The article “Helical Gear Mathematics Formulas and Examples” appeared in the May/June issue of Gear Technology. Summary The following excerpt is. Hobbing isa continuous gear generation process widely used in the industry between first and second cut so that a different formula isused. Spur Gear design formula for geometry, pitch, tooth clearance and critical functional data. Circular Pitches and Equivalent Diametral Pitches Table.

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The displacement of the helical rack, l, for one rotation of the mating gear is the product of the transverse pitch andnumber of teeth. Progressive Pitting Even after gear surfaces are worn in and load is equalized, with time more pitting starts to occur and pits get enlarged. Take an average of the measurements.

That is to say, there is a slide in the direction of the tooth trace. Here we hope to find the machine type and formula for differential gears, so this agony only occurs once! If the machine can handle running in reverse, and you wire in a reversing switch, then easy breezy! Can I use CPC software in full screen? There are four worm tooth profiles in JIS Bas defined below.

Basic Gear Terminology and Calculation | KHK Gears

If the machine can handle running in reverse, and you wire in a reversing switch, then you can leave all gear drives engaged, back the cutter away from the workpiece, and run the motor in reverse to the beginning point. Table Feed as discussed here is the cutter table feed in a direction parallel to the workpiece centerline. Adhesion Wear Wear commonly occurring between metals in sliding contact.

If instead, the modulem, center distance a and speed ratio i are given, then the number of teeth, z1 and z2, would be calculated using theformulas as shown in Table 4. The procedure is to check the “truth” of a simulated hobber hobing by traversing a gear tooth with the dial indicator. Other angles Figure 4. If this machine is non-differential it is important to use the exact feed constant or as many decimal places as possible when generating helical gears.


If your machine is a “horizontal” hobber raise the workpiece and bring the cutter under the workpiece. This is particularly handy for “getting it right” the first time, larger pitches, and some harder materials. Spur gears have a convex shaped tooth profile and internal gears havereentrant shaped tooth profile; this characteristic is opposite of Internal gears.

Gear Works in Springfield Vermont formmula in Fellows Gear Shapers, and I understand they can provide manuals for repair, operation, etc. A precalculated decimal feed ratio, based on desired table feed, is then adjusted to compensate for difference between calculated decimal index ratio and the actual ratio of index change gears.

The axial plane of worm corresponds with the transverse plane of worm wheel. If you are cutting a helical gear with synchronized index and feed gear sets, the cutter must pass beyond the blank before the feed drive disengages.

The fixed number values are probably different, but that’s okay. Here are a few more examples:.

Helical Gear Mathematics Formulas and Examples – May/June 1988

If the angle is too large, the change gear decimal ratio is too large. You need the following to specify a straight bevel gear:. There are at least 5 different “standard” cutter body diameters. Sharp cutting edges are a must. If you have reinstalled your program to a new PC and you have a backup copy of the program’s home folder, then the following tables show the files to copy from your backup.

Their search facility is quite good and easy to use. They are counted as shown in the Figure 2. When a two-start cutter rotates once, it advances its rack form by two teeth.


A LH hob requires additional idler s in index and differential to change the direction of workpiece rotation. There is the matter of hobber type that must be determined. Reversing the motor, raising the workpiece and running backward WITHOUT disengaging feed will work just as well for cutting a helical gear without differential.

Feed gear ratio is a simple decimal ratio. What is hobbimg software demo version? Are you sure of the Index constant? This can be confusing until you are familiar with the machine. Some shops use differential machines routinely to cut helical gears of all sizes because it is often thought that helicals are difficult on a non-differential machine. Therefore, the screw gears are not suitable for transmitting largepower.

The bigger difference, the better. Calculations of external dimensions eg. Therefore, at the point P, the direction of the tooth traces should be same, and thevelocity component of the both gears at right angle to the tooth traces should be equal. All “traditional” gear hobbing machines have an Index Constant.

This calculation is based on the idea that the amount of the tip and root clearance should be 0. The width will be less than half as wide as the distance between marks.

Calculation of Gear Dimensions | KHK Gears

Additionally, you need the following:. Backlash is a play between tooth surfaces of paired gears in mesh. For small prime numbers less than or slightly larger than teethyou likely have a change gear.

When you get to the “Choose Components” screen, choose “32 bit Version” and continue installing.