Deburring tool with cutting blade

A deburring tool has at least one cutting blade mounted in a guide recess of the tool for deburring and chamfering bores. The blade is of rectangular shape with forward, non-cutting end face and longitudinal side faces extending rearwardly from the end face. At least one side face has a non-cutting glide surface extending rearwardly from the end face at a first angle, and a cutting edge extending rearwardly from the glide surface at a second, different angle.

BACKGROUND OF THE INVENTION 
The invention involves a cutting tool for the deburring of bores and 
placing of chamfers at both ends of through bores with at least one 
cutting blade, consisting of a rectangular-edged cutting blade having 
tapering cutting edges which remove material from the bore. The cutting 
edges contain undercut, sharpened free spaces and the cutting blade has a 
bearing surface on its front end for setting inside the through hole. 
Such cutting blades are known from the applicant's U.S. Pat. No. 4,140,432, 
the underlying problem of which is to precisely position a chamfer with an 
exactly defined size on both sides of the through hole. 
Such cutting blades of this type, for removing burrs of through holes or 
placing of chamfers, are preferably used in pairs. In this case the 
cutting blades are installed in a rectangular reception slot in a rotary 
tool holder so as to face in opposite directions with radially, outward 
tilted, conical cutting edges. 
The cutting blades are urged outwards via pins on a shaft by a spring 
inside the tool holder. The pins each engage a slot on the cutting blades. 
The cutting blades are thus moveable radially in the same direction. In a 
resting, inoperative position the cutting blades are urged radially 
outward under spring tension. When operating to debur or chamfer the edges 
of a through hole, the cutting blades are progressively displaced radially 
inward against the spring tension until they finally reach the inside of 
the through hole in a non-cutting position within the tool holder. This is 
caused by the feed of the tool holder and the conical shape of the cutting 
edges which acts to progressively urge the blades inwards as the tool 
holder is fed into the bore. 
The tool holder with the cutting blades is then driven through the through 
hole in order to work on the rear edge of the through hole with the feed 
working in reverse. 
The cutting blades also have an additional cutting edge at the opposite 
end, so that the edge of the through hole can be deburred and chamfered 
from the rear also, after the through hole has been driven through and 
with the same cutting procedure but in the reverse feed direction. 
However, it has not been possible to place chamfers very precisely with 
existing deburring and cutting tools, particularly in soft materials. 
SUMMARY OF THE INVENTION 
It is an object of this invention to further develop a deburring tool as 
described above so as to allow more accurate placement of chamfers with a 
defined size, on the front as well as the rear of through holes. 
Until now, it has not been possible to cut chamfers with a precisely 
defined size, in soft materials. Some soft materials, especially soft 
metals, such as sheet metal for deep drawing or forming, copper, gold, or 
other soft alloys are provided with through holes which make it very 
difficult to cut chamfers with precisely defined size in the through hole. 
If the material is very soft the cutting blades of existing cutting tools 
work very aggressively and accordingly remove large shavings from the 
edges of a through hole, which is not desirable. 
Only with a more refined control of the cutting tool feed along the 
direction of the through hole and a decrease in pressure of the cutting 
blades on the edges of the through hole has it been made possible to 
attempt to control the removal of metal and achieve cleaner and level 
chamfers. 
The result was often inadequate. In particular it could not be guaranteed 
that both chamfers could be equal in form and condition. 
According to the present invention, a deburring tool is provided with at 
least one cutting blade of generally rectangular cross-section, an outer 
non-cutting, radial contact surface at the outer, forward end of the 
blade, a non-cutting, glide surface on at least one side of the blade 
extending rearwardly at a first angle from the outer contact surface, and 
at least one cutting edge extending rearwardly from the glide surface at a 
second angle different from the first angle. 
The focus of the invention is, therefore, that the cutting edge does not 
extend immediately into the glide radius or contact surface on the front 
side of the cutting blade, but to provide a glide surface at an angle, 
between the glide radius and the cutting edge. This glide surface does not 
cut, it only glides. 
