What's causing odd pattern on finish cut on lathe? - Page 3
Close
Login to Your Account
Page 3 of 4 FirstFirst 1234 LastLast
Results 41 to 60 of 63
  1. #41
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    1,971
    Post Thanks / Like
    Likes (Given)
    557
    Likes (Received)
    994

    Default

    Quote Originally Posted by sandiapaul View Post

    The only thing I have not tried and was suggested is the prybar under the chuck. I have never done that before, how much pressure should I use? It seems like you could get it to move if you wanted to with enough pressure. I'd like to try this test, so any advice on how to carry it out would be great.
    You don;t have issues when you are using Chuck, so why even use this exercise? You ran a dial on the Collet and it dialed dead on to the taper so the mating surfaces are verified. It MIGHT give you an idea of the condition of the spindle bearings, at what cost????

    Personally when people recommend "pry bars" AND indicators it sounds like using a Smelter to light a cigarette. I would not use a pry bar on recently rebuilt equipment, unless you want to do it again. HAND pressure would be enough to say a thing is wrong with the bearings, and the mating surfaces have been verified as Perpendicular and True.

    R

  2. Likes sandiapaul liked this post
  3. #42
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    7,979
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2111

    Default

    Quote Originally Posted by litlerob1 View Post
    You don;t have issues when you are using Chuck, so why even use this exercise? You ran a dial on the Collet and it dialed dead on to the taper so the mating surfaces are verified. It MIGHT give you an idea of the condition of the spindle bearings, at what cost????

    Personally when people recommend "pry bars" AND indicators it sounds like using a Smelter to light a cigarette. I would not use a pry bar on recently rebuilt equipment, unless you want to do it again. HAND pressure would be enough to say a thing is wrong with the bearings, and the mating surfaces have been verified as Perpendicular and True.

    R
    .
    .
    pry bar usually means a smaller one, not a 3 to 6 foot long one and most can handle gaging pressure applied with pry bar to lift up spindle
    .
    cutting pressure when using a lathe can easily exceed 200 lbs. many lathe manuals recommend using centers and pushing on a long bent shaft with the tool post to straighten shafts. obviously they mean gaging pressure applied to not damage machine. normal hand on handle turning with normal pressure not using abnormally high pressure trying to straighten a bent shaft
    .
    i have often indicated machinery rollers for parallelism. when tram gage held to higher roller often reading can vary if when applying seating pressure you pick up the roller and the excess clearance in bearing housing allows it to go up. often thick oil or sludge of whatever there is some resistance to movement. call it sticky oil or whatever you want. might have to apply a extra 10 lbs before it finally moves higher
    .
    Steel 1018
    machinability 0.8 cubic inches per min per hp
    600 sfpm
    Dia 1.000
    Doc Radius 0.100 (dia 0.2)
    feed .006 ipt
    cutting force 297 lbs
    5.4 hp required
    obviously little 2 hp lathe not going to handle heavy cuts just saying cutting forces of over 100 lbs is what causes dia differences with long parts bending away from the cutter from cutting forces

  4. #43
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    1,971
    Post Thanks / Like
    Likes (Given)
    557
    Likes (Received)
    994

    Default

    Quote Originally Posted by DMF_TomB View Post
    .
    .
    pry bar usually means a smaller one, not a 3 to 6 foot long one and most can handle gaging pressure applied with pry bar to lift up spindle
    Okay, so according to Dumb Mother Fucker TombB. you should ASSUME peoples intentions, when they say use of a pry bar "means a smaller one". Because that makes a difference, when it's not necessary in the first place. Thanks for clarifying that Tom, I was just about to use a Trackhoe to butter my toast, now I'm going to use a Snow Shovel instead.

    R

  5. #44
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    7,979
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2111

    Default

    Quote Originally Posted by litlerob1 View Post
    Okay, so according to Dumb Mother Fucker TombB. you should ASSUME peoples intentions, when they say use of a pry bar "means a smaller one". Because that makes a difference, when it's not necessary in the first place. Thanks for clarifying that Tom, I was just about to use a Trackhoe to butter my toast, now I'm going to use a Snow Shovel instead.

    R
    .
    talking impolitely and sarcastically, hows that working out at your job ?? you getting pay raises every year ?? any of your fellow workers like you ??
    .
    i worked at a place where for 20% of job performance rating i had to get 3 fellow workers to give rating on how well they felt i was doing. now i did not have a problem getting 3 fellow workers to have nice things to say about me.
    .
    .....but some people had trouble getting anybody, to say anything good about them. when company made the 3 fellow workers needing to give you 20% of job performance rating most everybody in the company were much more polite and treated each other much better.

  6. #45
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    9,222
    Post Thanks / Like
    Likes (Given)
    4980
    Likes (Received)
    4084

    Default

    Quote Originally Posted by litlerob1 View Post
    You don;t have issues when you are using Chuck, so why even use this exercise? You ran a dial on the Collet and it dialed dead on to the taper so the mating surfaces are verified. It MIGHT give you an idea of the condition of the spindle bearings, at what cost????

