Problem ID Expansion Clamps?


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  1. #1
    Member IsakAndersson's Avatar
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    Default ID Expansion Clamps?

    Hello. I've got a problem with workholding at work. The parts we make are mostly hydraulic chucks. That means thin walls that we are not allowed to clamp on due to deformation. Our solution so far has been soft jaws in a three-jaw chuck clamping on the OD. This got two problems. First problem is it's just not enough clamping force meaning the parts fly all over the place even with reduced feeds and speeds. Second problem is clearance, meaning we have to do things in multiple setups sometimes, which adds a lot of time.

    So the question is, is it possible to use ID expansion clamps where you only have about 6mm of surface to clamp on? Keeping in mind the inside diameter of the parts ranges anywhere from 20mm to 120mm. If so, what type of clamp should I use? Any brands to look for or avoid?

    I've marked the part in green where we are allowed to clamp. Obviously, this is not the real drawing because... you know.

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    Attached Thumbnails Attached Thumbnails ID Expansion Clamps?-hydraulic-chuck-1-jpg  


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    Member deadlykitten's Avatar
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    Default Re: ID Expansion Clamps?

    hy

    Our solution so far has been soft jaws in a three-jaw chuck clamping on the OD. This got two problems. First problem is it's just not enough clamping force meaning the parts fly all over the place even with reduced feeds and speeds. Second problem is clearance, meaning we have to do things in multiple setups sometimes, which adds a lot of time
    please explain a bit more why does your part fly off when soft jaws are use, or please share real/close to real image/drawings; normally, soft jaws should deliver

    if l/d increases, then there may be some contact issued; i don't know, i can't figure out what's hapenning there

    about multiple setups, if you wish for an opinion, i need to know your current approach

    is it possible to use ID expansion clamps where you only have about 6mm of surface to clamp on? Keeping in mind the inside diameter of the parts ranges anywhere from 20mm to 120mm. If so, what type of clamp should I use?
    on 6 mm, you can hold parts up to o200, or even more; issue is not the 6mm, but the l/d and the tir requirements

    i need more details, in order to try to provide a solution, maybe you can avoid entirely that id clamp / kindly



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    Member IsakAndersson's Avatar
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    Default Re: ID Expansion Clamps?

    I guess I can share a photo of my setup. The main issue is during milling operations the radial forces sort of "suck" the part out of the jaws. Drilling is usually fine.

    Attached Thumbnails Attached Thumbnails ID Expansion Clamps?-img_20210805_164132715-jpg  


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    Community Moderator Jim Dawson's Avatar
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    Default Re: ID Expansion Clamps?

    A stub arbor might work the best for overcoming the milling forces. Secured from the end with a screw would prevent the part from walking out.

    The goal is to locate on the ID, but hold the part axially.

    Jim Dawson
    Sandy, Oregon, USA


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    Member deadlykitten's Avatar
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    Default

    Inverse forrces, so to push instead of pull, by changing machinig strategi, and/or use mills with reversed helix, and/or change right to left hand tool

    you cant expect grip from a manual chuck; the archimedic spiral wears fast when being used inside cnc



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    Member IsakAndersson's Avatar
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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by Jim Dawson View Post
    A stub arbor might work the best for overcoming the milling forces.
    Excuse my ignorance, but what exactly is a stub arbor? Do you have a link to a seller or some other resource that could point me in the right direction? I'll admit workholding is one of the overlooked things at my workplace and so I don't really know much about it. I blame my boss, really.



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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by deadlykitten View Post
    Inverse forrces
    Yeah, I've tried that. Problem is it either pulls the part out on the way in or if you go the other way then it pulls the part on the way out. Not sure which scenario is better but both are a problem.
    Quote Originally Posted by deadlykitten View Post
    you cant expect grip from a manual chuck
    Heh, yeah. Tell it to my boss. Not easy convincing him of anything.



