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​DuoBore821 is a versatile rough boring tool that can be used in three different operation types: multi-edge, step, and single-edged boring. The slides can be adjusted individually, both axially and radially. The system consists of adapters with matching slides, shims, and covers, making it possible to adapt the tool to various materials and conditions.

 

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Benefits

  • Versatile, with three different operation types in one tool
  • Large standard assortment of CoroTurn® 107 and T-Max® P inserts
  • Available as dampened tools, 821D (Silent Tools™), for productive boring even at long overhangs

 

Features

  • Two insert design
  • Short, rigid, and compact, gives maximum stability
  • Optional slide assemblies, individually adjustable, both axially and radially, giving reduced inventory costs.
  • Cutting fluid through the tool for good chip evacuation

 

Application

  • Dedicated geometries and grades for all materials
  • Use CoroTurn® 107 screw clamping as first choice
  • Use T-Max® P and CoroTurn® RC for improved economy and process security in stable conditions
  • Use tool for various application types such as counterbore, through hole, and interrupted cut
Multi-edge boring
 
Step boring​
Single-edged boring

 

Counterbore Through hole Interrupted cuts Blind hole

 

  • 90° First Choice for counterbore and vibration-prone operations
  • 75° First Choice for stack boring, interrupted cut, sand inclusions, etc.
  • 84° RC slides, for through holes, stack boring, interrupted cut, sand inclusions, etc.
  • Round insert carriers are a productive solution for machining in cladded materials like the boring of Inconel® 625 weld in oil and gas applications
ISO application area
 

 

CoroBore® BR20 and CoroBore® BR10

A new generation of rough boring tools is available. For our latest boring solutions within the same application area as DuoBore™, see CoroBore® BR20 and CoroBore® BR10 (back boring).

 

Recommendations

  • Start with a roughing geometry, unless a small depth of cut is to be taken.
  • Choose a medium geometry for smaller cutting depths or improved chip breaking
  • Choose CoroTurn® 107 for lower cutting forces process security
  • Step boring is an effective way to increase the depth of cut without excessive vibrations
  • First Choice for roughing with DuoBore™ 821D, dampened tools:
    • Entering angle 90°/Lead angle 0°
    • Recommended radius R08, otherwise try R04

 



Product range

DuoBore™ 821
DuoBore™ 821 D
      ​
Boring range mm (inch)
​25–150
(0.984–5.906)
​25–101
(0.984–3.976 )
​99–150
(3.898–5.906)
Hole tolerance ​IT9 ​IT9 ​IT9
Slides are available for both ceramic and solid carbide CoroTurn® 107 inserts. CoroTurn® RC slides from diameter 69 mm (2.717 inches) in styles CN and SN.
Overview of assembly parts:
Conventional DuoBore™ 821​ DuoBore™ 821 dampened​
​ ​

1. Slides
2. Adapter​

1. Slides
2. Dampened adapter

 ​
Grades and geometries

 

​ ​ ​ Medium Roughing Complementary

Positive inserts

​​

CoroTurn® 107 screw clamping​ ​ ​ ​ ​

-PM / GC4225​ -PR / GC4225​ -WM / GC4215​
-MM / GC2025​ -MR / GC2025​ -WM / GC2015​
-KM / GC3215​ -KR / GC3215​ -WM / GC3215​
-AL / H10​ -AL / H10​ -AL / GC1810​
-MM / GC1105 -MM / GC1105 -UM / GC1115
    **
Negative inserts

T-Max® P, CoroTurn® RC rigid clamping

-PM / GC4225​ -PR / GC4225​ WMX / GC4215​
-MM / GC2025​ -PR / GC4225​ WMX / GC2015​
-KM / GC3215​ -KR / GC3215 WMX / GC3215​
-QM / GC1105​ -QM / GC1105​ -NM / GC1115
   **

