Do it myself focus gears.

G

Greg_E

Veteran
During some discussion in a printed focus gears thread, I decided that I could make my own gears for my lenses. After about $200 to $250 worth of addition tools and supplies, I had all the parts needed to start and be able to machine three sizes of gears with enough material for at least 6 gears in each size. Finished off the first try, a few key mistakes rendered it useless early on, but I carried it through to the end so I could get the entire process down. Need to heat it tomorrow and see how far it expands so I can get a final dimension to cut to. Have to get a picture or two up for those interested in seeing the process, and hopefully I'll have a working gear on the next one I cut. These are going on Canon FDn lenses right now, got a few others lenses after that.
 
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Getting ready to cut a new gear, hopefully I won't make any mistakes on this one.



Got another disk ready to get started sitting against the tail stock.
 
Well if they turn out well - get some calipers and let's measure some Nikkor Ai-S lenses. I bet we here at the forum could buy enough of them from you to turn an investment into a profit.
 
At the typical cost of these gears, I'll do better than break even just with my stuff. And that's considering the $35 printed gears. The big expense was getting the mill and all the rest of the tooling, I spent about $150 on new tools for this project which is actually pretty cheap. Right now I'm doing Canon FD and Mamiya 645 lenses, Nikon's might be tougher.

I can buy more Delrin, pretty cheap when you buy scraps. The hardest part is going to be correctly measuring the focus ring, and then hoping you don't crush it. Slip on gears would be easy, but I'm not sure how far to undersize the shrink fit gears. I did find that these gears expand a huge amount when they hit about 300 degrees F. The difference was around 0.040 inches, which is huge. I think I can guess at the size to cut, but I'm still a little worried about being out in the sun, thinking the next round of material might just be white to help with solar heating.

Once I get everything down to working, I'd be interested in giving a try to lenses I didn't have in my hands. Do you have a way of measuring accurately? If not you can buy a micrometer from Share on eBay for about $25, so far all my lenses needed a 2 to 3 inch micrometer. Caliper need a set of long jaws to reach properly, and those would have been about $200 for the quality I would buy for myself. I have cheap calipers, they are only accurate to about 2 inches out of 6. I have good Fowler that are accurate all the way out, but short jaws. The cheap micrometer seems the agree with both of my calipers to the level I need. I have material for 78.4 mm gears (96 teeth), 88mm gears, and whatever 120 teeth comes out to (97.6mm???).
 
Yeah, those micrometers would get a much better read for sure.

I just mentioned the Nikkors because I'd bet that between to 20mm, the 24mm, the 28mm, the 50mm, and the 85mm, there are probably 1,000 sales here just on those 5, and since I own 4 of those I'd wager that 2 or 3 of them have the same external diameters on the focus rings.

Just a thought.

Yesterday one of my strap-on rings broke its locking mechanism so it's trash, and I was thinking I really need to get better ones - but the big ones with the spokes are really not a great option for these lenses, at least not on my rig, which has very typical rails and follow-focus. A simple strip of cylinder with teeth that fits snugly is exactly what's called for.
 
The spoke based stuff is an answer to the problem, but not a real good answer. The belts are decent, but I don't like the bulk where they meet.
 
I'm doing an in window sunshine test on my prototype gear, and I'm not happy with the results. This plastic expands a huge amount when it gets hot and I'm starting to worry about crushing the focus ring on these FDn lenses since they are made out of plastic. It's a cool day and the sun has only been hitting the gear for about and hour, it has already expanded 0.010 which is a very large amount. I would expect it to hit this temperature on just about any daytime shoot where the camera is exposed to direct sunlight. At least this is giving me insight into how much smaller I need to cut the inner circle.

Stewart, let me know the size for one of your lenses and I'll see if I can cut something for you. Need diameter and width of the rubber part, though I'm now thinking of removing the rubber grip on my FD lenses and just shrinking to that decreased size if it will clear all the other protrusions. For guide line, the 96 tooth gear I'm cutting is 3.087 inch outside diameter. The lens is 2.442 inch diameter at the rubber grip, and this seems to be the smallest gear I would suggest for this lens diameter. I can cut 72, 84, 90, 96, 108, and 120 tooth gears which goes up to almost 4 inch outside diameter (97.6mm).

