Drilling metal with twist drills are much similar to the ones used on woodwork. Sizing from .0135 inches these drills have higher range. For drills larger in size then high speed steel are used or welded to it. Looking at their design, smaller drills are made with parallel shanks, as compared to large drills designed with a tapered shank.
Drill body is the part used for actual drilling and made as per specified size. They usually are not fully grounded towards the shank end with a clearance angle of not more than 1 inch’s.
The flutes aid to give perfect cutting angle with also assisting on waste material to flow out of the hole. This refers to the angle of twist made about 28 degrees. The cutting angle shows the sharpness of drill that changes depending upon the work piece material. Standard drills work with 59 degrees cutting angle that suits for general drilling work.
Note that care is involved for cutting angle and clearance angle to be maintained when a Drilling Machine is reground. Some faults that occur when drilling; when hole is larger than the drill then it shows that the two cutting angles are different. The fault would throw the drill out of center causing it to shake. And the result will make a bigger hole than needed.
When drills require grinding, it can be ground at a metal shop than trying to do with hands, because correct angles can’t be achieved with hands. So accurate regrinding is possible by performing a test where the drill is placed in the hole it made and then seeing if it drops vertically by its own weight. If it doesn’t fall, then its shows the hole is not larger than the drill, therefore proving drilling machine is accurate.
Also drill tip can be selected on the basis of hardness of the work piece material. Acute angles can be worked on soft metals with a 45 to 60 degree cutting in case of cast iron. Cutting angle of 45 degrees is enough for brass materials & cutting angle of 90 degrees work best upon soft metals of copper or aluminum. Also special drilling machine can be applied over brass with their flutes being straight.
It is important to consider that before drilling a large hole it is good to drill a small hole. Because this makes a center for larger drill and further reduces the chance of drilling a hole not required specifically