Help me understand what holding tenths means
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 34
  1. #1
    Join Date
    Dec 2018
    Country
    UNITED STATES
    State/Province
    Indiana
    Posts
    129
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    20

    Default Help me understand what holding tenths means

    I see this often and I don't think Im understanding it or my definition is different. I know a tenth is .0001" so holding that means +/-.00005" correct?

    Ok so given that that means you can hold that tolerance all day long once the machine is up and running? Don't have to adjust after the first hour running?

    How many parts in with measuring and tweaking the program or wear comp before you can claim that you hold tenths? 1? 5? 10?

    What if its a new job and new tooling you have to probe each tool? Hold tenths on the first part? I know you can program the part big then measure and readjust the program so is that considered holding tenths?

    Very dumb and basic I know but am curious as to when you can use "my machine can hold tenths"?

  2. #2
    Join Date
    Mar 2014
    Location
    Hondo, TX
    Posts
    24
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    11

    Default

    Not sure what the correct lingo is but I use it since I switched over from land based to aero based turbines. Ever since then 1/10's have been the bane of my existence. My 1/10's situation is just simply putting a hole where it is supposed to be typically with a max radial error of .0005. There are so many variables, to qualify parts we are required to have two separate CMM programs written by two different people. My CMM program results rarely (read never) ever match my colleagues'. Things I have learned in the 1/10ths world; no plane is flat nor is any hole round.

  3. Likes empwoer liked this post
  4. #3
    Join Date
    Sep 2007
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    5,427
    Post Thanks / Like
    Likes (Given)
    224
    Likes (Received)
    1698

    Default

    Holding tenths ... multiple tenths. Within a couple tenths. That's what it means to me. And that is difficult, except maybe boring and reaming holes -- that can be held within a couple tenths without working too hard. But milling a feature to +/- a couple tenths? Not easy. All sorts of ways things can go one way or the other.

    Half a tenth, that's a whole 'nuther ballgame. A lot of standard CNC machines aren't even programmable to partial tenths. Measuring gets very sporting sub-tenth. Temperature becomes a factor even on small parts if you are working to sub-tenths.

    Regards.

    Mike

  5. Likes Bobw, cameraman, gkoenig liked this post
  6. #4
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    31,255
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    9811

    Default

    Quote Originally Posted by turnworks View Post
    I see this often and I don't think Im understanding it or my definition is different. I know a tenth is .0001" so holding that means +/-.00005" correct?

    Ok so given that that means you can hold that tolerance all day long once the machine is up and running? Don't have to adjust after the first hour running?

    How many parts in with measuring and tweaking the program or wear comp before you can claim that you hold tenths? 1? 5? 10?

    What if its a new job and new tooling you have to probe each tool? Hold tenths on the first part? I know you can program the part big then measure and readjust the program so is that considered holding tenths?

    Very dumb and basic I know but am curious as to when you can use "my machine can hold tenths"?
    The actual NEED?

    Whatever the entity PAYING FOR IT demands. And can TEST for consistently.

    Not necessarily "+/-" , either. More likely plus one. minus ZERO (OD). Or the reverse (ID).

    Higher tech can "split a tenth". Semi-conductor industry mass-produces CPU at ever-decreasing feature scale. Around 4 nanometer at the moment?

    All yah need is MORE.

    More money invested in machine, tooling and metrology.

    More skill and patience trained-up and KEPT up as to set up and use.

    More stable environment and materials.

    More TIME.

    Some combination or all of the above.

    Genuine need to hit, hold, repeat all day, every day, all year?

    Yah start with a gawdawful costly machine-tool.... add money.. and work up.

    Can't "fake" this shit for very long and still get paid.

    "There is no 'try'. There is only do or do not."
    Last edited by thermite; 05-27-2020 at 11:41 PM.

  7. Likes wanispissd liked this post
  8. #5
    Join Date
    Jul 2006
    Location
    Hillsboro, New Hampshire
    Posts
    9,232
    Post Thanks / Like
    Likes (Given)
    2188
    Likes (Received)
    6393

    Default

    Quote Originally Posted by Finegrain View Post
    Holding tenths ... multiple tenths. Within a couple tenths. That's what it means to me. And that is difficult, except maybe boring and reaming holes -- that can be held within a couple tenths without working too hard. But milling a feature to +/- a couple tenths? Not easy. All sorts of ways things can go one way or the other.

    Half a tenth, that's a whole 'nuther ballgame. A lot of standard CNC machines aren't even programmable to partial tenths. Measuring gets very sporting sub-tenth. Temperature becomes a factor even on small parts if you are working to sub-tenths.

    Regards.

    Mike
    I agree with all of this. Sub tenths is tedious and can mean a lot of fiddle-farting unless it's a lapping process.

