Announcement

Collapse
No announcement yet.

Noise and chatter when milling, HF 42976 machine

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • J Tiers
    replied
    Originally posted by Black_Moons View Post
    Because the modern world has moved on to better taper systems for milling like R8. MT was kept for what it was originally intended for: drilling!

    Only ancient and hobbyist machines still use MT for milling so yes, you won't see MT collets much in photos of modern professional shops.
    The very similar B&S taper was used on virtually everything of a milling nature for a while...... although the collets for that are rare. So no need to look down on the MT at all.

    And, the R8 is a horrible invention, a big compromise, really. The main reason for it being considered "better" is that it releases a lot easier.... not always a good thing. ER are far better for nearly anything.

    Leave a comment:


  • Black_Moons
    replied
    Originally posted by dian View Post
    it might matter or not, but there is a difference between wearing out the spindle or a replacable toolholder. due to the smal taper, it will slide more than cat or er and even more, because it compresses. why is it, that mt collets are almost never used (i have never seen one, except on pictures). but never mind.
    Because the modern world has moved on to better taper systems for milling like R8. MT was kept for what it was originally intended for: drilling!

    Only ancient and hobbyist machines still use MT for milling so yes, you won't see MT collets much in photos of modern professional shops.

    Leave a comment:


  • Black_Moons
    replied
    Originally posted by becksmachine View Post
    I think you are saying that the chuck came loose from the Jacobs chuck adapter?
    That happens a lot on these machines and many folks have devised various fixes for that problem. The most robust fix is to not use the chuck for milling.
    They look good to me.
    Dave
    Agreed. Or let one drop of water get in between the chuck and JT33 taper. Once a little rust forms guaranteed that chuck is not going to come off again :P

    Leave a comment:


  • J Tiers
    replied
    With a tool held in it, the MT collet does not compress much if at all... the tool will be at close to the ideal size, so the combination will be almost like a center, or toolholder.

    MT collets were used on old Bridgeport, and other milling machines to hold tools. I don't think they are so useful for general holding of work in a lathe etc, so you see more of the 5C, 3C, ER, etc. for that.

    Leave a comment:


  • dian
    replied
    it might matter or not, but there is a difference between wearing out the spindle or a replacable toolholder. due to the smal taper, it will slide more than cat or er and even more, because it compresses. why is it, that mt collets are almost never used (i have never seen one, except on pictures). but never mind.

    Leave a comment:


  • Jaakko Fagerlund
    replied
    Originally posted by dian View Post
    you realise, that by using mt colets you will be wearing out your spindle, right?
    Hardly more if nothing compared to the wear of normal use otherwise. You do realise that the collet doesn't slide very much in there?

    Leave a comment:


  • Black_Moons
    replied
    Originally posted by dian View Post
    you realise, that by using mt colets you will be wearing out your spindle, right?
    You realize, that by turning the mill on and using it, you will be wearing out everything right?

    Leave a comment:


  • dian
    replied
    you realise, that by using mt colets you will be wearing out your spindle, right?

    Leave a comment:


  • Jaakko Fagerlund
    replied
    J Tiers explained the too small / big tool in a collet issue nicely, so I don't repeat it here.
    Originally posted by J Tiers View Post
    Even the ER collet is nowhere near perfect. But it is better.

    They are split from BOTH ends, so that they are "hinged" both places. That "tends" to make them better, as both ends expand and contract together. They have the exact same hinging problem, but it is compensated by the fact that both ends expand and contract, so the distortion of the grip is different, and both ends are nearly the same.
    ER hollets should never be used to hold anything larger than the nominal size. Smaller is okay, as they aer designed to compress quite much for a collet.

    One thing to know is that if one uses an ER collet and puts in a shorter workpiece or tool shank than the collet length, it will not grip properly but by the same small contact like J Tiers explained with the R8/5C/etc. situation. The proper way is to put something similar in size in the back of the collet if the tool or work piece is held by only a portion of the collet length so that the collet will grip evenly/parallel.

    That is the reason I have a collection of cut-offs near my collets, usually with a length of 2D, chamfered both ends and I can just push in the same size in the back of the collet, then put in my tool/workpiece from the front to the distance I need and tighten the collet without a fear of uneven clamping

    Leave a comment:


  • J Tiers
    replied
    Originally posted by becksmachine View Post
    "should" being the operative word here.
    The MT2 will hold fine with a drawbar. The real problem is releasing the tool and collet, which normally involves heavy pounding on the drawbar to push out the collet. I made up a "self releasing" drawbar to deal with MT tooling in the main horizontal spindle of my mill. It uses the retaining screw to push out the collet when unscrewed, to avoid banging away on the drawbar. The difficulty of releasing the MT tends to verify the good grip.

