. .

Thread: Is this normal?

Page 2 of 2 FirstFirst 12
  1. #11
    Quote Originally Posted by JAZZCNC View Post
    You have to remember these are rotary axis, not lathe's so the runout will hardly be noticeable for the majority of work and if you require higher precision then you either use 4 jaw chuck or use soft jaws and bore them as MC suggested. The pulley runout is of no concern whatsoever in this application.
    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.

  2. #12
    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!
    You think that's too expensive? You're not a Model Engineer are you? :D

  3. #13
    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.

  4. #14
    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

  5. #15
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 4 Days Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,908. Received thanks 360 times, giving thanks to others 8 times.
    Quote Originally Posted by mekanik View Post
    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.

    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.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  6. #16
    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
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

  7. #17
    Quote Originally Posted by Kitwn View Post
    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...

    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.

  8. #18
    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.

  9. #19
    Quote Originally Posted by cropwell View Post
    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.

  10. #20
    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.

Page 2 of 2 FirstFirst 12

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Strong vibrations in ball screw linear actuator - is it normal
    By mbridge87 in forum Gantry/Router Machines & Building
    Replies: 45
    Last Post: 25-01-2021, 06:27 PM
  2. Replies: 27
    Last Post: 23-12-2020, 09:49 PM
  3. Is having a wobbly bottom normal? Drill Vice...
    By Dangle_kt in forum Workshop & Equipment
    Replies: 9
    Last Post: 13-01-2017, 04:39 PM
  4. 1st time setting up.. whats normal..
    By Marlin in forum Motor Drivers & Controllers
    Replies: 26
    Last Post: 01-09-2014, 04:53 PM
  5. Looks like the normal first page has gone awry.... or is it my PC?
    By WandrinAndy in forum General Discussion
    Replies: 22
    Last Post: 03-10-2012, 08:05 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •