when it comes to milling steel and accuracy is part of the equation too.

    It is a fact that you climb mill with a CNC machine but if the rigidity allows the machine to flex and the cutter to dig in ….better be wearing a hard hat and waist coat too.

    My opinion is based on the 6040 moving gantry type router......never owned one, never seen one but have read a lot about them and what they CAN do...….however, a more rigid moving table or fixed gantry router is a different story.
    Ian.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by Goemon View Post
    I researched this topic to death when I was choosing my spindle and I have done a good bit of testing (with cutting steel and aluminum) since I finished my machine. There is a lot of regurgitated innacurate and outdated info out there.

    As a general point, you most definately can mill steel with even a basic wood router. There are a number of YouTube videos demonstrating this. E.g.





    Obviously there is a difference between milling an occasional steel pocket on a hobby CNC router and large VMCs making steel parts quickly all day every day. I wouldn't buy a Home Depot router for the latter...

    As with any other type of spindle, you need to choose tools and set feed speeds and spindle RPM etc at the appropriate level for your machine, spindle limitations and work piece.



    My personal experience has been that you run into other limitations like machine stiffness, poor spindle cooling, missed stepper steps and broken tools long before your spindle gets stuck due to a lack of torque. I have yet to see my 24,000 rpm spindle get stuck on any cuts when I use G Wizard, even in steel.


    You only have to look at how well the Datron routers cut steel with (ultra) high speed spindles (with smaller tools). They work as fast (with steel parts) as any comparably priced VMC and they do so with very little torque. Their accuracy is top notch too. Their machines are just appropriately stiff and heavy for metal milling and have great acoustics.


    It's also a myth that all mills have stronger, larger or better bearings. Obviously a $200,000 VMC spindle will have better bearings than a $300 Chinese eBay spindle. But, if you compare like with like, it's a different story. I have a 7.5hp PDS ADES 90 high speed spindle and an R8 spindle from LMS's high torque bench mill. The bearings on my PDS spindle are considerably stronger and higher quality than the cheap bench mill spindle.


    If you look at the various Chinese eBay belt drive milling spindles, they use the same cheap 7007 or even 6007 bearings as their comparably priced 24,000 rpm wood spindles.


    If you buy a high speed spindle that is cooled by water, electric fan or compressed air (instead of a shaft fan), you have the same (or a better) speed range as you would with any belt drive milling spindle. The main reason why cheap air cooled eBay spindles can not go below 12,000rpm is poor low speed cooling with shaft fans. My electric fan cooled spindle does fine from 50rpm up to 24,000rpm.


    The main advantage with belt drive spindles is that they can use gearing to increase low speed torque. It is / was a good way to take deeper cuts with smaller 1hp or 2hp motors on manual mills (where that matters). The trend has been shifting though. Newer high end VMCs are moving towards high speed direct drive spindles to take advantage of high speed machining with the newer generation of coated carbide tools. Motor sizes have increased accordingly to maintain torque. This is key as a 3hp milling head has no more torque at 12,000 rpm than a 3hp high speed 4 pole spindle at 12,000 rpm.


    Anyway, the advice I got here (and I'm glad I listened to) is to buy a spindle that is optimal for the material you will cut most often. Then, focus on building (or buying) a machine that is stiff enough to handle the work at the required level of precision. You can't put a 20hp cat 40 milling head on a cheap aluminum T slot router frame and expect good (or even safe) results.


    Even if that weren't the case, one look at the specs of your average Bridgeport milling head will shatter any illusions one might have about mounting one on a diy T-slot build. They weigh 300lb + and they are enormous. Many VMC heads are considerably larger.


    I mainly want to cut aluminum and the average RPM suggested for my 1/8", 1/4" and 3/8" carbide 2 flute end mills is between 12,000 rpm and 18,000 rpm. A low speed geared belt drive spindle would be sub-optimal for my needs.









