Free 173 Best Homemade Tools eBook:  
Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 27

Thread: Improving a lathe spindle head.

  1. #1
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    807
    Thanks
    328
    Thanked 1,328 Times in 404 Posts

    tonyfoale's Tools

    Improving a lathe spindle head.

    For some time I have been planning to change the single phase, single speed motor on my lathe for a larger 3 phase motor driven by a VFD (Variable Frequency Drive). The infinitely variable motor speed would allow me to eliminate the multiple pulley speed change system, but there is a problem when running a motor at low speed with a VFD. For a given spindle speed the spindle torque from a motor running at slow speed is less than achieving the same slow speed by mechanical gearing, for a given motor. A way around this problem is to use a vastly oversize motor.

    This post is not about fitting the motor but is about some changes to the lathe head that the motor and drive system enabled me to do. My motivation was to make the head stiffer and less prone to vibration and chatter. Not that I had particular problems in that area but I find it hard to resist when I see a better way of doing something.

    Although I show how I did this on my lathe, a 1240 JET, the ideas are certainly applicable to those lathes which do not have a closed in spindle head.

    Improving a lathe spindle head.-lathegbh005.jpg Improving a lathe spindle head.-lathegbh057.jpg Click images for full size.

    I have prepared a PDF file with all the reasoning and details at Inflicting GBH on a lathe

    I plan to put together a video about this but in the meantime here is a link to a 2 minute video showing some stiffness measuring.
    https://www.dropbox.com/s/7t7ho5x1qq...Lathe.mp4?dl=0

    Warning: The pdf shows images of severe GBH to a lathe and those with extreme sensitivity to mechanical abuse are advised to look away now.

  2. The Following 11 Users Say Thank You to tonyfoale For This Useful Post:

    DIYSwede (06-18-2019), jimfols (06-18-2019), Jon (06-18-2019), Little Rabbit (06-18-2019), olderdan (06-18-2019), Scotsman Hosie (06-22-2019), Seedtick (06-18-2019), threesixesinarow (06-21-2019), Tonyg (06-19-2019), Toolmaker51 (06-23-2019), Tule (06-19-2019)

  3. #2
    DIYSwede's Avatar
    Join Date
    May 2019
    Location
    Stockholm, Sweden...
    Posts
    85
    Thanks
    112
    Thanked 98 Times in 35 Posts

    DIYSwede's Tools
    Thanks for yet another excellent and humorous writeup, Tony!

    2 personal cents:
    -Having the headstock trapezoid-shaped (rather than just box square) should (at least in my empirical theory) make it more stable,
    and filling it with concrete will also add to that (apart of being over the top - but that goes without saying).

    Q: -What about you workshops temp differences thru the year, combined with the "linear thermal expansion" of CI vs steel and concrete?
    Any thoughts or hypotheses on that?

    -Please keep up all your different projects and good spirits!

    Cheers
    Johan

  4. #3
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    807
    Thanks
    328
    Thanked 1,328 Times in 404 Posts

    tonyfoale's Tools
    Quote Originally Posted by DIYSwede View Post
    Thanks for yet another excellent and humorous writeup, Tony!

    2 personal cents:
    -Having the headstock trapezoid-shaped (rather than just box square) should (at least in my empirical theory) make it more stable,
    and filling it with concrete will also add to that (apart of being over the top - but that goes without saying).

    Q: -What about you workshops temp differences thru the year, combined with the "linear thermal expansion" of CI vs steel and concrete?
    Any thoughts or hypotheses on that?

    Cheers
    Johan
    thanks for the nice words.
    I did think about thermal expansion differences. For the range involved I don't see much of a problem between the steel and CI. The concrete is an unknown quantity and my fingers are crossed as a preventative method. The internal shape will not allow significant movement even if the bond get broken but fretting could cause dust.

  5. The Following User Says Thank You to tonyfoale For This Useful Post:

    Tonyg (06-19-2019)

  6. #4
    olderdan's Avatar
    Join Date
    Jun 2016
    Location
    Devon UK
    Posts
    528
    Thanks
    1,078
    Thanked 1,016 Times in 339 Posts

    olderdan's Tools
    GBH indeed Tony but I like it. Could be the first ever lathe to suffer from concrete cancer (joking). Good move to eliminate the back gearing and I am with you on the merits of poly V belts. Thanks for another suburb write up.

