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  1. #21
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    Quote Originally Posted by metaltech View Post
    I've been asked to assist with the set-up of a job on a CNC lathe to cut female threads in a piece of steel tubing. I was given a hand-drawn "print" with basic dimensions, but not enough on the thread. The thread is tapered, has round crests and roots, 10 threads/inch. The notation that points to the thread says "1.315 x 10NU". The part itself is called a collar, and connects long pieces of pipe that go down into the ground. (At least these people call it a collar. I've also come across the terms pin and box, but I don't know if these are just oilfield terms for the male pipe and female coupling.)

    I need to know several things:

    1) taper angle
    2) how to check the thread - does someone make guages?
    3) what tooling company makes a good threading bar and inserts? I assume a topping-type insert is needed.

    I looked on the API website and found that they offer a few billion publications for the oil industry! I found a listing for threading tubing products, but it's well over $100 for 48 pages, and I don't even know if it's what I need. I only want the specs for one thread. Does anyone know of other sources for this info?

    I've put all the time I can afford into searching the PM website and not come up with my answer (maybe I don't know how to search properly). So, I'm appealing to all you smart types out there. Thanks for your help!!

    metaltech
    I'm in a similar situation!

    I'm going to make thread measurement inserts to measure pitch diameter of an external and internal API thread.

    The threads are API 4½ IF (Internal Flush) and can be seen on this link.
    DRILL PIPE USA - Drill Pipe Thread Data

    The way I intend to measure is to use the end of each part (D on the external thread and diameter B on the internal thread) as my starting point. I'll then measure the thread pitch diameter at a specified length/distance from these two starting points.

    My problem is that I can't find any standard that gives the distance (or distances) I need. I also need to know the pitch diameter tolerance at the measurement point (or points). It's very easy with NPT as all this is specified in detail.

    How are the two part supposed to relate to each other when tightened? Is there for example a certain distance (plus minus something) the shoulder at diameter C should be from the shoulder at diameter B?

    API seems to be the worst specified thread I know as far as the important dimensions are concerned.

    In addition to DRILL PIPE USA - Drill Pipe Thread Data (IF Internal Flush)
    then I've drawn this because as far as I can see it is a question of the max. min. length of "X" that is important.
    http://www.f-m-s.dk/API.JPG

    As already mentioned what I'm after is the pitch diameter size and tolerance at a specific depth but failing that then does anyone know the max. min. for "X" and I can then probably calculate backwards?

    I have received several links with technical information (and thanks for that) but so far not what I really need.
    Can anyone out there help me?

  2. #22
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    These are all checked with API gages Gordon, and I suppose those gages are detailed in the appropriate API publication. All the Drilco book gives is machining dimensions and gage stand off, which was .620/.635" on pin and flush to .010" in on box for 4 1/2 IF.

    J.O.

  3. #23
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    Quote Originally Posted by johnoder View Post
    These are all checked with API gages Gordon, and I suppose those gages are detailed in the appropriate API publication. All the Drilco book gives is machining dimensions and gage stand off, which was .620/.635" on pin and flush to .010" in on box for 4 1/2 IF.
    J.O.
    John, I've been told today that there is a (USA) company that supplies measuring equipment for API threads. As they charge almost $1,500 for a software program for dimensions and tolerances I can't even begin to guess how much hardware will cost

    If I could only get the dimensions and tolerances I need (and it is only a couple) I'm thinking it would cost less than $1,000 to be able to measure both a mating external and internal API thread. In fact I know it can.

    What is the most the two shoulders should be from each other when the thread is tightened? That's about all I need to know.

    Does anyone have a mating couple and let me know?

  4. #24
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    The name of the Drilco book is Rotary Shouldered Connections, and I gather there is no space beween the shoulders, by design.

    I.E. the male and female threads NEVER mate up metal to metal until the shoulders do.

    Completely different from, say, NPT

    J.O.

  5. #25
    Limy Sami is online now Diamond
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    Not knowing much about oil patch threads I googled ''rotary shouldered connections''

    Found this, which sort of explained things - a bit or in a word - YIKES!

    Fast make-up fatigue resistant rotary shouldered connection

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    Quote Originally Posted by johnoder View Post
    The name of the Drilco book is Rotary Shouldered Connections, and I gather there is no space beween the shoulders, by design.

    I.E. the male and female threads NEVER mate up metal to metal until the shoulders do.

