Hob Mounting Problems

Cause & Effect

Max Indicator reading 0.005mm (0.0002")

Hobs should be checked on the machine 

before gear's are cut if this is adhered to.

Gear's better than DIN 4 can be achieved

Max Indicator  reading 0.005mm (0.0002")

Hobs Run out one end gives better profiles on one side 

Gives variable results as you hob shift along the Hob.

Max Indicator reading 0.005mm (0.0002")

Hobs Run out on both end's "OUT of phase"

gives very poor profiles both side's. 

This is the worst case

Gives variable results as you hob shift along the Hob.

Max Indicator reading 0.005mm (0.0002")

Hobs Run out on both end's "IN phase"

gives very poor profiles both side's.

This is better than out of phase

Important Note when using Topping Hob's i.e.  Pulley's / Sprocket's

• When topping Hobs are used the tool run out will affect the Major & Minor Dia's produced by the Hob

• When Hobbing a gear and topping the OD if the correct gear tooth size is achieved the OD & Root dia will NOT be as designed

• When Non toping Hobs are used the Minor Dia will be affected

• Any error will increase as the amount or hob run out increases which can lead to premature belt failure for example

• The same problem applies to Sprockets as the Chain link seating radius will not be as designed

• This will also affect a straight sided spline's as more run out is introduced this will affect the quality of the spline sides hence they will not parallel

Checklist for Best Practice