C3 Mini-Lathe Metalworking Beginners
Making a telescope worm wheel and gear set on the mini-lathe for astrophotography . Step by Step.
This is my step by step guide to making a matched telescope worm gear and wheel set.
One of the most impressive things you can make on a mini-lathe is a matched worm wheel and worm gear set for a telescope mount.
It is critical to machine all parts concentrically to minimise periodic error, and the wheel and worm gear need to be lapped together to make the tracking as smooth as possible.
Commercial worm gears are very expensive, so making our own is a huge cost saving, as well as a lot of fun.
How accurate does a telescope worm wheel and gear set need to be?
The important factors are as follows
This section is still a work in progress, but I have completed the first section of my series on making a 7 inch or 6 inch worm wheel and gear set on a mini-lathe.
Success lies in taking time and care at every step. With many mini-lathe jobs your can measure and check your work at different stages, and know if you have made a mistake. With worm gears you genuinely have no idea if you've made a small mistake until the work gears are on a telescope and tracking the stars. Nothing the amateur can rig up is able to replicate the smooth motion of the night time stars - the only way to test is to get out there any put them on a telescope.
Testing of periodic error can only be done using a webcam and popular software such as k3ccdtools to draw a chart of the motion. Peak to peak periodic error of 30-60 arc seconds is acceptable - so long as it is smooth. If it is smooth, then it can be corrected with PEC and guiding. If there is a lot of high frequency noise, then it will be difficult to correct and not suitable for long exposure astrophotography.
Take care and time at each stage. Don't try and do it all in one weekend, spread the task out, and have a good rest / think / beer between stages.
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