    Completely different from, say, NPT

    J.O.
    Thanks John. Sounds to me like a glorified morse taper. I believe I can come up with something that'll do that - shoulders meet with a little thread slack as possible.

    A wee bit of "humour" now. I have never had BP as a customer so I had nothing to do with what happened in The Gulf!

  7. #27
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    Quote Originally Posted by Limy Sami View Post
    Not knowing much about oil patch threads I googled ''rotary shouldered connections''

    Found this, which sort of explained things - a bit or in a word - YIKES!

    Fast make-up fatigue resistant rotary shouldered connection
    It just goes to prove the old saying, "Why make things easy if they can be made complicated"

    I remember one guy who refused to look at my thread measurement inserts and gave the reason, "If they were as easy to use as you claim they'd have been invented years ago".

    Trying something and not liking it is one thing but refusing to try it is pretty stupid. There are some things I won't try but that's because I consider then dangerous or think they might taste like shit LOL Not that I know how that tastes

  8. #28
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    They have to take quite a bit of torque, maybe hold up 80 tons of drill string, plus by the way, not leak too much 15,000 psi dilling "mud".

    I suppose that is one more reason for having the shoulders jammed together nice and tight.

    J.O.

  9. #29
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    Quote Originally Posted by johnoder View Post
    They have to take quite a bit of torque, maybe hold up 80 tons of drill string, plus by the way, not leak too much 15,000 psi dilling "mud".

    I suppose that is one more reason for having the shoulders jammed together nice and tight.

    J.O.
    John, I've thought more after reading what you wrote and I'm 95% sure I can come up with something that'll work. As I'm at -1 GMT and it is 11.15 pm) I'll give it more thought tomorrow. The fact that the shoulders must touch makes it solvable

    When I've mulled it over I'll write in here how I intend doing it and then see what comments I get.

    G'night

  10. #30
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    Quote Originally Posted by edmontonguy2005 View Post
    Hello Guys
    Onyone Have A Api Thread Specs Drawing? Please Tell Me Where Do I Go To Buy Full Binder With All Type Api Thread ? Thanks Very Much Guys.
    API specification 5B covers it and here's one source:

    API Spec. 5B

    Here's the table of contents:

