lapping a VN spindle ID- insane? Or possible?
Close
Login to Your Account
Results 1 to 12 of 12
  1. #1
    Join Date
    Mar 2010
    Location
    pacific northwest
    Posts
    1,049
    Post Thanks / Like
    Likes (Given)
    6
    Likes (Received)
    220

    Default lapping a VN spindle ID- insane? Or possible?

    So along with the positioning question I have been spewing forth, I have another-

    The VN spindle seems to have about .0005- .001 runout, measured on a 1/2" ground shaft inserted into a collet. The measurement is taken an inch down from the collet.
    When I got this machine, the spindle had a bunch of built up material in the taper, like would result from spinning an unhardened collet or holder. So I used a steel scraper and got it out.
    Any collet or end mill holder used in the spindle ends up with a ring of "fretting" marks around the taper , about an 1/8" wide and located close to the small end of the taper. This wear cannot be felt with a fingernail. Nor can any burrs etc be felt in the spindle taper.
    I am thinking about making a brass lap, with the VN taper, and using a fine diamond compound to very gently lap the spindle, checking with bluing and a new collet. The object to remove any tiny high spots left on the taper ID.
    Is this nuts?

  2. #2
    Join Date
    Sep 2004
    Location
    RSA
    Posts
    1,101
    Post Thanks / Like
    Likes (Given)
    394
    Likes (Received)
    279

    Default

    It's not going to work. The lap will cut more on the larger diameters - more speed.

  3. #3
    Join Date
    Jan 2008
    Location
    emporium pa
    Posts
    422
    Post Thanks / Like
    Likes (Given)
    20
    Likes (Received)
    140

    Default

    Stoneaxe,
    Years ago we bought an Excello CNC mill with a #40 Taper that
    was pretty beat up. A new spindle was out of the question so
    we ground the existing taper without taking the machine apart.
    Using a Dumore Tool Post Grinder mounted to the table with shaft
    in a Vertical position. A bracket was custom made for the job.
    With the Spindle running slow we programed the Z and X axis
    movements to both dress the grinding wheel then grind the taper.
    It worked great. As the #40 taper is a Standard the dimensions
    were easily obtained. Bluing was used to check the fit to a new
    tapered holder. If yours is not real bad I'd try lapping it like
    you said as you would have nothing to lose. If you are able to
    machine a accurate lap from a piece of cast iron it should work.
    spaeth

  4. #4
    Join Date
    Mar 2010
    Location
    pacific northwest
    Posts
    1,049
    Post Thanks / Like
    Likes (Given)
    6
    Likes (Received)
    220

    Default

    Spent some time tonight playing with a bunch of different collets and end mill holders, both old VN and new Chinese. Big differences in runout. The low end was about .0005, the worst was about .005.
    Best of the lot was an old 1/2" end mill holder. I am now going through all the collets and end mill holders to separate the good from the bad.
    I think I will buy a new Hardinge 1/2" 5V if I can find one-
    Before I start meddling with the spindle , I better have a known quantity to measure.

  5. Likes Mike C., thebencarter liked this post
  6. #5
    Join Date
    Aug 2017
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    60
    Post Thanks / Like
    Likes (Given)
    27
    Likes (Received)
    23

    Default

    Quote Originally Posted by stoneaxe View Post
    Spent some time tonight playing with a bunch of different collets and end mill holders, both old VN and new Chinese. Big differences in runout. The low end was about .0005, the worst was about .005.
    Best of the lot was an old 1/2" end mill holder. I am now going through all the collets and end mill holders to separate the good from the bad.
    I think I will buy a new Hardinge 1/2" 5V if I can find one-
    Before I start meddling with the spindle , I better have a known quantity to measure.
    Good thought - as you know you weren't measuring the runout of the spindle taper, but rather the runout of a system that includes the spindle, the toolholder or collet and the tool itself. Lots of chances for error to stack up there. Is there a reason you can't indicate the taper directly?

    I don't know if VN C/5V tooling can be inserted in more than one orientation, but if it can, you should try different orientations of the tool in the spindle to see if you can get errors to cancel. If you find a good arrangement, you can mark the spindle nose and toolholder so you can repeat it (nail polish is good if you don't want the permanence of punch marks).

  7. Likes Paolo_MD liked this post
  8. #6
    Join Date
    Sep 2002
    Country
    UNITED STATES
    State/Province
    Arizona
    Posts
    3,658
    Post Thanks / Like
    Likes (Given)
    859
    Likes (Received)
    487

    Default

    I've thought about this from time to time. One thing you might consider is making the lap with a pilot that is a close fit to the cylindrical part of the spindle, so that any pumps on the ID of the taper can't push the lap out of line.

    How are you planning to cut the taper on your lap?

