Component Parts Continued

Here is what the screwdriver slot looks like on the 1/4-20 threaded ball plunger with the higher spring rate. While I was working on the previous one, I forgot to take a picture of it before I sanded it.
 

Now that I've narrowed down the one I'll be using, I drilled and tapped the three shafts for 1/4-20 threads. Now I only bought 'one' each of the ball plungers but for testing I'll use them both.

The placement of threads in the shaft were based on a few factors and was calculated earlier. I added up all the components that I'd be using and came up with what you see below. And once the gear has been placed on the shaft, the gear will have a small amount of play between the ball plunger and a permanent stop, which I'll talk more about later.
 

With the screwdriver slot now gone I'll need another way of threading in these ball plungers. If you notice in the picture above (the area around the ball), there are small slots on both sides of it. These slots are an alternate method of screwing these units in, but you need to overcome the spring pressure behind the ball first. To make matters worse the round ball makes it very hard to find those slots because your screwdriver blade wants to slip off them very easily. What I plan on doing is making a custom screwdriver blade so I can use this slot to thread them in with.
 

I used my Dremel to put a half-round slot in the screwdriver blade which worked great and it was quick. I also found out this blade was very hard so if you're in the market for a Milwaukee screwdriver set like I'm using, it should last a long time.
 

I'm using a scrap piece of wood for testing here. I drilled three clearance holes through the wood, a 9/16" hole for the shaft and 11/32" for the bolts (1/32" oversize for the bolts).
 

This round  piece is called a 'shaft collar' and is 1 1/8" O.D. (outside diameter) X 13/32" thick and has a 1/2" hole through it. This collar has a 8-32 socket head cap screw (you need a hex key to tighten it) and can be placed where ever you want on the shaft. Once it's tightened it stays in place and works great. I bought three of these for testing and so far I really like them. This is what I'll be using as my 'stop'.
 

This close-up will be easier to see what I'm working with. The lighter colored piece on top of the collar is a 'thrust bearing' and again I'm testing here so I'm not sure what I'll end up using. Once the gear slides onto the shaft, it will be captured by the ball plunger and won't come off. And this is the main objective here, not having the gear come back off the shaft because once they're all spinning, they'll need to stay put. And so far it works great!
 

Backlash: One more thing you should also know about gears, it's called 'backlash'. This is very important because all gears have some kind of backlash which is the slop (or play) between each gear tooth. If you have too much backlash the gears will rattle and wear wrong. If to little backlash, the gears will bind. I'm lucky here because the gears I'll be working with won't have a 'load' on them so I can get away with the backlash tolerance being larger than normal.

Notice the larger gear is not fastened to the wood yet. I'm just getting a feel here of how I'm going to get it in the right location.
 

I played with the backlash between these two gears and after a few minutes I came up with a plan. By placing a shaft collar under the larger gear (above), this would allow me to align both gears on the same plane. Once I had the two gears adjusted with the correct backlash, I used a pencil and drew around two corners of the aluminum block.