McNeil, Defense, Supersession of the specification is clearly defined at the top of the first page of the specification. Unless a customer has specifically stated in their contract or related documents that supersession is not allowed without prior authorization, the anodizer should immediately follow and reference MIL-PRF, Revision F, Amendment 2.
Either may be used, but control documents and test reports must reference the method used. Otherwise in an audit, the anodizer risks have a finding for lack of material control in purchasing or receiving.
Military specifications are now labeled Department of Defense Specifications and are updated as follows. Referenced here in relation to touching up anodize scratches and rack marks. The specifications are related to statistical sampling for inspection and acceptance of product.
If statistical sampling is employed for product acceptance of anodized parts, a thorough review of MIL-STD must be performed by the anodizer. Section 3. There is minimal effect of this change, at least at initial examination. The 3M tape is still available in the 1" wide size. However, it will be a special order item and the cost is not pretty. If you have your own tape distributor, they should be able to contact 3M for the product.
If you do not, "Tapes, Etc. If you're doing any work for Boeing or Boeing related you must use a shelf life for the 3M tape of only 6 months per BSS This means the distributors have to keep very new tape in stock and the cost will only go up. Can you give us a sample of tape name. You might purchase a suitable tape from Elcometer Ltd.
This company has local distributors all over the world and they supply ASTM tapes. Thank you for your time. There used to be a QPL that listed the 3M tape.
Check with the prime office for the spec for their qualified products. I do not think that they can expect the lay person to do testing on tape. When you find it, put it in a baggie and keep it in a cool, dry, dark place.
Drawing and Drafting. Telecommunications Standards. AWS D1. Means, Inc. Active Only. Complete Document. Detail Summary View all details. Price USD. In Stock. Need it fast? Ask for rush delivery. Similarly, the above principles observed in setting the pitch and major diameter limits on the fine series class 5 external thread may be followed in deriving the pitch and minor diameters of the internal thread for the fine series.
The 8-thread series is now being investigated. For example, sufficient tension must be produced in pipe flange bolts to exceed the longitudinal force caused by the pressure in the piping, so that the flanged connection does not leak. The same problem is faced in tightening the nuts on the cylinder head of an engine block, so that the studs are all stressed equally and to a tension that precludes leakage. In statically loaded structures in which there is a clearance between the bolt and the members held together the clamping tension is important where rigidity of joints is desired to prevent relative motion of such members.
In structures subjected to varying or alternating stresses, the range of the dynamic stress in the members varies with the bolt tension, and consequently the fatigue strength varies with the bolt tension. Factors affecting the maintenance of bolt tension are the proportion of seating area to thread cross-section, elastic properties of the stating material, stretch of the bolt, or creep of the bolt under load. The use of washers or other springy members in a fastener assembly tends to reduce the amount of external load that can be applied to a prestressed fastener before the load becomes additive to the initial bolt tension.
In the design of bolted connections, enough experience is generally available to determine the amount of the required tension. To assure that such tension is actually induced in the bolt, screw, or stud when the joint is assembled requires a method that either directly or indirectly measures or determines the amount of tension.
In the laboratory the tension induced in a bolt by tightening nut can be accurately determined in a tensile testing machine. In the practical application of fasteners there are five generally used methods for setting bolt tension, as follows: 1.
Micrometer method, in which both ends of the bolt must be accessible to measure the change in the overall length of the bolt. Torque measurement methods, which require that the torque-tension relationship be established for the specific conditions of assembly. Angular turn-of-the-nut method. Use of special devices for controlling tension. The bolt is then tightened until it has elongated the required amount. This method is not practical for general one but may be used for spot checking.
It may also be applicable in establishing torque-tension relationships when a tensile testing machine is not available. When a skilled workman is tightening a nut, he can "feet" a very slight yield in the bolt when the yield point line been reached, and he stops tightening when he feels this yield.
Fortunately, for many applications the tension may be controlled within satisfactory limits by applying known torques in tightening the nuts on the bolts or studs. Tests in numerous laboratories have shown that satisfactory torque-tension relationships may be established for a given set of conditions, but that the change of any one variable may alter the of the fact that most of indeterminate friction, a change in the surface roughness of the bearing surfaces or of the threads, or a change in lubrication will drastically affect the friction and thus the torque-tension relationship.
