GB1569266A - Cutting tool for a machine tool - Google Patents

Description

(54) A CUTTING TOOL FOR A MACHINE TOOL (71) We, GRINDING AIDS LIMITED of Tamworth Road, Kettle brook, Tam worth, Staffordshire, a British Company do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a cutting tool for a machine tool.

The present invention consists in a cutting tool for a machine tool and comprising a body capable of being secured to a tool carrier of the machine tool, and a series of cutter blades releasably mounted at a series of blade locations of the body, each blade having a cutting edge and having a seating face which seats against a support face of a respective location of the body, the support face being arranged to maintain the cutting edge of the blade at a predetermined dis tance from a datum which is either the axis of rotation in the case of a peripheral cutting, rotary tool or a plane of relative movement in use between the tool and a work apiece, wherein from the second to the last of the series, each blade is smaller from its cutting edge to its seating face than the preceding blade of the series by a predeter mined dimension and correspondingly, each support face from the second to the last of the series of locations is at a greater distance from the datum than is the support face of the preceding location by that same prede termined dimension.

The first blade of the series may be the first of the series of the blades to contact the work piece in use as in the case of a broach or like cutting tool.

When, due to wear, the cutting edge of a cutting tool has to be reformed, for exam pie, by grinding, the nominal size of the tool is reduced. Hitherto in certain types of tool where the blades are integral with the body this will eventually necessitate the whole tool being discarded or in the case where the tool has replaceable blades, the original set of blades will have to be discarded and replaced by a complete new set.

In one cutting tool according to the present invention when regrinding of the cutting edges of the blades has reduced the overall dimension of the tool below an acceptable level, each of the blades of the series can be reground so that its dimension from its cutting edge to its seating face is smaller than its original dimension by the predetermined dimension. The blades can then be remounted to the body, each blade being mounted to the blade location of the series following its original location, one new blade only being required, that blade being inserted in the first blade location.

Thus the cutting tool, by the addition of one new blade only and the discard of one blade is re-established at its original dimensions.

It is also possible to grind down the blades by a dimension which is a multiple of the predetermined dimension, correspondingly remounting each of the blades in a location following their original location by the number of the multiple and, providing the same number of new blades as the multiple, and discarding the same number of blades.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic sketches. in which: Figure 1 is a sectional side view of a peripheral cutting milling cutter according to the invention, and Figure 2 is a sectional side view of part of a broach.

The milling cutter comprises a cylindrical body 10 formed on its axis with a central aperture 11 and key way 12 for securing the tool on the arbor of a milling machine. At equally spaced intervals around its periphery, the body has a series of blade locations in the form of slots 13 extending parallel to the axis of the body and in each of which is received a generally rectangular cutter blade 14 of a series of such blades.

The cutter blades 14 are releasably secured in the slots 13 in any suitable manner, for example, one manner of securing cutter blades in a milling cutter body is fully described in the specification of British Patent No. 1241950.

Each cutter blade 14 has a cutting edge 15 and a base face 16. At each cutter blade location or slot 13 in the body there is a support face 17 constituted by the bottom surface of the slot 13, against which seats the base face 16 of the blade 14 constituting the seating face of the blade and which is arranged to maintain the cutting edge 15 at a predetermined distance from the datum which is the axis of rotation of the tool.

As illustrated in Figure 1 the series of blades 14 extends from the first which is at the 12 o'clock position as shown in the drawing in an anti-clockwise direction to the last of the series of blades which is at the 1 o'clock position as shown in the drawing.

The second cutter blade is smaller from its cutting edge to its seating face than the first cutter blade by a predetermined dimension which may for example be 0.005 of an inch (for the purpose of illustration the predetermined dimension is exaggerated in the drawing and an inner chain dotted circle concentric with the body axis is shown to assist comparison) and each subsequent blade is smaller than the preceeding blade by that same predetermined dimension.

Correspondingly, each of the support faces 17 of the blade locations of the body from the second to the last of the series is at a greater distance from the datum, which is the axis of rotation of the tool, than the support face of the preceding slot by that same predetermined dimension.

When re-grinding of the cutting edges of the blades has reduced the overall diameter of the tool to an unacceptable level, each of the cutter blades except the last of the series is, on the last re-grinding, reduced to a dimension, from its base to its cutting edge, which is smaller than its original dimension by that same predetermined dimension. On reassembly of the blades to the body each blade except the last is mounted to the body location following its original location, the last blade being discarded and a new first blade being introduced. The cutting tool is thereby restored to its original dimensions, with the introduction of only one new blade into the cutting tool.

Each blade is located in the body at an angle of inclination to a radius of the body so that the necessary clearance angle is automatically provided, the clearance face of each blade being at right angles to the length of the blade.

In describing the embodiment shown in Figure 2 of the accompanying drawings parts or features which are same as those described in the construction shown in Figure 1 will be referred to by the same reference numeral.

