STAR swiss lathe collet extension
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  1. #1
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    Default STAR swiss lathe collet extension

    So, my company picked up some Star swiss machines. I know, keep your opinions to yourself I probably agree. Anyway, the owner designed a collet extension to remove/replace the guide bushing, but it in my opinion will not work.

    The spindle extension will spin in a sleeve with no bearing. The tolerance is very tight, and is only cooled/lubricated by the intermittent way oil. I believe this will seize very quickly.

    I suggest to the manager (owner in different state) that we scrap the plan and start new. My suggestion uses the same set up as our Hanwas. It is essentially an extension that is housed with bearing support in the housing. The whole assembly moves with the main head. This may or may not be possible and why I am here posting. The problem is simply that the seat/flange ID that holds the guide bushing is significantly smaller (hence why there is no bearing in design) I suggest we pull this flange and make a new one that is the size needed. But the bigger issue is the ID on the cast housing behind it. I think we can bore it out with the machine. The issue is there is a flat on the casting behind the cast ID (I know, vague). I am not sure how thick the cast is there and If I can make the ID the size I want or will I have to go smaller? Also, is the machine even capable of opening this up with the proper tooling?

    Note: I am not a cnc machinist. I am a toolmaker. I am working on this project with our swiss cnc guy. Also, it is a VERY new company that is still getting on its feet so the owner/ management still have yet to truely let the reigns go and let us do our job, and with the equipment required. Lastly, we got these machines basically for free and the intended use is a hand load. I do not anticipate the need for bar feed in future. Plus, if we can run these on this one job we will meet our investment very quickly.

    Any thoughts?

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    I take it you’re trying to end up with a machine that works like the one in this video (starting at 0:45)

    CITIZEN A2-Vll Swiss Turning - YouTube

    Not sure what to suggest but maybe the video will give you some ideas?

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    Yes, thank you, that is what we would like to achieve. Unfortunately the owner does not yet see the importance behind purchasing quality new equipment. Anyway. The problem we run into is clearance. The spacing between the furthest forward position of the existing collet and the guide bushing (the place we would like tge collet if not even further extention) it a bit of a stretch. I'd guess it at 8 in or so. So we are going to be hanging out there a good 12 in I'd say. Forgive the guess work. I just got handed this puzxle today.

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    So he bought a Swiss.... and wants to turn it into a chucker.... Can I ask WHY? Are these new machines, or used? How old? Which models? What advantage does he hope to see from this?

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    Regarding your "no bearing and min lube" concern:

    I have an old Tornos that uses air to open and close the collet, and this runs originally at about a .001 total clearance between the rotating and the stationary parts, with no seal. I have had it stick dog-fast a few times over the years, and each time it gets a little more clearance in it after honing and turning away all the guald.

    This unit has good bearings on either side of the assembly. I kan't imagine if it was supported on one side only. ... And I only spin it up to around 2500 too.


    The rest of your concerns are really impossible to address without seeing (with my own eyes rather than pics and drawings) your machine and your proposal. I'm all for editing a stock tool to make what you want, but editing a Swiss to get a std chucker seems loonie to me too. Sounds like a loser.


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

    Think Snow Eh!
    Ox

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    That is a dumb idea. They weren't designed to be chuckers. It isn't as easy as yanking out the guide bushing. The headstock on a Star is not sturdy enough to accept the radial load from machining, that is what the guide bushing does. Without altering the mechanical limits of the headstock travel I would think your headstock collet extension would have to be real long which will reduce the rigidity even more. I have ran Stars for almost 30 years, including owning them and all maintenance work. In fact I am doing the final disassembly on one to haul it to the scrap yard as we speak. I am curious what model they are. On the other hand go ahead with the project and total all the time and money spent,when complete post a video here of it in action so we can laugh our ass off.

    P.S. If you need a chucker go buy one, it will be a lot cheaper in the long run and will work as intended.

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    Quote Originally Posted by TeachMePlease View Post
    So he bought a Swiss.... and wants to turn it into a chucker.... Can I ask WHY? Are these new machines, or used? How old? Which models? What advantage does he hope to see from this?
    Being able to convert to chucker mode is offered as a selling point on most new swiss these days. My L12 does it... but I've never bothered to put it in chucker mode.

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    Quote Originally Posted by danrudolph View Post
    Being able to convert to chucker mode is offered as a selling point on most new swiss these days. My L12 does it... but I've never bothered to put it in chucker mode.
    This guy doesn't have "new swiss" so the point is moot.

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    Quote Originally Posted by danrudolph View Post
    Being able to convert to chucker mode is offered as a selling point on most new swiss these days. My L12 does it... but I've never bothered to put it in chucker mode.

    And if you want the option to use it as a chucker, you buy one that was meant to do that, you don't buy one and try to modify it, that was my point.

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    Quote Originally Posted by TeachMePlease View Post
    And if you want the option to use it as a chucker, you buy one that was meant to do that, you don't buy one and try to modify it, that was my point.
    Was my point as well...

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    Quote Originally Posted by Dualkit View Post
    That is a dumb idea. They weren't designed to be chuckers. It isn't as easy as yanking out the guide bushing. The headstock on a Star is not sturdy enough to accept the radial load from machining, that is what the guide bushing does. Without altering the mechanical limits of the headstock travel I would think your headstock collet extension would have to be real long which will reduce the rigidity even more. I have ran Stars for almost 30 years, including owning them and all maintenance work. In fact I am doing the final disassembly on one to haul it to the scrap yard as we speak. I am curious what model they are. On the other hand go ahead with the project and total all the time and money spent,when complete post a video here of it in action so we can laugh our ass off.

    P.S. If you need a chucker go buy one, it will be a lot cheaper in the long run and will work as intended.
    I agree, it is a "dumb idea". But, unfortunately for myself and the swiss machininst, it is what the Co. owner bought and what he wants. He picked these machines up for dirt and wants to turn some kind of profit on them. Unfortunately for us this company is very new and the owner has not yet seen the value of his machinist's word. So, this is what he wants and what we will try to deliver.

    On the support issue, I would hope to house the spindle, and this housing would be supported by a flange where the guide bushing would normally be. A sort of guide bushing for the spindle housing if you will.

    As far as a model, I will have to get back to you tomorrow. I know they are old and I am fairly certain that STAR will no longer support/service the systems. They are from what I gathered from our swiss expert, POS machines.

    I also agree, If we need chuckers, then buy chuckers. Unfortunately, the owner does not yet see it this way. I do hope he begins to see the light when he realizes all the time and money he has wasted. If it were my company, we would be much better equip. But, I am not, and the owner is no machinist. He is an engineer who is running numbers and designing things that just won't work. The "Practical Machinist" in him just isn't there. We are going to just have to learn him over time. But for now, this is our order and so is our task.


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