1950's collet question
Close
Login to Your Account
Results 1 to 15 of 15
  1. #1
    Join Date
    Jun 2007
    Country
    UNITED STATES
    State/Province
    Nevada
    Posts
    529
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    66

    Default 1950's collet question

    I got a manual for a Hamilton hobber, because who doesn't like reading old hobber manuals? It includes a print of the work spindle so the necessary collet holders can be made by the user. Here it is, the collet angle is 9 degrees 32 minutes. That works out to 2.0153 inches per foot total or 1.0076 inch per foot that is the physical setting of a taper attachment.

    Can anyone provide a rational for such an odd angle? I am at a loss.

    img_0934.jpg

  2. #2
    Join Date
    Apr 2004
    Location
    Modesto, CA USA
    Posts
    7,154
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    1219

    Default

    It is like a morse taper. They shot for a nice number and missed a little bit. rather then toss thousands of existing machines and collets they just accepted the existing standards after measurement equipment became good enough to measure it was not perfect.
    They tried for 1 inch per foot and got 1.00 per foot or better. The modern micrometer came out around 1867.
    Bil lD.

  3. #3
    Join Date
    Nov 2003
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    5,192
    Post Thanks / Like
    Likes (Given)
    184
    Likes (Received)
    1661

    Default

    They used a 12" arbor between standard, 60 degree centers. They offset the tailstock center by exactly ONE inch. The arbor had the standard 60 degree holes to fit those 60 degree centers.

    BUT the one inch offset did not allow the centers to seat properly in the holes and the effective distance was NOT 12 inches. It was less. So the taper is greater than 1" in 12".

    I have always wondered about the use of offset centers for turning a taper. It can't work right. It just can't.

    Alternate theory: they used a taper attachment with a stamped scale for the taper. The markings are probably 0.005" or more wide. And they were probably an equal amount off their proper locations. So an error between 0.005" and 0.010" is what you would expect.

    Either way, they probably made a million of them on the same machine with the same set-up so they were all the same. And they made the reamers for the tapered holes on that machine too. By then, it was too late to change it. So then they had to copy the error in that original set up.

    When I read some of the short cuts that many machinists on THIS board think are good enough, I cringe. These things still go on today.

    PS: They had micrometers in 1950. Good ones too. I have one from that time frame and it checks out to +/- 0.0002" or better over it's full range. My worst complaint about it is the anvils are not completely flat: I can see a 0.0001" difference from one side to the other. It is not my best mike, but I do use it.

  4. #4
    Join Date
    Oct 2009
    Location
    Louisville, KY, USA
    Posts
    972
    Post Thanks / Like
    Likes (Given)
    214
    Likes (Received)
    217

    Default

    If I recall correctly, Brown and Sharpe taper is the only Self holding taper that in any way uses round numbers and it's no longer in use.

    Blame it on the engineers and move on.

  5. #5
    Join Date
    Apr 2004
    Location
    Modesto, CA USA
    Posts
    7,154
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    1219

    Default

    What makes you think the collet. was standardized in 1950 and not 1850? I found no reference to a Hamilton collet standard dimensions.
    Bill D.

    My Drill press was made around 1952 but the mt3 quill taper was standardized around 1864. Drills and arbors made today still follow the slightly off taper from 1864. 0.60235" per foot is what it is supposed to be, 5/8' per foot or 0.625. If you are in china and make it 0.625 like it should be all you will make is garbage since it will not engage existing tooling.

  6. #6
    Join Date
    Sep 2002
    Location
    Riddells Creek,Victoria,Australia
    Posts
    471
    Post Thanks / Like
    Likes (Given)
    90
    Likes (Received)
    65

    Default

    Your maths is slightly out, 9 degrees 32 minutes is very close to 2.0 inches per foot (1.000638 per side) but not close enough for a spindle.

  7. Likes Red James liked this post
  8. #7
    Join Date
    Jun 2007
    Country
    UNITED STATES
    State/Province
    Nevada
    Posts
    529
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    66

    Default

    Thanks for checking, On my calculator the tan(9degrees 32'=9.533 degrees)*12 = 2.0153.

    For arctan(2*1.000638/12) I get 9.4653 = 9 degrees 27.9'

    Can you check again?

    Even before I saw Australia I knew you from the UK. When I went to 5th grade in Oxford they called it "Maths." The other kids thought I was funny because I said "Math."

  9. #8
    Join Date
    Sep 2002
    Location
    Riddells Creek,Victoria,Australia
    Posts
    471
    Post Thanks / Like
    Likes (Given)
    90
    Likes (Received)
    65

    Default

    Yes, Math always sounded wrong to me too.
    I did check my Trig calculations again and came up with the same answer, can someone else check it please?

