Drill

Shank Type

Twist Drill with parallel shank

Twist Drill with typer shank

General dimensions of morse taper shanks

Structure

Cutting portion

In the context of cutting technology,land width bα is the body clearance land width which is to be by bfαn, see DIN 6581

Angle at the cutting edges
- The corner has been adopted as the observed edge point.

In the context of cutting technology,land width bα is the body clearance land width which is to be by bfαn, see DIN 6581

• αx Side clearance angle (alpha)
• αxθ Effective side clearance angle
• βx Side wedge angle (beta)
• Γxθ Front rake angle (gamma)
• Γxθ Working front rake angle
• η Resultant cutting speed angle (eta)

Clearance angle α.wedge angle β and rake angle Γ are measured in the tool orthogonal plane.For details, see DIN 6581, deginitions of metal-outting technology. geometry at the tool edge.

Web thickness k

• Test values : The web thickness according to Fig.1 shall not be less than the minimum value k.min indicated in Fig.2.
• Test point : At the point of the drill.
• Testing equipment : Slide gauge with measuring points.

Margin width bα

• Test values :The land width as in Fig. 3 shall lie within the limitting values indicated in Fig.4.
• Test point : 5mm behind the corner
• Testing equipment : Slide gauge

Angle on twist drills
(1) Side rake angle rf (Helix angle)

• Test values :Recommended ranges depending on the tool types N,H and W according DIN 1836 and the diameter of the drill included in Fig 5.
• Test point : At the corner, see Fif.6.
• According to VDI Guideline3331 Part1, Section Margin width bα

(2) Point angle

• Test values :Usual executin for tool types N and H : ∂ =118 °, for tool type W : ∂ =130
• Test point : At the cutting, see Fig 7.
• According to VDI Guideline3331 Part1, Section Margin width bα

Resharpening Twist Drills
(1) Drills are worn off irregularly. It should be sharpened prior to developing into excessive wear.
(2) esharpening

• Grind the correct point angle to suit your application. (figure 8)
• Check that both cutting lips have the angle.On a 130° point,each lip should be 65° toward the axis,The point must be on center,i.e., the chisel edge must produce cutting lips of equal length. (figure 8)
• Grind Primary relief and Secondary clearance. (figure 9)

Web thinning

(1) Without thinning - Suitable for drill of general purpose. Thanks to thin web thickness, web thinning is not need.This without web thinning type is applied to design of drills for mild steel, alloy steels, cast iron, stainless steel, titanium, inconel, etc. and conventional cutting conditons.

(2) Type C thinning(DIN1412FROM C,SPLIT POINT) - Because Split point enables good centering when drilling and breaks the chips, chip removals is easy. Suitable for drill design in high hardened tough materials, i.e, heat treated steel, titanium alloy. Stainless steel, incoroy inconel, nimonic, etc.

(3) Type R thinning(HELICAL THINNING) - Helical thinning ensure to frequent chip breaking and removal. The different direction force of cutting edges and helical thinning parts enables that chip curl, break and remove through the flutes. In addition. Helical thinning makes the chip room up to center, remove the chisel and enables good centering.

(4) Type A thinning(DIN1412 FROM A) - A type thinnings makes thin chisel,good chip removal and favorable centering. This type is the easiest type to grind the thinning. In narrow web and wide fluted drills, keeping of the rigidity and smooth chip removal are possible.

(5) Type B thinning(DIN1412FORM B) - In case of work materials with low cutting resistance and good chip removal, ie, cast iron, aluminum,plastic etc.,B type thinning is suitable.Especially when drills for high hardended steels are designed, this type is applied to decrease rake angle and avoid chipping of cutting lips.

(6) Type D thinning(DIN1412FORM D) - Gray Castiron thinning; bevelling of external edges strengthens the cutting edge. Used for medium to high gray cast iron hardness and for abrasives.

(7) Type E thinning(DIN1412FORM E) - Center drill bit thinning; ensures optimal center drilling and does not leave burs in through-holes. As the bit and cutting edges are delicate,this bit should be used far drilling thin sheet metal.