Combination polycrystalline diamond bit and bit holder
A quick change type bit/bit holder includes several different structures for holding the item in a bit block without the necessity of a fastener. The bit portion of the bit/bit holder combination includes a ductile steel insert with a polycrystalline diamond coated tungsten carbide bit positioned therein. The ductility of the steel insert acts as a shock absorber to allow the bit to successfully remove concrete as well as asphalt in a road milling machine.
1. A bit/bit holder for road milling, mining and trenching machinery comprising:
a body of rounded shape having an upper end diametrically smaller than a lower end thereof, said body being solid in a substantial portion thereof,
a generally cylindrical shank extending from said lower end of said body, said shank includes a hollow portion substantially along its entire length and includes a termination axially adjacent said lower end of said body, and including at least one axially oriented elongate slot through a side wall of said shank,
said upper end of said body including a forward extension axially extending from said upper end, the forward extension diametrically smaller than the upper end and the forward extension including a first bore extending axially therein to the upper end, an insert retained in said first bore forming a unitary structure therewith
said first bore extending axially in said forward extension to said upper end of said body, the forward extension including a generally cylindrical side wall, said insert having a complementary shape side wall for matingly fitting therein, and
the top of said insert including a central second cylindrical bore therein, and a diamond topped bit retained in said second central bore as a unitary structure therewith.
2. The bit/bit holder as defined in claim 1 wherein said diamond topped bit includes a PCD layer thereon.
3. The bit/bit holder as defined in claim 1 wherein said diamond topped bit includes a PCD coating thereon.
4. The bit/bit holder as defined in claim 1 wherein said diamond topped bit includes one of an industrial diamond coating and industrial diamond layer thereon.
5. The bit/bit holder as defined in claim 1 wherein said insert is made of tungsten carbide.
6. The bit/bit holder as defined in claim 1 wherein said insert is press fit in said first bore in said body.
7. The bit/bit holder as defined in claim 1 wherein said insert is brazed in said body.
8. The bit/bit holder as defined in claim 1 wherein said insert is shrink fitted in said body.
9. The bit/bit holder as defined in claim 1 , wherein the shank comprises:
a first tapered portion axially extending from a stepped shoulder adjacent a distal end of the shank;
an annular shoulder axially extending from the first tapered portion;
a second portion axially extending from the annular shoulder; and
a generally cylindrical expanded diameter upper portion axially extending from the second portion, the upper expanded diameter portion being subjacent the lower end of the body.
10. The bit/bit holder as defined in claim 1 , wherein said first bore axially extends a predetermined distance from the forward extension toward the lower end of the body, and wherein the predetermined distance is less than a distance from the upper end to the lower end of the body.
11. The bit/bit holder as defined in claim 1 , wherein the first bore comprises a slight draft angle.
12. The bit/bit holder as defined in claim 1 , wherein the diamond topped bit comprises a base made of tungsten carbide.
13. The bit/bit holder as defined in claim 1 wherein said body, shank, insert and bit form a unitary structure.
14. The bit/bit holder as defined in claim 1 wherein said hollow portion of said shank defines a constant diameter and said termination thereof is of said diameter.