How to choose a drill? Part 1
Sources of a sverlovedeniye originate in antiquity. The monkey did not manage to turn into the primitive person as she needed to make a hole in something at once. Try to make a hole in something soft a finger. You will notice at once that you reflex try to turn a finger in an opening. Here it, first drill!
A stick to pick even more conveniently. But neither a finger, nor a stick you will not drill a stone. Something is necessary firmer. And here flint plates, and there were put to use and business reached metals. The form of drills was continuously improved too. Drills became much, drills became different.
To buy a drill not a problem now. The problem - to choose the best. Types, types and designs of drills it is invented very much what to choose necessary as difficult as to the woman of fashion a dress style. And not to get lost in the sea of information, we will try we will divide drills into groups by the form of material which is required to be drilled:
Feather or flat drills as well as possible are suitable for the drilling of wood, gypsum cardboard, plastic and other soft materials which are giving in to a knife blade, they are brace bits. They are so simple that they can be made independently.
Feather drills do not suit for works on metal, strong plasticity and other materials which the knife does not cut any more, but still scratches. Here thicker and strong cutting edges are necessary. Spiral drills cope with it. They are produced from tool carbonaceous, alloyed or quick cutting steels. It is the most widespread type of drills. Spiral drills are suitable for drilling and solid steel, and rather soft wood.
It is clear, that if durability of material is commensurable or exceeds drill material durability, then the last will very quickly become blunted. Therefore apply drills with hard-alloy nozzles to works on concrete, a stone, glass, ceramics and other solid and nonplastic materials which and steel does not take or with inclusions of abrasive material.
There are also many other kinds of drills for special application, but they are, as a rule, not necessary to the house master, and we will not consider them.
The house master does not need many drills. Therefore we advise at first to get a small standard set, and further to fill up it with the drills necessary for performance of specific objectives.
Buying drills, pay attention to their appearance. Drills have to be without dents and scratches, with identical on length, sharp, equal and pure, without agnails, the cutting edges, identical color on all length.
Domestic drills with hard-alloy plates, as a rule, sell unpacked, nevertheless, they are very quite good and rather cheap.
It is easily possible to determine by color of a drill how carried out its strengthening finishing processing.
- is gray - steel - processing was not carried out;
- black - for wear resistance increase processed a drill superheated water vapor.
- golden - spent holidays for removal of internal tension;
- bright golden - applied the strengthening layer of nitride of the titan (TiN) on a surface. Hardness of a surface of such drills reaches 80 HRc, however when sharpening the layer is erased.
For domestic drills existence and content of marking depends on diameter of a drill.
On drills less than 2 mm - marking do not put;
from 2 to 3 mm - put diameter and brand of steel;
more than 3 mm - put the trademark of the manufacturer, diameter, brand of steel or a firm alloy of a plate, sometimes a drill accuracy class.
The famous foreign producers care for the reputation, and let out expensive high-quality drills. On their packing and on drills specify:
trademark of the producer, country of production;
for what drilling of material is intended a drill;
steel brand, for example HSS - High Speed Steel - quick cutting steel (English);
diameter and length of a drill.
However on sale cheap drills which have neither marking, nor packing meet. It is in advance impossible to tell something about their quality, buying them, you buy a pig in a poke.
To be continued