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Thread: Worm & wheel gears
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10th Feb 2019, 05:44 PM #16Most Valued Member
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Some clearance adjustment between worm and wheel can be used to find a sweet spot but only to a point. A properly set up gear system has a pre-determined spacing and if they are moved, it starts to affect the smooth operation of the gear movement. (For want of a better term) If they are too close then their movement becomes notchy.
Some worm and gear systems have the ability to adjust clearance to do exactly what you suggest (such as dividing heads and rotary tables) but it's more to reduce backlash caused by wear.
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10th Feb 2019, 06:31 PM #17Gear expert in training
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Technically, yes you could do that but depending on how accurately both gears are cut (and whether the worm is cut to full size or slightly under the theory OD) you may end up bottoming out on the OD of the worm before the teeth fully contact on both sides.
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10th Feb 2019, 07:37 PM #18Philomath in training
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If the mesh is notchy, then the movement has gone too far. In a commercial box the shafts are fixed so you can't but for a special application where zero backlash is critical, there would be a way. As you point out, rotary tables and dividing heads do it, and I can think of another method that would probably work too. It helps that this application is slow speed so less vibration that whill shake things out of adjustment.
However, normal gear cutters are cut with an allowance to make sure the teeth do not bottom out ('D+f' is bigger than twice the distance between the OD and the PCD). A proper wormgear cutter should have a similar allowance built in to provide clearance when the wormgear is mated with a nominal size worm. If the worm is oversize, then there may be problems...
Michael
Michael
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11th Feb 2019, 07:47 AM #19Member
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11th Feb 2019, 10:23 PM #20Golden Member
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Look for Neil Wyatt posts
The editor of the Model Engineer Workshop magazine is a keen astronomer who makes his own gear and does astronomy photographs. He has made comments that you might find helpful in various posts.
https://www.model-engineer.co.uk/for...?th=112201&p=1
Other posts in those forums might also be helpful.
Bill
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