A minimum diametral clearance is provided at the minor diameter of all external threads by establishing the maximum minor diameter 0.020 inch below the basic minor diameter of the nut for pitches of 10 threads per inch and coarser, and 0.10 inch for finer pitches. A minimum diametral clearance at the major diameter is obtained by establishing the minimum major diameter of the internal thread 0.020 inch above the basic major diameter of the screw for pitches of 10 threads per inch and coarser, and 0.010 inch for finer pitches.

This American National Standard ASME/ANSI B1.5-1997 is a revision of American Standard ANSI B1.5-1988 and provides for two general applications of Acme threads, namely, General Purpose and Centralizing. The limits and tolerances in this standard relate to single-start Acme threads, and may be used, if considered suitable, for multi-start Acme threads, which provide fast relative traversing motion when this is necessary. For information on additional allowances for multistart Acme threads. see later section on page 1827.

The next major challenge is that of the material composition. In the case of most ropes and cords used as personal protective equipment (PPE), both the sheath and the core are made from polyamide 6. This can be easily melted and thus sealed. The best tools for doing this are special rope cutting devices, which are essentially just soldering irons with a cutting blade.

The process becomes more complicated if the rope or cord is made up of different materials. There are cords with a Dyneema® core and a polyamide sheath, an aramid core and a sheath containing polyester, a polyamide core and a polyester sheath, or a sheath made of both polyamide and aramid, and all other conceivable combinations. The problem in such cases is that the materials don’t bond together when melted or, as in the case of aramid, burn rather than melt.

Climb cutting on a router table

Providing an extensive range of difficult to source, special Fasteners and Forgings that may require CNC machining to provide complex dimensional shape.

Three classes of General Purpose threads, 2G, 3G, and 4G, are provided in the standard, each having clearance on all diameters for free movement, and may be used in assemblies with the internal thread rigidly fixed and movement of the external thread in a direction perpendicular to its axis limited by its bearing or bearings. It is suggested that external and internal threads of the same class be used together for general purpose assemblies, Class 2G being the preferred choice. If less backlash or end play is desired, Classes 3G and 4G are provided. Class 5G is not recommended for new designs.

The tolerances specified in this standard are applicable to lengths of engagement not exceeding twice the nominal major diameter.

Climbcutcircular saw

The work described below should be performed outdoors, with the use of extraction equipment, or, as a minimum, in well-ventilated rooms. When melting and bonding synthetic fibers, toxic vapors are generated that should not be inhaled. In addition, heat-resistant gloves, ideally thin leather gloves, should be worn. The work should also be performed on a heat-resistant surface.

First, the hot cutting device’s flat blade is used to smooth down the sheath in the intended cut area so the sheath yarn fibers melt to form a transparent surface. The rope is then severed by applying light pressure with the pre-heated blade. The resulting burrs can be smoothed down with the blade.

The accompanying Fig. 1 shows the thread form of these General Purpose threads, and the formulas accompanying the figure determine their basic dimensions. Table 1 gives the basic dimensions for the most generally used pitches.

Climb cutting vs conventional

The tolerance on the external thread major diameter is 0.05P, where P is the pitch, with a minimum of 0.005 inch. The tolerance on the internal thread major diameter is 0.020 inch for 10 threads per inch and coarser and 0.010 for finer pitches. The tolerance on the external thread minor diameter is 1.5 × pitch diameter tolerance. The tolerance on the internal thread minor diameter is 0.05P with a minimum of 0.005 inch.

General Purpose external threads may have the crest corner chamfered to an angle of 45 degrees with the axis to a maximum width of P/15, where P is the pitch. This corresponds to a maximum depth of chamfer fiat of 0.0945P.

PPE ropes for mountain sports and work safety uses are usually produced by the manufacturer with a specific length. During this process, the ends of the rope are ultrasonically welded and labeled.

The max major diameter of the external thread is basic and is the nominal major diameter for all classes. The min pitch diameter of the internal thread is basic and is equal to the basic major diameter minus the basic height of the thread, h. The basic minor diameter is the min minor diameter of the internal thread. It is equal to the basic major diameter minus twice the basic thread height, 2h.

The process of cutting a rope always starts with stripping the last meter of rope. This makes the sheath sit firmly on the core. If the core disappears into the sheath while stripping the rope, sufficient clearance must be left when making the cut to ensure that the entire core is available at the point where the cut is made.

A series of diameters and associated pitches is recommended in the Standard as preferred. These diameters and pitches have been chosen to meet present needs with the fewest number of items in order to reduce to a minimum the inventory of both tools and gages. This series of diameters and associated pitches.

Anyone who doesn’t have a hot cutting device can use a Bunsen burner, camping stove, or lighter instead. In such cases, start by stripping the rope and melting the sheath in the intended cut area over the flame until it is smooth. A carpet knife can then be used to cleanly sever the rope in the melted area. Next, melt the exposed fibers at the end over the flame and press the cut section smooth by rubbing it over the still warm plastic (gloves).

In the case of the combined use of polyamide and polyester, the easiest solution is to sever the rope with a hot cutting device and then use the device’s blade to make a transversal cut in the rope end before rotating the rope by 90° and making a further such cut. This significantly enlarges the melted area and creates a positive fit between the fibers once they harden instead of a chemical bond. The surface of the melted areas can then be smoothed with the blade again.

In the case of cords made with Dyneema® (UHMWPE) or aramid, heat is often not the ideal tool. Instead, such combinations of materials should ideally be bound with adhesive. This occurs as follows: first, adhesive tape is wrapped around the cord at the intended cut point. A sharp knife, ideally a carpet knife, is now used to sever the cord in the middle of the tape. Low viscosity, i.e. very runny, glue, ideally cyanoacrylate-based (super glue), is now applied to the exposed cut. Caution: a suitable surface and gloves as well as sufficient ventilation are required! Due to the capillary effect, the glue is quickly absorbed into the fabric and binds the fibers. The tape can then (but does not have to) be removed. If you like, you can also apply a little glue to the last few centimeters before the end of the rope and allow it to absorb. This additionally stiffens and glues the end.

In many practical applications, however, ropes and cords also have to be regularly cut by the users themselves. This Knowledge Base article explains how ropes are cut and, above all, how they can be permanently sealed to prevent them from fraying.

The angle between the sides of the thread, measured in an axial plane, is 29 degrees. The line bisecting this 29-degree angle shall be perpendicular to the axis of the screw thread.