Placing a glide surface between a cutting edge and a frontal glide radius 
has several advantages. 
It is now possible, for the first time, especially in soft materials, to 
form precisely defined chamfer sizes reproducibly to a tolerance of 
plus/minus 0.0005 mm. 
Depth of cut, angle and form of chamfer are evidently determined by the 
combination of the cutting edge and the glide plane extending radially 
outward from the cutting edge. 
When positioning the cutting tool inside the through hole the cutting edges 
first touch the upper edge of the through hole and remove material. In 
this procedure, after a predetermined depth of cut, controlled by the 
transition from the cutting edge to the angled, non-cutting glide surface, 
the cutting edges are automatically disengaged from the bore and are held 
away from the walls of the bore as the tool holder travels on through. 
The cutting edge is preferably at a fixed 90.degree. angle to the outer end 
face or feed direction, while the glide surface is at a smaller angle. In 
this case, the smaller angle of the glide surface determines the angle of 
the chamfer to the horizontal axis of the through hole and thus the 
removal of material proceeds at a right angle to the direction of cut. 
Since the distance from the outer end of the blade to the transition to the 
cutting edge exactly sets the desired diameter of cut, the cutting edges 
of the opposite cutting blades arranged on the tool head make the cut 
accurate in size. Hence the chamfer is precisely defined. If the tool then 
proceeds further into the through hole in the feed direction no additional 
material will be removed. 
The glide surface and the adjoining glide radius on the front side of each 
blade lying against the wall of the through hole hold the blades in the 
through bore of the tool head under spring tension which urges the blades 
radially outward. 
A further feed of the cutting tool lets the tool head protrude at the 
opposite end of the through bore in the material to be worked, and the 
same procedure as described before is repeated, but in reverse feed 
direction. This means that when the tool head protrudes through the 
through hole, the cutting blades are urged outwardly under spring tension 
into their extended initial position. As the tool head is moved back into 
the bore in a reverse direction, a cut is made into the rear of the 
material by means of a matching cutting edge and glide surface on the 
opposite side of the blades which match the corresponding edges on the 
first side of the blades. 
Hence the focus of the invention is a combination of an existing cutting 
edge and an adjoining glide or sliding surface which extends between the 
cutting edge and the glide radius or contact face on the front side of the 
blade. The glide surface does not itself act as a cutter. 
The cutting blade is integrated in the tool head and is preferably provided 
with opposing pairs of gliding non-cutting surfaces and cutting edges on 
the upper and lower sides of each blade set to the desired angle of cut. 
The cutting edge of this blade may be at an angle from about 45.degree. to 
90.degree. and the glide surface is at an angle of about 40.degree. to the 
longitudinal axis or feed direction of the tool head, in a preferred 
design. 
An angle difference of around 5.degree. is preferred, because it allows for 
easy grinding of the cutting edge without interfering with the glide 
surface. It also gives the glide surface a well defined conical form and 
thus makes it easier to place the cutting blades into the through hole. A 
preferred design of this invention provides a cutting edge which removes 
the material at a right angle to the feed direction of the tool. In this 
case, the angle of the chamfer to be cut with respect to the horizontal 
axis of the through hole and the chamfer's form are solely determined by 
the alignment of the glide surface to the vertical axis, or by the shaping 
of the glide surface. The glide surface, lying against the formed chamfer, 
pushes the spring-loaded blade as the tool head feeds it through the bore. 
The design of such a blade provides the arrangement of the cutting edge of 
the cutting blade which is at a right angle to the direction of cut at a 
90.degree. angle and the arrangement of the glide surface in any other 
smaller angle with respect to the vertical axis. The glide surface can be 
straight, concave, convex or curved irregularly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 2 illustrates a cutting tool having a tool head 1 similar to that 
described in U.S. Pat. No. 4,140,432 of the same applicant. The tool head 
has a transverse through bore 11, and opposing cutting blades 8, 9 
according to a preferred embodiment of this invention are mounted for 
sliding movement in opposite axial directions into and out of bore 11, as 
indicated by the arrows 21 in FIG. 2. 
