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'''[[Nuts, Bolts and Washers|Screwthreads]]''' may be cut by hand using [https://en.wikipedia.org/wiki/Tap_and_die '''Taps and Dies'''].  
'''[[Nuts, Bolts and Washers|Screwthreads]]''' may be cut by hand using '''[[Taps and Dies]]''' or on a '''[[Centre Lathe]]''' which is fitted with a screw-cutting gearbox.




As with many cutting operations, a cutting lubricant can be helpful when cutting a screwthread. But not all metals need an extra lubricant to be applied. The different lubricants can be summarised as follows:
[[File:LatheScrewCutting.png|300px|right]]
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. Similarly, 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:
* [https://en.wikipedia.org/wiki/Cast_iron 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.
* [https://en.wikipedia.org/wiki/Cast_iron 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.
* [https://en.wikipedia.org/wiki/Steel Steel] - use oil-based [https://en.wikipedia.org/wiki/Cutting_fluid Cutting Fluid] - ideally in paste form.
* [https://en.wikipedia.org/wiki/Steel Steel] - use oil-based [https://en.wikipedia.org/wiki/Cutting_fluid Cutting Fluid] - ideally in paste form.
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When cutting a screwthread with either a '''Tap''' or a '''Die''' it is commonly accepted practice to advance one turn forwards then half a turn in reverse to break off the chip being cut. It is more important however, to '''''feel''''' the cutting action and gain a sense of when to cut and when to go backwards to cut off the chip - this may vary with the size of thread being cut and choice of material. Gaining such a '''''feel''''' for the cutting action is most important when using '''Taps''' to cut a thread inside a ''blind hole''. The danger is that if too much force is applied as the '''Bottoming Tap''' reaches the bottom of the hole, it may break. Note also that chips of metal will fall to the bottom of the hole during the cutting operation and these need frequently to be cleared out.
A lathe tool or '''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, olive or vegetable oil)'' and wrapping it in ‘cling film’ overnight, can reduce the risk of the tips of the threads breaking off.
 
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[[Category:Tools and Equipment]]

Latest revision as of 12:57, 13 March 2016

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


LatheScrewCutting.png

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. Similarly, 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:


A lathe tool or 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, olive or vegetable oil) and wrapping it in ‘cling film’ overnight, can reduce the risk of the tips of the threads breaking off.

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