Worm Gear/Spur Gear 1

[shwagy357]

Does anyone know if it is possible to get a worm gear mechanism to work using a spur gear. I am just trying to make a small model of a worm gear out of acetal plastic for demonstration purposes only. I am thinking it might work as long as the pitch on the lead screw, is the same or a little larger than the pitch on the spur gear. What do you guys think?

 

[gearcutter]

You can use a spur gear but you will not be able to assemble the set if the shafts are at 90deg. Use the same pitch and pressure angle for both the gear and worm.
If the shafts need to be at 90deg you'll have to use a helical gear which has the same lead/helix angle as the worm's.
If you're cutting the gear in a milling machine it's actualy easier cutting a worm gear rather than a helical.
Another option is if you you end up screw cutting the worm and using a standard acme type of pitch and happen to have a tap the same pitch and slightly larger diameter than the worm, you can actualy "hob" the gear in a milling machine or even a lathe.

 

[smah]

Just make your spur gear infinately thin and it will work fine . Seriously though, you could try to make several very thin spur gears & stack them together, rotated according to the worm lead.

 

[Spurs]

The sum of the helix angles of the worm and the gear equals the shaft angle.

Therefore if you mount a 10 degree lead angle (80 deg helix angle) worm and a spur gear (0 deg helix angle) they must be mouonted at 80 degrees to function properly.

This is a technique which is widely overlooked in todays gearing world.

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