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Hobs

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Hobs enable precision gear processing and are widely used in automobiles, construction and industrial machineries, as well as for processing of power transmission gears in marine vessels and aircrafts.
Processing can be designed according to your selection of outer diameter, overall length, bore diameter, number of gash as well as optimum assembly of tool and material coating. This selection includes various lineups for arc other than involute gear and non-involute gear such as cycloid and sprocket gears.
Moreover, small sized shank hob, large sized gash mill cutter can be also be processed.
Dry cut by high hobbing that features our "SuperDry coating" applied to the cutting face makes improvement not only in the work environment that requires no cutting oil but rapid processing even at a cutting rate of 250 m/min.or more is possible, achieving highly effi cient processing with multiple starts.

SuperDry III Hob

Beyond the limit of high speed processing… "SuperDry III" Coating hob
High-speed machining at a cutting speed of 250 m/min. or more reduces the cycle time, extends tool life and achieves precision processing.

SuperDry III Hob

SuperDry III Hob

Feature

  • In comparison to SuperDry II, it has enhanced the tolerance temperature rate over oxidation to prevent reduction of coating hardness at high temperatures and to further strengthen wear and tear resistance.
  • Improvement in coating structure raises coating strength and bonding power by increasing adhesion with the base material.

Example of processing

Work: Module 2.25
Pressure angle 17.5
Number of teeth 52
Helix angle 23° LH
Material 18CrMo4(HB180)
Hob: Outer diameter 75 mm, Material MACH7
Number of start 3□LH
Number of gash 14
with cutting face coating
Cutting condition: Cutting speed 250 m/min.
Axial feed 2.4 mm/rev
Coaxial winding climb, no shift

Tool wear
Appearance of cutting work piece

Appearance of cutting work piece

Picture illustrating wear after processing 80 units of work pieces

SuperDry III

SuperDry III

>0.09mm (left hand side)

SuperDry II

SuperDry II

>0.19mm (left radius)

Profile precision X 500 X 4

Profile precision X 500 X 4

Lead precision X 500 X 2

Lead precision X 500 X 2

Processing by hobbing

Mount a hob on the hobbing machine, position the hob and the work piece in rack and pinion order, perform synchronous rotation, and feed the hob to work piece’s gear width direction; this enables highly efficient and accurate gear processing.

Processing by hobbing1

Hob identifies itself either as numerous number of teeth or as a single tooth.
One tooth of a work piece is generated per one rotation.

Processing by hobbing2


Feeds the hob to a work piece' s gear width direction
Efficiency in processing may improve if the number of starts for the hob is increases but the number of blade will decrease and polygonal error may be formed at the same time.
Machine must have sufficient rigidity and strength.

Gear cutting method in hobbing

■Conventional hobbing

Hob rotates from the top face to the bottom face of a work piece.
Conventional hobbing

■Climb hobbing

Hob rotates from the bottom face to the top face of a work piece.
Climb hobbing

Precaution for sharpening

Hob needs grinding as cutting edge surface may become worn; this process is called "Resharpening". Improper resharpening may affect the precision of the hob. Following indicates the typical example of errors in the cutter form:

Precaution for sharpening

Δγδ=hobbing lateral face lip clearance (tanΔγδ=tanε・tanαn・cosγ),
ε=external lip clearance
αn=tooth pressure angle
γ=hobbing feeding angle,
rρ=hobbing pitch circle diameter

Influence from cutting load fluctuation

Influence from cutting load fluctuation

Hob setting angle error and tooth thickness

Hob setting angle error and tooth thickness 1
Hob setting angle error and tooth thickness 2

Number of starts and polygonal error

Number of starts and polygonal error
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Business contact: Strategic Sales Operation Department
Phone: +81-77-552-9760

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