Thread Chatter
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 29

Thread: Thread Chatter

  1. #1
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Missouri
    Posts
    20
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    0

    Default Thread Chatter

    I have ran lathes before in my younger years at a machine shop. I recently purchased a 1700lbs lathe and have had great success other than a few minor issues. One being that I can not for the life of me get all of the chatter out of my single point threading. I have the correct set up, my brother-in-law is a machinist...a good one, and he can’t figure it out either. So I’m guessing it is in my tooling at this point. Any advice is welcome, it is a stock lathe that bolted to the floor and leveled. Runout on both 3 and 4 jaw chucks are less than .0003. Stock tool post, Shars tool holders and tooling. I have adjusted spindle bearings, backlash and the gibs. I have a slight vibration in the lathe which I believe is coming from the fairly light base the machine comes with. Thought about bolting lathe to the wall with all thread for stability. Please advise.

  2. #2
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    9,651
    Post Thanks / Like
    Likes (Given)
    3275
    Likes (Received)
    3451

    Default

    1700 lb seems should not be chattering.
    Tool bit side rake angle perhaps 5* and very sharp for mild steel.
    pick up on spindle with a 2x2 pry to see less than .003 slop under an indicator.
    check for pulleys and things being lose or out of balance at high speeds.
    A bad gear or chips in gears.
    Too much part hang out with not using you tail.
    Compound at angle and set too far to the left side of saddle.
    loose gibbs.

    Threading going straight in (not at 29- 30*or so)causes both sides of the tool bit to try to cut. the right side of the tool bit may be having a negative rake angle so very much stress in the cut.

    Using insert, some are not that sharp so perhaps use an aluminum designated insert.Yes for mild steel..but going straight in makes both side of the insert try to cut and that may be a big bite.

    https://www.amazon.com/carbide-inser...h=n%3A16310091
    Last edited by michiganbuck; 07-11-2019 at 05:58 PM.

  3. Likes RueBear, AD Design liked this post
  4. #3
    Join Date
    Dec 2015
    Country
    UNITED STATES
    State/Province
    Illinois
    Posts
    343
    Post Thanks / Like
    Likes (Given)
    110
    Likes (Received)
    187

    Default

    Do you have a picture of the chatter?

  5. #4
    Join Date
    Oct 2010
    Location
    Dewees Texas
    Posts
    2,212
    Post Thanks / Like
    Likes (Given)
    26
    Likes (Received)
    579

    Default

    Quote Originally Posted by kenton View Post
    Do you have a picture of the chatter?
    While your taking photos a picture of the set may help.

  6. #5
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Missouri
    Posts
    20
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    0

    Default

    d06adfc6-cc69-4765-896c-660fb9e9550f.jpg here is a pic of the threads

  7. #6
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Missouri
    Posts
    20
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    0

    Default

    I have experimented with that, using dycam on threads and picking them up and and at varying speeds

  8. #7
    Join Date
    Dec 2015
    Country
    UNITED STATES
    State/Province
    Illinois
    Posts
    343
    Post Thanks / Like
    Likes (Given)
    110
    Likes (Received)
    187

    Default

    it's not a great picture but I think I'm with michiganbuck. I would say use a more positive insert, like inserts intended for aluminum, or a nice sharp piece of hss. Also if you haven't already, set your compound at 29 degrees (or 61 depending on how your compound is oriented) and feed in with your compound so you are only cutting on one flank of the thread.

  9. #8
    Join Date
    Jan 2015
    Country
    UNITED STATES
    State/Province
    Alabama
    Posts
    265
    Post Thanks / Like
    Likes (Given)
    196
    Likes (Received)
    128

    Default

    Is the tool above center possibly?

  10. #9
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Idaho
    Posts
    3,096
    Post Thanks / Like
    Likes (Given)
    1706
    Likes (Received)
    2032

    Default

    Tool looks looks above center
    or not sharp enough insert
    or
    if a HSS ground tool,not enuff rake

  11. #10
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Missouri
    Posts
    20
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    0

    Default

    This is the tool holder I’m using. Do I need to go to a positive insert holder.752fa559-0a98-43f6-92f9-609e653390f1.jpg

  12. #11
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    9,651
    Post Thanks / Like
    Likes (Given)
    3275
    Likes (Received)
    3451

    Default

    Another good check is to just run a normal turning of a mild steel part...that is just a very fine thread going toward the tail. If it is good then no reason a turning toward the head stock should not be just as good if the cutting tool and set-up are correct.

  13. #12
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    9,651
    Post Thanks / Like
    Likes (Given)
    3275
    Likes (Received)
    3451

    Default

    Quote Originally Posted by RueBear View Post
    This is the tool holder I’m using. Do I need to go to a positive insert holder.752fa559-0a98-43f6-92f9-609e653390f1.jpg
    I like a little positive rake attitude..with a HSS bit I put on 5* side cutting edge rake. (I know How to run a lathe seems to say 5* back rake for mild steel if I remember right.)

    So for my choice/liking I would bring that insert up to the part at center and look at how the cutting edge looks to the part..wishing to see some clearance below the touching and some positive rake attitude at the top of the insert... yes positive would touch the part and then angle down about 5 degrees going away from where it touches.
    I would have my compound swung 29 -29 1/2 or 30* going to the right off of being straight. and in-feed with the compound dial that started out zero and intended to go to .005 short of my thread depth target...
    You don't want to go all the way home on the first part because off center whip in the part or error in the point flat may make your cut/depth too deep/or short.

