As a general discussion, the thread taps are meant for the purpose of cutting a thread inside a hole. This hole being cut can bs used for cutting another new thread as well as can be used for the restoring purpose in an internal thread. Metric thread taps are one of the kinds of such thread taps. 

There are many other various kinds of thread taps such as above-mentioned metric thread tap, UN thread taps, BSPT thread taps, BSPP thread taps, Trapezoidal thread taps, ACME thread taps, and many more. These all are used to make different thread forms.

Taking hand taps in consideration, they have three kinds of styles; taper, plug and the bottoming style. All these types are distinguished by their quantity of chamfered threads which are present at the end of the tap. Usually the taper taps of metric thread taps have 8-10 chamfered threads. The plug ones have 3-5 chamfered threads while the bottoming taps have 1-1.5 chamfered taps. Machines taps generally just have the bottoming taps.

The user is allowed to check the metric thread tap drill size with the help of chart table. The users also can account out the drill size by himself. For example; M1.8×0.2 (the tap drill size is 1.6mm). Manu users find the ideal rule that is; subtracting pitch from the diameter and then get 1.8-0.2=1.6 mm.

Another example is M1.8×0.35 where the drill size is 1.45mm (1.8-0.35=1.45 mm). For the special United Inch threads the rule is simply by subtracting 1/thread/inch from the diameter. Take this example; 1-8 UN, 1- 1/8= 7/8″, 7/8″ is the tap drill size, 1/4-20 UN, 1/5″ is another tap drill size (1/4-1/20=1/5″).

For the purpose of tapping with the help of metric thread taps, it is important to make sure you use enough lubricant. For all the carbon steels, it is ideal to use the sulphurated cutting oil as a lubricant. This lubricant is often used for pipe threading. For aluminum material, it is suggested to use WD-40. When it comes to cast iron, unlike prior ones, there is no need of any lubricant.

Some special tips that are needed to be kept in mind are; the metric thread tap generally cannot be threaded all the way of a blind hole to the bottom. Due to this, a blind hole needs to be a little deeper as compared to other required thread depth.  When tapping is done with metric thread taps, it is important to keep the tap straight when you turn. This is very important as the metric thread tap should be kept perpendicular to your workpiece. 

After to taking few turns, the user needs to back the tap into much away side of the chip, this is especially important in a blind hole when done by metric thread tap. Small taps are very easy to break hence, you should further pay more attention over using the small taps.

Keeping the above-mentioned tips regarding metric thread taps, one can work flawlessly on the workpiece. 





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