I think it is 6mm in, 12mm out.
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Well enough:
https://www.youtube.com/watch?v=lVuBEEceWJ4
http://www.mycncuk.com/threads/3341-...illing-machine
http://www.mycncuk.com/threads/11220...-as-a-4th-Axis
Unfortunately I ran the stepper motor on the rotary table into my milling machine column (wasn't looking) last year and bent the worm gear, so I do have another doorstop! I'm now wondering if these are better than the price suggests:
http://www.ebay.co.uk/itm/Precision-...sAAOSwZ4dZHZkC
The problem with the direct belt drive method is the stiffness of the belt is quite poor compared to a harmonic or worm drive. Of course, it can be useful but that depends somewhat on the diameter of the material, your accuracy requirement and other factors. If the rotary table above is any good - i.e. "most" of the backlash can be adjusted out, then that plus a 1Nm stepper motor seems like an attractive option.
Robin if it's like mine in size 11, then it's probably 6mm in, 10mm out.
And Jonathan, I also have a size 50 monster that I use on a crane rig, weighs a bit that one:)
Edward
I just took that harmonic drive apart, one screw head decided to snap off, one had to be drilled off.
Much as expected, only remarkable thing is how fine the gear pitch is.
These gears are about 28mm diameter...
Attachment 22685Attachment 22686
Not just the fine pitch but also the fact that they are flexible to mesh and I am not totally sure about the inner workings, but I think they have one more tooth than the gears they mesh with, or vice versa. Incredible concept and I guess very difficult to machine such precision.
Edward
I have to get those headless screws out before I can reassemble.
M2.5 and darned close to the bendy cog. I don't have anything suitable to grab them with.
Any ideas?
Have you tried two or three nuts locked together perhaps with heavy duty locktite retainer as well