DuoBore 821/821D Rough boring tool with two insert design

​DuoBore™ 821 is a versatile rough boring tool that can be used in three different operation types: multi edge- , step- and single edge boring. The slides can be adjusted individually, both axially and radially. The system consists of adaptors 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-edge 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, e.g. boring of Inconel 625 weld in oil and gas applications

ISO application area

 

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 inch) in styles CN and SN.​

Overview of assembly parts:

Conventional DuoBore 821​		DuoBore 821 dampened​
​		​
​ ​	1. Slides 2. Adaptor​	​	1. Slides 2. Dampened adaptor​

 ​

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 / GC 1105​	-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 recommendation 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, se 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 recommendation on fine boring in ISO H material, see technical guide, General turning.
Cutting data recommendations, see main catalogue.

​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 adaptors can be used in different applications and machines. This makes it possible to standardize on one tooling system for the entire workshop. Remember the following:

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

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

• Reduced tool inventory with standardized tools minimizing machine downtime
• For boring operations requiring long reach, as in large machining centres in the diameter range of 1–36 mm (0.039–1.42 inch). Deep pockets is a typical application where the Coromant EH system offers the required reach without limiting process security