As illustrated in FIGS. 2 and 3, the cutting blades 8, 9 are biased 
outwardly in direction of arrows 21 by a compression or torsion spring 23 
in central axial bore 50 of tool head 1. 
The spring has a pair of pins 24, 25 which project from its lower end and 
engage in transverse slots 27, 28 in the respective cutting blade. Thus, 
rotation of the spring in the direction of arrow 29 in FIG. 3 will urge 
the blades outwardly. When the blades are pushed inwardly, the spring will 
be rotated in the opposite direction and will be compressed or loaded. An 
eccentric stop or screw 26 projects into bore 50 to engage and stop one of 
the pins 24 in a predetermined position, to control the distance the 
cutting blades move outwardly from bore 11. This distance can be varied by 
adjusting the screw inwardly or outwardly, controlling the diameter 30 of 
the cut (see FIG. 2). 
FIGS. 2 to 7 illustrate one of the cutting blades according to a preferred 
embodiment of the invention. For reasons of simplicity, only one cutting 
blade is illustrated in FIGS. 4 to 7, because the opposite cutting blade 
is identical. 
It is naturally possible to only use one cutting blade in a cutting tool. 
Each cutting blade 8, 9 has an upper and lower horizontal bearing surface 
10, which slide between corresponding upper and lower horizontal surfaces 
of through bore 11 with little tolerance. Upper and lower cutting edges 13 
are formed adjoining the outermost edge of each bearing surface 10. Each 
blade has a glide surface 20 at its outer end which is substantially 
parallel to the feed direction of the tool head and which is a sliding, 
non-cutting face. An additional non-cutting glide surface 14 extends at an 
angle between end surface 20 and each cutting edge 13. The upper and lower 
cutting edges are symmetrical about the blade central axis. 
In the illustrated embodiment, cutting edges 13 are horizontal, or at an 
angle of 90.degree. to the vertical or feed direction 34 of the tool 
through bore 2. Glide surfaces 14 are at an angle 33 to the vertical. 
Cutting edges 13 may be at different angles in an alternative embodiment, 
but the angle 33 should be smaller than the angle of the cutting edge 13. 
This makes it convenient to sharpen the cutting edge 13 without damaging 
the glide plane 14, which can also reach a greater conicity. Consequently 
the cutting blades 8, 9 can be retracted more easily into the tool body 
through bore against the pressure of torsion spring urging them outwardly, 
when the cutting blades are positioned inside the through hole 2. 
This design makes it possible to cut an accurately defined chamfer 4-7 of 
e.g. 12.4 mm diameter, with a defined angle of e.g. 45.degree. and a 
through hole diameter 35 of e.g. 12 mm. This is possible due to the 
limitation of the rotation angle of the spring 23, which limits the 
outward movement of the cutting blades 8, 9. 
The effect of the cutting edge 13 is exactly limited, because a non-cutting 
glide surface 14 extends from the front of the cutting edges and becomes a 
non-cutting glide radius 20. 
The following is a more detailed description of the cutting blade. 
The blade having horizontal cutting edges 13 perpendicular to the feed 
direction allows not only straight chamfers to be made with any possible 
angle to the horizontal axis of the through hole, but also allows chamfers 
to be cut which are curved, i.e. concave, convex or any other curved cut. 
With this arrangement, the chamfer can now have almost any kind of shape, 
dependent on the shape of the glide surface 14. As mentioned above the 
glide surface can now be concave, convex or curved irregularly. The 
procedure is always started with a straight, horizontal cutting edge 13 
and only the glide surface 14 (see FIGS. 5 and 7) is adjusted according to 
the desired form of the chamfer. The angle 33 and the shaping of the glide 
surface 14 consequently determine and define the angle of cut and the form 
of the chamfer in the case of this design of the cutting blade. 