    Personally when people recommend "pry bars" AND indicators it sounds like using a Smelter to light a cigarette. I would not use a pry bar on recently rebuilt equipment, unless you want to do it again. HAND pressure would be enough to say a thing is wrong with the bearings, and the mating surfaces have been verified as Perpendicular and True.

    R
    Get your head out, Rob.

    The "pry bar" isn't applied to rip the f****r off the ways.

    It's mechanical advantage allows VERY fallible human muscle to be utilized at the more sensitive eg: "light touch" end of their range rather than being overly strained, tired, hence less sensitive or accurate.

    Where is there a dumb M(ike) F(oxtrot) issue in that? Other than somewhere in Utah, and even then hopefully only self-imposed and - we shall hope - TEMPORARY?


  7. Likes eKretz, digger doug liked this post
  8. #46
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    8,092
    Post Thanks / Like
    Likes (Given)
    2344
    Likes (Received)
    2608

    Default

    Way OT: this has nothing to do with surface finish some times on lathe.

    [fellow workers rating?] I don't think much of that.. finished good work out the door/ least amount of scrap / day on the job/ up time making parts/mind your own business and do your job..

    I remember jerks who did not like somebody so that somebody would never get a good rating...
    I have seen poorly holding collects.. too long draw bars.. not going tight collar nuts.. bugs and taper parts.. running too fast for the machine setting.vibration for something,dull or wrong centered bits, part too far out, .an off sighted laser beam for Mars.. ops not the laser beam.

  9. Likes Screwmachine liked this post
  10. #47
    Join Date
    Mar 2005
    Location
    Northwest Indiana
    Posts
    3,299
    Post Thanks / Like
    Likes (Given)
    312
    Likes (Received)
    416

    Default

    Jeez Rob, slow your roll buddy. The prybar isn't being used with a lot of force in this situation, just gives a little leverage to make it so you don't get a hernia yanking on the chuck. I'm sure you already know this but basically it amounts to checking backlash/free space in the bearing. Not really useful for ball/roller bearings which shouldn't have any real significant free play but can be helpful for plain bearings.

  11. Likes Monarchist liked this post
  12. #48
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    1,971
    Post Thanks / Like
    Likes (Given)
    557
    Likes (Received)
    994

    Default

    Quote Originally Posted by Monarchist View Post
    Get your head out, Rob.

    The "pry bar" isn't applied to rip the f****r off the ways.

    It's mechanical advantage allows VERY fallible human muscle to be utilized at the more sensitive eg: "light touch" end of their range rather than being overly strained, tired, hence less sensitive or accurate.

    Where is there a dumb M(ike) F(oxtrot) issue in that? Other than somewhere in Utah, and even then hopefully only self-imposed and - we shall hope - TEMPORARY?

    Quote Originally Posted by eKretz View Post
    Jeez Rob, slow your roll buddy. The prybar isn't being used with a lot of force in this situation, just gives a little leverage to make it so you don't get a hernia yanking on the chuck. I'm sure you already know this but basically it amounts to checking backlash/free space in the bearing. Not really useful for ball/roller bearings which shouldn't have any real significant free play but can be helpful for plain bearings.
    Okay, but holy hell!!

    SORRY Tom. BTW several of my coworkers do not like me, as I am not one to sugar coat an issue and am not afraid of taking responsibility for the faults and failures of the shop floor, when we are wrong. BUT I don not lose any sleep over it, their opinions of me (like your opinion of me) is irrelevant. But if you want to look at throughput and results there is not one person in the building that would say "nope not Robert". I get the job done every time.

    R

  13. Likes B-Mathews liked this post
  14. #49
    Join Date
    Sep 2004
    Location
    Rugeley UK
    Posts
    946
    Post Thanks / Like
    Likes (Given)
    19
    Likes (Received)
    91

    Default

    We need to find what the difference is between collet and chuck workholding, I would put the 3jaw back on, put the bar in it and turn a little off it to fit the next size down collet that you have. Now try your tests again, if the finish is still poor look at the collect setup, is the location key sticking into the bore too much,muck in the bore, drawrube thread fault etc. It is unlikely that you have two bad collets.

  15. #50
    Join Date
    Apr 2009
    Location
    Beaver County Alb. Canada
    Posts
    1,667
    Post Thanks / Like
    Likes (Given)
    445
    Likes (Received)
    826

    Default

    Southbend Lathes has a proceedure for checking headstock bearings by prying the headstock with a lever, but they say max 80 lbs. If I remember correctly.

  16. #51
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    1,971
    Post Thanks / Like
    Likes (Given)
    557
    Likes (Received)
    994

    Default

    Quote Originally Posted by redlee View Post
    Southbend Lathes has a proceedure for checking headstock bearings by prying the headstock with a lever, but they say max 80 lbs. If I remember correctly.
    But if I can lift 80# from the ground.......get me a F%@$#ing Crowbar, slide hammer, 20 Ton press, a Lift Truck and Rosebud...and some Vaseline®.