Thus, it must be recognized that a given torque will not always produce a definite stress in the bolt but will probably induce a stress that lies in a stress range that is satisfactory. The torque-tension relationship for a given set of conditions may he established by means of a torque-wrench in combination with a tensile testing machine or by the micrometer method described above. When both ends of a fastener are not accessible for measurement, if the diameter of the bolt or stud is sufficiently large an axial hole may be drilled in it, see figure A By applying a micrometer depth gage to determine the change in depth of the hole during tightening of the fastener the tension can be determined.
The nut, is first tightened to seat the contacting surfaces firmly. It is then loosened sufficiently, if deemed necessary, to just release the bolt tension. This nut is then tightened through a specified fraction of a turn to produce the required bolt tension.
The angle through which the nut should be turned will be different for each bolt size, length, material, threads per inch, and will also vary with the elastic properties of the abutting material. These devices are operative even when both ends of the fastener an not available for measurement. They are known as preload indicating washers, load sensitive screws, and tru-load bolts. The inner ring is smaller in diameter and higher than the outer by a predetermined amount.
A known preload in the bolt is indicated when the inner ring is compressed to the point where the outer ring can no longer be moved freely by means of a pin inserted into one of the peripheral holes. The change in resistance of the strain gage is read on a calibrated potentiometer as actual bolt tension.
It consists of almost any kind of bolt modified to contain a pin inserted along the axis of the bolt. The pin is in contact with the bolt only at the inner end. The pin usually is made to be flush with the bolt head surface before loading. As the bolt is loaded, the elongation produced in the bolt causes the pin surface to move below the reference surface.
This change is distance is converted directly into unit stress by gaging with a calibrated dial gage. For some applications, it may be desirable to have the indicating pin extend above the top of the bolt before tightening. When the load is applied, the pin withdraws into the bolt. The length of the pin is such that when the full load has been applied, the pin will be drawn in until it is flush with the top of the bolt. A dial depth gage reading of zero then indicates full preload.
Poncelet, Frottement des vis et des ecroux, Crelles Jour. Grashof, Theoretische Machinenlebre, 2, Voss, leipzig. Casler, Effect of initial tension in flange bolts. Whittemore, C. Nusbaum, and E. Seaquist, The relation of torque to tension for threadlocking devices. Goodier, The distribution of load on the threads of screws. ASME, 62, A Almen, How tight should a bolt be? Fasteners, 1, 1. Stewart, What torque? Fasteners, 1, 4, 8 Carr, Draw up flange bolts more uniformly. Fasteners, 3, 4, 7 ; Power, Feb.
Manley, Predicting bolt tension. Hillman, Engineering aspects of bolt variables. Iron Age, , 62 Brunot and W. Schmittner, Studies of the bolting of a fabricated steam chest. Fasteners, 3, 5,16 Lenzen, Strength and clamping force of bolts. Milliken, How tight is too tight? Fasteners, 6, 1, 14 Pickel, Tightening characteristics of nut and stud Assemblies, Fasteners, 6. Stewart, Torque for bolts and nuts.
Fasteners, 10, 1, 12 Walter M. Hanneman, The simultaneous measurement of torque and tension in machine screws. Fasteners, 12, 2 and 3, 4 Richard B. Skidmore, New bolt tension calibrator. Fasteners, 13, 2, 7 Belford, A review of the use of structural fasteners for greatest economy, safety, and dependability. Fasteners, 14, 2 and 3, 5 ACME, 29 deg.
In order to measure the pitch diameter of a screw-thread gage to an accuracy of 0. Accordingly, it in necessary to use a measuring instrument which read accurately to 0. Variations in diameter around the wire should be determined by rotating the wire between a measuring contact and an anvil having the form of a V-groove cut on a cylinder and having the same flank angles, 14 deg. As thus measured the limit on roundness deviation shall be 0.
To avoid a permanent deformation of the material of the wires and gages it is necessary to limit the contact load, and for consistent results a standard practice as to contact load in making wire measurements of hardened screw thread gages is necessary. In the case of Acme threads the wire presses against the sides of the thread with a pressure of approximately twice that of the measuring instrument. This would indicate that the diameter of the wires should be measured against a hardened cylinder having a radius equal to the radius of curvature of the helical surface of the, thread at the point of contact, using approximately twice the load to be used in making pitch diameter readings.
