Boring bars

• US 4,061,438 A
• Filed: 01/26/1977
• Issued: 12/06/1977
• Est. Priority Date: 02/05/1976
• Status: Expired due to Term

• Current Assignee: National Research Development Corporation
• Original Assignee: National Research Development Corporation
• Inventors: New, Ronald William
• Primary Examiner(s): Hinson, Harrison L.
• Application Number:
  US05/762,666
• Time in Patent Office: 314 Days
• Field of Search: 408/143, 408/144, 408/714
• US Class Current: 408/143
• CPC Class Codes: B23B 29/022 with vibration reducing means
• CPC Class Codes: Y10T 408/76 Tool-carrier with vibration-damping means

Abstract

The overhung ratio of a boring bar having a damper formed by a damper mass located in a cavity near the cutting tool, with a fluid-filled clearance between the mass and the cavity wall, may be increased by shrink-fitting a tungsten carbide core or bung into the root end of the bar and/or by fitting a second damper to the free end of the bar beyond the cutting tool.

Claims

1. A boring bar comprising a tubular shank having a rearward end, by which it is mounted, and a forward end having means for mounting a cutting tool, a bung tight-fitted into at least a rear portion of the shank, said bung having a modulus of elasticity substantially greater than that of the shank, the shank having adjacent the tool mounting means a closed cavity in which is positioned a damper mass with a damping clearance between the mass and the inner wall of the cavity, said damping clearance containing a damping fluid.

2. A boring bar according to claim 1, in which the front end of the bung is spaced from the rearward end of the cavity by a hollow portion of the shank.

3. A boring bar according to claim 1, in which said damping fluid is air.

4. A boring bar according to claim 1, in which the bung is shrink-fitted into the hollow shank.

5. A boring bar according to claim 1 and including a second damper assembly, said cutting tool lying between said second damper assembly and the first mentioned damper assembly, said second damper assembly comprising a cylindrical damper mass located in a sealed cavity with a damping clearance between said mass and the inner wall of said cavity, said clearance containg a damping fluid.

6. A boring bar according to claim 5, in which said second damper assembly forms a capsule detachably secured to the forward end of said bar.

7. A boring bar according to claim 1, in which said bung is made of tungsten carbide.

8. A boring bar according to claim 7, in which said shank is made of steel.

9. A boring bar according to claim 8, in which said bung is shrink-fitted into said hollow shank.

13. A boring bar according to claim 2, in which the forward end of said shank is open and said damper assembly is secured in said open shank end with said damper spaced from said bung.

10. A boring bar comprising a shank having a rearward end by which it is mounted, and a forward end having means for mounting a cutting tool, said bar including a first damper assembly adjacent and behind the cutting tool, said first damper assembly consisting of a closed cavity in the bar in which is located a damper mass having a damping clearance around it, said clearance containing a damping fluid, a second damper assembly forward of said cutting tool, said second damper assembly also consisting of a closed cavity containing a second damper mass circumferentially surrounded by a damping clearance containing a damping fluid.

11. A boring bar according to claim 10, in which said second damper assembly forms a capsule and said capsule is detachable secured to said bar.

12. A boring bar according to claim 10, in which said first and second damper masses and their respective cavities are cylindrical.

14. A boring bar according to claim 12, in which said tool mounting means is secured to said damper assembly.

15. A boring bar according to claim 10, in which the second damper assembly is proportioned to damp the second mode of oscillation of the bar.