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method of mounting tooling on a mill/drill

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  • J Tiers
    replied
    Originally posted by Paul Alciatore View Post

    I do see your point about a mid length, 45 degree taper. It would have good accuracy in all directions, but you still have that one inch or so of length. Perhaps it would not be much of a problem when changing tools as only a fraction of an inch would be needed for the tool to be rotated out or in, [b]but there is that one inch of lost vertical work envelope. I was looking at a way to keep that down to 1/2 to 1/4 of that amount.[b/]
    If in the spindle, the entire holder could be swallowed up to the top rim.... that would mean ZERO lost to the holder, aside from removal. Of course, removal IS the issue, but in this road of thinking, there are two choices, you decision as to which poison you take.

    1) Have toolholder swallowed in spindle, but then have a need to remove it which means extracting it, presumably axially. That takes a distance which at worst is the full depth of the holder PLUS the length of the tool axially.

    2) Have toolholder slide out sideways somehow. never mind whether it is practical. That requires a depth at worst of the full depth of toolholder, PLUS the length of the tool axially.

    Hey... those are almost exactly the same!

    So....

    Now consider a larger spindle diameter..... toolholder goes down the length of it, on the end of an inside "push bar". The push bar forces it against a taper inside the spindle, trapping the holder in position and securing it.

    ZERO loss of daylight inder the spindle, AND the fairly steep, maybe 45 deg included angle tapers give very accurate positioning.

    Hey... we might have a potential winner here.

    What consideration does it not cover?

    Leave a comment:


  • spinningwheels
    replied
    This system uses a iso 30 , but it seems to be a quick change toolholerd that also needs a lot les hight to change the tools
    http://www.marktplaats.nl/a/doe-het-...reviousPage=lr

    Leave a comment:


  • Paul Alciatore
    replied
    Hey, J, calm down. I was just trying to present a different idea here. Original thinking.

    I was attempting to address the OP's concern. He wanted a way to change tools without cranking up and down. Sure there are other ways to change tools and I as well as most of the folks here who use a vertical mill have done things like cranking the work to the side.

    You say, "I expect it illustrates more clearly my responding to your extreme concern about axial location.... not any actual concern about it on my part......". OK, you are not concerned. That is fine. Perhaps I should not have added this to the original requirement, but it does seem logical. I have observed that tapers have very poor axial positional control. At least shallow ones do. So, as far as my concern being extreme, I doubt it. Wouldn't that be a real plus on a CNC machine? Probably on a manual one when identical parts are being made. Anyway, yes I was concerned about it as I looked at the problem, but hardly extremely concerned.

    Then you say, "Then also, "approximating a sphere" is not really applicable.... You need to have a very large ratio of diameter to length to cause that to be a serious problem if any care is taken to align the tapers. I suppose a 3" diameter, with a 1/4" length might be getting to a "spherical section".... but that's rather extreme." Well, a very short taper is exactly what I was discussing. If you want to avoid cranking up and down (or cranking the work sideways which can take just as long) then you need a mounting method that does not require a very long axial movement. If you read my post carefully, you will see that a very short, wide diameter taper is exactly what I was talking about. To quote myself, "That short taper starts to approximate a spherical surface." Notice the word "short" in there.

    I know that the CAT type tapers are widely used and they DO work with good positional accuracy in all directions. But I assumed that the OP has an R8 or other small angle taper style spindle and adding a CAT type adapter would be somewhat awkward at best. I would think you are going to lose at least two inches of vertical clearance under the tool to the taper alone. By the time you get down to the tool tip, it will be hanging WAY out there.