  7. #5
    DIYSwede's Avatar
    Join Date
    May 2019
    Location
    Stockholm, Sweden...
    Posts
    85
    Thanks
    112
    Thanked 98 Times in 35 Posts

    DIYSwede's Tools
    Thanks for a quickie reply, Tony!
    EngineeringToolbox re: Coefficients of Linear Thermal Expansion:

    Cast Grey Iron: 10,8
    Steel: 11- 12,5
    Concrete (unreinforced): 13-14
    Concrete Structure (assumed Rebar): 9.8

    unit: micrometer/ meter x deg C diff

    -How steel reinforced concrete can have a lower thermal expansion than any of its constituents has, was above my paygrade.
    Then - checking into that* - aggregate/ filler material makes this difference - quartz/ gravel has the highest and granite the lowest LTE coeff.

    Paper below measures differences in shrinkage in just-poured concrete, as well as LTE with different wetting methods applied,
    this could perhaps be of interest?

    *Shrinkage of Concrete and Development of Cracks | Concrete Technology

    Cheers
    Johan, "also a Reader - and I'm PROUD of it!"

  8. #6
    Content Editor DIYer's Avatar
    Join Date
    Aug 2013
    Posts
    3,091
    Thanks
    429
    Thanked 913 Times in 840 Posts


    Thanks tonyfoale! We've added your Lathe Spindle Head Modification to our Lathes category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:




  9. #7
    bruce.desertrat's Avatar
    Join Date
    Nov 2017
    Posts
    259
    Thanks
    135
    Thanked 251 Times in 138 Posts

    bruce.desertrat's Tools
    I think this is why many modern folks have gone to a granite-filled epoxy resin for this purpose...(and reading quickly I see that Tony has mentioned this in the PDF!)

  10. #8
    metric_taper's Avatar
    Join Date
    Mar 2017
    Location
    Marion, Iowa
    Posts
    181
    Thanks
    62
    Thanked 82 Times in 51 Posts

    metric_taper's Tools
    Major modification to your lathe. I applaud your lathe improvement.
    I have a 1976 Jet 10x24 lathe. Very similar head stock construction. I found when I had pulled the spindle many years ago (because of an oil leak), that the oil level sight glass, had a single hole going straight back to the area between the taper bearing cup, and the seal (annulus). If the level dropped below this hole, the sight glass indicated there was oil, but the bearing was dry. I modified my head stock by hand drilling a 1/8" hole from the bottom of the oil sight glass reservoir to the bottom of this bearing cup and seal annulus space (both front and rear bearings). I do see now when it runs that the bearing pulls oil in from the reservoir, and shows a low level, but returns when the spindle is stopped.
    I too have installed a 3phase motor on my lathe, and a VFD, but still use the belts. I did change the standard v-belts with the segmented type, which greatly reduced vibration and noise.
    This lathe was originally on a wood bench, and then a sheet metal stand. I could never do parting operations as it would go into a harmonic oscillation of the headstock and ways. I purchased a 2 inch slab of steel to bolt the lathe onto. I put that slab on my Wells-Index vertical mill, and faced the hot rolled slag off. Then drill and tapped the 6 mounting holes that mate with the mounting ears on the lathe way casting. This fixed the rigidity of the lathe to where I have no more issues with cutoff operations.

  11. #9

    Join Date
    Oct 2018
    Posts
    1
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Your removal of the back gears puzzles me. They lock the spindle when trying to change the chuck or faceplate on a threaded spindle. They may not be needed for machining because of the VFD, however certain operations such as tapping would have much more torque with the back gears engaged with a higher motor speed.

  12. #10
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    807
    Thanks
    328
    Thanked 1,328 Times in 404 Posts

    tonyfoale's Tools
    Quote Originally Posted by metric_taper View Post
    I found when I had pulled the spindle many years ago (because of an oil leak), that the oil level sight glass, had a single hole going straight back to the area between the taper bearing cup, and the seal (annulus). If the level dropped below this hole, the sight glass indicated there was oil, but the bearing was dry. I modified my head stock by hand drilling a 1/8" hole from the bottom of the oil sight glass reservoir to the bottom of this bearing cup and seal annulus space (both front and rear bearings).
    I was preparing a post on this very topic. What a crazy design feature that was, I wonder how many other lathe models have the same problem. The degree of incompetence that exists in some design offices never ceases to amaze me.

  13. The Following User Says Thank You to tonyfoale For This Useful Post:

    Toolmaker51 (06-23-2019)

Thread Information

Users Browsing this Thread

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

Tags for this Thread

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
  •