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    Member deadlykitten's Avatar
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    Default Re: ID Expansion Clamps?

    maybe there is an aproach that can handle differently the way in, out. I need a video, or simulation, or something. Try smaller tools, they are less agresive. If grip lowers, you need to reduce specs, thus increase machining time

    maybe the stub arbor will be pulled from the chuck

    if chucks are failing, try to create a custom fixture, like bolting those arbors directly to the triunion just like jim said, kind of secured with a screw



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    Default Re: ID Expansion Clamps?

    Haha, use a bigger hydra chuck, so to grip a smaler one . You said you are crafting those



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    Community Moderator Jim Dawson's Avatar
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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by IsakAndersson View Post
    Excuse my ignorance, but what exactly is a stub arbor? Do you have a link to a seller or some other resource that could point me in the right direction? I'll admit workholding is one of the overlooked things at my workplace and so I don't really know much about it. I blame my boss, really.
    A stub arbor is an arbor that you make to hold a part from the ID, but grips the part axially. You just make them as needed for the job at hand.

    Here is an example of a quick one I made to hold a cylinder with a 1'' bore so I could do the machining on the OD. Because the operations are all done in basically one setup, the ID is perfectly concentric to the OD.

    The arbor made from 2'' stock.
    ID Expansion Clamps?-img_0608-jpg

    Threaded the end and slid the cylinder on the arbor

    ID Expansion Clamps?-img_0614-jpg

    And the finished part, ready for the second operation in the mill.
    ID Expansion Clamps?-img_0617-jpg

    Sometimes I drill & tap the end of the arbor for a bolt, other times, like the example above, I thread the arbor OD. This part is on the edge of having too much stick out for the operation, so I elected to use a center, many times I do not use a center. I have used this technique on both manual and CNC machines, including 4th axis work in the mill.
    .
    .

    Attached Thumbnails Attached Thumbnails ID Expansion Clamps?-img_0617-jpg   ID Expansion Clamps?-img_0608-jpg   ID Expansion Clamps?-img_0614-jpg  
    Jim Dawson
    Sandy, Oregon, USA


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    Member IsakAndersson's Avatar
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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by Jim Dawson View Post
    A stub arbor is an arbor that you make to hold a part from the ID, but grips the part axially. You just make them as needed for the job at hand.
    I see. Wouldn't that put a force on the thin walls tho? These parts are very delicate and if they're out of round by just 0.01mm it's a scraped part. Maybe I'm missing a way to clamp them where it only puts pressure on the "hat" portion of the part (the 20mm portion)?



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    Default Re: ID Expansion Clamps?

    Just to clarify what I'm trying to do I made a rough cad sketch. The idea is to have a tapered screw that expands the collet to hold the part. Do you think this will work or no?

    Attached Thumbnails Attached Thumbnails ID Expansion Clamps?-hydraulic-chuck-id-collet-1-png   ID Expansion Clamps?-hydraulic-chuck-id-collet-2-png  


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    Default Re: ID Expansion Clamps?

    This thread is really good - I'm always interested in learning more about workingholding from you guys.

    Regarding the OP's question - I know Mitee Bite makes ID clamps, and you may want to check them out and see if they might work for you. You can even have different coatings to increase friction. However, if you've got a big moment arm on the area you're machining, that may be difficult to hold true.

    Have you considered changing your order of operations? It may be a good idea to drill the center hole out undersized initially to provide a larger clamping area, or even threading it to provide a holding place. And then you can finish boring it out at the end.



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    Community Moderator Jim Dawson's Avatar
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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by IsakAndersson View Post
    Just to clarify what I'm trying to do I made a rough cad sketch. The idea is to have a tapered screw that expands the collet to hold the part. Do you think this will work or no?

    What you are proposing there is called an expanding mandrel, or as you correctly state, an expanding collet, a common way of holding difficult to hold parts.

    Will the concept work? Absolutely. Will it work for this specific application? Maybe.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by burbingus View Post
    I know Mitee Bite makes ID clamps, and you may want to check them out and see if they might work for you.
    Yes, I have checked them out. Maybe ill send them an email and see what they recommend.
    Quote Originally Posted by burbingus View Post
    Have you considered changing your order of operations?
    Yes, I have and I, as a mill-guy, agree that it would be better to do it that way. Problem is the lathe-guys think it's the other way around and they usually decide the order of operations. I mean the only drawback I can see to doing the milling first is that you get some Intermittent cutting over some of the features which can make the surface finish not quite as good. But that's about it I think.