    Again, we are not talking about a new spindle, just a method of attaching tools to the existing one. So, your comments about a pin/socket not being easily replaced are not valid. The spindle end of my proposed adapter would change just as easily as a Weldon style holder. It may be a bit more expensive, but it would be easy to change. I have never used one or even held one in my hand, but are Weldon holders, regardless of price and quality level, really accurate to fractional tenths? I mean, do they actually hold a tool that well centered? Wouldn't at least part of that depend on the accuracy of the size of the shank on the tool itself? And there has to be some allowance to allow the tools to be inserted and removed: I would imagine a few tenths, at least. Or do they use an interference fit? Seems that would make inserting them very difficult and removal almost impossible. But, as I said, I have not used them so I don't know.

    I do see your point about a mid length, 45 degree taper. It would have good accuracy in all directions, but you still have that one inch or so of length. Perhaps it would not be much of a problem when changing tools as only a fraction of an inch would be needed for the tool to be rotated out or in, but there is that one inch of lost vertical work envelope. I was looking at a way to keep that down to 1/2 to 1/4 of that amount.

    Leave a comment:


  • mattthemuppet
    replied
    Originally posted by Rosco-P View Post

    Maybe the OP needs to start using stub or screw machine drills instead of jobbers length.
    that's something I keep coming back to, it would make switching back and forth between milling, drilling and countersinking/ chamfering a lot easier. Just have to save up the pennies, looks like there are 29pc fractional sets for ~$60 which isn't too bad.

    Leave a comment:


  • Rosco-P
    replied
    Originally posted by Paul Alciatore View Post
    That sounds like more trouble than cranking the head up and down. But usable if you are at the limit of vertical travel.
    Three pins/points is a common part locating method for both wood and metal work. Maybe you never used toggle clamps: http://www.destaco.com/horizontal-hold-down-clamps.html They are very quick and hold securely.

    With the vise slid out of the way, tooling could probably be changed without moving the head. A power draw bar would still speed things up.

    Maybe the OP needs to start using stub or screw machine drills instead of jobbers length.
    Last edited by Rosco-P; 08-22-2014, 11:52 AM.

    Leave a comment:


  • MrFluffy
    replied
    In the "tips and tricks" book, it mentions cutting toolholder shanks down to save cranking the knee as far for toolchanges when its appropriate, ie drill chucks, smaller mills etc.

    Leave a comment:


  • J Tiers
    replied
    if the tool can be pulled out of the work enough to crank the work sideways out of the way, I don't suppose there would be much problem changing tools. That's most often possible, and seems a lot simpler than some sort of magic 2-way dovetail or the like.

    But, a smaller taper length than typical with MT or B&S is obviously going to be much nicer to work with than the typical tapers on older machines. At least those NOT using CAT type tapers.


    Originally posted by Paul Alciatore View Post
    Your comments on the taper in the third paragraph illustrate my thought that you do need better control in the axial direction. This is why lathe collets have stops fitted to them so that multiple parts can be located in the same position on the same day, hour, even minute.

    The problem with a shallow taper is you start to lose angular accuracy.
    I expect it illustrates more clearly my responding to your extreme concern about axial location.... not any actual concern about it on my part......

    I see a lot of "may have", and "could" type concerns, what might be characterized as "theoretical" concerns.... But as a practical matter, the CAT series tapers, which are pretty steep as tapers go, are sufficiently good that they have become a standard.

    A shallow taper with a lot of wedging action has much more response to axial tension than a steeper taper. "One up" for steeper tapers, I'd say.... They do not let the tension wedge the socket open.

    Then also, "approximating a sphere" is not really applicable.... You need to have a very large ratio of diameter to length to cause that to be a serious problem if any care is taken to align the tapers. I suppose a 3" diameter, with a 1/4" length might be getting to a "spherical section".... but that's rather extreme. You can mis-align nearly anything if you try hard enough, but again, the CAT tapers work well, without troubles.

    Vertical turret mill tooling, most of which is 0.5" or smaller, would work fine with a diameter of say 1.25" and a taper of 45 deg included angle, taper being an inch long axially. I don't suppose anyone would have problems with spherical sections at that taper, and there would be almost a half inch end for drawbars.