FIG. 5 demonstrates some alternative examples for the possibility of 
shaping of the glide surface plane 14. It is apparent that, apart from the 
straight glide surface 14, also a concave glide surface 14' or convex 
glide surface 14" could be provided. This would allow, instead of a 
straight chamfer 4 and 5 according to FIG. 1, for a curved chamfer 4' and 
4" which is a mirror image of the respective glide surface 14', 14" on the 
workpiece, as illustrated by the interrupted lines 4' and 4" in FIG. 5. 
This implies therefore that the chamfer 4, 5 is cut into the hole of the 
workpiece in a mirror image of the shaping of the glide surface 14 of the 
cutting blade 37, 38. In this case it is required that the cutting edge 13 
be aligned horizontally or perpendicular to the feed direction or vertical 
34 as shown in FIGS. 5 and 8. 
However it is not mandatory for the cutting edge 13 to be aligned 
horizontally for this design of the invention. This cutting edge can be at 
any other angle to the horizontal; however, the angles must not deviate 
too far from the horizontal, otherwise the shape of the cutting edges 
themselves would control the shape of the chamfer. 
It is therefore important that the cutting blade 37, 38 according to FIGS. 
4 to 7 has an extending non-cutting glide surface, beginning from a 
horizontal cutting edge 13 and in a radially outward angle to the glide 
radius 20. This glide surface 14 can have any shape in a relatively wide 
range as exemplified by alternative glide surfaces 14' and 14" illustrated 
in FIG. 5. 
As already mentioned, the glide surface 14 extends to the glide radius 20, 
which runs parallel to the vertical 34. 
It is apparent from FIGS. 4 and 7 that the transition from cutting edge 13 
to the glide surface 14 is a curve at position 22 resulting in a curved 
chamfer. 
The cutting edge shows a positive polished surface and hence a positive 
cut, whereas the glide surface 14, 14' and 14" has a negative polished 
surface in order to avoid a cutting effect. 
Shavings groove or surface 12 extends between the upper and lower cutting 
edges 13 to carry away cut shavings from the cutting edges. The shaving 
groove edge 17 is curved to follow the line of a bow, with a curving 
radius which can be varied widely. The smaller the curving radius of this 
shaving groove 12 the sharper and more aggressive is the cutting effect of 
the cutting blade. 
FIG. 6 also illustrates that a clearance angle edge 42 extends from the 
shaving groove 12, tilting forward on the front side of the cutting blade. 
This clearance angle edge shows an angle 41 to the horizontal. 
FIG. 8 illustrates the operation of this cutting blade to remove material 
from a bore. In particular, a horizontal cutting effect is obtained with 
the cutting edge 13 in the cutting plane; in this procedure, as mentioned 
above, the shaping of the chamfer can be curved to any degree, which in 
turn depends on the shape of the glide surface 14. As the cutting tool is 
urged downwardly into through bore 2 of the workpiece, the cutting edges 
13 first touch the upper edge of the through bore at the transition point 
22 between edges 13 and glide surfaces 14. The removal of material then 
proceeds at a right angle to the direction of cut, with the shape and 
angle of cut 4 being determined by the shape and angle of glide surface 
14. The blades are progressively urged back into the tool head as the tool 
head moves down into the bore. Once the transition point reaches the lower 
end of chamfer 4, the cutting edges are completely retracted and will be 
held away from the walls of bore 20 so that no further material can be 
removed. The maximum diameter 30 of the cut defines the transition 22 
between the non-cutting glide surface and the cutting edge. The distance 
between end face 20 and transition point 22 controls the depth of the 
chamfer. After the chamfer is cut, the cutting edges are disengaged and 
retracted into the tool head, which continues on through the bore and out 
of its opposite end. The chamfer 5 is made in the same manner by reversing 
the direction of tool head 1 and moving it back upwardly through bore 2, 
with the uppermost cutting edges forming the chamfer. 
Although a preferred embodiment of the invention has been described above 
by way of example only, it will be understood by those skilled in the 
field that modifications may be made to the disclosed embodiment without 
departing from the scope of the invention, which is defined by the 
appended claims.