As with 60 deg. To limit the tendency of the wires to wedge in and deform the sides of an Acme thread, it is recommended that pitch diameter measurements on 8 tpi and finer be made at 1 lb. For coarser pitches and larger wires the deformation of wires and threads is less than for finer pitches. Furthermore, the coarser pitches are used on larger and heavier product, on which pitch diameter tolerance is greater and a larger measuring load may be required to make satisfactory measurements.
The standard specification for wires and standard practice in the measurement of wires stated in H28 Part I, Appendix 4, p. The combination of small flank angle and large lead angle that is characteristic of Acme threads results in a relatively large lead-angle correction to be applied in wire measurements of pitch diameter of such threads.
In the case of multiple-start threads the geometry is such that it is no longer feasible to make the usual simplifying assumptions as to the positions of contact of the wire the thread.
Accordingly, in this appendix measurement of single-start threads with lead angles generally less than 5 deg. For a half-angle of 14 deg. The best-size wire, to be applied only where the lead angle does not exceed approximately 3 deg. Values for intermediate lead angles may be determined by determined by interpolation.
The three-wire measurement of Stub Acme threads corresponds to that of 29 deg. Acme threads. However, because of the shallower root on the Stub, Acme threads, no smaller wire than the best-size wire given in table A There can be instances when the best-size wire will touch the thread root.
Hence, a check should always be made to ensure that the wires do not touch the thread root. In those exceptional cases that have smaller lead angles the procedures described above may be applied. FED-STD-H28 31 March For larger lead angles there are two procedures available that give almost identical results; that is the discrepancy between the values obtained for the lead angle correction, c, is well within the possible observational error in making the measurement of pitch diameter.
It is necessary to determine the best-wire size for the individual thread, as this size is dependent on the lead angle of the thread. This determination is simplified by extracting from table A In figureA Under certain conditions a wire may contact one flank at two points, in which case it is advisable to use a ball, equal in diameter to the wire.
The value of c is the same for a ball as for a wire. This process is repeated until the values of [beta] and [gamma] repeat themselves to the required degree of accuracy. Their final values are then entered in eq 11 and 12 to obtain the lead angle correction given by eq.
The following calculation exemplifies the process, and the result may be compared with that obtained for the same example by the Vogel method [21] or the Van Keuren method utilizing tables [15,21]. This equation may likewise be solved for [beta] by iteration, but various short cuts are presented in reference [21], including a short, highly accurate, and nontranscendent formula for [beta].
The value of [beta] in the above example which satisfies this equation is 0. As this discrepancy is small compared with the possible error in measurement of Mu omega, either set of formulas is applicable. For accurate measurement with wires single contact on each flank must occur. If the formula is satisfied, double contact does not occur.
In both formulas 20 and 21, c is a correction depending on the angle the wires make with a plane perpendicular to the axis of the thread plug gage. For all possible single-start combinations of diameters and pitches listed in tables XIV.
As Buttress threads are designed to avoid metal-to-metal fits in all cases, it is not essential that the absolute value of the pitch diameter be accurately determined by 85 FED-STD-H28 31 March applying the correction c. Accordingly, it is recommended that the wire angle correction be neglected for these combinations and all other single-start buttress thread plug gages.
However, if it is desired to take the lead-angle correction into account, the following formula to determine pitch diameter derived in reference [13] may be applied where the lead angle does not exceed 5 deg.
For the 7 deg. Because of the wide difference in the flank angles of a buttress thread it is impossible for the thread measuring wires to contact both flanks simultaneously at the pitch line. For this reason it was decided that the diameter of the "best size" wire should be such that it will contact the pressure flank at a point twice the distance above the pitch line that the contact point on the trailing flank is below the pitch line.
This wire diameter for flank angle 7 deg. If this wire fails to project above the crest of the thread in an actual case, a larger wire, having a diameter of 0. The relation of the "best" and "max" size wire to the flanks and crests of the 7 deg. Buttress thread is shown in figure A The diameter of "best" and "max" wires and the protection above the crest of the thread are shown in table A Because of the small pressure flank angle of 7 deg. Double contact is less likely with the "max" wire than with the "best" wire, as the former contacts this flank nearer the thread crest.
Therefore, it is desirable in such cases to check the pitch diameter measurement obtained with "best" wires by measurement with "max" wires also.
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