Threading Tools: Difference between revisions

Screwthreads may be cut by hand using Taps and Dies or on a Centre Lathe which is fitted with a screw-cutting gearbox.

A suitably shaped lathe tool can be clamped into a Centre Lathe Toolpost or Cross Slide and an external thread cut making use of the Leadscrew gearing to advance the tool one screw thread Pitch for each revolution of the lathe. Simlarly, a Boring Tool can be shaped and used to cut internal threads.

As with many cutting operations in metal, a cutting lubricant can be helpful when cutting a screwthread, either by hand or machine. But not all metals need an extra lubricant to be applied. The different lubricants can be summarised as follows:

• Cast Iron - this should be cut dry because, by its nature (i.e. contains in excess of 2% Carbon), the free Carbon within it acts as a cutting lubricant.
• Steel - use oil-based Cutting Fluid - ideally in paste form.
• Non-Ferrous metals - in general, White Spirit can be used.

A Router with a suitably shaped cutter can be mounted on the Cross Slide and used to cut threads in dense and fine-grained woods (e.g. such as: beech, cherry and pear). Coarser grain timbers, such as pine and oak are unsuitable except for large diameter threads. Soaking the wood to be threaded in oil (e.g. linseed or vegetable oil) and wrapping it in ‘cling film’ overnight, can reduce the risk of tear-out at the tips of the threads.