    Page
    1 Scope . . . . 1
    1.1 Coverage . . . . 1
    1.2 Inspection . . . . 1
    1.3 Other Requirements. . . . 1
    2 References . . . . 1
    2.1 General . . . . 1
    2.2 Requirements . . . . 1
    3 Definitions . . . . 1
    4 Thread Dimensions and Tolerances . . . . . 2
    4.1 Line Pipe, Round Thread Casing and Tubing, and Buttress Thread Casing . . . . . 2
    5 Thread Inspection . . . . 22
    5.1 Line Pipe, Round Thread Casing and Tubing, and Buttress Thread Casing . . . . . 22
    6 Gauging Practice . . . . 36
    6.1 Line Pipe, Round Thread Casing and Tubing, and Buttress Thread Casing . . . . 36
    7 Gauge Specification . . . . . 39
    7.1 Line Pipe, Round Thread Casing and Tubing, and Buttress Thread Casing . . . . . 39
    8 API Gauge Certification . . . . . . . . . 56
    8.1 Line Pipe, Round Thread Casing and Tubing, and Buttress Thread Casing . . . . . 56
    9 Thread Marking . . . . . . 57
    Appendix A Instructions for Shipment of Master Gauges.. . . . . 59
    Appendix B Marking Instructions for API Licensees . . . . . 61
    Appendix C API Gauge Certification Agency Requirements . . . . . 63
    Appendix D Supplementary Requirements (Normative) . . . . . 65
    Appendix E Tables in International Standard Units . . . . . 69
    Appendix F Figures in International Standard Units . . . . .91
    Appendix G Extreme-Line Casing . . . . .97
    Figures
    1 Line Pipe Thread Form . . . 5
    2 Basic Dimensions of Line Pipe Thread Hand-Tight Make-Up . . . . . . 5
    3 Basic Dimensions of Casing Round Threads Hand-Tight Make-Up . . . . . 8
    4 Casing Round Thread Form . . . . 8
    5 Basic Dimensions of Buttress Casing Threads Hand-Tight Make-Up. . . . . . 12
    6 Buttress Casing Thread Form and Dimensions—for Casing Sizes 41/2 through 133/8. . . . 13
    7 Buttress Casing Thread Form and Dimensions—for Casing Sizes 16 and Larger . . . . . 14
    8 Basic Dimensions of Tubing Round Threads Hand-Tight Make-Up . . . . 17
    9 Tubing Round Thread Form . . . 17
    v
    Page
    10 Typical External-Thread Taper Gauge . . . . 25
    11 Typical Internal-Thread Taper Gauge for Threads in Sizes 41/2 and Larger . . . . 25
    12 Typical Internal-Thread Taper Gauge for Threads in Sizes Smaller than 41/2 . . . . 26
    13 Typical Run-Out Gauge for Buttress Thread Casing. . . . . . 26
    14 Typical Lead Gauges . . . . . . 28
    15 Typical Thread Height Gauges. . . 30
    16 Typical Thread Height Gauge for Internal Threads in Nominal Sizes Smaller than 3. . . . 30
    17 Typical Thread-Contour Microscope for Measuring Thread Angle and Checking Thread Form . . . . . 31
    18 Typical Single Dial Gauge for Buttress Threads . . .. . 33
    19 Typical Check Pieces for Setting Dial Gauges . . . . . 33
    20 Typical Machine for Checking Coupling-Thread Alignment. . . . . . 34
    21 Typical Application of Coupling-Thread Alignment Gauge . . . . . . 35
    22 Gauging Practice for Line Pipe Threads and Casing and Tubing Round Thread
    Hand-Tight Assembly . . . . . . 37
    23 Gauging Practice for Buttress Casing Threads Hand-Tight Assembly. . . . . . 37
    24 Comparison of Line Pipe Gauges Made Subsequent to 1940 and Gauges Made Prior to 1940. . . . . . 40
    25 Thread Gauge for Line Pipe and Round Thread Casing and Tubing. . . . . 44
    26 Thread Gauge for Buttress Casing. . . .. 44
    27 Gauge Thread Form for Line Pipe and Round Thread Casing and Tubing. . . . . 45
    28 Gauge Thread Form and Dimensions for Buttress Casing . . . . 45
    29 Gauge Thread Form and Dimensions for Buttress Casing .. . . . 46
    30 Bolt Circles and Back-Up Plate Dimensions for Line Pipe, Buttress Casing and Short or
    Long Round Casing Master Plug Gauges . . . . . 46
    D1 Basic Dimension of Power Tight Make-Up . . . . . 65
    D2 SR22 Casing Round Thread Form . . . . . . 66
    5M Basic Dimensions of Buttress Casing Threads Hand-Tight Make-Up. . . . . . 92
    6M Buttress Casing Thread Form and Dimensions—for Casing Sizes 41/2 through 133/8. . . . . 93
    7M Buttress Casing Thread Form and Dimensions—for Casing Sizes 16 and Larger. . . . 94
    D2M SR22 Casing Round Thread Form . . . . . 95
    G1 Machining Details—Sizes 5 through 75/8. . . . . 104
    G2 Machining Details—Sizes 85/8 through 103/4. . . . . 105
    G3 Box and Pin Entrance Threads—Sizes 5 through 75/8. . . . . 106
    G4 Product Thread Form—Sizes 5 through 75/8. . . . 107
    G5 Box and Pin Entrance Threads—Sizes 85/8 through 103/4 . . . . . 108
    G6 Product Thread Form—Sizes 85/8 through 103/4 . . . . . 109
    G7 Gauging Practice for Extreme-Line Casing . . . . . . . . . 110
    G8 Bolt Circles and Back-Up Plate Dimensions for Extreme-Line Casing Master Plug Gauges. . . . . . . 111
    G9 Gauge Details—Size Designations 5 through 75/8 . . . . . . 112
    G10 Gauge Details—Size Designations 85/8 through 103/4 . . . . . . . 113
    G11 Gauge Thread Form—Size Designations 5 through 75/8. . . . . 114
    G12 Gauge Thread Form—Size Designations 85/8 through 103/4 . . . . . . . 115

