This is a 4-jaw chuck... which is why I expected higher precision, but sure, I understand that for most things this error will not make a difference.Quote:
Originally Posted by JAZZCNC
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This is a 4-jaw chuck... which is why I expected higher precision, but sure, I understand that for most things this error will not make a difference.Quote:
Originally Posted by JAZZCNC
4 Jaw INDEPENDENT chucks give better precision than 3 jaw chucks because each jaw is adjusted INDEPENDENTLY.
What you have is a 4 jaw scroll chuck with nothing to give you better precision than a 3 jaw scroll chuck.
You can get scroll chucks to meet your expectations but expect to spend a lot of money, more than you expect!
Yes, I understand the independent chuck jaws can give good precision because each jaw can be adjusted individually, that's obvious. But it also means a lot of extra time before the work piece starts spinning. Anyway, it looks like that I could get MUCH bigger and better precision by just cleaning the surfaces.
I seem to recall you can get 3 jaw chucks that have adjustment in the backplate, you put a short mandrel in the jaws and dial out the runout then lock it.
Regards
Mike
I don't think I've ever seen a scroll chuck with that kind of adjustment, but I have seen collet chucks with that kind of setup.Quote:
Originally Posted by mekanik
I should have said independent 4 jaw in my original post, but Magicniner has already clarified that.
You can improve accuracy by grinding/boring the jaws (remember you need to clamp them onto something near the correct size first, to preload them, and standard jaws are generally hardened to some extent), but as I mentioned, that accuracy is likely to vary over the scroll. Scrolls are rarely a precision component, and accuracy varies over the scroll.
This link is to a video by Dan Gelbert who started from nothing and built up a whole business based on high precision machining. In this video he demonstrates a scratch-built lathe accurate to one micron, including details of the chuck. This is only one of many videos by Dan. Fascinating stuff for geeks like us.
Kit
https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=40s
Thank you for the link. It's really interesting to watch, too bad it ended so suddenly. I wish there was a part two and three also...Quote:
Originally Posted by Kitwn
He said it's "very easy" to make a machine like that, though I think that's overestimating most of the humanity, because even though I regard myself as very capable of doing many things, I doubt I could make one which is as good as his machine. Anyway, it was a joy to watch that. I love the idea of air bearings also and his demonstration of it. I also love how quiet that machine runs, but I suppose that's largely one benefit of the air bearings as well.
Back to the topic, yes his chuck is special, like the rest of the machine. The idea of moving pins in the chuck jaw is good, but again, requires very high precision, so in the end, I think traditional chucks are better for the "average Joe" most of us are.
A 4 jaw chuck allows you to hold square stock. An independant 4 jaw allows you to do offset milling, but is a PITA to set up every time if you don't need it.
Yes. That's why I was only interested in the self centering type. Individually adjustable chucks are very good when really needed, but I figured that an independent 4 jaw is a real PITA most of the time because every time you swap a work piece you must recenter it, so in the end you might not get better accuracy in general due to lack of patience, even if on occasions you can get 100% accuracy after spending a lot of effort on centering. I don't think I will buy a 4-jaw chuck with independent jaws, but will however buy a 3-jaw chuck later on since that is more suitable for some work.Quote:
Originally Posted by cropwell
Another option is multisize collet chucks. https://www.ebay.co.uk/b/burnerd-collet/bn_7024823313
Still quite a few around and a set will cover a wide range of sizes with very good runout. There are several types but mine (EC?) go up to 38mm with no gaps. You might get a chuck for £200 and a set of collets for a similar price if you keep your eyes open.