Notes on using twist drills

There are many different drilling tools on the market today, including the common twist drill, the indexable shallow hole drill and the flat drill. The common twist drill is usually used for drilling on machining centres and consists mainly of a working part and a shank. The shank part of the tool is of two types: straight shank and tapered shank. The shanks of straight shank tools are mainly collet shanks, which have the advantage of automatic centring and elimination of deflection, so it is best to use this type for small size tools. The cutting part of the twist drill has 2 main cutting edges, 2 secondary cutting edges and 1 horizontal edge. 

The guiding part of the twist drill is used for guiding, trimming and chip removal and for conveying cutting fluid. The twist drill is generally used for the rough machining of low precision holes. As the fixture used in the machining centre does not have a drill sleeve to guide the centre, the drill is prone to eccentric movement when rotating and cutting at high speed, and the cross edge of the drill is long, so when drilling, a centre hole is made with the centre drill to guide the drill. The following points should be noted when using twist drills for machining.

1. What is the difference between straight shank twist drills and tapered shank twist drills and what are they mainly used for? The twist drill is generally divided into: straight-shank twist drill and tapered-shank twist drill, the difference between them is: straight-shank twist drill contend with the sea generally with a drill card to tighten the drill shank processing parts, straight-shank twist drill and tapered-shank twist drill drill shank end with a flat tongue, can be directly clamped to the machine tool to process parts, or clamped to the drill sleeve and then clamped to the machine tool to process parts, tapered-shank twist drill usually small drill with a straight shank, large drill with a tapered shank.

2、When using twist drills to process some high hardness, thicker metal plates, stainless steel, you should control the drilling speed, the speed should not be too fast, and at the same time with the use of coolant, which is more conducive to twist 

3、The twist drill bits should be packed in a special box to avoid vibration and mutual collision.

When in use, the drill should be taken out of the box and put into the collet of the spindle or into the tool magazine for automatic bit replacement.

4. Always check the concentricity of the spindle and collet and the clamping force of the collet. Poor concentricity will cause broken drills and large hole diameters in small diameter drills, and poor clamping force will cause the actual speed to be out of line with the set speed and slippage between the collet and twist drill.

5. The spindle presser foot should be checked frequently. The contact surface of the presser foot should be horizontal and perpendicular to the spindle without wobbling to prevent broken drills and deviated holes from being produced in the drilling.

6、Re-sharpening at the right time can increase the number of times the twist drill bit is used and resharpened, prolong the life of the drill bit and reduce production costs and expenses.