  10. #9
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    10,443
    Post Thanks / Like
    Likes (Given)
    3558
    Likes (Received)
    3716

    Default

    QT: [Can anyone provide a rational for such an odd angle? I am at a loss.]
    It is hard to rationalize machine tapers when one looks at Morse and Brown and Sharpe with many only a few thousandth or tenths difference in TPI or TPF, when many or most could have been the same taper like Jarno did. Even Jacobe has some only a few thousandths difference.

    Dimensions of Standard Tapers - VintageMachinery.org Knowledge Base (Wiki)

  11. #10
    Join Date
    Jan 2013
    Location
    Plainfield, Indiana, USA
    Posts
    1,762
    Post Thanks / Like
    Likes (Given)
    1344
    Likes (Received)
    935

    Default

    Sorry Bill, but you need to use the angle PER SIDE which is 4.76666 degrees. Then do the same math and you get the same as LexD

  12. #11
    Join Date
    Sep 2002
    Location
    Riddells Creek,Victoria,Australia
    Posts
    471
    Post Thanks / Like
    Likes (Given)
    90
    Likes (Received)
    65

    Default

    Thanks for checking Red.

  13. #12
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    28,844
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8957

    Default

    Quote Originally Posted by bll230 View Post
    Even before I saw Australia I knew you from the UK. When I went to 5th grade in Oxford they called it "Maths." The other kids thought I was funny because I said "Math."
    They've had a rapacious Feudal system and lying pols longer is all.

    Wait 'til we elect a Sandalista as Prez, and we'll have a dozen flavours of "maths", plural, to empty one pocket or pay envelope into another "hole" as well. "Free" anything means free of ass and related ass-ettes, no more "money worries" 'coz you won't HAVE any. Money, nor ass, either one. Just worries. Humankind is meant to keep doing this shit until they get it all, right?



    Tapers: Oscar "jarno" Beale was B&S head guru when he invented jarno. Note from MT, B&S, Jacobs that it only NEEDS a very slight change in angle to get easy-release MT - good for drills - walk-out resistant B&S - good for mills - or damned-near WELDED-on Jacobs tapers.

    Also note they all have CHANGES within their size ranges off the back of pragmatic experience and minor optimizations.

    Beale tried to eliminate those with a mathematically regular plan. ANY size of jarno - even in-between or imaginary ones - has the same angle and has its size specs embedded right in its nomenclature.

    As with the Metric system vs "US" fasteners, it looked right sweet as a "standard" ...on paper. But...didn't work as well in practice as all those irregular ones, each OPTIMIZED to do the job best in their size.

    Run into any GENUINE oddball taper? Don't bitch. Just prepare to duplicate it, and be glad that isn't all that difficult to do that.

    Probability is VERY high it was the result of testing to get best results for the mating alloys, hardness, wall thicknesses, balance of working stresses, hold & release, etc. - to serve its given application as well as it could BE served.

    I did say "optimize"?

  14. #13
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    28,844
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8957

    Default

    Quote Originally Posted by EPAIII View Post
    I have always wondered about the use of offset centers for turning a taper. It can't work right. It just can't.
    It works better if your TS end can be "aimed" along the axis, not held parallel to it. Which isn't actually hard, especially if the job is to do "many", not just the odd one-off.

    And why d'you think "bell" mouth curved side center drills and ball-end centres or cup centres with "the old bearing-ball trick" came to exist?

    Not "perfect". Yah still have to compensate. Just less IMperfect as wear during the cut accrues.

  15. #14
    Join Date
    Jun 2007
    Country
    UNITED STATES
    State/Province
    Nevada
    Posts
    529
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    66

    Default

    Red, Lex, thanks for pursuing this and straightening me out. I was conflating the included taper, which is the taper attachment tickmark setting, with the triangle math of one side, which is the dial indicator setting of the taper.

    You are absolutely right, I had the wrong result. Now taking your result and extending it, if I work backwards at 1 inch per foot, then the arctan of 1/12 gives 9.5273 degrees included angle which is then 9 degrees 31.637 minutes, or rounded to 9 degrees 32 minutes. Now we are back to EPA's comment, they used a inch offset in some fashion to get their taper.

    I doubt I'll ever have need to make that taper, but I am thinking about a B&S 9 part I need to make, and this thread will help me stay straight on any taper attachment setting.

    John

  16. #15
    Join Date
    May 2011
    Location
    southern in.
    Posts
    1,480
    Post Thanks / Like
    Likes (Given)
    1968
    Likes (Received)
    400

    Default

    Any time you can't figure out the answer to a problem, you have left out the dollar sign. That being said, many oddball designs such as tapers are different so as to avoid copyright or patent litigation.

    JH


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
  •