    No you can not do what this video shows with your normal wood router spindle, if you did this on a regular bases you would be needing a new spindle in no time, all it showed is a chewed up mess, not successful at cutting steel at all

    You can cut steel with a Dremal so this spindle will do a similar job, I put my money on the Dremal to last longer, because of the bearing design arrangement

    They do make some of these spindles that can cut steel but the Bearing arrangement is completely different

    Mactec54


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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    I would not attempt to cut any steel even with a Dremel tool on light weight stuff the bearings are crap. They are intended for lightweight hobby use. A spindle has better bearings but it would not last long. I

    Last edited by wmgeorge; 05-22-2019 at 05:59 PM.
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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Asking if a tool will fail quickly is a different question to "can it be done?". Any spindle will fail if you apply more cutting force than it can handle but that would be user error. It's why we use Gwizard, so things like that don't happen.

    Steel is most definately a hard material but it's really not as hard to cut as some suggest. I cut it semi-regularly with a cheap angle grinder. By hand... I'd rather cut steel than epoxy granite any day.

    If you are milling steel with a 1/4" or a 1/8" end mill, the cutting forces are well within what router bearings can handle. If excess force is applied due to user error (I.e. Feeding too fast or taking cuts that are too deep), the end mill will snap long before the router bearings fail. The same is true if you are milling aluminum or hard wood.

    What you can't do with a router on smaller / lighter machines is cut quickly or with large diameter tools. That limitation applies to most Mini mills and mini lathes too with their flimsy plastic gears. You get what you pay for.

    it sounds like I am saying that a router is the right tool for milling steel, I am not. There are no small / hobby level devices that are suitable for making steel parts for resale in a commercial setting. It is possible to mill an occasional steel part (slowly) with a rigid CNC router though. That is just a fact. There is video evidence.

    There are also plenty of high speed spindles with built in motors that are designed to heavy steel work. They just cost more. Check out brands like Omlat and Ibag.

    - - - Updated - - -

    Asking if a tool will fail quickly is a different question to "can it be done?". Any spindle will fail if you apply more cutting force than it can handle but that would be user error. It's why we use Gwizard, so things like that don't happen.

    Steel is most definately a hard material but it's really not as hard to cut as some suggest. I cut it semi-regularly with a cheap angle grinder. By hand... I'd rather cut steel than epoxy granite any day.

    If you are milling steel with a 1/4" or a 1/8" end mill, the cutting forces are well within what router bearings can handle. If excess force is applied due to user error (I.e. Feeding too fast or taking cuts that are too deep), the end mill will snap long before the router bearings fail. The same is true if you are milling aluminum or hard wood.

    What you can't do with a router on smaller / lighter machines is cut quickly or with large diameter tools. That limitation applies to most Mini mills and mini lathes too with their flimsy plastic gears. You get what you pay for.

    it sounds like I am saying that a router is the right tool for milling steel, I am not. There are no small / hobby level devices that are suitable for making steel parts for resale in a commercial setting. It is possible to mill an occasional steel part (slowly) with a rigid CNC router though. That is just a fact. There is video evidence.

    There are also plenty of high speed spindles with built in motors that are designed to heavy steel work. They just cost more. Check out brands like Omlat and Ibag.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    I suppose it could be said that a small cutter revving at high speed so it only nicks a bit off is almost the same as grinding a work piece.....except the grind wheel loses grit as it becomes blunted and so you get new cutting edges more or less as the work progresses......steel or carbide cutters soon break down if the infrastructure of the machine itself is not rigid enough......the vibration that eventuates is actually the flexing of the machine and the cutter hammering against the work piece...…... carbide is not forgiving with shock treatment.
    Ian.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by Goemon View Post
    If you are milling steel with a 1/4" or a 1/8" end mill, the cutting forces are well within what router bearings can handle. If excess force is applied due to user error (I.e. Feeding too fast or taking cuts that are too deep), the end mill will snap long before the router bearings fail. The same is true if you are milling aluminum or hard wood.

