Posted by Ron V on February 24, 2008 at 08:41:06:
In Reply to: Re: Double envaloping worm posted by frank on February 24, 2008 at 05:13:45:
These days double enveloping worms are cut in vertical hobbing machines. The hobbing tool is replaced with the worm blank and a helical shaper cutter is mounted on the work table. The shaper cutter is then radial plunged into the worm. The shaper cutter has the same number of teeth as the worm's mating gear.
I know of a chap who has a variation on this arrangement and rather than a disc shaper cutter uses form tools set up in a jig which replicates either 1 or 3 teeth of the gear.
Either set up is very tricky (as you can imagine) and requires side cutting to achieve the correct contact, backlash & end relief.
I've never seen a double enveloping worm with more than one start; although this doesn't mean they don't exist.
Fellows use to manufacture an attachment that would allow you to cut the Fellows version of this type of worm on their gear shapers.
Post a Followup