Frequently Asked Questions on worms and wheels

1. Why use a worm and wheel system?

This system permits an important reduction ratio. In certain conditions the system is irreversible. The efficiency of this system is low but increases in relationship with the lead angle of the teeth. The direction of the helix is the same for the worm and the wheel.

2. What can I do if the wheel in a worm and wheel system is damaged or worn ?

There is no standardisation for worms and wheels. In the case of a breakage, the defective element must be replaced with an absolutely identical model. Most of the time, this will have to be custom-made. Indeed, each manufacturer chooses the worm diameter he likes. This has an influence on the Helical Angle, the Pitch Diameter and the centre to centre distance.

3. How are anti-recoil wormwheels used ?

As their name indicates, these wheels allow the absorption of the recoil which would exist in a classical worm and wheel setup. Springs are placed in channels between two wheels of the same dimensions, which are attached together with a circlip. On assembly, the two discs should be offset by a few degrees, this compresses the springs in order to allow them to absorb the recoil.

Attention, Anti-recoil wormwheels can be only used with Single Start worms.

4. Can you custom-produce worms and wheels?

Yes, we can custom-produce couples of worms and wheels. Contact us on: +33 (0)437 496 496.

5. How do I determine the principal characteristics of a worm and wheel couple?

 For worm screws

 

Four principal parameters characterise a worm

• the thread p
• the number of starts Z
• the external diameter d
• the teeth's slant direction and helix angle

These parameters are bound by a complicated mathematical relation.

 

The helix angle is difficult to control. The direction of slant of the teeth is done visually: hold the screw in driving position: when the nets go up towards the line, threading is tilted to the right, and when they go up towards the left, threading is tilted to the left.

Left hand threaded	Right hand threaded

 

To measure the thread, take the dimension of a top of a start at the following start.

 

To control the number of starts, it is necessary to look at the starting number of starts (to look at the screw in the axis, or vis-a-vis with boring).

Don't count the starts like this	They should be counted in this direction

 

 For the wheels for worms

 

Four principal parameters characterise a wheel

• the pitch m
• the number of teeths Z
• the external diameter de
• the teeth's slant direction and helix angle

The first three parameters are bound by the mathematical relation
de = m x (Z+2) or m = de/(Z+2) or Z = (de/m)-2

 

The determination of the slant direction of the teeth is made visually (put the gears flat on a table: if the teeth go up towards the line, the teeth are tilted to the right, if the teeth go up towards the left, the teeth are tilted to the left.

 

The helix angle is difficult to control. The only way is to put the wheel with the worm that was made for it (even module and even number of starts).

This screw with four starts cannot function with this wheel planned for a single start.	On the other hand, this wheel and this screw are compatible