    You are missing the point completely

    The bearings are not going to fail, for there normal intended use, they are the same Bearings that are you in milling machines

    It's how the bearings are arranged in the High Speed spindle's that make them fail

    When you use an end mill it will try to pull down into the metal so when it does this with these High Speed Spindles it takes the preload off the Bearings this you will see the rough cuts chowed up steel and even aluminum sometimes you will see this everyone says it's because of rigidity, when in most cases it is what is happening to the spindle bearings mostly, rigidity help but is not the main problem this can happen even with a small end mill, router Cutters have different geometry so don't cause this Bearing problem

    The preload on these bearings is only 4lbs to 6lbs so it does not take much to unload the bearings, I know your next question is going to be so why can't they preload the Bearing different, for a High Speed Spindle to have a different Bearing arrangement they have to be manufactured more precisely and they have to be serviced more regularly, the cost of these spindles would be out of the reach of most hobby builders

    Mactec54


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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Can you cut steel with a high speed spindle? Sure you can, but....

    So I've not read all of this thread, but enough to see some people ardently exclaiming that a high speed spindle can be used to cut steel, and it certainly can. However I want to point out a few things to consider about high speed spindles:

    1. Never really going to be able to use a fly cutter in one due to balance at high rpm. (Even at the slowest practical spindle rpm you will shake like crazy)
    2. In steel you will likely be limited to smaller diameter cutters and carbide at that.
    . a. On this topic, HSS roughing mills will be out and they work fantastic on steel
    . b. I mentioned not being able to use fly cutters, but even face mills will be limited because the larger ones will be running too fast.
    . c. Can't run things like boring heads (Yes you can interpolate, but boring heads work great even on CNC for deep bores or bores that need to be perfectly round.)
    3. Most times the spindles in question are ER style holders, which for a spindle kind of sucks for tool changing although I concede that tool length can be taken care of with a tool setter and a macro.

    So, if you are looking to do steel more than just occasionally, I would not go with one of the typical high speed spindles used on routers.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by mactec54 View Post
    You are missing the point completely

    The bearings are not going to fail, for there normal intended use, they are the same Bearings that are you in milling machines

    It's how the bearings are arranged in the High Speed spindle's that make them fail

    When you use an end mill it will try to pull down into the metal so when it does this with these High Speed Spindles it takes the preload off the Bearings this you will see the rough cuts chowed up steel and even aluminum sometimes you will see this everyone says it's because of rigidity, when in most cases it is what is happening to the spindle bearings mostly, rigidity help but is not the main problem this can happen even with a small end mill, router Cutters have different geometry so don't cause this Bearing problem

    The preload on these bearings is only 4lbs to 6lbs so it does not take much to unload the bearings, I know your next question is going to be so why can't they preload the Bearing different, for a High Speed Spindle to have a different Bearing arrangement they have to be manufactured more precisely and they have to be serviced more regularly, the cost of these spindles would be out of the reach of most hobby builders

    I'm not missing any of that. I just don't agree.

    I've taken apart (and put back together) my router and my R8 spindle multiple times. I know exactly how the bearings are arranged. I understand that high speed spindles can be made with 2, 3, 4 or 5 bearings and that more bearings (particularly at the tool end) can help to make it stiffer / stronger, more robust etc.

    My personal experience has been that a spindle capable of making deep cuts with 1/2" + diameter router bits in hard wood, is capable of (slowly) milling steel with 1/8" or 1/4" end mills. And, if I follow Gwizard, it can do so without the bearings failing.

    And, as I said, a small diameter end mill will snap before the spindle bearings fail, if you don't follow gwizard. I have been learning that the hard way.

    But, if fed correctly, the cutting forces with a light (shallow) cut in non-hardened steel with a 1/8" end mill with a high speed spindle is minuscule. The force required to snap a 1/8" end mill is similarly minuscule.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by Goemon View Post
    I'm not missing any of that. I just don't agree.