  9. #6
    Join Date
    Nov 2014
    Country
    UNITED STATES
    State/Province
    Colorado
    Posts
    3,305
    Post Thanks / Like
    Likes (Given)
    3790
    Likes (Received)
    941

    Default

    Quote Originally Posted by Finegrain View Post
    Holding tenths ... multiple tenths. Within a couple tenths. That's what it means to me. And that is difficult, except maybe boring and reaming holes -- that can be held within a couple tenths without working too hard. But milling a feature to +/- a couple tenths? Not easy. All sorts of ways things can go one way or the other.

    Half a tenth, that's a whole 'nuther ballgame. A lot of standard CNC machines aren't even programmable to partial tenths. Measuring gets very sporting sub-tenth. Temperature becomes a factor even on small parts if you are working to sub-tenths.

    Regards.

    Mike
    Yeah "ditto"

    On a conventional cnc turning center "tenths" = "couple of tenths" not +/- fifty millionths (roughly +/- 1 micron is not what is meant by holding "tenths" especially "Tenths all day". ).

    _____________________________________



    On a mill if someone says "tenths" I "Think" sub-thou... unless it's something special.

    Positioning (remember positioning !) accuracies vaguely to iso 230-2 for a standard but pretty good cnc machine +/- one tenth to +/- two tenths.

    ____

    "Tenths" also doesn't tell you how straight a machine can cut either nor actual roundness values for turning.

  10. #7
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    31,255
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    9811

    Default

    Quote Originally Posted by Milland View Post
    I agree with all of this. Sub tenths is tedious and can mean a lot of fiddle-farting unless it's a lapping process.
    Well yeah.. but WTF? BOTH grinding AND lapping ARE "fiddle farting".

    Just invested-in and "productized" to make 'em even possible at any reasonable "per-unit" cost.

    Right stiff up-front investment, usually. Worse -one as can go obsolete rapidly as well.

    See prices for the wafer prep machinery used by Intel and competitors. Obsolete at roughly one to two year intervals off the back of "fab shrink", some of them.

    Then - back in "our world" - try to buy an ignorant collet that can hold any better than a quarter-tenth reliably. If-even at all.

    And it is not the only player in the game, even if it can do.

    Wanna know where the practical limits on your machine might be?

    Don't ignore the workholding.

  11. #8
    Join Date
    Dec 2018
    Country
    UNITED STATES
    State/Province
    Indiana
    Posts
    129
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    20

    Default

    So if I see or hear "that lathe/mill can hold tenths" roughly means it can hold .0003" whether +/-.00015" or -.0003/+0" ect.?

  12. #9
    Join Date
    Jan 2014
    Location
    Temecula, Ca
    Posts
    3,276
    Post Thanks / Like
    Likes (Given)
    1396
    Likes (Received)
    4259

    Default

    holding +/- .00005 would be splitting tenths.

  13. Likes mkd, litlerob1 liked this post
  14. #10
    Join Date
    May 2019
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    1,432
    Post Thanks / Like
    Likes (Given)
    395
    Likes (Received)
    639

    Default

    Once someone plunges below the surface of "thousandths" a whole gang of genies raise their heads.

    All kinds of culprits you wouldn't dream of in the +-.003 world.

    Kind of a fun challenge, but the first part is usually not in tolerance in my experience........

  15. Likes LockNut, Fancuku liked this post
  16. #11
    Join Date
    Mar 2005
    Location
    Kansas
    Posts
    7,897
    Post Thanks / Like
    Likes (Given)
    486
    Likes (Received)
    3757

    Default

    Holding tenths is easy. I like to hold at least 50 of them at a time.

  17. Likes Murf, mkd, Greg White, mountie, TeachMePlease and 3 others liked this post
  18. #12
    Join Date
    Dec 2018
    Country
    UNITED STATES
    State/Province
    Indiana
    Posts
    129
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    20

    Default

    Ok think I just say it differently. If the print says .250" +/-.005" I say it as I have to hold that part within ten thousandths. Or .250" +/-.0005" I say I have to hold it within a thou. .250 +/-.00005" I have to hold a tenth.

  19. Likes bryan_machine liked this post
  20. #13
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    31,255
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    9811

    Default

    Quote Originally Posted by Larry Dickman View Post
    holding +/- .00005 would be splitting tenths.
    Or wasting the hours of yer life if it is for "braggin' rights", not a genuine need .. preferably one being PAID FOR.

    By "others." Not yer own sweaty arse!



    Love it when... the brag is heard that a 10EE has had new bearings fitted.. TIR actually measured.. at 35 millionths.... and then?

    There's a beat half to shit used 3-J scroll-operated chuck or a recycled and badly "lobed" 5C closer on the spindle!

    Even ER-series only spec an average TIR of .00006 or "premium" @ .00002 brand-new.


    Chain is only as strong as its weakest link kind of thing?

  21. #14
    Join Date
    May 2017
    Country
    UNITED STATES
    State/Province
    Minnesota
    Posts
    1,220
    Post Thanks / Like
    Likes (Given)
    1529
    Likes (Received)
    822

    Default

    Anything tighter than +/- .001" is holding tenths. +/- .0001" is within a tenth. But if you really want to know capability you have to do a capability study.

