Worm gears

[Nate]

Perhaps there could be tools for designing, machining, and printing worm wheels that work with standard threaded rods and maybe standard acme screws. Print the wheel, buy the worm.

I did try to model some worm gears for acme screws a while ago.  They weren't mechanically great. (http://www.thingiverse.com/thing:270309)

If you know the thread form of the drive screw, and you have a lathe it should be relatively easy to use the same thread form to make a primitive hobbing set up like this: https://www.youtube.com/watch?v=J0o3W4_LRBw

[MJBoluijt]

Hi,

Just looking if there is the possibility to make worm wheels wit Gearotic, as I see at the moment not.
Art say that is must maybe a 5 axis job, but in this article they do it with the 4th axis, I think with a form cutter (40 degrees?)


http://blog.cnccookbook.com/2013/04/08/ ... roduction/

Rien Netherlands.

[ArtF]

Hi Rien:

  That mating gear to a worm I suspect can be done, its the longitudinal worm thats harder.. but I do think a form cutter could
do it. Just a matter of making the Gcode for the cutter.. I see that as a kind of threading operation using the 4th axis..

Art

[MJBoluijt]

Hi Art,

I think it is no problem for the most of us to make the Worm in the lathe, dimensions from Gearotic.
And the Wormwheel in the 4t axis with code from Gearotic.

regards,  Rien.

[Nate]

...
I think it is no problem for the most of us to make the Worm in the lathe, dimensions from Gearotic.
And the Wormwheel in the 4t axis with code from Gearotic.
...

If you have a lathe and a mill it may be easier and faster to build a hobbing jig for making worm gears.

https://www.youtube.com/watch?v=J0o3W4_LRBw

[ArtF]

brilliant..

[Google Feedfetcher]

Only problem with this method is, as the tap starts it's running on the OD and it will generate OD*Pi / pitch of tap which will be totally different from the Pitch circle * Pi / pitch of tap.
Many people using this method say it's a toss up on how many teeth you finish up with. Many pre gash the number of teeth they want with a slitting saw to ensure they get the correct number they need.

I used to hob worm wheels on a hobbing machine, full enveloping wheels, 40 T or 60 T and the odd time I forgot to fully tighten the blank it finished up being driven by the hob and not the machines with 42 or 43 teeth of incorrect form being cut.  Wasn't bad on a 60T wheel as it could be saved and made into a 40T but a I really wanted a market for 30T wheels to use up the scrap 40's

[ArtF]

John:

  Interesting..  So really to do the pinion would only require the current tangential code for a normal spur, with an added radius of the arc of the envelopment of the worm itself put into the Z, so the arc bottom is center of the spur.. ?

  That at least sounds do-able, but the worm itself, short of a shaped tool I don't think is possible.. Am I wrong in that thought?
(Yours being the opinion on such things I would at all times take to the bank...) 

Art

[Google Feedfetcher]

Art
Pinion I feel would be easy, it's a low helix gear with an additional z axis move in the centre.

I'll include this picture stolen without credits from Bob Whorefields site as he steals everything and credits no one  ;D



It would be easier using a vee cutter and as most pinions / wheels are done in a soft material i single flute cutter similar to an engraving cutter could be used. After all the most common angles would be 20 and 29 degrees or 30 for the trapezoidal guys in EU land.

Worms them selves are just screws so using anything other than a lathe is just an exercise in getting a good spanking [ mind you that's not bad at the right hands  ]

If you were serious though it's simple job to hand write a code and mill one with the exact same cutter, or Gearotic could even spit the code out given you fill a few boxes in.

This was just a test once to see how easy iy would be to do a square thread.

[ArtF]

John:

  I never knew there was any helix to the pinion,  it is a function of the cross angle one wants? Like 90 degree would be standard, no helix?

Art