Cutting a 130mm worm gear pair

My camera tracker used to work with belts and pulleys and I decided to replace these with a single stage consiting of a large worm gear pair. I tested my ability to make a worm gear by trying to make a 65mm worm gear. As can be seen in one of my previous posts it worked out ok.  I then tried to repeat the process with a 130mm gear.

The gear is made from an aluminium disk, 130mm diameter and about 14mm thick. The diameter has to be worked down by a lathe (or in my case, with a mill) to an exact multiple of the worm pitch. I am using an M10 1.5mm pitch threaded rod as the basis for the worm. I managed to get an accurate diameter of about 128.438mm and this translates to 269 teeth. I am using a stepper with 1/16th steps and therefore I can expect quite a good resolution on the camera tracker.

I have attached a few photos of the process and I have also uploaded a video on YouTube:  http://youtu.be/19jKlq8Ofd4

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Using a mill as a lathe is tricky but can be done.

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I used a M10 tap to cut the worm gear on the mill.

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The results are not too bad.

Note the finish on the stainless steel worm. The surface quality is quite rough and it would be unsuitable for use with the aluminium worm. I later used a high grade stainless steel threaded rod as the basis for my new worm.

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Turning the M10 threaded rod down to a 6mm shaft at both ends.

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Be careful when clamping the threaded rod in the mill collet not to damage the threads. I used aluminium from a coke can to protect the thread.

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The end results looks great.

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The aluminium worm gear and  stainless steel worm should be lapped together to remove all rough edges to esure that the resulting movement will be very smooth.

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I made a hub to mount the worm gear on a 10mm shaft.

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I am now waiting for the delivery of a set of bearings mounted in pillow blocks to mount the worm and then to joint everything together and to start testing again.

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