Page 1 of 17 12311 ... LastLast
Results 1 to 10 of 161

Thread: Measuring spline shaft

  1. #1
    Join Date
    Apr 2009
    Location
    Columbus Texas
    Posts
    683

    Default Measuring spline shaft

    I was measuring a spline shaft and couldn’t come up with any thing that looks right or common. So was I doing it right? It was 24 teeth and came out to be 1.264 I measured the tops of the opposing teeth. Doesn’t sound right and doesn’t look worn out either. So is this just an oddball or what.

  2. #2
    Join Date
    Nov 1999
    Location
    SE OZ
    Posts
    2,164

    Default Look a bit further

    I doubt it.

    A spline is very similar to a spur gear in many respects - as are the calculations.

    It will have a pitch circle, addendum, dedendum, tooth depth (includes clearance below the base circle) as well as pressure angle, clearance/back-lash etc. It may have teeth with parallel or radial teeth or teeth with involute or other forms or profiles.

    Machinery's Handbook and/or the manufacturers hand-book/manual or catalogue etc. should set you right.

  3. #3
    Join Date
    Jun 2006
    Location
    Austin, Texas
    Posts
    15,651

    Default

    Quote Originally Posted by oldtiffie
    A spline is very similar to a spur gear in many respects - as are the calculations.

    It will have a pitch circle, addendum, dedendum, tooth depth (includes clearance below the base circle) as well as pressure angle, clearance/back-lash etc.
    Depends on the spline.

    A common spline has straight sides -- there are no involute curves involved.

    If you're talking about an automotive involute spline, they almost always use a stub form, typically 12/24 DP, or 16/32DP. The numerator defines the diametral pitch, and the denominator is the stub pitch. Involute splines are almost always 30° pressure angle.

    By the way, involute splines support a lot more torque than a straight-sided spline, because of their self-centering behavior.

    Edit: DP = (Num Teeth + 2)/OD, so I'm getting 26/1.264 = 20.57 DP, which probably means it's not an involute spline.
    Last edited by lazlo; 07-30-2009 at 12:15 PM.
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

  4. #4
    Join Date
    Mar 2003
    Location
    LAS CRUCES NM
    Posts
    443

    Default SAE Involute spline outside dia's.

    Old SAE spline OD equations:

    Basic Flat root side fit Outside Diameter = ((N+0.8)/DP) -0.004".



    Basic Flat root Major Fit Outside Diameter = ((N+1)/DP) -0.0001".



    Basic Fillet Root Side Fit Outside Diameter = ((N+1)/DP).

    Use the primary Pitch number: 12 as in 12/24. 16 as in 16/32. 20 as in 20/40.



    Your example does not apear to fit either of the 20/40 DP possibles, maybe a Metric Involute Spline?

    Laslo, need another edit?



    Cheers,
    Les H.
    The Impossible Takes Just A Little Bit Longer!

  5. #5
    Join Date
    Jun 2006
    Location
    Austin, Texas
    Posts
    15,651

    Default

    Les, you're the Gear Master, but my notes from Boston Gear say:

    Diametral Pitch (P) = Outside diameter (OD), Number of teeth(N):

    P=(N+2)/OD

    Edit: Ah, I see the problem: the stub tooth form uses 80% of the full DP addendum, hence the:

    Outside Diameter = ((N+0.8)/DP)
    Last edited by lazlo; 07-30-2009 at 05:25 PM.
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

  6. #6
    Join Date
    Nov 1999
    Location
    SE OZ
    Posts
    2,164

    Default Spline type?

    Quote Originally Posted by jeremy13
    I was measuring a spline shaft and couldn’t come up with any thing that looks right or common. So was I doing it right? It was 24 teeth and came out to be 1.264 I measured the tops of the opposing teeth. Doesn’t sound right and doesn’t look worn out either. So is this just an oddball or what.
    There will be considerable less guessing if the OP were to post a pic or two and any related sketches or notes.

    The spline need not necessarily be straight or involute or stub - as it is small enough and with 24 teeth it may well be a micro-spline.

    The requested/suggested pics etc will narrow the "way ahead" down considerably as well as confine the discussion to the specific job instead of gears and splines generally.

    Micro-splines - with straight faces - are very strong and are self-centre-ing as well.

    Its all guess-work until or unless we get more information from the OP - jeremy13

  7. #7
    Join Date
    Apr 2009
    Location
    Columbus Texas
    Posts
    683

    Default

    The shaft is the male part of a stub shaft that fits into the female output shaft on an 350hp gasturbine, a Garrett 85. My dial cal blades are not fine enough to go to the root of the spline but it is close to 1.087 A few camera phone pic. will get better ones later.



  8. #8
    Join Date
    Jun 2006
    Location
    Austin, Texas
    Posts
    15,651

    Default

    Quote Originally Posted by oldtiffie
    Micro-splines - with straight faces - are very strong and are self-centre-ing as well.
    Straight-sided splines aren't self-centering Mick. With an involute splines, like an involute gear, the teeth roll into- and out-of mesh, which creates a self-centering action under load even when there is backlash between mating members.

    They're a PITA to cut, so unless you need to minimize backlash, or need the increased torque load, it's vastly easier to cut a straight-sided spline.

    Jeremy, that's an involute spline. Have fun

    A lot of guys in the Off-Road world take the short-cut of using a 60* TPG insert in a flycutter to cut triangular splines to mate with the involute female spline. Can't say how well that will work or how long it would last in a gas turbine. Maybe Les or Sir John can comment...
    Last edited by lazlo; 07-30-2009 at 07:43 PM.
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

  9. #9
    Join Date
    Nov 1999
    Location
    SE OZ
    Posts
    2,164

    Default All geared up

    Lazlo.

    I agree that it is probably an involute form and as such will be self-centre-ing in that situation.

    A micro-spline has straight flanks that are not radial nor are they parallel. They have the form of a vee and as such are also self-centre-ing.

    Some splines are gears - as they are a 1:1 drive (same direction) in a mating female and also in mesh with a mating gear (reversal of direction) - as this may or may not be.

    The up-coming pics and measurements from the OP should clarify the issues somewhat and enable the discussion to keep addressing specific instead of general issues.

  10. #10
    Join Date
    Mar 2001
    Location
    Nottingham, England
    Posts
    15,247

    Default

    You can't take the outside of a gear or spline as gospel as the tips don't do anything. A gear 30 thou undersize will still run the same as one on size provided that the calculations based on the PCD are the same.

    Only way to sort this is to measure across pins or 3 or more teeth.

    Chances are it's a 20/40 DP either on size but with underside OD or it's been corrected.

    Loads of automotive gears / splines are corrected to keep you in the spares supply chain.

    .
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •