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  1. #37
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    Mike;
    You are right about lower spindle speeds. I've cut many, many profiles in some very difficult plastices with .017 diam, cutters on a mill that maxxed out at 6000 rpm on the spindle. A lot of the seceret to cutting is not running the cutter at MACH ONE, but rather getting the load per tooth of the cutter correct and getting the chips out of the way.

    Tony



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    Default spindle design

    i've been following this thread about spindles and googling all over to learn about it myself.
    what i seem to get is that the worst problem will be heat induced elongation of the shaft and consequent excessive loading of the bearings.
    ? - if the spindle chassis and the shaft are made of identical material, will this not obviate the problem entirely?
    ? - if each end of the spindle is in a roller bearing only, and a thin disk on the lower end of the shaft is captured between thrust bearings, then will not the thin-ness of the disk obviate any problem of elongation just simply because it's not very long?

    obviously the smaller the diameter of the shaft, the faster it will max because the bearing travel will be proportionately shorter each rev than on larger diameter.

    these look like good clues to start making a test spindle - anybody see flaws or something i overlook?



  3. #39
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    Quote Originally Posted by MikeAber
    H500
    You could try this,

    Clean the housing inside where the bearing is and remove the foam rubber then oil the bearing, shaft and housing. Mix some epoxy putty (Home Depot) and place into the housing area that holds the bearing in both halves (just enough to fill the area when the bearing is inserted or a little less) then reassemble. The oil will prevent the epoxy from sticking to anything.
    Mike, thanks for the suggestion. I might try wrapping the parts in Saran wrap and doing it half at a time, so that it can still be disassembled.



  4. #40
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    Quote Originally Posted by toolmkr13
    Mike;
    You are right about lower spindle speeds. I've cut many, many profiles in some very difficult plastices with .017 diam, cutters on a mill that maxxed out at 6000 rpm on the spindle. A lot of the seceret to cutting is not running the cutter at MACH ONE, but rather getting the load per tooth of the cutter correct and getting the chips out of the way.

    Tony
    I agree with you completely. Learn how to make chips not dust.

    Mike

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  5. #41
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    Quote Originally Posted by gcz
    i've been following this thread about spindles and googling all over to learn about it myself.
    what i seem to get is that the worst problem will be heat induced elongation of the shaft and consequent excessive loading of the bearings.
    ? - if the spindle chassis and the shaft are made of identical material, will this not obviate the problem entirely?
    ? - if each end of the spindle is in a roller bearing only, and a thin disk on the lower end of the shaft is captured between thrust bearings, then will not the thin-ness of the disk obviate any problem of elongation just simply because it's not very long?

    obviously the smaller the diameter of the shaft, the faster it will max because the bearing travel will be proportionately shorter each rev than on larger diameter.

    these look like good clues to start making a test spindle - anybody see flaws or something i overlook?
    Hi gcz,

    Now we really get into the meat of the problem/solution.

    If you had a company that hired the engineers, did the research, the countless hours of testing various metal alloy expansion rates, developing theories, testing theoritical solutions, etc. and could manufacture a quality spindle that is stable and stays within tolerances required at say 1,000 -- 30,000 rpm then run sweetly for years with continuous heavy/light/no load cycles without a rebuild. Would that be worth something? Would you be able to sell it inepensively to a limited market? Would you share the information with the world? I think not. ebay really does rock!

    The rest of us mortals must learn to live with compromise.

    Mike

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  6. #42
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    won't know til i get a testable model done...have to get a friend or someone to turn some parts, but sure, i'll share the notion - here's a stupid bmp done in paint to suggest the design
    er...lemme jpg that first...
    well, lemme make a note or 2 on it first...
    but i think it sort of makes the problems i've learned of go away.
    this would be only 1/4 shaft - that's gonna maximize rpm - i don't care if there's a bigger chuck on the end - plz keep in mind, though, that this is for high speed laptop mills - not your 10 ton hog !

    Attached Thumbnails Attached Thumbnails Spindle Idea-spindle-gif  


  7. #43
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    Quote Originally Posted by gcz
    won't know til i get a testable model done...have to get a friend or someone to turn some parts, but sure, i'll share the notion - here's a stupid bmp done in paint to suggest the design
    er...lemme jpg that first...
    well, lemme make a note or 2 on it first...
    but i think it sort of makes the problems i've learned of go away.
    this would be only 1/4 shaft - that's gonna maximize rpm - i don't care if there's a bigger chuck on the end - plz keep in mind, though, that this is for high speed laptop mills - not your 10 ton hog !
    gcz;

    Check these out:
    http://www.vxb.com/page/bearings/PRO...ONTACT/Kit6930
    http://www.vxb.com/page/bearings/PROD/12mm/6201ZZ10-1

    How about $13.00 + shipping for bearings that will go 15K+ rpm.