    Tables

    1 Line Pipe Thread Height Dimensions . . . . 6
    2 Tolerances on Line Pipe Dimensions . . . . 6
    3 Line Pipe Thread Dimensions .... 7
    4 Casing Round Thread Height Dimensions . . . . 9
    5 Tolerances on Casing Round Thread Dimensions . . . . . 9
    6 Casing Short-Thread Dimensions . . . . . 10
    7 Casing Long-Thread Dimensions . . . . . . . 11
    8 Tolerances on Buttress Casing Thread Dimensions. . . . . . 15
    9 Buttress Casing Thread Dimensions . . . . 16
    10 Tubing Round Thread Height Dimensions . . . . . 18
    11 Tolerances on Tubing Round Thread Dimensions. . . . . . 19
    12 Non-Upset Tubing Thread Dimensions . . . . . 20
    13 External-Upset Tubing Thread Dimensions . . . . . 20
    14 External-Upset Long Round Thread Dimensions for Fiberglass Pipe. . . 21
    15 Integral-Joint Tubing Thread Dimensions . . . . . 21
    16 Round Nosed Ends . . . . . 22
    17 Compensated Thread Lengths for Measurements Parallel to the Taper Cone. . . . . . 28
    18 Line Pipe Thread Gauge Dimensions . . . . 47
    19 Short and Long Round Casing Thread Gauge Dimensions . . . . 48
    20 Buttress Casing Thread Gauge Dimensions . . . . . 49
    21 Non-Upset Tubing Thread Gauge Dimensions. . . . . 50
    22 External-Upset Tubing Thread Gauge Dimensions . . . . 51
    23 Integral-Joint Tubing Thread Gauge Dimensions . . . . . 51
    24 Gauge Thread Height Dimensions for Line Pipe . . . . . 52
    25 Gauge Thread Height Dimensions for Round Thread Casing and Tubing. . . . . 52
    26 Tolerances on Gauge Dimensions for Line Pipe . . . . . . . 53
    27 Tolerances on Gauge Dimensions for Round Thread Casing and Tubing . . . . . . 54
    28 Tolerances on Gauge Dimensions for Buttress Casing . . . . . . 55
    D1 Enhanced Leak Resistance LTC Thread Dimensions . . . . . 67
    D2 Dimensional Tolerances on SR22 Casing 8-Round Thread Dimensions . . . . . 68
    1M Line Pipe Thread Dimensions ...70
    2M Tolerances on Line Pipe Thread Dimensions. . . . . 70
    3M Line Pipe Thread Dimensions. . . . 71
    4M Casing Round Thread Height Dimensions . . . . . 72
    5M Tolerances on Casing Round Dimensions . . . . . 73
    6M Casing Short-Thread Dimensions . . . . . 74
    7M Casing Long-Thread Dimensions. . . . . . 75
    8M Tolerances on Buttress Casing Thread Dimensions. . . . . 76
    9M Buttress Casing Thread Dimensions . . . . . . 77
    10M Tubing Round Thread Height Dimensions. . . . . 77
    11M Tolerances on Tubing Round Thread Dimensions . . . . 78
    12M Non-Upset Tubing Thread Dimensions . . . . . . 79
    13M External-Upset Tubing Thread Dimensions.. . . . 79
    14M External-Upset Long Round Thread Dimensions for Fiberglass Pipe . . . . . 80
    15M Integral-Joint Tubing Thread Dimensions . . . . . . 80
    16M Round Nosed Ends. . . . . 81
    17M Compensated Thread Lengths for Measurements Parallel to the Taper Cone . . . . 81
    D1M Enhanced Leak Resistance LTC Thread Dimensions. . . . . 82
    D2M Dimensional Tolerances on SR22 Casing 8-Round Thread Dimensions . . . . 83
    G1M Extreme-Line Casing—Label 1—5 through 75/8 . . . . 84
    G2M Extreme-Line Casing—Label 1—85/8 through 103/4 . . . . . 86
    G3M Inspection of Extreme-Line Threads and Seals with Dimensions and Tolerances. . . . . 88
    G1 Extreme-Line Casing—Sizes 5 through 75/8 . . . 116
    G2 Extreme-Line Casing—Sizes 85/8 through 103/4.. . . . 118
    G3 Inspection of Extreme-Line Threads and Seals with Dimensions and Tolerances . . . . 120
    G4 Gauge Dimensions for Extreme-Line Casing . . . . . 123
    G5 Tolerances on Gauge Dimensions for Extreme-Line Casing . . . . . 124

  11. #31
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    A quick update.

    I'm concentrating at the moment only on API Internal Flush type threads.