  22. #15
    Join Date
    Nov 2005
    Country
    UNITED STATES
    State/Province
    Illinois
    Posts
    2,099
    Post Thanks / Like
    Likes (Given)
    216
    Likes (Received)
    1761

    Default

    Holding tenths is all about making variables disappear and keeping things constant. From strict climate control, allowing incoming material to climatize ( sometimes for days) to ambient temperature, and even maintaining consistent air pressure. Even a new lathe with a perfectly clean curvic coupling can vary 10-20 millionths every index. Do you think a tapered tool holder goes into a spindle the same every tool change, nope!

  23. Likes aarongough, PegroProX440 liked this post
  24. #16
    Join Date
    Jun 2013
    Country
    UNITED STATES
    State/Province
    California
    Posts
    1,054
    Post Thanks / Like
    Likes (Given)
    739
    Likes (Received)
    465

    Default

    attended a tech meeting this week. Our coolcore spindle is reported by a customer to be holding .0001" all day long. Go figure; keeping your spindle shaft at a constant temperature has benefits.

  25. #17
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    31,255
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    9811

    Default

    Quote Originally Posted by mkd View Post
    attended a tech meeting this week. Our coolcore spindle is reported by a customer to be holding .0001" all day long. Go figure; keeping your spindle shaft at a constant temperature has benefits.
    Yah but.... also a "benefit" if yah let her disengage now and then to go wash and fetch yah a cold beer as well, aint it?

    Holding "repeatability" through second and thirds was challenge enough... "tenths" more often brag than reality.

  26. Likes Vancbiker liked this post
  27. #18
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    4,880
    Post Thanks / Like
    Likes (Given)
    1289
    Likes (Received)
    2758

    Default

    To the OP, if you're holding Tenths it's plural. If you're holding a Tenth it ain't. If you're holding a Thousandth, you're holding Ten Tenths, but if you're holding Eleven of them.....?

    I gave up trying to learn shop lingo, it varies too much shop to shop. So I speak exactly what I mean, and ask for clarity when someone starts talking about Spiders and Cat Faces. I might know exactly what they are referring to, but it can cost you in the end.

    R

  28. #19
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    31,255
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    9811

    Default

    Quote Originally Posted by turnworks View Post
    So if I see or hear "that lathe/mill can hold tenths" roughly means it can hold .0003" whether +/-.00015" or -.0003/+0" ect.?
    Half a THOU is "five tenths".

    So what it REALLY means.. "all manual", AKA anything BUT high-end, reasonably new, and above all well maintained, expertly tooled, and respectfully, professionally don't-fuck-this-machine-up operated uber-kicker CNC?

    "I don't have to work at all hard to hit +/- ONE thou."

    +/- TEN TENTHS or +/- FIVE TENTHS ....is still "working to tenths" ain't it?



    ..there isn't really all that much in the way of uber-precision bearings and seals, bleeding(NOT) edge hydraulics, laser optics, silicon wafer, or such out there in the typical small / medium machine shop's economic reach.

    "Deep Pocket" investment. Big Dog turf. And the "niche" markets of their speciality contractors. DoD, Aerospace. NASA, etc.

    The environmental control needs, metrology and calibration cost a lot of money, even before yah roll-in the machine as can "JFDI".

    Half the places as CAN do it didn't really HAVE TO. Just came in the door with the territory as the capabilities of their machining gear was ramped-up in general to raise throughput, reduce costs, extend tool life, and reduce labour component and scrap rates at lesser specs.

    And then they could. And then they advertised it to whomp-up on competitors who still could NOT. And then products as could benefit found affordable capacity.

    Lather, rinse, repeat, up yer game, do to again, better and faster... and take it as "standard".

  29. #20
    Join Date
    Jan 2002
    Location
    West Coast, USA
    Posts
    8,428
    Post Thanks / Like
    Likes (Given)
    570
    Likes (Received)
    5946

    Default

    Another way to look at it is machine capability versus required part tolerance.

    A machine that can run "tenths" (however, many that may be) will stay within tolerance over a run of multiple parts. Usually takes a "capability study" and a long run of parts. To do so it would have to be both inherently precise and accomodate for thermal effects, variations in material, check for tool wear, and so on. Very few ordinary machine tools are capable of staying within +/- .0001" pretty much on their own; much less +/- .00005"

    The trick is trying meeting a part spec closer than your machine capability. That can require a whole lot of fiddling, in-process measurement, holding your tongue just right while you sneak up on dimensions, and likely scrapping some parts until you get the hang of it. If at all.

    I'd think that when a typical lathe or mill hand talks about working to "tenths" - they mean the occassional hole locations, bearing fits, sliding fits, etc. where a few critical dimensions need to be held a whole lot closer than .001". Different story with something like turbines, automotive valve bodies, etc. - where there may be dozens of tight and critical dimensions -- and require machine tools and operators capable of holding those tolerances.

  30. Likes mhajicek liked this post

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
  •