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  1. #1
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    Default R8 Spindle Speeder - new member

    Hello, It's good to finally be a member. I have frequented PM for years and spend a lot of time on the forum but usually can find the answers to my questions by searching. I finally have a question I would like to ask and get some different perspectives on. This is pertaining to spindle speeders.

    I have been needing to use as small as a 1/32" EM on my CNC kneemill. For the last couple projects most all of the tools have been smaller than 1/4" and I am struggling with the max RPM of the bridgeport. 4500 rpm is still very slow for such small tools and I hate running the machine wide open for hrs at a time. I searched for a high speed spindle option but could not find one for an R8. I have designed a spindle speeder/multiplier instead that I think could be used when I need higher RPM's. I considered several other methods such as air or electric spindle or gear drive but felt this had its own set of benefits. My plan is to build this for myself, but was hoping I could get some input on this concept. I guess I am also trying to gauge whether this is a common issue others encounter and how they solve it, i.e. is there a larger need. If spindle speed on bridgeport's is a common issue, is there an aftermarket solution I have overlooked? (Everything I have found is several thousand dollars and designed for a CAT40)

    Pros:
    -1:6 ratio
    -timing belt drive, dampens vibrations and easy to maintain
    -power taken from main spindle
    -maintains original zero
    -easy tool change
    -ER20 collet

    Cons:
    -Run out, TIR of main spindle is compounded with run out of speeder. Hope to achieve .0002-.0004" TIR on the speeder assy alone.
    -Deflection, I expect 1/4" EM max in aluminum.
    -Loss of ~.5" Z travel due to torque clamp

    Usage:
    I would use this for 1/8" tools or smaller. Engraving would be a good use. Expected max rpm would be around 20K. Not meant to replace an actual high speed spindle, just provide a stop-gap measure if you must use a tiny tool on a bridgeport.

    I look forward to your replies. Thanks, Paul
    spindle-assy.jpg

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    You'll need super precision angular contact bearings in your spindle. Your drawing shows what would appear to be plain ball bearings, due to the simplistic construction of the high speed spindle and its housing. Angular contacts require more components and more complex construction details.

    Plain ball bearings will permit your spindle to float way too much, be noisy at 20,000 rpm and probably will overheat.

    I would also be concerned about all the additional rotating mass that you have to spin with the countershaft speed up. Little timing belts may not handle the start up jolt very well. I'm also hazy on the engineering of timing belt speeds, but those belts sing like a high speed zipper when you run them really fast

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    If spindle speed on bridgeport's is a common issue, is there an aftermarket solution I have overlooked? (Everything I have found is several thousand dollars and designed for a CAT40)

    I did a Google search "R8 Spindle Multiplier" and came up with lots of hits ???
    I did not investigate further,but it looks like they are out there.

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    here is a Yuasa for $175 needs a nut, I am not sure how many rpms
    Yuasa Speed Multiplier R8 Milling Machine Needs Collet Nut | eBay

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    Are you aware of the Yuasa speed multiplier (not sure of the ratio)?

    Here's one on eBay. No connection to the seller.

    Yuasa Speed Multiplier R8 Milling Machine | eBay

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    Quote Originally Posted by vmipacman View Post
    i.e. is there a larger need. If spindle speed on bridgeport's is a common issue, is there an aftermarket solution I have overlooked? (Everything I have found is several thousand dollars and designed for a CAT40)
    General solution has been to go and use a different mill that was built for the higher RPM, often a lighter X-Y-Z, more precise positioning and readouts, probably with CNC, and usually a different spindle taper and collet system(s) as well.

    If a given BP host mill has ANY imperfections, (which even Superman's BP may have.) any rig hung onto it with an R8 tail is going to magnify those imperfections and add a few of its own, not correct anything but the RPM famine.

    As to most being CAT 40.. well. a typical "older" 40-taper equipped mill has lower max RPM than a BP to begin with, so is more likely to need this sort of help. Such mills are also usually stiffer than a BP. Sometimes by more than you can easily imagine.

    NEWER 40-taper mills include some capable of 20K RPM as-shipped, more-yet capable of 8K or 10K. Those do not need a spindle speeder, nor would one have much chance of balancing it as part of the overall system.


    Bill

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    I like your design. For the most part I think it's pretty good if your bearings are very good.

    However I think the yuasa is hard to beat for the price and it's very well proven.

    Also, anything driven by the r8 is going to orbit, magnified by the overhung distance. For that reason I think you would like a design that is not driven by the rotating spindle. -Which brings me back to the router motor option.

