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CoroBore 820 Rough boring tool with three insert designs

CoroBore® 820 is your first choice for rough boring. The comprehensive program of tool bodies, slides, shims, and cutting inserts allow CoroBore 820 to be configured to suit the widest possible range of applications. The same program can be utilized for productive boring, step boring, and single-edge boring. The system consists of adapters with matching slides, shims, and covers, making it possible to adapt the tool to various materials and conditions.


  • Versatile, with three different operation types in one tool
  • Large standard assortment of CoroTurn 107 and T-Max P inserts
  • Dedicated geometries and grades for all materials
  • High metal removal rate due to three insert design


  • Short, rigid and compact giving maximum stability
  • Optional slide assemblies, individually adjustable axially and radially, giving reduced inventory costs.
  • Cutting fluid through the tool for good chip evacuation
CoroTurn® 107 screw clamping
- First choice, wide choice of inserts​
T-Max® P, CoroTurn® RC rigid clamping
- For improved economy and process security in stable conditions​


  • 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.
  • Can also be used when working with blind holes and interrupted cuts.


Large diameter Weak machines Interrupted cuts
Blind hole Large depth of cut Off-center hole

ISO application area


  • 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
  • Choose negative inserts (T-Max P) for tough applications that require strong inserts and improved process security.
  • Step boring is an effective way to increase the depth of cut without excessive vibrations

Product range

Boring range, mm
Boring depth​ 4xDCSFMS​
Hole tolerance​ IT9​


Overview of assembly parts:



  1. Slide
  2. Coolant
  3. Shim set
  4. Cover
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 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 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 coupling or CoroChuck 930.

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 on one tooling system for the entire workshop. Remember the following:

  • Choose shortest possible adapter
  • Choose strongest possible adapter
  • If reduction is needed, use tapered version if possible
  • For long overhangs (>4 x DCSFMS), use dampened adapters
  • For long overhangs, ensure rigid clamping with flange contact to spindle if possible
Choice of adapters/chucks for boring 
​ ​ Adapter and chuck systems​
Choose coupling/chuck first,
then adapters/chucks​​
Coromant Capto​ CoroChuck 930​
Shrink fit
Collet chuck
+++ Very good Torque transmission +++ +++ +++ +++
++ Good Run-out +++ +++ +++ +++
+ OK Balance +++ +++ +++ +++
Boring tool couplings​ ​
CoroBore 820​ Coromant Capto​ 1​
DuoBore​ Coromant Capto​ 1​
HeavyDuty​ Coromant Capto​ 1​
CoroBore 825​ 1​ 2​ 3​
Cylindrical​ 1​
Fine boring head 391.37A/B​ Coromant Capto
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​
Fine boring head​
Heavy duty boring tools

CoroChuck 930 – first choice for boring tools with cylindrical shanks


CoroChuck 930 precision chucks have a 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
Complementary adapters


Shrink fit adapters can be used for accessibility purposes. However, CoroBore 825 with integrated dampening mechanism is preferable if accessibility is required.​
Shrink fit adapter​ CoroBore 825
Cylindrical shank​
Reamer 830
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 CoroChuck 930. Furthermore, it is not individually balanced. ​
Collet chuck adapter​ CoroBore 825 Cylindrical shank​​
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