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Thread: Using a Manual Chuck on a CnC lathe.

  1. #1
    Solar71 is offline Titanium
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    Default Using a Manual Chuck on a CnC lathe.

    Hey guys.

    Have any of you tried to do this ?
    Are there any reasons to NOT use a manual chuck on a CnC lathe ?

    We have this new (to us) CnC lathe. It came with a 6 jaw, 10 inch manual chuck.
    We are thinking about getting a hydrolic 10 inch chuck for it, but just wondering if using a manual would be ok ? Or is this just stupid ?

    PS : We are working in metals, not plastics or anything else.

    Thanks

  2. #2
    gregormarwick is offline Stainless
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    Top speed is usually a factor. Most manual chucks have a much lower max. permissible rpm.

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    Mud's Avatar
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    A manual doesn't have anywhere near the gripping force of a hydraulic. And you'll get very tired of tightening the manual chuck by hand.

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    Solar71 is offline Titanium
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    So basicly the RPM of the programs need to stay in the 500 or less would you say ?

    Thanks you guys.

  5. #5
    CNCJockey is offline Plastic
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    We use a 10" and a 8" 4-jaw manual chuck on a Milltronics CNC and run them up to the rated RPM of the chucks for small items that can be SECURELY held, I think the 10" chuck is rated for 1500 RPM and the 8" is 2000 Rpm, you just have to use common sense, don't chuck a big heavy part and spin it wide open!!!

  6. #6
    alphonso is online now Stainless
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    I have a CNC lathe with a POS control, Anilam 1200T, that uses a 15 inch, 3 jaw manual chuck. Top speed of machine is 1800 rpm. Don't have any issues with the chuck. I use an electric impact wrench to operate the chuck. No problems with chuck for 9+ years.
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  7. #7
    jdj
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    There are times where it is handy, and times where it is not. Pretty much the same as anything else. If you have parts that require you to open the chuck up a little more than the stroke of a power chuck, a manual chuck is pretty handy. If you run a lot of the same parts with a short cycle time, not fun. The gripping power is low on the list of worries. IF...you keep it lubed, use common sense and have a chuck wrench that has a long enough handle or use a cheater bar on it.
    Not that I run much stuff at super high RPM's but a manual chuck in good shape, certainly is NOT going to be letting go of parts, JUST because you spin it fast. If it does, there are one of two problems. That PARTICULAR CHUCK, or YOU not tightening it hard enough. Hydraulic and pneumatics lose gripping power as the RPM's go up also! Not just manuals!


    Jeff

  8. #8
    jdj
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    Quote Originally Posted by Solar71 View Post
    So basicly the RPM of the programs need to stay in the 500 or less would you say ?

    Thanks you guys.

    No.
    Leblond lathe manual (while NOT the actual chuck maker) lists top speeds for manual chucks.
    12" chuck max RPM=2500. As long as you can (not crushing the part) put a little muscle on that chuck wrench, it isn't something to be paranoid of. Hell, shouldn't you make sure that you chuck on something securely anyways? How in the hell are you going to get any accuracy with the part moving in the chuck? Not moving, except of course, rotationally!

    Jeff

  9. #9
    bryan_machine is online now Titanium
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    Will this chuck be accurate enough for your needs? Is it a slider or a scroll? Or 6 way independent so you have to tighten down 3 pairs of jaws? (But could presumably get great concentricity, deal with out-of-round parts, and so on.) Power chucks are usually (always?) sliders with good concentricity, etc.

    So depending on the task it might be better than a power chuck, eh?

    Also, you might want to consider using a torque wrench to tighten it, especially if your operators range from petit to gorrila.

  10. #10
    IronReb is offline Stainless
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    I have a pair of soft jaws I bored just for a manual 4 jaw chuck I use.It has worked well for me for years now.

    As mentioned,DO NOT GO FASTER THAN RATED RPM for manual chuck.

    I do not have a clue what the max RPM is for the 4 jaw chuck we use,so what I do is set G50 spindle speed clamp to max RPM the manual machine the chuck came off of to.I haven't eat a chuck jaw yet


    Just so you are aware,I use the 4 jaw for odd shaped parts from time to time.The max RPM is some thing like 1200.
    The hydraulic chuck on the CNC I use daily is 4500 RPM.It's worth the money for the hydraulic chuck if you plan on turning things smaller than 3''.The smaller the part the faster the RPM,if you are limited on RPM running small diameters the manual chuck will cost you in the long run in cycle time due to not being able to crank up the R's.

  11. #11
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    Manual chuck = no draw tyube = more bar capacity.


    I think you could twist it a little higher than 500.

    I have a 15" 6 jaw that I twist as high as the machine will go = 900.

    I have a 32" 3 jaw that will twist to 800.


    I think your big 10" record will be fine.