    I've taken apart (and put back together) my router and my R8 spindle multiple times. I know exactly how the bearings are arranged. I understand that high speed spindles can be made with 2, 3, 4 or 5 bearings and that more bearings (particularly at the tool end) can help to make it stiffer / stronger, more robust etc.

    My personal experience has been that a spindle capable of making deep cuts with 1/2" + diameter router bits in hard wood, is capable of (slowly) milling steel with 1/8" or 1/4" end mills. And, if I follow Gwizard, it can do so without the bearings failing.

    And, as I said, a small diameter end mill will snap before the spindle bearings fail, if you don't follow gwizard. I have been learning that the hard way.

    But, if fed correctly, the cutting forces with a light (shallow) cut in non-hardened steel with a 1/8" end mill with a high speed spindle is minuscule. The force required to snap a 1/8" end mill is similarly minuscule.
    And I have never seen a direct drive milling machine I am sure they exist, usually the motor is mounted on one end and the head on the other with with either step pulleys or adjustable variable speed belt drive. The milling machine bearings are (large) and made for heavy loads side to side and downward. The spindle bearings we use on our 2.2 kw motors preload ? or not are never made for those forces. However what your saying is with a small mill perhaps 1/8 inch I think you said... you could mill steel. Sure you could. The mill would snap if the forces became to much, but with very light cuts it could be done. Would I do it? More than likely not.

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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    I could imagine that if you had a 1:4 despeeder attached to the end of a high speed spindle to give you 6,000 rpm top speed and it had an ER something chuck you could get away with it...…...as long as the basic machine itself was fairly rigid then it would work.

    I'm thinking of a set of gear wheels made from Nylon in a small gearbox bolted to the spindle body end face and driven directly by the high speed spindle......at 6,000 the VFD would get you down to about 1,500 rpm and you'd have bags of torque too.....that's well within the range for a carbide cutter even at 10mm diam.

    Possibly the Nylon gears on the HSS would not like being driven at 24,000 rpm even at a reduction as the friction would probably heat them up and …...kaboom......but if you had a steel gear as the first reduction and a Nylon set as the secondary reduction.....that is a 20 tooth steel gear driving a 40 tooth gear in steel or bronze ….whatever....and then a 20 tooth Nylon gear driving a 40 tooth Nylon gear.....I think that would be possible and very doable for a DIY project.

    I would also think that a primary reduction using a worm drive at 1:10 would give you 2,400 rpm top wack, but with the output at right angles to the spindle so a set of bevel gears at 1:1 would correct that and bring the drive in line with the spindle.

    A 1:10 reduction would give you 10 time the torque without the motor overheating.
    Ian.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    On the topic of wanting to use a high speed spindle ….because you have one and nothing else will do...…..I would think that if you used the worm drive gearbox I mentioned and mounted the HSS at 90 degrees so that it pointed straight out from the Z axis face, (like an angle grinder).and parallel to the router table, you would not need any other reduction as the output at 90 degrees could be the actual spindle for milling......just thinking.
    Ian.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by wmgeorge View Post
    And I have never seen a direct drive milling machine I am sure they exist, usually the motor is mounted on one end and the head on the other with with either step pulleys or adjustable variable speed belt drive. The milling machine bearings are (large) and made for heavy loads side to side and downward. The spindle bearings we use on our 2.2 kw motors preload ? or not are never made for those forces. However what your saying is with a small mill perhaps 1/8 inch I think you said... you could mill steel. Sure you could. The mill would snap if the forces became to much, but with very light cuts it could be done. Would I do it? More than likely not.

    There are plenty. Even Haas, the entry level brand of VMCs, uses direct drive on their high speed spindles. Most high speed milling heads will be direct drive because belts and gears don't do so well at 24,000rpm+. It's also the reason why average motor sizes have gone up.