    R8 were invented to release better, while still holding "pretty tight".


    Originally posted by becksmachine View Post
    If you think about it, the taper should not be affected as the collet will either stick out farther to accommodate a larger shank or pull in farther to accommodate a smaller shank, but the parallelism of the sides of the hole should not change. The only mis-match that would occur is if difference is large enough that the hole in the collet does not have complete contact with the shank of the tool due to the differing radii. And this is one reason for many collet systems having more than 3 "splits".
    Actually, the parallelism is ONLY correct for one specific perfect size. The regular collet is split one way, so all the segments, three or three dozen, are "hinged" at the fixed end. That means they "swing" instead of moving evenly in and out.

    The natural tendency is for the collet to hold ONLY by the "heel" of the bore (part nearest the drawbar) for oversized shanks, and ONLY by the "toe" (tip) of the bore if the shank is smaller than the bore.

    This is partly compensated by the fact that the taper tends to force the collet to be parallel to it, and hold the bore parallel to the axis. That isn't at all perfect, but it's pretty good for most close sizes, and is much better with MT than 5C/3C/R8.

    Luckily, the shanks of any quality end mills will be very closely accurate to size, and will be held well in a collet. With a weldon holder, they normally bounce on an air cushion when put in, and come out with a "pop", attesting to the size accuracy and close fit.

    if you get cutters from HF, they might be just the closest metric size.... and not fit well.

    Even the ER collet is nowhere near perfect. But it is better.

    They are split from BOTH ends, so that they are "hinged" both places. That "tends" to make them better, as both ends expand and contract together. They have the exact same hinging problem, but it is compensated by the fact that both ends expand and contract, so the distortion of the grip is different, and both ends are nearly the same.

    Only the Jacobs "rubberflex" collets really grip work or toolshanks truly parallel, but the ER do in fact work much better than R8/3C/5C/MT over a range of sizes. The shallow taper grips more like an MT than the common but weaker 5C or R8.
    Last edited by J Tiers; 05-29-2014, 09:39 AM.

    Leave a comment:


  • becksmachine
    replied
    Originally posted by PStechPaul View Post

    It holds the Jacobs chuck taper adapter in place in the spindle, but the chuck still came loose since there was nothing to hold it.
    [edit] I found this deal on a 7 piece set of MT2 collets for $55 and free shipping. Think they might be OK (at least for my machine)?
    http://www.ebay.com/itm/7-PC-2-MORSE...-/111360385655
    It holds the Jacobs chuck taper adapter in place in the spindle, but the chuck still came loose since there was nothing to hold it.
    I think you are saying that the chuck came loose from the Jacobs chuck adapter?
    That happens a lot on these machines and many folks have devised various fixes for that problem. The most robust fix is to not use the chuck for milling.


    I found this deal on a 7 piece set of MT2 collets for $55 and free shipping. Think they might be OK (at least for my machine)?
    They look good to me.

    Dave

    Leave a comment:


  • PStechPaul
    replied
    My introductory post on this forum was about the problems I had with the drawbar in my machine:
    http://bbs.homeshopmachinist.net/thr...hlight=drawbar

    It holds the Jacobs chuck taper adapter in place in the spindle, but the chuck still came loose since there was nothing to hold it. I really need to make another drawbar, or modify the one I have. It is too long and extends through the top of the pulley / belt cover, and the washers rub inside the spline when I extend the spindle.









    [edit] I found this deal on a 7 piece set of MT2 collets for $55 and free shipping. Think they might be OK (at least for my machine)?
    http://www.ebay.com/itm/7-PC-2-MORSE...-/111360385655
    Last edited by PStechPaul; 05-29-2014, 03:54 AM. Reason: collets

    Leave a comment:


  • becksmachine
    replied
    Originally posted by PStechPaul View Post

    I would assume that the taper will fit pretty far into the spindle, and the drawbar will cause the jaws to tighten onto the end mill. As long as the mill diameter closely matches that of the collet ID, it should grip tightly and the taper should keep it from spinning. If the mill is slightly over or under size, however, the jaws may not close fully on the mill, and/or the angle of the taper may be compromised. But I think the tolerances are tight enough to make it work just fine, at least as far as the (admittedly limited) abilities of the machine.

