No, the previous website has been decomissioned.
Please refer to the "HOME" page on this site for more information on past Hercus and Durden Products.
or go direct to www.fwhercus.com.au
To show case Hercus's current Products and Services that we offer to our valued clients.
For redunant and obsolete products from Hercus and Durden please visit the following website for more information. www.fwhercus.com.au
Gear Data and Calculations
Imperial ( DP )
To calculate Outside Diameter of a Gear OD = No. of teeth + 2 / DP
To calculate Pitch Diameter of a Gear PD = No. of teeth / DP
Metric ( Mod )
To calculate Outside Diameter of a Gear OD = No. of teeth + 2 * Mod
To calculate Pitch Diameter of a Gear PD = No. of teeth * Mod
MOUNTING DATA - Spur Gears
The centre distance for a pair of spur gears is determined by adding their pitch diameters and dividing by two. Gears are cut to give the correct running clearance at this distance. Shafts should be set parallel to each other and spaced to a tolerance of -.000 to + .002" of the correct centre distance. For gears operating at slow speeds and not subject to reversal, this tolerance may be doubled.
For the best operating conditions the total number of teeth in a pair of spur gears should not be less than 45.
The capacity of steel gears may be increased by subjecting them to suitable heat treatment. This is achieved by heating to 840ºC and quenching in oil, followed by tempering at 430 - 450ºC for approximately one hour per inch of ruling cross section. This treatment will produce a hardness of approximately 380 - 400 B. H. N., permitting wear ratings to be multiplied by 2.5 and strength ratings by 1.8. In this condition the gears will not be machinable so that machining operations such as boring, slotting, drilling, etc. should be carried out prior to heat treatment, leaving approximately 0.15mm (0.006") in the bore diameter for grinding to size after hardening.
Should it be desired to toughen the gears whilst still leaving them in a machinable condition, tempering should be carried out at 530 - 550ºC for approximately one hour per inch of cross section. This treatment will produce a hardness of approximately 300 - 320 B. H. N., permitting wear ratings to be multiplied by 2.0 and strength ratings by 2.0. In this condition, the material, while very tough will still be machinable.
Flame or induction hardening of gear teeth gives a greater wear capacity at the expense of decreasing strength. For gears hardened by this process wear ratings may be multiplied by 2.0 whilst strength ratings must be multiplied by 0.8. To give best results flame or induction hardening should be followed by tempering at 200 - 220ºC for approximately 1 hour. Flame hardening is not recommended for spur gears finer than 8DP or bevel gears finer than 6DP except for lightly loaded applications.