    On the bearing preload for cheaper high speed spindles, I seriously doubt anybody here has reliable and accurate info on how much force is required to cause a major failure. It certainly isn't published. Common sense though, would tell you that they have to be able to cope with multiples of the rotational force for the size of motor and multiples of the horizontal force when cutting hard woods with 1/2" + router bits.

    On a cnc machine, the horizontal force is largely a factor of the stepper or servo being used to push it. If I feed my steppers too fast for the cut I am making, either the end mill will snap or the stepper will stall. This is the case with any material being cut (in that you have to feed it correctly to avoid issues). The force required to cause my steppers to stall, or to break a 1/4" end mill is significantly lower than the force it would take to destroy the steel bearings and spindle shaft in a router.

    Anyway, I think it is best to buy the spindle best suited for the work you'll do most often. If you plan to only cut steel and titanium, it makes sense to invest in the best milling head you can afford. If you mainly cut aluminum and wood, it doesn't make sense to buy a low speed milling head for an occasional steel part imo (unless money is no object). As many have demonstrated, you can make an occasional steel part (slowly) with a well made CNC router. It's just not the right tool to do it every day, or quickly.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Quote Originally Posted by handlewanker View Post
    On the topic of wanting to use a high speed spindle ….because you have one and nothing else will do...…..I would think that if you used the worm drive gearbox I mentioned and mounted the HSS at 90 degrees so that it pointed straight out from the Z axis face, (like an angle grinder).and parallel to the router table, you would not need any other reduction as the output at 90 degrees could be the actual spindle for milling......just thinking.
    Ian.
    I looked into that a while ago (when I was spindle shopping). The issue I found was that most gear boxes (worm or otherwise) were limited to a fairly low input speed. The few that were rated to accept an input of 10,000rpm + were very expensive. Far more than buying a decent used cat40 cartridge from an old VMC.

    If you wanted to use a high speed ER spindle as the motor to drive a milling spindle cartridge, it would probably only make (financial) sense to use a belt / pulley reduction with a spindle cooled by water, compressed air or electric fan (I.e. Not shaft fan). You could then gear down from 2000 rpm.

    It is worth noting though that the whole point of using a gear reduction is to increase low speed torque. This assumes that low torque is the limiting factor with high speed spindles. It isn't, unless you plan to use large diameter end mills at low speed. The main limitation with CNC routers and smaller benchtop mills is machine stiffness and spindle cooling.

    Check out the specs of the Datron high speed spindles (which mill steel easily and quickly). There is very little torque, even in the largest spindle they offer as it is not necessary with high speed milling with smaller diameter end mills.



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    Default Re: Why most (non-router) milling machines don't use self-contained spindle?

    Cost, it's the main factor in any equation......if you have a grand or two to throw at a spindle solution I'm sure there are many spindles that will fit the bill, but it all comes down to what you intend to put the spindle to and what your part time or full time work is.

    Deriving your income from your machine is one factor that justifies breaking the bank for the short term, but a week end or evening trip to the garage won't go down too well for a bank balance watcher.

    For a hobbiest or small time backyard producer, just cutting steel occasionally with a gantry router will be the main consideration for what you embrace, and I doubt mega bucks is part of that pipe dream.

    The other factor is space......if you have space then for steel a milling machine is the way to go and leave the router to cut wood and plastics etc which it will happily do.

    I think it's far more the rigidity of the machine itself that is the limiting factor as you could lower the speed of the HSS to 10,000 rpm and using a 4 flute carbide cutter still have enough torque to maintain that speed provided your DOT and feed rate didn't overwhelm the spindle power, but if the machine is flimsy you won't cut steel no matter which god you pray to.

    The title of the thread is about a milling machine, not a router, using a HSS, so as I said, at 10,000 rpm it is doable as a mill is much more rigid.
    Ian.



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Why most (non-router) milling machines don't use self-contained spindle?

Why most (non-router) milling machines don't use self-contained spindle?

Why most (non-router) milling machines don't use self-contained spindle?