    With watching the thread top to just make to or near a point getting near my dial size. Coming to a a point before my dial target I would stop in-feeding and check my numbers. With compound about 30* the cut should be only on the left edge of the insert.

  14. #13
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Missouri
    Posts
    20
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    0

    Default

    That’s exactly how I set it up.

  15. #14
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Missouri
    Posts
    20
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    0

    Default

    Also, I’ve ground my own Hss tool and still get chatter with that as well.

  16. #15
    Join Date
    Aug 2015
    Country
    UNITED STATES
    State/Province
    Illinois
    Posts
    1,282
    Post Thanks / Like
    Likes (Given)
    914
    Likes (Received)
    534

    Default

    I can't tell from the photo if the problem is chatter or tearing. If it is tearing, use a high sulfur cutting oil.

  17. Likes michiganbuck liked this post
  18. #16
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    24,675
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    7714

    Default

    Quote Originally Posted by RueBear View Post
    Also, I’ve ground my own Hss tool and still get chatter with that as well.
    Have the compound off, then.

    Shim a tool to height, top bridge bar, two bolts, one each side to keep it there. Prolly borrow them out of you mil'ls clamp set.

    Place the tip of the tool right about over where the compound's pivot center was. Support extends further toward centreline than the tool-tip above it. "negative" hang-out or overhang, IOW.

    Set the stock well-back in your collet.

    Advance straight-in, each pass, clamping the carriage cross top-slide to the saddle for the duration of the pass.

    Age-old tradeoff, light lathes with wear.

    Pain in the ass setup || chatter.

    Pick any ONE.


  19. #17
    Join Date
    Oct 2009
    Location
    Louisville, KY, USA
    Posts
    891
    Post Thanks / Like
    Likes (Given)
    213
    Likes (Received)
    190

    Default

    How far out from the chuck are you cutting the threads? Could it be the party chattering rather than the tool?

    I just got a well worn lathe and the carriage could rock back and forth on in the bed. Easy test is to tap the four corners of the carriage and listen for a "hollow" sound. That means one or more corners isn't touching the bed.

    I think someone back at the beginning mentioned checking the spindle for play as well.

  20. Likes michiganbuck, Bobw liked this post
  21. #18
    Join Date
    Feb 2005
    Location
    Hatch, NM Chile capital of the WORLD
    Posts
    8,916
    Post Thanks / Like
    Likes (Given)
    13241
    Likes (Received)
    10374

    Default

    Backstory: My primary use now of a manual 3 jaw is to grab round things in the mill. Its a POS cheap chinese chuck. And she's a bit sprung after a decade of use.. I found this out the hard way, with inconsistent sizes and chatter..

    CNC lathe... Same damn thing. Too much or not enough tapered bored into the soft jaws. CHATTER..

    Solution. TAPE.. High temp masking tape. Its thick (for tape) and one wrap cures a lot of ills.

    Why does tape cure the problem.. A sprung chuck isn't grabbing on 3 lines, its grabbing on 3 points, allowing your material to bounce around all kinds of way, and that mean CHATTER..


    This may not be your problem, but its a quick check. Wrap the part of the part that is grabbed in the chuck in tape. Masking tape works.. If its really bad, you can pick up this problem with a feeler gage..


    I'll also ask. Material? Thread? Diamter? Stickout? DEPTH of cut??

    In your really bad picture, I can see BAD chatter.. I just did a left hand 3/4-16 on 3/4" 17-4 sticking out 4.5" yesterday. there was a bit of choppy-ness in the thread. But it was acceptable...

    Long story short.. Unless you are doing something incredibly stupid (massive L/D ratio).. Something is moving, you just need to figure out what.. And then you need to figure out why (not always easy) and fix it.
    Last edited by Bobw; 07-11-2019 at 09:38 PM. Reason: doh

  22. Likes michiganbuck, RueBear liked this post
  23. #19
    Join Date
    Sep 2010
    Location
    moscow,ohio
    Posts
    5,754
    Post Thanks / Like
    Likes (Given)
    559
    Likes (Received)
    1827

    Default

    yes, what Bob said...something is moving that shouldn't.

    Stick mag base and indicator on things while running to isolate and narrow it down....just like you would look for a short in wiring....work your way through logically.

  24. Likes RueBear liked this post
  25. #20
    Join Date
    Jan 2005
    Country
    CANADA
    State/Province
    Saskatchewan
    Posts
    10,150
    Post Thanks / Like
    Likes (Given)
    1366
    Likes (Received)
    3623

    Default

    Use a tail center to steady the part, if not tried already.

    A vibration pattern will self replicate to quite some extent. So you want to avoid having it even begin to chatter.

    Chatter is often due to too much cutting edge engaged, and too light of a cut. I am not a compound rest 'set to 29°' type of machinist; I have it set at 90° So I cut with the tool straight in, cutting both sides at equal cuts. When the depth gets so great that chatter begins, then I tweak the compound ahead a little bit so the tool cuts on only the front edge. Still take a fairly heavy cut to prevent chatter from occurring. I might on a subsequent cut move the compound backwards and cut with the rear edge of the tool.

    If you get chatter starting to happen, it can be beneficial to speed the spindle up a gear for one pass. Then drop back a gear. Anything to defeat the harmonic vibration.

    Make sure the gib in the compound is set tight. It should be difficult to turn its crank.

    I quite like the laydown threading inserts. Should have the one with the slightly raised edge chipformer as it will really roll the chips out nicely, on both sides of the cut at once.


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
  •