    I've been doing some thinking, calculations and drawing and I'm 95% certain I've come up with a way so that all 6 sizes of external Internal Flush threads can be measured with one pair of thread inserts and just one pair for all 6 sizes of internal threads.
    There will also be a calibration piece to check set up before measuring, a piece for a quick angle check and a table with all relevant data - i.e. nominal pitch diameter and pitch diameter tolerances for all 6 sizes.

    I'll be getting a friend to check my calculations and, if OK, have some made. I'll take photos when I have something to show - hopefully in about 3 weeks time.

  12. #32
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    Quote Originally Posted by Curt B View Post
    API specification 5B covers it and here's one source:

    API Spec. 5B
    Curt, it would appear that you have this lengthy standard

    Could you (or anyone else) let me know the pitch diameter tolerance given for 4½ API Internal Flush thread for both the external and internal thread?
    Also if there is an allowance on either or both from nominal pitch diameter.

    This would help me check if my calculations are correct.

    "Thanks in advance", he says optimistically
    Gordon

  13. #33
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    “API Internal flush thread” needs to be clarified. The nominal pitch diameter is different for casing, non upset, external upset, and other forms so more specifics are necessary however + - .006” is usually very close when the math is done. Commonly I see drawings where next to the thread designation is stated “modified as follows”. The counter bored area in front of the thread is commonly called the coupling recess and can be as per the API specs, a giant chamfer or shaved off up to the entire depth recess if an engineer chooses however the 3-4 turns hand tight make up is unaffected. $114.00 for the information I linked which is enough to start an API gauge business and remove all mystery from this subject seems like a bargain to me. 4 ½” casing nominal P.D. is 4.403”

  14. #34
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    Quote Originally Posted by Curt B View Post
    “API Internal flush thread” needs to be clarified. The nominal pitch diameter is different for casing, non upset, external upset, and other forms so more specifics are necessary however + - .006” is usually very close when the math is done. Commonly I see drawings where next to the thread designation is stated “modified as follows”. The counter bored area in front of the thread is commonly called the coupling recess and can be as per the API specs, a giant chamfer or shaved off up to the entire depth recess if an engineer chooses however the 3-4 turns hand tight make up is unaffected. $114.00 for the information I linked which is enough to start an API gauge business and remove all mystery from this subject seems like a bargain to me. 4 ½” casing nominal P.D. is 4.403”
    Curt I don't intend to be ungrateful but I can’t seem to be able to convey what information I need.

    4 ½” casing nominal P.D. is 4.403” - the thread is 4½" inches long so at which point in that length (measuring from diameter D and measuring from diameter E) should the thread pitch diameter be measured? It is after all a tapered thread so the pitch diameter will vary depending on where on the thread length it is measured. From the nominal pitch diameter you give (4.403") and from that it would appear that the pitch diameter should be measured very near to the smallest diameter on the external thread - near diameter D. Personally I'd have thought it better to measure closer to diameter C as the two parts must be together at diameter C when tightened.

    The task is to measure the pitch diameter on the external and internal thread shown in the following link for A.P.I. Internal Flush type/size 4½

    DRILL PIPE USA - Drill Pipe Thread Data

    I am only interested in the information re nominal pitch diameter for the 4½ API Internal Flush thread and at which specific depth with this specific API IF size it should be measured. I’d also like the pitch diameter tolerance for both the external and internal thread at the measurement point. If the standard doesn’t give me this information then I don’t know what I’d use the standard for. I don't even feel certain that the information I want (i.e. pitch diameter and tolerance at what distance from the shoulder at diameter C for type 4½) is in the standard. I have no intention of starting an API gauge business It’s the first time I’ve ever been asked for thread inserts for any type of API thread.

    To give an example. When measuring a tapered thread such as NPT then the nominal pitch diameter is specified for a specific depth. At this depth the pitch diameter tolerance is also specified. The taper for an API Internal Flush thread is 2" per foot which is 2 : 12. Half this is 1 :12 which is I believe 4.76 degrees.

    It is only this information (pitch diameter and tolerance and the distance this is applicable at, I am interested in for the 4½ API IF thread – no more, no less.

    The pitch diameter tolerance you give (+/- 0.06”) amazes me as a standard pitch diameter tolerance on for example an ordinary UN (straight) thread with 4 TPI (For example 4½-4 UN) is max. 4.3341 min. 4.3225 (tolerance 0.0116”) for an external thread and min. 4.3376 max. 4.3527 (tolerance 0.0151”) for internal. With the +/- 0.06 you give is + 0.06/-0 for internal and +0/- 0.06 for external?

