JPS62136306A - Two-flute gun drill - Google Patents

Abstract

PURPOSE:To improve the finished surface precision by forming the sectional shape of two oil holes into nearly triangular form, in conformity with the sectional shape of two cutting oil feeding holes on a gun drill body and increasing the feed quantity of cutting oil. CONSTITUTION:In a two-flute gun drill 2, each sectional shape of two oil holes 21a and 21a is formed into nearly triangular form in conformity with the sectional shape of the cutting oil feeding holes 13b and 13b of a shank 13. Therefore, the fluid passing sectional area of the joint part between a solid tip 21 and the shank 13 can be made equal to the fluid passing sectional area of two cutting oil feeding holes 13b and 13b. Therefore, the feeding quantity of cutting oil can be increased, and the finished surface precision can be improved.

Description

Detailed Description of the Invention: "Industrial Application Field J This invention provides a two-blade gun drill in which the cross-sectional shape of the oil hole of the solid tip is formed into a substantially triangular cross-sectional shape to match the cross-sectional shape of the cutting oil supply hole of the gun drill body. It is related to.

``Conventional technology'' Since gun drills are generally intended for deep hole drilling, a cutting oil supply hole is provided at the tip of the drill, and pressurized oil is spouted from this supply hole to forcefully discharge chips from the cutting hole. I try to do that. Among these gun drills, there is a two-flute gun drill that is intended for high-feed cutting.

Conventionally, as such a two-flute gun drill, one shown by reference numeral l in FIG. 2 is known.

This gun drill I has a gun drill main body 1'l. The gun drill main body 11 is composed of a cylindrical driver 12 and a shank 13 connected to the tip of the driver 12. As shown in FIG. 3, this shank 13 is composed of a tubular member, and has two tube walls 13a, 13a spaced apart from each other by 180 degrees in the circumferential direction on its distal end side.
is formed to protrude radially inward. and,
These two inwardly protruding tube walls 13aS 13a are
Two cutting oil supply holes 13b are provided inside the shank 13.
, 13b, and this cutting oil supply hole 13b is
The cross section is formed into a substantially triangular shape so that the width in the radial direction becomes gradually narrower from the outer circumferential side toward the inner circumferential side. Further, the outer wall surfaces of the tube walls 13a, 13a define chip discharge grooves 13c, 13c, respectively.

A solid tip 14 made of cemented carbide is fixed to the tip of the shank 13 by brazing.

This solid tip 14 has a larger diameter than the shank 13, and has two cutting edges 14aS 14a at its tip.
is provided. On the other hand, as shown in FIG. 4, chip discharge grooves 14b, 14b extending in the axial direction are provided at two positions spaced apart by 180 degrees in the circumferential direction on the outer peripheral surface of the solid chip 14. Further, inside this solid chip 14, oil holes 14c, 14C are located at positions rotated 90° in the circumferential direction from the positions where the chip discharge grooves 14b, 14b are provided.
is provided extending in the axial direction, and this oil hole 14c
, 14c has both ends opened at the front end and rear end surfaces of the solid tip. This kind of mukdetsu 1
lI communicates its oil holes 14c, 14c with the cutting curve supply holes 13b, 13b, connects its chip discharge grooves 14b, +4b with the chip discharge grooves 13c, 13c, and connects the rear end of the shank 13 with the chip discharge grooves 13c, 13c. fixed at the front end.

At this time, the detailed positional relationship between the hole 14c and the cutting oil supply hole 13b is as shown in FIG. That is, the positional relationship between the two is such that among the inner wall surfaces of the cutting oil supply hole 13b having a substantially triangular cross section, the inner wall surface at the apex of the triangle is radially outward from the inner wall surface of the oil hole 14c having a circular cross section. Among the inner wall surfaces of the cutting oil supply hole +3b, the inner wall surface at the center of each side of the triangle is located radially inward than the inner wall surface of the oil hole 14c.

[Problems to be Solved by the Invention] Incidentally, in the above-mentioned two-flute gun drill I, at the joint between the shank 13 and the solid tip 14, the oil hole 14c is arranged as shown in FIG. 5 relative to the cutting oil supply hole 13b. It is located as shown. For this reason, the cutting oil supply hole 13b
There was a problem in that the fluid passage cross-sectional area of the joint shown by diagonal lines in FIG. 6 was smaller than that of the fluid passage cross-sectional area of . Also, with respect to the cross-sectional area of the shank 13, the shank 1 shown with diagonal lines in FIG.
There was a problem that the bonding area between No. 3 and the solid chip I4 became small, and the bonding strength decreased.