    Your drawing is cool

    Make the housing out of 1.5" watter hardening drill rod, 3" to 4" long.
    Bore and ream a hole in one end to 32mm +0,-.001" (press-fit) 15.9mm deep.
    Bore and ream a hole in the other end to 32mm +.0,-.001" (use same reamer for press-fit) 10mm deep.

    Make the spindle shaft out of .5" --- all the way up to 1.5" watter hardening drill rod 4" to 5" long. This depends on the type of spindle taper you desire.
    Turn the shaft down to 12mm +.001" (press-fit) at the business end for the double row angular contact bearing.
    Turn the other end of the shaft down to 12mm +.0, - .001" (slip-fit).
    Assemble with arbor press.

    This configuration would allow the spindle shaft to grow in length as it heats.
    It will get longer as the larger housing must be clamped/held to the Z axis in some manner and the housing will be exposed to air and coolant in some cases, the spindle shaft will not.

    This level of precision is beyond most hobbyists, including me!

    I may try to make one anyway!

    I like your enthusiasm; it's contagious.

    Mike

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  8. #44
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    By the way, I like the ten ton hogs; I just can't find any more room in my shop for one.

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  9. #45
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    Quote Originally Posted by MikeAber
    gcz;
    How about $13.00 + shipping for bearings that will go 15K+ rpm.

    Mike
    one thing to consider is the class of bearing - the $12 ones are the lowest and you can easily spend a couple of hundred for the (what is it, class 7?, not sure) same size in a high class. Depending on what you are using the spindle for that might be a consideration - for a pcb mill the $12 are fine, for a grinder, forget it, you need the expensive ones. I don’t know that I’d want to use the $12 ones at 15k though

    I'm also not sure about the double row angular contacts. I think you need to consider separate bearings so you can preload them. Some of the nicer diy spindle designs, such as that used in Quorn, use springs to load the bearings.

    I wouldn't bother using tool steel, just nice free cutting mild steel. Often tool steel or tougher chrome moly steels are used for spindles, but as diy's we don't need this toughness - we'll avoid dings and such by being careful. The reason is that these steels are tougher to work and you don't get the advantage until you heat treat them. When you heat treat, the parts warp slightly and you need to finish by grinding, especially for an accurate part such as a spindle. This is a lot of extra work and requires more specialized equipment.

    Definitely agree with speed comments. In theory, the ability of a machine to remove cubic units of material is a function of horsepower and rigidity. Spinning the cutter 4x as fast as it needs to be doesn't remove materials 4x faster, it just wears the cutter out 4x faster.

    Making spindles is a common home shop endeavor so by all means go for it. Many successful designs have been described in Model Engineer over the years, if you can find some via library or club they will help.



  10. #46
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    Quote Originally Posted by Mcgyver
    Definitely agree with speed comments. In theory, the ability of a machine to remove cubic units of material is a function of horsepower and rigidity. Spinning the cutter 4x as fast as it needs to be doesn't remove materials 4x faster, it just wears the cutter out 4x faster.

    Making spindles is a common home shop endeavor so by all means go for it. Many successful designs have been described in Model Engineer over the years, if you can find some via library or club they will help.
    Mcgyver,

    Your comments are right on target.

    It seems that so many are using sloppy machines and spindles that grinding the material away with a carbide end mill or bur at 30,000 rpm has become the norm. If your machine can move at 200+ ipm to keep the cutting tool climbing this is fine, otherwise you are just polishing the cutting tool's edges until they no longer cut and then they break. "Learn how to make chips, not dust"

    I hope that thru this thread we can collectively explore several spindle designs, and levels of performance. Most important of all, is that we also collectively improve our level of understanding.

    There are many, many Machine and CNC Technology professionals on this website that have forgotten more than I will ever know. Maybe they, like yourself, will share some of that knowledge with the rest of us.

    Thanks

    Mike

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  11. #47
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    the point about chips not dust is indisputably good.
    one thing that the numbers show clearly is this:
    if you're using tiny cutters, to get any real tooth travel - to get chip load - you NEED high speeds...but i'm not up for making a table atm to illustrate the point...
    however, plz check out the cutters you CAN get - http://www.pmtnow.com/
    at a certain scale, legitimate chip size is indistinguishable from talc.
    there IS a niche for high speed
    i have a 120 ct ruby i'm dying to carve up with tiny diamond bits completely submerged. for such as this, forget 6000 rpm - i need more like 60,000!



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    I can't find a place for this but I'd like to add a dwg of a spindle idea. What format is uploadable? And how can I convert a dxf file to whatever format is used here>



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