    I might think about a motor running a belt drive to the quill like an old dental drill. maybe a 9mm timing belt with a piece of extra long pulley stock and let the belt walk along the pulley. that might get you a couple inches of z.

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    Quote Originally Posted by dsergison View Post
    .. anything driven by the r8 is going to orbit, magnified by the overhung distance. For that reason I think you would like a design that is not driven by the rotating spindle. -Which brings me back to the router motor option.
    One might even make the case for a complete system built with that sort of 'packaged spindle'.

    There are now tons of choices - including air and water cooled. Some are right economical...a decent design could provide for swap-out and upgrade of the spindle itself.. precision long-nose or short. Design it with all it needed to do its job...

    And then....attach to the aft-end of the ram, just as BP did for slotter or cherrying heads.

    Or to any OTHER mill, horizontal as well as BP. One could see more 'leverage' in going to the effort if the 'gadget' ended up more universal as to where one could use it. That's how BP itself got started, after all...

    Bill

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    Quote Originally Posted by thermite View Post
    One might even make the case for a complete system built with that sort of 'packaged spindle'.

    There are now tons of choices - including air and water cooled. Some are right economical...a decent design could provide for swap-out and upgrade of the spindle itself.. precision long-nose or short. Design it with all it needed to do its job...

    And then....attach to the aft-end of the ram, just as BP did for slotter or cherrying heads.

    Or to any OTHER mill, horizontal as well as BP. One could see more 'leverage' in going to the effort if the 'gadget' ended up more universal as to where one could use it. That's how BP itself got started, after all...

    Bill
    that's right smart.

    spin the turret around and use or make make some servo controlled linear rail or box way slide etc and put a decent router spindle on it. this gets you past the crappy cnc quill drive some turret mill cnc conversions have.

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    Quote Originally Posted by dsergison View Post
    that's right smart.

    spin the turret around and use or make make some servo controlled linear rail or box way slide etc and put a decent router spindle on it. this gets you past the crappy cnc quill drive some turret mill cnc conversions have.
    Bridgeport's idea, not mine. Or in my case the "Quartet" mill that may become an "Octet", given that its vertical-head motor sits horizontally at mid-ram already, and has shafts at both ends.

    Either machine, that lets a body use readily-available modular components and not be limited by - nor have to alter or even reconfigure - the 'ordinary' functions of the stock head on the other end of the ram.

    Next logical step would be a nice and precise linear-rail sub-plate X-Y positioner table to fasten atop the BP's table.

    Whether CNC or just a lighter touch on the controls and mini DRO, those tiny bores could become a good deal less stressful to knock out quickly.

    Bill

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    Thank you for the comments.
    You'll need super precision angular contact bearings in your spindle.
    I absolutely agree. I did intend to use precision angular bearings but the model does not show them. McMaster is just so easy to drag and drop parts from. I should have caught that before taking the screenshot. I am not sure about the missing complexity to use the precison bearings though? I have it setup with matched bearings (model aside), spacer, and preload nut. I need a way to lock the nut (like a setscew) and some shims possibly but what else would you recomend? One other thing, I planned to have the R8 taper ground insitu after the bearing cartidge was assembled and preload set.
    I did a Google search "R8 Spindle Multiplier" and came up with lots of hits ???
    I'm sorry but I did not... Lots of pictures of homemade offset spindles, some super high speed air driven spindles for VMC's, did touch on the Yuasa!, and several pictures of a Tormach unit (not sure the taper). Lots of hits, but not many that really fit the search.
    Are you aware of the Yuasa speed multiplier (not sure of the ratio)?

    Here's one on eBay. No connection to the seller.

    Yuasa Speed Multiplier R8 Milling Machine | eBay
    Only vaguely, Thanks! I looked a couple weeks ago and did not see one. I did not know they could be had as readily as that. Do they still make/support them? Or when did they go out of production?

    However I think the yuasa is hard to beat for the price and it's very well proven.

    Also, anything driven by the r8 is going to orbit, magnified by the overhung distance. For that reason I think you would like a design that is not driven by the rotating spindle. -Which brings me back to the router motor option.
    I am not sure I understand your comment completely. The two comments seem to contradict one another. I understand and completely agree that any runnout would be magnified. Does the Yuasa deal with this issue differently so as to make it a very well proven design?

    Thanks

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    Quote Originally Posted by vmipacman View Post
    Does the Yuasa deal with this issue differently so as to make it a very well proven design?