Therefore, as shown in FIG. 8, it is conceivable to form the circular cross-sectional shape of the oil hole 14c so as to circumscribe the approximately triangular cross-sectional shape of the cutting oil supply hole tab. The fluid passage cross-sectional area of the cutting oil supply hole 13b
Although it is possible to improve the supply amount of cutting oil by matching the fluid passage cross-sectional area of will decrease. Further, as shown in FIG. 9, it is also possible to form the circular cross-sectional shape of the oil hole 14c so as to be inscribed in the approximately triangular cross-sectional shape of the cutting oil supply hole 13b. The joint area between 14 and shank 13 is shank 1
Although it is possible to improve the joint strength by increasing the cross-sectional area of 3, the fluid passage cross-sectional area (the shaded area in the figure) decreases, and the amount of cutting oil supplied decreases. It's put away.

``Object of the Invention'' The object of the present invention is to provide a two-blade gun drill that can increase the amount of cutting oil supplied and improve the strength of the joint between the solid tip and the gun drill body. .

[Configuration of the Invention] The present invention has a configuration in which the cross-sectional shape of the two oil holes is formed into a substantially triangular shape to match the cross-sectional shape of the two cutting oil supply holes of the gun drill body.

"Embodiment" An embodiment of the present invention will be described below with reference to FIG. In addition, in these figures, the same reference numerals are given to the parts having the same configuration as those of the conventional example, and the explanation thereof will be omitted.

FIG. 1 is a diagram showing a solid tip 21 of a two-blade gun drill 2 according to the present invention. Similar to the conventional example, this mucchib 21 is fixed to the tip of the shank 13, and has two oil holes 2Ia and 21a extending in the axial direction.

In such a two-blade gun drill 2, the cross-sectional shape of the two oil holes 21a, 21a is substantially triangular in accordance with the cross-sectional shape of the cutting oil supply holes 13b, 13b of the shank 13.

In this way, in this two-blade gun drill 2, the cross section of the two oil holes 21a and 21a is formed into a substantially triangular shape to match the two cutting oil supply holes 13b and 113b. 13 can be made the same as the fluid passage cross-sectional area of the two cutting oil supply holes 13b, 13b, and the amount of cutting oil supplied can be increased. Therefore, it is possible to improve finishing (desurface accuracy) and perform high-feed cutting.
The joint area of the joint with the shank 13 can be made the same as the cross-sectional area of the shank 13, and the joint strength between the solid tip 21 and the shank 13 can be improved.

In addition, in the above-mentioned embodiment, the solid tip and the noyank are fixed by a solder joint, but there is no need to be limited to this, and other fixing methods may be used.

"Effects of the Invention" As explained above, according to the present invention, the cross-sectional shape of the two oil holes is formed into a substantially triangular shape to match the cross-sectional shape of the two cutting oil supply holes of the gun drill body. As a result, the amount of cutting oil supplied can be increased, and the strength of the joint between the solid tip and the gun drill body can be improved.

[Brief explanation of drawings]

FIG. 1 is an axial tip end view showing an embodiment of the present invention, FIGS. 2 to 7 are views showing a conventional two-flute gun drill, FIG. 2 is a side view thereof, and FIG. ■-■ in Figure 2
Linear sectional view, Figure 4 is a view from the ■ arrow in Figure 2, Figure 5 is a
Figure 6 is an enlarged cross-sectional view taken along the line ■-■ in the figure, Figure 6 is a diagram showing a fluid passage cross section at the joint between the Muku tip and the shank, Figure 7 is a diagram showing the joint area of the joint between the Muku tip and the shank, and Figure 8 is a diagram showing the joint area of the joint between the Muku tip and the shank.
9 and 9 are diagrams showing a state in which the relationship between the oil hole and the cutting oil supply hole at the junction between the solid tip and the shank is changed as appropriate. 2...Two-blade gun drill, 11...Gun drill body, 13b...Cutting oil supply hole, 21
...Mukuchip, 21a...Oil hole.

Claims (1)

[Claims] A solid carbide tip made of cemented carbide having oil holes communicating with each of the cutting oil supply holes is provided at the tip of a gun drill body having two cutting oil supply holes extending in the axial direction. In a two-blade gun drill having a substantially triangular cross-section so that the width in the radial direction gradually narrows from the outer circumferential side to the inner circumferential side, the cross-sectional shape of the two oil holes is formed by two cutting oils in the gun drill body. A two-blade gun drill characterized by being formed into a substantially triangular shape to match the cross-sectional shape of the supply hole.