<<< Back        A.G.S. Parts For Aircraft (Page 3)
Aircraft General Standard.

STANDARD NUTS
All standard nuts are hexagonal in shape and are made of similar material to that used for bolts. A nut must be of the same material as the bolt on which it is fitted, with the exception that high tensile steel bolts are fitted with mild steel nuts, unless otherwise stated.

Steel Nuts. All nuts of 3/8 in. dia. and over are marked with their part number on one of the hexagonal faces; the part number is also marked on the label of all cartons containing nuts. Other markings and the size code used for the part number are as described for bolts

Aluminium Alloy Nuts. These nuts are identified by the washer face machined on the base or on both faces of the nut. There is no part number marked on the nut.

Note. All nuts have a 30 deg. chamfer on the edge of the upper face of the hexagon and may be also chamfered on the opposite face. The thin nuts, which are used as locknuts, are always chamfered on the edge of both faces.

STIFFNUTS
Stiffnuts are provided with means whereby the friction between the threads of the nut and bolt is so increased that the nut may be considered self-locking. Several types of stiffnut have been designed, and the following are standardised for use on aircraft.
 

Nyloc. This nut is counterbored at the top and spun over to retain a nylon insert. The insert is not threaded initially and has an internal diameter slightly less than the effective diameter of the bolt to which it is fitted. On assembly, the bolt displaces the nylon in forming a thread, and a high friction value is set up between the load-carrying sides of the thread in contact with the nylon.
Nyloc Cap Nut. Similar action to above, but incorporates a nylon insert in cap form to seal the end of the bolt or screw to which the nut is fitted . The cap nut is used for special applications such as pressurised cabins, fuel and oil tanks, etc., when leakage or seepage along the bolt thread is undesirable.
Oddie. The top of the nut is counterbored, slotted vertically in three places, and depressed inwards to form a circle of six tongues with a diameter slightly smaller than the bolt core diameter. As the nut is screwed on to the bolt the threads of the bolt displace the tongues upwards, and a load is applied to the contacting thread faces.
Philidas.  This nut is made with a circular crown in which two slots are cut, one above the other, with arc of about 270 degrees. The wings thus formed are de-pitched to provide locking tension.
Aerotight. The Mk 1 nut- is made with a circular crown which is slotted across the diameter and also on each side through about 150 degrees, The resultant wings are de-pitched and forced inwards, thus causing a sideways as well as a downwards tension on the bolt threads. The Mk 2 nut has a similar action, but it is slotted on one side only.
Lightweight The top of this nut is distorted to an oval or three-cornered shape. When the nut is screwed on to the bolt, the top of the nut is forced to assume the round shape of the bolt and thus provide a locking device. When the nut is removed from the bolt, it assumes its original shape. Notes. 1. Care must be taken not ' to reject these stiffnuts as unserviceable due to the distortion which is an integral feature of their design. 2. The term "lightweight" is used because this type of stiffnut has equivalent strength of larger nuts with the same thread diameter.
Clinch. This term is used to describe a stiffnut which has a spigot at the bottom of the nut by means of which it is mounted on its support.
Anchor Nuts. This term is applied to stiffnuts which are secured to anchor plates. The anchor plates are fixed at the back of a component so that the bolt or screw can be inserted or removed from the front ; two rivets are used to secure the anchor plate to the component. Notes. 1. If the friction value is so low that the stiffnut on the bolt or screw can be turned with the fingers, the nut is unserviceable and must be renewed. 2. Before renewing a stiffnut, ensure that it is not the bolt or screw thread that is unserviceable. 3. Under no circumstances should a stiffnut be tapped out as this destroys its self-locking properties. 4. When assembled, the end of the bolt should protrude from the nut by a minimum of one thread.

Next Page >>>>>