will this 4th axis work

Er, no they don't and no it certainly is NOT!

https://en.wikipedia.org/wiki/Harmonic_drive

https://en.wikipedia.org/wiki/Epicyclic_gearing

Both have teeth, that's about it for similarity.

I stand corrected.
So its a Strain wave gearing.

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Originally Posted by magicniner

Er, no they don't and no it certainly is NOT!

https://en.wikipedia.org/wiki/Harmonic_drive

https://en.wikipedia.org/wiki/Epicyclic_gearing

Both have teeth, that's about it for similarity.

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Harmonic drives are the perfect solution for high gear ratios, high torque, lightweight, and the most important, they have no backlash. Widely used in multi-axis cnc, articulated robots, etc.

There are a lot of them on ebay, SH from Korea, the only ones at an affordable price...

I was surprised that the Chinese claim to have 4th axis with harmonic drive... possibly used ones fitted inside..

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Originally Posted by johngoodrich

http://www.ebay.co.uk/itm/1523042469...&ul_noapp=true

i'm looking to machine wood only on it, no metal and maybe some plastics. do you think this will be ok. Tolerance is not too important as it will be all arty type stuff. opinions please

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I have been considering something similar for quite some time now, but can't make up my mind about it. In theory it would be very useful for me, it would save time because it would turn around the work piece automatically, but maybe the work piece would vibrate too much so it would be useless for what I am doing, so I am not sure. Never the less, there are plenty on eBay as well, shipping from Germany most of the ones I found.

Anyway, I am interested in the subject, as well as the use of it and the experience people have.

Has anyone bought one of these harmonic drive index chuck thingies? Are they any good? Is the lack of a through shaft putting you off? Who will Magicniner contradict next? So many questions, life is too short for all these questions.

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Originally Posted by Robin Hewitt

Who will Magicniner contradict next?

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As you clearly prefer your information to be of the non-factual variety I'll leave you to it :D

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Originally Posted by Robin Hewitt

Has anyone bought one of these harmonic drive index chuck thingies? Are they any good?

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I am sure they are pretty good otherwise they would not be sellable.

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Originally Posted by Robin Hewitt

Is the lack of a through shaft putting you off?

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Yes. That and the fact that it is considerably more expensive.

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Originally Posted by Robin Hewitt

Who will Magicniner contradict next?

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I found his comments very informative and valuable. I don't know what you see was wrong with his comments or choice of words, but I did not find them contradicting, quite the opposite. I would actually be interested in hearing more about his experience and the modifications he did, as well as how he is using it.

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Originally Posted by Robin Hewitt

So many questions, life is too short for all these questions.

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...so why did you ask the last one then? It was pretty rude and unnecessary. His comments were pretty valuable, as opposed to your last question... :disturbed:

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Originally Posted by A_Camera

I...so why did you ask the last one then? It was pretty rude and unnecessary.

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Don't worry, he's a Yorkshireman, he's already retaliated.

magicniner, do you have any photos of the mods you have done to your 4th axis. I would like to see it. from your experience with these, do you thinkit would be ok for 4th axis wood milling as is, or a bit of modding

John,
I have an early pic of the "proof of concept" I knocked up with what I had lying around,

Attachment 22607

I've subsequently re-worked the spacer support with alternate bearings to reinstate the through capacity of the spindle, it does what I need in brass, bronze, aluminium and steel.
I don't think it would have been up to much without the tensioner to remove backlash, without the support the stepper shaft bends if you tension the belt,
Regards,
Nick