    Thanks
    I'd suspect that the only thing the several folk who made these 'proved' was that there wasn't an enduring market for the resulting gadgets that was large enough to support their continued production and profitable sale.

    You can DO what you seek to do. But it is an uphill battle 'against the odds' all the way, and isn't likely to beat Yuasa or Tormach if it is even as good. Neither of 'em were exactly Virgins at making precise goods.

    The clean-start, modular stock-component approach Denis and I have posited, OTOH, almost guarantees success. Brackets to fab, perhaps a bit of shimming to do to get a mount one can tram that dasn't vibrate. No bearing, gearing, nor power engineering involved. Others have done it for you arredy, and both the spindles and the traverse mechanisms long-since well-proven in thousands of other applications.

    Pride in a DIY made-in-USA device is wonderful. Also frustrating as all get-out when a year of your life and a large chunk of change dasn't hold the accuracy of a mass-produced Chinee item that even turns out to last longer.

    Some days, you eat the bear, other days..... you just tries to stay out of the woods.. and go find a project the bears have overlooked entirely.

    Bill

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    Quote Originally Posted by vmipacman View Post
    Thank you for the comments.

    I absolutely agree. I did intend to use precision angular bearings but the model does not show them. McMaster is just so easy to drag and drop parts from. I should have caught that before taking the screenshot. I am not sure about the missing complexity to use the precison bearings though? I have it setup with matched bearings (model aside), spacer, and preload nut. I need a way to lock the nut (like a setscew) and some shims possibly but what else would you recomend? One other thing, I planned to have the R8 taper ground insitu after the bearing cartidge was assembled and preload set.
    You need a locknut on top of the spindle to retain the bearing inner races and the spacer, otherwise the spindle will just work its way out. Then you could set the preload with the cap. I see you have something rather skinny drawn there, it looked more like a dust cap than a nut, but as long as you know it needs to be there.

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    Could you use a miniature air die grinder (1/8" collet capacity) in a bracket held coaxial with the quill? They can spin up to 50k RPM but can be throttled back to about 30k. The other accessory needed is a miniature sign to hang on the spindle switch "CAUTION -TURNING SWITCH ON WITH DIE GRINDER MOUNTED MAY RESULT IN PROFANITY".

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    Quote Originally Posted by Scottl View Post
    Could you use a miniature air die grinder (1/8" collet capacity) in a bracket held coaxial with the quill? They can spin up to 50k RPM but can be throttled back to about 30k. The other accessory needed is a miniature sign to hang on the spindle switch "CAUTION -TURNING SWITCH ON WITH DIE GRINDER MOUNTED MAY RESULT IN PROFANITY".
    I have two or three of those. Not the best bearings in the world once you start loading them with a tool more 'grippy' than an abrasive. OTOH, cheap enough for frequent replacement.

    The small CNC spindles are better suited. Some already have ER-family collets - themselves not a bad choice.

    Just avoid the Huanyang alleged-VFD some of 'em are packaged with and use a real VFD.

    Or hunt-down a vintage 'Porter Cable' electric router head. One of the best of that tribe, ever.

    Bill

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    I have a $3k / 60k rpm air spindle and I have accidentally turned the spindle on with it. profanity does ensue.

    luckily it's fed with a push lock air hose fitting that rips the hose out, but not until it's ripped the filter/regulator off the side of the mill and thrown it on the floor.

    <$100 air handpieces are not up to cnc engraving duty for long.
    I wanted to pack a cheap handpiece one up inside a cat40 toolholder once, but it was not nearly good enough for .010" endmills so I bought a $3k air spindle.
    http://www.airturbinetools.com/spind...ecs/602js.html

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    I use one of these - about $590 new....

    High Speed Air Spindle

    From time to time they have repaired units for half price. They work VERY well - but are loud.

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    FWIW, the input shaft on Tormach speeder fits into a 3/4-in R8 collet in the spindle; Tormach specifies that their collet, which has a flat nose, be used. The output shaft spins at 3x the mill spindle speed.

    Mike

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    This person is looking for the most cost-effective solution, otherwise a KERN might be the right answer (lol).
    For milling a lot of materials and for very small end mills, you will still want a spindle speeder on a CAT 40 Machine, even one with 20k RPM.

    Dan

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    Quote Originally Posted by DanielGilbert View Post
    This person is looking for the most cost-effective solution, otherwise a KERN might be the right answer (lol).
    For milling a lot of materials and for very small end mills, you will still want a spindle speeder on a CAT 40 Machine, even one with 20k RPM.

    Dan
    Well Dan, thanks for digging up a 5 year old thread to let us know!

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