Moving Gears

Gear Tech Tips

Technical Information For The Gear Industry

 by Koepfer Logo AMERICA
 

This Edition is Sponsored by: ims.koepfer cutting tools gmbh

Tech Tip Edition #1

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Hob Life and Shifting Strategy (Part 1 of 2)

With the emphasis on longer hobs today, shifting strategies have become an important part of the hobbing process.  Each hobbing application has a different strategy that will produce the best tool life.  One of the first items needed to achieve optimum tool life is to calculate the usable shifting length of the hob for the particular part being hobbed.  To do this, the following information is required:

  • Diametral Pitch (Pnd)
  • Helix Angle (Ψ)
  • Number of Teeth in Part (N)
  • Length of Hob Without Hubs (L)

Step 1) Calculate the Axial Pitch (px). 

                px =  p / Pnd

Step 2) Estimate the non-usable axial pitch factors (X & Y) on each side of the hob. These values are interpolated from the chart. (See Diagram #2)

Step 3) Calculate the non-usable axial pitches (X & Y) on each side of the hob.

                   X = x * px

                   Y = y * px  

Step 4) Calculate the usable cutting face length (UL) of the hob.

                   UL = L - (X + Y)

(In the next edition of Gear Tech Tips, we will discuss Part 2 - "Calculation of Shift Amount".)

Diagram #1 - Usable shifting length of hob

Usable shifting length of hob image

  

Diagram #2 - Non-usable pitch chart

Non-usable pitch chart

              

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