DIY Delrin Follow Focus Gears
 

The below text is an excerpt from the DPvisualmedia blog, found here:
DIY Delrin Follow Focus Gears | DP Visual Media

This post shows a great way to use ServoCity Delrin gears to create a simple follow focus setup.
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"WHAT WORKS FOR ME:
I really need to be able to change lenses quickly, I need an affordable and reliable gear that can stay on the lens at all times. I have decided to make my own:

32p Delrin gears from Servo City (32 Pitch Acetal Hub Gears (3/16" Face))

First I buy a 32p Delrin Gear from Servo City , I like the one with an 85mm outside diameter, since a larger diameter will increase your gear ratio – giving you more precision when you pull focus.

Then I take them over to my friend Ben Kailer’s shop, and bore the centers out to an inside diameter about 1mm smaller than the outside diameter of the lens. How will I fit a bigger circle into a smaller circle you ask? …… HEAT! – yes, I simply drop this “under-bored” gear ring into a pot of almost simmering water, and as the delrin heats up, it expands. I lubricate the lens with a little bit of soapy water, and the gear ring slides on without too much trouble.

After the gear ring cools to room temperature and the lubricating agent evaporates, it’s on there quite permanently. I think for me to remove these gears, I will probably have to cut them off with bolt cutters, because they are not just gonna slide off. This is exactly what I want – an inexpensive, semi-permanent gear ring for my lens, that will stay on the lens at all times, and never slide around as I’m pulling lenses from my case or putting them away. Having one of these on every lens in just one of the things I do to minimize my setup times. Please check back often for more DIY projects, and tips on how to work more efficiently!

Finished result, very reliable, and quite handsome!"
- JPandone

Here are some images:
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If you have questions about how to make a follow focus like this, you can contact DPVisualMedia: Contact | DP Visual Media or e-mail tech@servocity.com.

Thanks!