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    Default Re: ID Expansion Clamps?

    BTW. Just for ****s and giggles. This is what the chuck key looks like after about 200 of these damn parts. I think I must've gone thru about 10 of these poor things by now.

    Attached Thumbnails Attached Thumbnails ID Expansion Clamps?-poor-chuck-key-jpg  


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    Community Moderator Jim Dawson's Avatar
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    Default Re: ID Expansion Clamps?

    I'm guessing here that your main problem is milling the clearance pocket in the ''Hat''

    If you grab the 6mm area with the chuck jaws or any other work holding device, you may still have the problem of it pulling out of the chuck because there is just not much to grab onto. But if you put a ''bolt'' through the center of the part to secure it axially, that would prevent it from pulling away from the chuck. This ''bolt'' could be a shaft that is passed through the 4th axis and puts some pressure on the part axially, wouldn't take much to hold the part in position while the chuck is holding the part radially.

    Jim Dawson
    Sandy, Oregon, USA


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    Member deadlykitten's Avatar
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    Default Re: ID Expansion Clamps?

    hello again so far, i understood why your soft jaws are failing etc, and you shared that photo at #3, in which the big diameter is far from the chuck; proposed solution was the one with the arbor, and if you wonder about pressure/deformation, simply feel it at hand, and use a dial to check tir, or the probe in the machine; however, even if tir exists, this does not mean that your part is a fail ( there is elastic and plastic deformation/tir, thus part may flex, or may deformate ), simply because, the milling operations should not be true with the turning operations, but within a tolerance that can be > tir between od and id ... it may seem messy, but, to clarify, i need drawings, etc; not all operations must run true, but only some, and the difference may be reduced by final balancing and removing weight, just like when crafting a crankshaft; i have seen such operations on hydraulic chucks

    also, you seem to wonder how to clamp the part, from the inside, on that 6mm area, and i guess, that, in such a case, the big diameter will be closer to the chuck, thus it seems that you are discussing a fixture that is different from the image that you shared at #3, so i am confused

    no one knows what you know, so ... / kindly


    BTW. Just for ****s and giggles. This is what the chuck key looks like after about 200 of these damn parts. I think I must've gone thru about 10 of these poor things by now.
    if the key looks like that, may be a good idea to recut the jaws at a different arhimedic spiral phase, so to get it back into the elastic behaviour, where is more grip; however, considering that the key looks like that, maybe is from soft metal, or maybe there is too much excess force; by the way, for the setup in image 3, what is the tir ? is it checked ? i mean if guys are holding to that key like thier life depends on it, and the clamping tir is <0.01, then you are lucky



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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by Jim Dawson View Post
    I'm guessing here that your main problem is milling the clearance pocket in the ''Hat''
    Correct.
    Quote Originally Posted by Jim Dawson View Post
    But if you put a ''bolt'' through the center of the part to secure it axially, that would prevent it from pulling away from the chuck.
    Not a bad idea, honestly. I'll have to think about that one. Still doesn't fix the issue with multiple setups, tho, and if someone else is gonna run the parts we better use a torque wrench, or those parts are getting scraped for sure.



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    Default Re: ID Expansion Clamps?

    Quote Originally Posted by deadlykitten View Post
    so i am confused
    Well, obviously the photo that I shared is what we are doing now. The CAD image that I shared is what I'm thinking about doing instead. Sorry if I wasn't clear on that.
    Quote Originally Posted by deadlykitten View Post
    what is the tir ?
    You mean the runout of the 3-jaw shuck itself? It's pretty bad, to be honest, but I don't think it's because of the clamping force. If I clamp hard or lightly the runout is still about 0.15mm. Not sure if it comes from the shuck itself, the jaws, or the spiral being worn. Probably all of the above. That being said, those chucks were pretty bad even when they were completely new. You get what you pay for I guess.



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