    That was quite an adventure, and sometimes the chuck would come loose or it would catch and twist the head on the column. I "got 'er done" but the mill holders are a great improvement, and the collets will probably provide another two-fold improvement. If and when I get a "real" milling machine I may be surprised at how easy it is to do stuff like this. Actually, though, I think this was a bigger mill, maybe 5/8" or 3/4"?
    it should grip tightly and the taper should keep it from spinning.
    "should" being the operative word here.

    If the mill is slightly over or under size, however, the jaws may not close fully on the mill, and/or the angle of the taper may be compromised.
    If you think about it, the taper should not be affected as the collet will either stick out farther to accommodate a larger shank or pull in farther to accommodate a smaller shank, but the parallelism of the sides of the hole should not change. The only mis-match that would occur is if difference is large enough that the hole in the collet does not have complete contact with the shank of the tool due to the differing radii. And this is one reason for many collet systems having more than 3 "splits".

    But I think the tolerances are tight enough to make it work just fine, at least as far as the (admittedly limited) abilities of the machine.
    You are getting the idea.

    That was quite an adventure, and sometimes the chuck would come loose
    This begs the question, this chuck was not retained by a drawbar? Does the machine have a drawbar to use with those collets that you are going to order?

    That was quite an adventure, and sometimes the chuck would come loose or it would catch and twist the head on the column. I "got 'er done" but the mill holders are a great improvement, and the collets will probably provide another two-fold improvement. If and when I get a "real" milling machine I may be surprised at how easy it is to do stuff like this.
    You are probably unwittingly, but not unwillingly, reliving the historical process that led to the development of more modern tool holding systems. Morse tapers worked fairly well for retaining tools that had large thrust forces with relatively minor side load forces. When side loads are present, especially with even the relatively small withdrawing force that the helix of the end mill causes when it is cutting, no taper will hold without some means of retention. A drawbar for most of these applications, or a retaining key as it has been adapted to the morse taper.

    Dave

    Leave a comment:


  • PStechPaul
    replied
    I was unfamiliar with the ER type collet, so I found this:
    http://gemprecisiontools.com/er_type-collets.html

    The spindle of my machine has an MT2 taper and a 3/8-16 drawbar, and the collets I plan to buy look like this:



    I would assume that the taper will fit pretty far into the spindle, and the drawbar will cause the jaws to tighten onto the end mill. As long as the mill diameter closely matches that of the collet ID, it should grip tightly and the taper should keep it from spinning. If the mill is slightly over or under size, however, the jaws may not close fully on the mill, and/or the angle of the taper may be compromised. But I think the tolerances are tight enough to make it work just fine, at least as far as the (admittedly limited) abilities of the machine.

    This half-inch mill is very likely the same one I had used previously, in the Jacobs chuck, to mill off an irregular surface of an axle bracket for a small tractor, so I could install a ball bearing. That was quite an adventure, and sometimes the chuck would come loose or it would catch and twist the head on the column. I "got 'er done" but the mill holders are a great improvement, and the collets will probably provide another two-fold improvement. If and when I get a "real" milling machine I may be surprised at how easy it is to do stuff like this. Actually, though, I think this was a bigger mill, maybe 5/8" or 3/4"?





    Leave a comment:


  • J Tiers
    replied
    Originally posted by Jaakko Fagerlund View Post

    J Tiers, there are collet holders that fit the machine, as in have an MT2 taper in it and they cost next to nothing.
    Yes, I know there are holders with MT shank. But the original issue was the holder that stuck out too far. Adding a different holder, for ER instead of being weldon type, is not changing that.

    And, the holder plus collets may cost little.... although I think it is maybe a bit more than "next to nothing". However, the HF machines cost very little also. The one in question is basically a cheap drill press with a slightly better quill setup to more-or-less work for milling. It is a "Round column mill-drill", and not the heavier-duty type of those.

    point is that machines of this type do not provide for a collet of the ER type in the spindle. So the option is only for an adapter. If the adapter is a problem, as it may be here, then the user is stuck with whatever collet fits the spindle taper.

    Manual here

    http://images.harborfreight.com/manu...2999/42976.pdf

    Leave a comment:

Working...
X