The broach, a part only of which is shown in Figure 2, comprises an elongated body 20 to which is releasably mounted a series of cutter blades 14 each having a cutting edge 15 and a base face 16 forming a seating face.

The body 20 has a series of blade locations in the form of slots 13 each of which has a support face 17 formed by its bottom surface and which is arranged to maintain the cutting edge of the cutter blade in that slot at a predetermined distance from a datum which is a plane of relative movement (indicated by arrow 21) in use between the tool and a work piece. Each blade 14 from the second to the last of the series is smaller from its cutting edge to its seating face than the preceding blade by a predetermined dimension which, as in the case of the embodiment described in conjunction with Figure 1, is of the order of 0.005 of an inch although the dimension is exaggerated for the purpose of illustration in Figure 2 of the drawing and a chain dotted line parallel to the datum is shown to assist comparison.

Correspondingly each support face 17 from the second to the last of the series of locations is at a greater distance from the datum than the preceding support face by that same predetermined dimension. When required, the cutting edges of the cutter blades can be reground to reduce the dimension of each blade from its cutting edge to its base by that same predetermined dimension from its original dimension. The blades can then be remounted in the body 20, each blade being located in the location following its original location, the last blade of the series being discarded and a new first blade being introduced.

Each blade 14 is mounted at an angle of inclination in the body 20 so that a clearance angle is automatically provided, the outer face being normal to its rear face.

In another embodiment not illustrated, but falling within the scope of the present invention, a series of groups of two or more cutter blades of similar dimensions from their cutting edges to their bases are mounted to a body and correspondingly the body has a series of groups of two or more blade locations having supports at the same predetermined distance from the datum as each other. From the second to the last of the series, each group has blades smaller from their cutting edges to their seating faces than the blades of the preceding group and correspondingly, the support faces of each group of locations are at greater distance from the datum than those of the preceding group by that same predetermined dimension.

WHAT WE CLAIM IS: 1. A cutting tool for a machine tool and comprising a body capable of being secured to a tool carrier of the machine tool, and a series of cutter blades releasably mounted at a series of blade locations of the body, each blade having a cutting edge and having a seating face which seats against a support face of a respective location of the body, the support face being arranged to maintain the cutting edge of the blade at a predetermined distance from a datum which is either the axis of rotation in the case of a peripheral cutting rotary tool or a plane of relative movement in use between the tool and a work piece, wherein from the second to the last of the series, each blade is smaller from its cutting edge to its seating face than the preceding blade of the series by a predetermined dimension and correspondingly, each support face from the second to the last of the series of locations is at a greater distance from the datum than is the support face of the preceding location by that same predetermined dimension.

2. The cutting tool of claim 1 wherein the seating face of each cutter blade is its base face which is located at the opposite end of the blade to its cutting edge.

3. The cutting tool of either claim 1 or claim 2 wherein the blade locations are in the form of slots.

4. The cutting tool of claim 3 as dependent upon claim 2 wherein the support faces of the blade locations are formed by the bottom surfaces of the slots.

5. The cutting tool of any preceding claim wherein each cutter blade is located in the body at an angle of inclination whereby the necessary clearance is automatically provided when the clearance face of the blade is at right angles to the length of the blade.

6. A cutting tool substantially as described herein with reference to and as shown in Figure 1 of the accompanying drawings.

7. A cutting tool substantially as described herein with reference to and as shown in Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. preceding group by that same predetermined dimension. WHAT WE CLAIM IS:

1. A cutting tool for a machine tool and comprising a body capable of being secured to a tool carrier of the machine tool, and a series of cutter blades releasably mounted at a series of blade locations of the body, each blade having a cutting edge and having a seating face which seats against a support face of a respective location of the body, the support face being arranged to maintain the cutting edge of the blade at a predetermined distance from a datum which is either the axis of rotation in the case of a peripheral cutting rotary tool or a plane of relative movement in use between the tool and a work piece, wherein from the second to the last of the series, each blade is smaller from its cutting edge to its seating face than the preceding blade of the series by a predetermined dimension and correspondingly, each support face from the second to the last of the series of locations is at a greater distance from the datum than is the support face of the preceding location by that same predetermined dimension.

2. The cutting tool of claim 1 wherein the seating face of each cutter blade is its base face which is located at the opposite end of the blade to its cutting edge.

3. The cutting tool of either claim 1 or claim 2 wherein the blade locations are in the form of slots.

4. The cutting tool of claim 3 as dependent upon claim 2 wherein the support faces of the blade locations are formed by the bottom surfaces of the slots.

5. The cutting tool of any preceding claim wherein each cutter blade is located in the body at an angle of inclination whereby the necessary clearance is automatically provided when the clearance face of the blade is at right angles to the length of the blade.

6. A cutting tool substantially as described herein with reference to and as shown in Figure 1 of the accompanying drawings.

7. A cutting tool substantially as described herein with reference to and as shown in Figure 2 of the accompanying drawings.