    It would be about as easy as can be to pop in even if it had to be canted a bit to get past the workpiece.

    And I strongly doubt any serious issue with axial location would come up.


    Some of your other comments relate to weldon holders. And there is some point to it..... but if a fractional tenth of axial misalignment is a concern for you, then you are already not considering any weldon type holder, both from an axial location point of view, plus due to what you would consider an unacceptable centering.

    Alternates, such as collets, suffer from other issues, and *still* have basic concentricity issues. A new collet in the $200 class will be quite accurate... Ones in the $5 a pop class are just "pretty decent for the price". Errors of a thou or more are to be expected in the $5 class, which is likely to exceed whatever concentricity issues the weldon holder may have, without considering errors due to off-center drawtubes, etc. The weldon holder is aligned by the typical MT taper shank, and is not as easily canted off-axis by a drawbar, nor does it have the long flexible and misalignable "fingers" of the collet.

    Now, it is also VERY important to note here that there is a *big difference* between a weldon holder, which can be easily scrapped and replaced if worn, and a machine spindle, which needs a robust tooling recess, since the spindle is not intended to be regularly scrapped and replaced....

    What can be tolerated for a replaceable holder is quite unacceptable for a more permanent spindle feature. I think attention should be paid to the difference when making these sorts of comparisons............
    Last edited by J Tiers; 08-21-2014, 07:39 PM.

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  • Paul Alciatore
    replied
    That sounds like more trouble than cranking the head up and down. But usable if you are at the limit of vertical travel.


    Originally posted by Rosco-P View Post
    I'm familiar with fixturing sub-plates The OP needs something "magical" that will overcome the lack of room between top of workpiece (probably in vise) and the spindle. He could use three dowels to locate the vise on the mill table and toggle clamps to hold the vise in position. Unlock the vise, slide it out of the way, change tooling, slide vise back into position and lock it down.

    Leave a comment:


  • Paul Alciatore
    replied
    Looks like you're a big fan of Lincoln.


    Originally posted by RichR View Post
    Why not make a side loading tool holder, something like this:



    Too change a tool, remove the socket head screws and the C shaped piece, swap cutters, bolt the C shaped piece back on.
    I too save and use those return envelopes. Great for filing things like receipts and, of course, scratch paper. One more reason for not converting to paperless bills.

    Leave a comment:


  • Paul Alciatore
    replied
    Your comments on the taper in the third paragraph illustrate my thought that you do need better control in the axial direction. This is why lathe collets have stops fitted to them so that multiple parts can be located in the same position on the same day, hour, even minute.

    The problem with a shallow taper is you start to lose angular accuracy. So, at the taper you may have very good X, Y, Z positional accuracy, but at the tool tip, which is hanging out several inches lower, you can get a lot of run out. The length of a conventional taper controls this, but a shorter taper and especially one at a larger angle, like 45 degrees, will rotate sideways much more easily. That short taper starts to approximate a spherical surface.

    By the way, it is not just the wear that changes the axial position of a taper when tightened. Also the amount of force used in tightening it will make a major change. Even if you use a torque wrench, you will still have variations due to lubrication and contaminants between the surfaces. Oh, and temperature.

    The added length of some of these schemes has been mentioned. Well, yes they would reduce the tool to table space would be reduced unless you can bury some of the mechanism inside the mill's spindle. I don't see this happening with a R8 taper and will probably be difficult with most of the other tapers currently in common use. If you want a new tool mounting method that does not require so much up-down cranking, then you are going to have to separate this requirement from the requirement for a maximum amount of space under the tool. If you really need the maximum amount of vertical working space, you can just mount each tool in a matching collet, but this brings you back to the cranking problem. Life is a series of compromises.