You would also need a way to heat the ring up to about 200 degrees F, any kitchen oven should work, I noticed no real fumes coming off of the plastic when I tested it and I cranked mine up to about 325 degrees F to see what would happen. The plastic stays strong but it does expand a lot, about 0.040 inches in the inside diameter at that temperature.
 
I have a similar issue. I own a gear ring from "Helicopter Sean" for an anamorphic lens that was perfectly snug indoors, but it would slip after ten minutes in the sun. I just applied a thin coat of Liquid Electrical Tape to the interior of the gear, let it dry and this has made for a much stronger, rubbery grip not he lens housing without making it a tighter fit.

im3maxb.jpg
 
Ultimately I may need to do the same on the FD lenses, I think the Nikon are aluminum focus rings and should be much stronger so I wouldn't worry too much. The older FD breach lock should also be fine because they are aluminum rings.
 
GotGot a bit of work done on the next attempt, looking much nicer this time, hope I don't screw up cutting it from the arbor. Picture is part way through cutting the teeth. Silver Sharpie on the plastic so I can see where it is cutting.

 
Got the first one finished.

Heating on a circuit board preheater.



And in place ready for use on an FDn 24mm f2.8 lens, still need to buy an EF mount for this lens.



Up next is to work on the gear for my FDn 15f2.8 with EF mount.
 
And here is the 15mm, it came out really good. Had to go up to an 88mm gear to fit the focus ring which means I had to start from scratch with cutting a disk off the bigger stock. So I still have a 78.4mm blank sitting here that may not get used, all the other lenses I am planning to use look like they need the 88mm gears or maybe 96mm gears.

Also you can see the metal EF mount on this lens, pretty simple swap. Need to buy a mount for the 24mm above.

 
Wrapping paper around the lens to measure the diameter, I'm getting a half of a millimeter of difference, but only have a single lens to compare at this moment. That may be down to the micrometer slightly crushing the rubber grip and I think I can allow for this. Thin marks on the paper are better.

 
Work is a mess right now, and I need to make a part for my car, but if someone wants to test the paper measurement, let me know. Prefer someone in the USA to keep shipping low.
 
Did you make that rotary axis or buy it? I'm looking for something to adapt to a servo controlled 4th axis on my mill. All the worm gear driven ones have too much slop to be used for CNC control. I can't make up my mind what to buy.
 
I bought it, and yes there is a lot of slop. I'm told the phase II tables can be adjusted for very little backlash and I'm thinking of buying one. The 6 and 8 inch tables are generally better, but I don't think they will fit on my little mill. The Sherline CNC table is also supposed to be good, but it is $1000.

I may try buying a new worm and cutting a new spur gear for my table to see if I can tighten it up, but right now I have a different issue to fix with this table. The "cheap" Chinese stuff always seems to have little areas for improvement. The nut holding the table in place has a high spot, and the table casting has a high spot, so I get a point where they bind a little. Need to scrape those down flat for better rotation. Might toss a big thrust bearing in there too.

One thing I noticed on YouTube, they all have a lot of play. One guy had a standalone table controller on his big table. Every time he backed up it was programmed to back up way past the point, and then go forward to the point to account for the backlash. It was a neat rig and would take some of the repetitive work out of cutting these. Wish I had some CNC on my mill, lots of back and forth cranking.
 
Had to modify my FF unit, the thumbscrew holding the gear on stuck out too far, put a 4mm bolt in to gain some clearance.

 
Greg.. Greg.. Greg.....

How can you work with such inferior video equipment?

Really man.

Allow me to show you what REAL professional video equipment looks like:

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Drumroll please.
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photo.jpg


Ha!

May I compliment you on your fine taste Sir!
 
May I suggest that you upgrade to an m4x15mm cap head bolt to hold your FF gears on the FF? I gives you the full width of that thumbscrew back which I've already found invaluable.

It's cheap stuff, but fully functional, I do need to upgrade the FF to quick release and make a new sliding mount arm for it, way too much flex in there for me to allow. I think I'm also going to drill holes in the thumb screw so I can insert a metal rod to really tighten it, I can barely get my fingers on it now, and I don't want to raise the rods any higher off the tripod plate, center of gravity gets too high and does odd things with the tripod head during tilts.
 
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