Metalwork Threading Threading Materials As with tapping threading

Metalwork Threading

Threading Materials As with tapping, threading can be carried out on a wide range of materials including: n Metal n Plastic n Wood n Ceramic

Threading which can also be referred to as screwing, involves the creation of a thread on the outside of a cylindrical bar or pipe which will cause it to act similar to a bolt.

Threading

Threading This external thread will allow a nut of the correct size to be screwed onto it.

Threading The bar to be threaded must be larger than the die which will be used to cut the thread.

Threading Die A die is used to create the external thread on a bar. Dies are made from either: n High speed steel n High carbon steel

Threading Die A die is similar to a nut that has cutting edges. The cutting edges in the die are formed by the holes drilled in it.

Threading Die These holes are similar to the flutes in a tap because as well as forming cutting edges they provide space for the chips of metal cut from the work piece.

Threading Die A small portion of the die is tapered which helps the die to rest square on the bar to be threaded.

Threading Die The most common type of die used in school workshops are circular split dies.

Threading Circular Split Die

Threading Circular Split Die

Threading Die The split permits a small amount of opening and closing of the die which facilitates increasing or decreasing the depth of the thread.

Threading Stocks The stocks are used to hold the die during the threading process.

Threading Stocks

Threading Stocks

Threading Stocks Before the die is placed in the stocks it should be cleaned to allow the die to sit properly in it.

Threading Stocks The die should be fitted with its tapered end to the underside and the stocks retaining shoulder on the top.

Threading Stocks

Threading Procedure For the threading process to be carried out successfully the following steps should be followed:

Threading Procedure 1. The end of the bar to be threaded should be chamfered to help the die start the thread. 2. If a circular split pin die is being used it should be opened fully to take a light first cut.

Threading Procedure 3. The die should now be placed on the end of the bar with its tapered end facing down. 4. Whilst keeping the die square with the bar it should be rotated clockwise and downward pressure should be exerted on it until it begins to cut.

Threading Procedure

Threaded Fasteners Procedure

Threading Procedure 5. When it has gripped first check that it has remained square with the work. 6. Apply cutting fluid if necessary.

Threading Procedure

Threading Procedure 7. Continue rotating the die clockwise for a full revolution. 8. Reverse it about a half a revolution to break off the chips that have been cut.

Threading Procedure 9. When the required length of thread has been created remove the die by turning it in the opposite direction. 10. Clean the thread and try it in a nut or a tapped hole.

Threading Procedure

Threading Procedure 11. If it is too tight close the die slightly and take another cut following the same procedures.

Threading Safety 1. Always ensure that the material being threaded is always held square and securely in the vice. 2. Make sure that the correct die is being used for the size of bar being threaded.

Threading Safety

Threading Safety 3. Always have the die held tightly in the stock wrench when carrying out the process. 4. Always check the bar that has been threaded with a nut or in a hole to make sure it fits properly.

Threading Safety

Threading Safety 5. If the bars to be threaded are turned on the lathe before threading remember the safety rules which apply when using the lathe: n n Never put hands near moving parts. No loose clothing or long hair.