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Save time by not having to hassle with using rings, spiders or dummy pieces of round bar to bore your Soft Jaws.
Simply slide the keys into position, close the chuck, mount and bore the jaws in the usual way.
The slot width and key width can be designed to allow for both internal and external clamping.
The keys are mounted below the surface of the serrated face of the sliding block and so the jaws can be mounted in any posiition as normal.
Click to watch the animated gif.
Seems a bit pricey having to replace all my chucks just so I can machine soft jaws easily.
Is that just and idea or is it available?
My first thought is that those little keys do not seem very beefy and they are going to cant in the slots which will probably finish up getting bellmouthed.
They also don't load the mechanism in quite the same manner as a ring out at the front of the jaws does and this can be important for getting best contact along the length of the jaws.
An open mind is a virtue...so long as all the common sense has not leaked out.
Hi Geoff, tnx for your reply.
Yes at this stage it is just an idea, I`m gonna get hold a second hand chuck
and try it out on that. It`s actually very cheap to do.
Firstly strip the chuck.
The Sliding Block (as Pictured) just needs a Wire Eroded/Spark Eroded or even Surface Ground slot.
I`ll need a steel disc that will sit on the back face of the chuck, using cap screws I can pull the inner ring of the chuck (this inner ring has the angled Tee Slots that drive the jaws) back toward the steel disc, the jaws must close onto a bit of round bar that is around 1-2mm bigger in dia than what you measure between the jaws when the inner ring is fully back (ie. the jaws are on full stroke inwards)
Take this whole arangement to a Milling machine and machine in the slots and tapped holes into the chuck body.
Make the keys, or design it around standard key steel as beefy as you like and you`re done.
Regarding the load mechanism you mentioned, well normally the bit of round bar being used for machining soft jaws is clamped pretty close to the line of the sliding blocks, I`m guessing the action of closing against the keys will also produce the flex you see of the jaws when the strain of the mechanism takes place.
I`m thinking that the key steel will be softer than the chuck body steel and will probably show signs of indentation before bellmouthing the slots. But even if you have to refurbish the slots and keys after months of use I still reckon it will be a great time saver.
Where I work we do low batch, typically between 3 and 15 parts and I`m forever messing about with rings and sh*t to bore the jaws. My lathe a Hyundai KIA SKT 250 MS has a sub spindle as well.
Joey-
First, cool animated gif - it presents your idea well.
I think that the Geof is onto something - the Jaws need to be preloaded against each other, not the body of the chuck. Imagine that two of the jaws are a bit sloppy where they engage the scroll, and one is tight. When the chuck is tightened, the tight jaw will contact the keys first, and you will feel resistance when only this one jaw is tight, and the other two jaws could potentially stay loose.
Keith
hi NEATman
I appreciate what you`re saying, they way I`m figuring is when you clamp the inner ring back, the bar the jaws are closing on must be clocked concentric with the OD prior to machining the body slots to blend with the sliding block slot. So by tapping the bar concentric it is hopefully taking into account any differing movement on each jaw position.
I was also wondering if perhaps I`d need to make slight adjustments to the thickness of the individual keys whilst machining of jaws and subsequent checking, to allow the a bit of adjustment in concentricity.
I know this statement is going to get hammered, but rarely, and I mean rarely, do I bore standard soft jaws with a ring on a hydraulic chuck. Typically I would bore them on the top of travel about .001-.002 oversize the diameter I am chucking -this also doubles as a good in process diameter check!. Typical concentricity is .001-.0015. Next time they need boring, which on some chucks is not everytime, I just move them in a serration and repeat. I am very tedious about deburring jaws and cleaning jaws, which helps! I have been doing this technique for over 18 years! Exceptions are extreme runout / concentric callouts (<.001) and extended length jaws that can flex, then the rules change. I also have ran machines with pnuematic chucks that required boring to a ring, but rarely do I preload standard length hydraulic chuck jaws !
Let the blood letting begin!
Mark T.
Hi Mark
hehe you must have a pretty ridgid set of slides on that chuck. My chuck is around 1 1/2 yrs old and i`d be lucky to hold .002 - .003" TIR.
But yeah there will be jobs when this key method wont be good enough and I`ll take the extra effort.
But hey if it works for even 70% of my work it`ll save me plenty agro.
Actually there are 9 different chucks at this operation where I do that technique on, 6 Kitagawas and 3 Pratt Burnerds. They vary from 8" to 15" chucks. Chucks vary in age from 3 years old to 14 years old. I use the same technique on all. The work varies from shaft work, to rigid slug work to thin walled work. Different materials can cause certian precautions, but 80% of the time with aluminum, crs, hrs, 4140 & stainless = standard jaw and never a plug! I just bore them very close to size and it works for me. I also bore jaws in a very particular fashion - relieving the diameter & face ...actually finishing the face of the jaw in a manner that it forms a small pad to bank the existing part face on...never full contact over the length of the face.
Give it a try! Even on the old chuck. Flip the switch to external chucking, bore to +.0015 the diameter you intend to chuck on ( assuming you held size! ) j/k
I will concede that even the older chucks here are well maintained.
Mark T.
Joey-
If you were to cut the grooves in the jaws and the body at the same time, while the chuck was tightened down on a round piece of stock, everything should repeat well when you add the keys.
I'm not sure you could do it all in one setup (unless you die-sink EDM it), as you had said the jaws are hardened, etc. Perhaps make the cuts with the chuck in pieces, and go back in and kiss grind the surfaces with a small grinder with the chuck assembled while the jaws are clamped on a pin?
Keith
NEATman
Basic research is what I'm doing when I don't know what I'm doing. Wernher von Braun
Yes that is my plan. To cut the slot in the hardened slides seperately first. Then rebuild the chuck using a plate on the back face of the chuck to pull the jaws tight against a pin and clock that concentric with the OD, and then mill the slots in the body and blend the sides into the hardened slot.
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