    Cal

  9. Likes Paolo_MD liked this post
  10. #7
    Join Date
    Mar 2010
    Location
    pacific northwest
    Posts
    1,049
    Post Thanks / Like
    Likes (Given)
    6
    Likes (Received)
    220

    Default

    I will put my most accurate VN endmill holder in the lathe, and set the compound to the taper using a .0001 indicator. then I will double chh a couple others. Then I will turn the brass lap, matching both the cylindrical size and taper. Then I will blue the lap and see how close the spindle is, then go to lapping compound. This will be done by hand to start, then, if it cuts too slow, the lap will be driven by a low speed cordless drill using a short length of hose to drive the lap, so as not to introduce side forces.

    This evening I put a .0001 indicator on the taper directly, of course it had a little angularity to get a reading, but there seems to be about .0003" difference from the high side to the low side. I am hoping that knowing the high side, and turning the lap to a slip fit in the cylindrical portion of the spindle, will allow careful hand work to bring it in.

    I ordered a 1/2" collet today from Hardinge- $117, 18 days to make it. They were pleasant and professional people to deal with. I figured the collet, which will grip any number of other tools like a chuck , end mills etc, needed to be accurate. Absolutely no sense worrying about a spindle if the tool holders are out of whack.

    The other option here is to grind the spindle, by using a die grinder in a vise on the mill table, and setting the VN head to a 15.25 degree (or whatever it is) angle and using the Y axis to feed the grinder, and the Z axis to control depth of cut. Exact centering of the stone becomes critical here, or the angle will be off. My main worry though is the fineness of the adjustment on the Z axis-it would be easy to take to deep a cut.

  11. #8
    Join Date
    Jan 2016
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    242
    Post Thanks / Like
    Likes (Given)
    6
    Likes (Received)
    64

    Default Runout

    Quote Originally Posted by stoneaxe View Post
    So along with the positioning question I have been spewing forth, I have another-

    The VN spindle seems to have about .0005- .001 runout, measured on a 1/2" ground shaft inserted into a collet. The measurement is taken an inch down from the collet.
    When I got this machine, the spindle had a bunch of built up material in the taper, like would result from spinning an unhardened collet or holder. So I used a steel scraper and got it out.
    Any collet or end mill holder used in the spindle ends up with a ring of "fretting" marks around the taper , about an 1/8" wide and located close to the small end of the taper. This wear cannot be felt with a fingernail. Nor can any burrs etc be felt in the spindle taper.
    I am thinking about making a brass lap, with the VN taper, and using a fine diamond compound to very gently lap the spindle, checking with bluing and a new collet. The object to remove any tiny high spots left on the taper ID.
    Is this nuts?
    If I understand your assuming the collet holding the ground shaft is running true on center. It in all likelihood is not. Turn a mandrel on centers or a spud mandrel and polish to a ring fit for your collet and re-inspect.

    Roger

  12. #9
    Join Date
    Nov 2004
    Location
    Birmingham, AL
    Posts
    13,230
    Post Thanks / Like
    Likes (Given)
    6617
    Likes (Received)
    2561

    Default

    I made a VN #2 to R-8 sleeve for the 22L at the museum, years ago. I laid the head horizontal and adapted the compound from the SB10L to mount on the table. Dial the compound in to the taper angle and have at it. Put your toolpost grinder into the compound. I made an adapter for a Dremel and used that to grind the taper. Worked.

  13. #10
    Join Date
    Mar 2005
    Location
    Kansas
    Posts
    7,624
    Post Thanks / Like
    Likes (Given)
    440
    Likes (Received)
    3533

    Default

    Make your lap so it just makes contact in the area where your toolholders show contact, or just put the lapping compound in this area. If the mouth of the taper is good don't waste your time trying to rework it. If you remove a little to much material at the small end of the taper you will never notice the performance.

  14. #11
    Join Date
    Mar 2011
    Location
    Dayton, MN, USA
    Posts
    119
    Post Thanks / Like
    Likes (Given)
    51
    Likes (Received)
    18

    Default

    Check the key.
    My VN6 has runout if I don't seat the collets very carefully over the keystock in the spindle.
    This was improved by fabing a new key. But, I still need to be careful about seating the collets and watching how they draw in.

    Daryl
    MN

  15. Likes Mike C. liked this post
  16. #12
    Join Date
    Mar 2010
    Location
    pacific northwest
    Posts
    1,049
    Post Thanks / Like
    Likes (Given)
    6
    Likes (Received)
    220

    Default

    Quote Originally Posted by Uglydog View Post
    Check the key.
    My VN6 has runout if I don't seat the collets very carefully over the keystock in the spindle.
    This was improved by fabing a new key. But, I still need to be careful about seating the collets and watching how they draw in.

    Daryl
    MN
    Yes, that makes good sense. I have been watching to make sure the key does not bind- also put a .0001 indicator directly on the taper and it is out a couple tenths.


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
  •