    -----------------

    Think Snow Eh!
    Ox
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    Philabuster's Avatar
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    Quote Originally Posted by Ox View Post
    I have a 32" 3 jaw that will twist to 800.

    Think Snow Eh!
    Ox
    Pucker factor for sure.

    The welders get freaked out when they watch me spin the 21" 3 jaw in the engine lathe past 500.

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    digger doug is offline Titanium
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    I saw this in a local shop, the owner ordered a brand new c.n.c. lathe
    with a manual 4-jaw chuck.

    He does very odd shaped casting's, involving many contours, on exotic materials,
    meaning long cycle times, and small qty's.

  14. #14
    sinha is offline Cast Iron
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    Chucks with centrifugal force compensation are also available, which can be run at very high rpm without loosening the grip.

  15. #15
    gorrilla is offline Stainless
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    Default Manual chuck on a cnc lathe

    I've been running a manual chuck (12" Adjusta-Tru) on our M20 Romi since the machine was new,approx 6 years ago. It is used for short run production and reworks. Occasional fixtures and tooling, basic onesy twosy work. It slows down the process on long run production, but if you can juggle the work load to mix cycle times just right, it isn't a real big problem. Actually save a lot of setup time. I have an assortment of soft jaws cut for various repeat jobs. That helps a lot.
    As far as holding the work, I've never run into any problems. I seldom run over 1500 rpm's, as we are usually running castings. I can and do get up to 2000 occasionally on small diameter parts like our mainshafts, with the diameter on the pilots running .985. But that's only the pilot section, with the balance of the shaft stepping up to as large as 2" or more. So the G96 kicks in to slow things down as the diameter increases.
    You have to contend with the scroll getting full of chips and dust. Remove the masters from the scroll and clean it out when the chuck starts to act stiff. General maintenance, keep it clean an lubed.
    One thing you'll notice, if you run a delicate part, is the scroll type chuck will want to loosen itself if you try to run at extremely low jaw pressure. Has to do with the inertia of the scroll inside the chuck wanting to resist spinning with the chuck at startup of the spindle. CNC has nothing to do with this, same thing happens on a manual. There is just a limit as to how far down you can go with jaw pressure in a three jaw. 4 jaw should be immune to this, but of course would be very slow in production work.
    I've never run a 4 jaw on a cnc, wanted to once, running rework from a cnc shop, would have been great for getting all the runout from a part. Jst couldn't justify slowing down the production from a cnc lathe to do reworks.

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    scudzuki is offline Stainless
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    Quote Originally Posted by gorrilla View Post
    One thing you'll notice, if you run a delicate part, is the scroll type chuck will want to loosen itself if you try to run at extremely low jaw pressure. Has to do with the inertia of the scroll inside the chuck wanting to resist spinning with the chuck at startup of the spindle.
    IOW why they don't reverse the scroll direction to eliminate this inertia effect.

    Of course this would also reverse the direction of the pinion... unless they put it on the other side of the scroll.

    Joe

  17. #17
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    Quote Originally Posted by scudzuki View Post
    IOW why they don't reverse the scroll direction to eliminate this inertia effect.

    Of course this would also reverse the direction of the pinion... unless they put it on the other side of the scroll.

    Joe


    I have yet to believe the "inertia" effect on a scroll.
    (on a CNC no less.)


    Now - if you want to go with direction vs vibes - I may bite. There is a reason that some shafts use LH threads. Even some wheel studs have used LH threads on one side of the Vee Hickle, and those are not on C/L even.


    Your machines must have some awfully impressive ramp up/down rates to have inertia effect a scroll....



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    Think Snow Eh!
    Ox
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    Chuck_Jaws's Avatar
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    Another thing to think of is when you open the chuck up a ways, the jaws will be sticking way out possilble creating clearance issues with long tools in the turret.

  19. #19
    gregormarwick is offline Stainless
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    Quote Originally Posted by Ox View Post
    I have yet to believe the "inertia" effect on a scroll.
    (on a CNC no less.)


    Now - if you want to go with direction vs vibes - I may bite. There is a reason that some shafts use LH threads. Even some wheel studs have used LH threads on one side of the Vee Hickle, and those are not on C/L even.


    Your machines must have some awfully impressive ramp up/down rates to have inertia effect a scroll....



    -----------------

    Think Snow Eh!
    Ox

    I have had a scroll chuck open on a manual lathe when stopping from running in reverse. 2000rpm to stop with a good spindle brake, when it came to rest the part fell out of the chuck. No damage done, brake turned off for remainder.
    Last edited by gregormarwick; 08-30-2011 at 07:59 AM. Reason: Quoted wrong post!

  20. #20
    Dave K is offline Diamond
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    I think your big 10" record will be fine
    lmao!!! I know what that means. Knew it, as soon as I saw it. I'm surprised from you that it wasn't turned into a link with that song.

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