    I know that the pitch diameter is greater for a tapered thread than a straight one but so much for API?

    As I’d only be supplying the customer with thread inserts to measure pitch diameter (at a specific depth) then I’d advise him to make (or buy) a thread plug and a ring gage at nominal pitch diameter so that he can also at least check for correct pitch and thread profile before starting production.

    Looking on the bright side - when I've had the thread inserts made I'll put photos in here so all can see what I've done. If it works (and I'm pretty sure it will) then a small fortune can be saved for those who might want to do it the "new" way.
    Last edited by Gordon B. Clarke; 11-19-2010 at 09:44 PM. Reason: more info

  15. #35
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    Gordon,
    I apologize as you did refer to drill pipe thread in a previous post which is completely different and a specification I don’t have but is available as API spec. 5 D:

    API spec. 5 D

    Interestingly when product in this category is manufactured API has a list of items that are to be provided by the purchaser aiding to making standards vague. See here:

    http://api.org/Standards/addenda/upload/5D_PGH_2009.pdf

    Regarding P.D. tolerance I wrote .006” not .06” but was referring to line pipe/casing and as such is irrelevant to you.

    Good luck.

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    Quote Originally Posted by Curt B View Post
    Gordon,
    I apologize as you did refer to drill pipe thread in a previous post which is completely different and a specification I don’t have but is available as API spec. 5 D:

    API spec. 5 D

    Interestingly when product in this category is manufactured API has a list of items that are to be provided by the purchaser aiding to making standards vague. See here:

    http://api.org/Standards/addenda/upload/5D_PGH_2009.pdf

    Regarding P.D. tolerance I wrote .006” not .06” but was referring to line pipe/casing and as such is irrelevant to you.

    Good luck.
    Curt, at least nothing has been made yet although I am finished drawing everything that needs to me made to allow pitch diameter measurement.

    As the 0.006" doesn't refer to pitch diameter tolerance then I think I'll use the tolerance for a standard 4 TPI UN thread of a suitable diameter.

    As API IF threads go from 2 7/8" to 6 25/64" (it's as if some commitee tried to make things as complicated as possible) I'll use tolerances for 4 TPI as close as I can get to the relevant OD from ASME B1.1. By doing this then the worst thing that can happen is that the thread will be made better than necessary but until I get the correct tolerances I see no other way out.

    For 3UNC-4 the pitch diameter tolerance for an external thread is 0.0107" and for an internal 0.0139". There is an allowance on the external thread of 0.0032" so the largest external will never meet the smallest internal. This is from a 2A/2B fit but I might even go for a 1A/1B fit as this'll give me almost 50% more tolerance size.

    A thing that really surprises me is that specifications for actually making these threads seem to be as well kept as the gold in Fort Knox

    I live in hope as someone must know what I'm after.

    When I am finished I will put everything I come up with in here and then we can find out if the men in white coats should come for me

    Visions of, "One flew over the cuckoo's nest" spring to mind.

  17. #37
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    I notice on a drawing of the API thread form it states, " pitch tolerance +/- .0015 per inch". I'm assuming this means how much the actual pitch is allowed to vary over 4 threads (4 TPI per inch) and has nothing to do with the actual pitch diameter tolerance?

  18. #38
    gorrilla is offline Stainless
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    I've cut miles of API thread for Baker Hughes, few years back. That's the problem, those few years. Anyway, the 3/4 per foot is pretty much standard for API threads if I remember correctly. Inside, outside, whatever size was called for, the taper stays the same.

  19. #39
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    Most of the major insert manufacturers such as Iscar, kennametal etc also make inserts for api threads.

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    Quote Originally Posted by gorrilla View Post
    I've cut miles of API thread for Baker Hughes, few years back. That's the problem, those few years. Anyway, the 3/4 per foot is pretty much standard for API threads if I remember correctly. Inside, outside, whatever size was called for, the taper stays the same.
    3/4 per foot? The thread form says +/- .0015 per inch. What has either or both to do with the pitch diameter tolerace, which is just about the only thing I'm interested in.

    As you say, the taper is the same 2 per foot which I make to 9.524 or 4.762 degrees per side.

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