The Design and Construction of a 'Backlash-Free' Rotary Table

[Eddard_Stark]

Roger,

I enjoyed the write up, thx for taking the time. Of particular interest was your 'home brew' metrology device. Very cool.

[RCaffin]

Hi Eddard

Thanks.
Measurement per se is/was my career.

Cheers
Roger

[RCaffin]

Someone asked for a photo of the RT in actual use. Herewith.


Machining a 30 tooth GT2 pulley using a custom fly cutter.
My own program to make the cutter on the CNC lathe, to the publish specs. Silver steel (drill rod), heat treated.
My own program to make the pulley. It can be adjusted to cut any number of teeth.
I want 30 teeth and 90 teeth, with a custom taperlock core for the shaft (also my own design and program).

The RT works fine, and I believe that the resulting pulley complies with the GT2 specs. A pity the Chinese GT2 (RepRap) belts and pulleys do not seem to comply with the published specs ... The 2 mm pitch is OK, but the tooth profile seems wrong. But I need to do some more measurements to see just where they differ.

Incidentally, machining a small toothed pulley like this really does require that the TIR on the chuck be very small! This one has been adjusted to be under 25 microns radius. That took some time.

Cheers
Roger

[RCaffin]

Subsequent research shows that just about every GT2 profile I have seen is different. The published profiles don't match the machined profiles either. There is a separate thread about this.

In theory Gates owns the GT2 name and you need a licence from them to use it, but some vendors, especially the Chinese, do not seem to have noticed this.

Cheers
Roger

[lillian22_2]

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it's let me learn a lot.
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[RCaffin]

Thank you Lillian.
Cheers
Roger