  17. #52
    Join Date
    Apr 2009
    Location
    Beaver County Alb. Canada
    Posts
    1,667
    Post Thanks / Like
    Likes (Given)
    445
    Likes (Received)
    826

    Default

    Quote Originally Posted by litlerob1 View Post
    But if I can lift 80# from the ground.......get me a F%@$#ing Crowbar, slide hammer, 20 Ton press, a Lift Truck and Rosebud...and some Vaseline®.
    Just trying to add something intelligent to the thread.

  18. #53
    Join Date
    Jun 2016
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    759
    Post Thanks / Like
    Likes (Given)
    279
    Likes (Received)
    251

    Default

    think the amazing thing on this thread is the assumption (by most, not all) that a 5C should have the same ability to grip the work and dampen vibration as a good tight 3 jaw.

    a 5C works on a single taper, and has a limited grip length even if all is working as it should. what, maybe .100? the rest of the workpiece is pivoting on that gripped portion, (unless supported at the other end). that could be a considerable length in the headstock, and possibly out beyond too. all that material can be vibrating like a piano string, or if more rigid, acting as a powerful lever it's self. that would naturally have an effect on the cut.

    dont mistake concentric for rigid, and don't forget that the most rigid setup in the world is still going to vibrate at some level.

  19. Likes Monarchist liked this post
  20. #54
    Join Date
    Sep 2011
    Location
    North Plains, OR
    Posts
    84
    Post Thanks / Like
    Likes (Given)
    26
    Likes (Received)
    25

    Default

    Would it be possible to post a good clear photo of the banding?

  21. #55
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    1,971
    Post Thanks / Like
    Likes (Given)
    557
    Likes (Received)
    994

    Default

    Quote Originally Posted by cyanidekid View Post
    think the amazing thing on this thread is the assumption (by most, not all) that a 5C should have the same ability to grip the work and dampen vibration as a good tight 3 jaw.

    a 5C works on a single taper, and has a limited grip length even if all is working as it should. what, maybe .100? the rest of the workpiece is pivoting on that gripped portion, (unless supported at the other end). that could be a considerable length in the headstock, and possibly out beyond too. all that material can be vibrating like a piano string, or if more rigid, acting as a powerful lever it's self. that would naturally have an effect on the cut.

    dont mistake concentric for rigid, and don't forget that the most rigid setup in the world is still going to vibrate at some level.
    we would all be in a bunch of trouble if that were true.

  22. #56
    Join Date
    Mar 2005
    Location
    Northwest Indiana
    Posts
    3,299
    Post Thanks / Like
    Likes (Given)
    312
    Likes (Received)
    416

    Default

    I'd guess the grip length in a 5C collet would be dependent on the parallelism and roundness of the workpiece where it's being gripped. I'd damn sure hope it's better than .100" in length. I confess to originally thinking to myself that the problem described in the O.P. could well be a slight chatter with ca. 4:1 stickout in the collet chuck though. Personally I don't believe that it has anything to do with the bearings or stick-slip of the ways in this case.

  23. Likes michiganbuck liked this post
  24. #57
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    9,222
    Post Thanks / Like
    Likes (Given)
    4980
    Likes (Received)
    4084

    Default

    Quote Originally Posted by litlerob1 View Post
    we would all be in a bunch of trouble if that were true.
    Actually..... we'd not even have been conceived, if
    the most rigid setup in the world
    did NOT

    vibrate at some level
    NOW may we lighten-up?


  25. Likes digger doug, cyanidekid liked this post
  26. #58
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    8,092
    Post Thanks / Like
    Likes (Given)
    2344
    Likes (Received)
    2608

    Default

    Quote Originally Posted by eKretz View Post
    I'd guess the grip length in a 5C collet would be dependent on the parallelism and roundness of the workpiece where it's being gripped. I'd damn sure hope it's better than .100" in length. I confess to originally thinking to myself that the problem described in the O.P. could well be a slight chatter with ca. 4:1 stickout in the collet chuck though. Personally I don't believe that it has anything to do with the bearings or stick-slip of the ways in this case.
    Good point..How much was in the chuck or collect.
    And many collects only hold tight at the taper zone on the high places of the part.. with the latter at the mercy of the tube.

  27. #59
    Join Date
    Jun 2016
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    759
    Post Thanks / Like
    Likes (Given)
    279
    Likes (Received)
    251

    Default

    Quote Originally Posted by litlerob1 View Post
    we would all be in a bunch of trouble if that were true.
    yes, you are right, that is the "worst case". usually more like 1"...( for a 1" dia). but the gripping force does diminish as you go back away from the face, as the collet fingers are "hinged" at the rear.

  28. #60
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    1,971
    Post Thanks / Like
    Likes (Given)
    557
    Likes (Received)
    994

    Default

    Quote Originally Posted by Monarchist View Post
    NOW may we lighten-up?

    But Dad, it wasn't me!! I didn't say anything to him.


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
  •