    A further thought on the need for using a taper. One of the mostly highly regarded methods of mounting a milling cutter is the fixed hole holder, with a set screw for fixing the milling cutter in place. Personally, I always worry about the buildup of tolerances and allowances in this system. It seems to me that an off axis tool is almost the inevitable result of this system. I mean, that set screw is just constantly forcing it off center, isn't is? And do you always buy a dedicated holder for each and every tool that you own? I suspect that many will be constantly changing holders/tools for many jobs, so what about wear there? Yet, this system is widely used and many swear by it. Oh, all those milling cutters swinging around off center and cutting extra wide swaths with only one of their 4 or 5 flutes.

    I still feel that a short pin, without any taper, is a workable device. Even with a little clearance (tenths?), if the angular alignment is good (my outer ring surface), then the error at the tool tip will be small. Not a perfect solution, but workable. And, as I showed above, it can be done with only 1/2" or less of extra vertical space for tool changing.

    As far as different tools having different lengths, yes they do. It is hard to get around that. Live with it.


    Originally posted by J Tiers View Post
    While I am convinced you require a taper for any credible mounting of a rotating tool, the taper should not need to be long.... We think of tapers like an MT or the like, but there are chuck mounting tapers that are quite short relative to their diameter, and which work very well indeed.

    The taper also may not be a shallow taper (shallow being closer to parallel with axis). Steeper tapers alleviate the problem of axial location more-or-less in proportion to their steepness.

    With a shallow taper, a slight amount of wear or error makes a very large (in relative terms) change in axial position. The taper changes very little in diameter per thou of length, and ratio may be 10:1 or more.

    A steeper taper reduces that problem. a 45 degree taper reduces it to 1.414 :1, which is likely to be as far as you need to go. And the steeper taper gives more area per unit of length axially, as well, reducing the wear problem, ans well as being easier to clean.

    A steeper taper then would allow a shorter taper to be made without needing ridiculous accuracy to maintain axial position. It may be possible to minimize table or head cranking.

    Since all tools have some length if they are useful, I do not see the idea of avoiding table cranking etc as being realistic. Even if you had a magical slide-in-from-the-side mount with perfect alignment, the tool length is bound to give problems in some setups at least.

    And it is possible in many cases to bring the tool in at an angle and slide it into the socket. That is easier with a steep taper and more "open" socket than with a longer shallower taper.

    Leave a comment:


  • Paul Alciatore
    replied
    Originally posted by RussZHC View Post
    ...<snip>...

    To me it sounds like motorizing some axis is a "solution".

    ...<snip>...
    Gee, I wonder why they don't do that? Sounds like a "no brainer".



    Don't look here:

    http://www.grizzly.com/products/Heav...wer-Feed/G0755

    Leave a comment:


  • Rosco-P
    replied
    I'm familiar with fixturing sub-plates The OP needs something "magical" that will overcome the lack of room between top of workpiece (probably in vise) and the spindle. He could use three dowels to locate the vise on the mill table and toggle clamps to hold the vise in position. Unlock the vise, slide it out of the way, change tooling, slide vise back into position and lock it down.

    Leave a comment:


  • RichR
    replied
    Why not make a side loading tool holder, something like this:



    Too change a tool, remove the socket head screws and the C shaped piece, swap cutters, bolt the C shaped piece back on.

    Leave a comment:


  • Toolguy
    replied
    You can do that with a tooling plate bolted to the bed. It has tapped holes for bolts and reamed holes for dowel pins, usually in an alternating pattern.

    Leave a comment:


  • Rosco-P
    replied
    Originally posted by J Tiers View Post
    Since all tools have some length if they are useful, I do not see the idea of avoiding table cranking etc as being realistic. Even if you had a magical slide-in-from-the-side mount with perfect alignment, the tool length is bound to give problems in some setups at least.
    What about a different approach. a "magical", slide in from the side work alignment method/device. Clearing the vise or workpiece fixturing from under the spindle might give you enough space to change tooling. It would require a positive way to reposition the work holder on the table within a couple thou. Then you might not have to crank the head up every time to change tooling.

    Leave a comment:

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