*H13A for Ti-based ISO S materials
** For recommendations on fine boring in ISO H material, see technical guide, General Turning.
Note: Grade recommendations are valid for average conditions
For recommendations on when an alternative grade should be used, see below:

Application Toughness First Choice Wear resistance
Roughing GC4235 GC4225​ GC4215​
GC2035 GC2025 GC2015
GC4215 GC3215 GC3210/GC3205*
GC1115 H10 GC1810
GC1115/H13A GC1105 GC1105

*GC3210 Nodular cast iron, GC3205 Gray cast iron
For recommendations on fine boring in ISO H material, see technical guide, General Turning.
For cutting data recommendations, see main catalog.

​Tool holding

Bending stiffness and torque transmissions are the most important factors when choosing a tool holder for boring operations. For best stability and hole quality, use Coromant Capto® or the Coromant EH system.

Coromant Capto® coupling is the only modular tooling system designed for all metal cutting operations, including all hole making methods. The same cutting tools and adapters can be used in different applications and machines. This makes it possible to standardize one tooling system for the entire workshop. Remember the following:

  • Choose the shortest possible adapter
  • Choose the strongest possible adapter
  • If reduction is needed, use tapered version, if possible
  • For long overhangs (> 4 x DCON), use dampened adapters
  • For long overhangs, ensure rigid clamping with flange contact to the spindle, if possible

The Coromant EH system delivers great tooling flexibility – Choose from an extensive variety of heads, adapters, and shanks.

  • Reduced tool inventory with standardized tools, minimizing machine downtime
  • For boring operations requiring long reach, as in large machining centers in the diameter range of 1–36 mm (0.039–1.42 inches). Deep pockets are a typical application where the Coromant EH system offers the required reach without limiting process security
Choice of adapters/chucks for boring 
 
​ ​ Adapter and chuck systems​
Choose coupling/chuck first,
then adapters/chucks​​
Coromant Capto​® CoroChuck™ 930​
Shrink fit
adapter​
Collet chuck
adapter​
+++ Very good Torque transmission +++ +++ +++ +++
++ Good Run-out +++ +++ +++ +++
+ OK Balance +++ +++ +++ +++
Boring tool couplings​ ​
CoroBore® 820​ Coromant Capto​® 1​
DuoBore™ Coromant Capto​® 1​
CoroBore® XL​ Coromant Capto​® 1​
CoroBore® 825​ 1​ 2​ 3​
Cylindrical​ 1​
EH​ 1​
Fine boring head 391.37A/B​ Coromant Capto®
CoroBore® 824 XS​ Coromant Capto​® 1​
CoroBore® 824 XS​ EH​ 1​
1 ​ = First Choice​
2​ 3​ = Complementary choice​

 

Coromant Capto® system – First Choice

 

First Choice should always be tools with Coromant Capto® coupling, which offers excellent repeatability and the best stability characteristics on the market. ​
CoroBore® 820​
Coromant Capto® basic holders and adapters​ CoroBore® 825​
DuoBore™
Fine boring head​
CoroBore® XL

 

CoroChuck™ 930 – First Choice for boring tools with cylindrical shanks. 

 

CoroChuck™ 930 precision chucks have very good run-out precision and high torque transmission thanks to the latest Fulcrum technology. This technology delivers the best pull-out security on the market.​ ​
HD version​ CoroBore® 825 Cylindrical shank​
Slender version
CoroBore® 824 XS​ EH
Complementary adapters

 

Shrink fit adapters can be used for accessibility purposes. However, CoroBore® 825 with an integrated dampening mechanism is preferable if accessibility is required.​
Shrink fit adapter​ CoroBore® 825 Cylindrical shank​
Collet chucks can be used together with CoroBore® 825 cylindrical shanks. However, it is not the optimal solution due to lower clamping forces and larger run out compared to HydroGrip. Furthermore, it is not individually balanced. ​
Collet chuck adapter​ CoroBore® 825 Cylindrical shank​​
 
 
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