Component Parts Continued

Once I removed the gear from the shaft, I realigned the block to my pencil marks (arrows), then I transferred the location of the bolt holes with a pencil placed through each threaded hole. I then used my trim piece and lined up those two holes over the pencil marks, which would also give me the location for the shaft as well. Once they were all marked I drilled a 9/16 clearance hole for the shaft and two 11/32 holes for the bolts.

This sounds complicated but it's not and it went fast. This method also worked like I planned because with the three holes in the wood being much larger than they needed to be, this would allow me to fine tune the backlash for the gears.
 

What you see below is a ball plunger that went all wrong. So....what happened exactly? Remember how I needed to sand the back of the first ball plunger so it would fit the shaft? While I was sanding this one, I would stop and measure it to make sure it matched the other one but I ended up making this one just a little shorter. Once I put pressure on the ball with my custom screwdriver blade, the spring flew out the back.

What I didn't realize was the wall thickness next to the spring was paper thin and it broke free. Although when I had finished sanding it I had no idea how thin this was and it made me re-think this whole ball plunger idea. I mean what if this happened while the escape game was in progress, not a good thing. It made me realize something else, if one of these ever needed to be replaced down the road, it would be very hard to do, even with the custom screwdriver blade. Time to rethink this ball plunger idea....or is it?
 

After thinking about my problem and looking a little harder I found another ball plunger and ordered some. This one doesn't have any threads. And it's the right length. And no screwdriver slot. How did I miss this style the first time?

These new ball plungers were similar to the others: they had a pound rating from two to five, the same stainless steel ball size, but these were designed to be pressed in. And they should be much easier to change if need be. Bingo, we have a winner!!

What you see below is the opposite end of the threaded test shaft but this time I drilled and reamed the hole. I also had to counterbore for the head which was not hard at all. After experimenting with it I was sold and decided to use this style of ball plunger. Hot damn we're back in business!!
 

I quickly ordered more material and cut it up, turned them to length, chamfered them, including the opposite end of the three test shafts. I also made two extras just in case I needed them.
 

With a new way of holding the gears on now, it's time to move forward. What I'm doing is center drilling, drilling with two sizes of drills and then reaming. As you can see I'm using a 'mill stop' at the end of the shaft so all the holes are in the same location.

These new ball plungers have a .190" body diameter and I'm using a .191" diameter reamer. If you do the math this 'won't be a press fit', which is my fault. In this case it will be a slip fit, which I'll explain: while I was reading about these new ball plungers on McMaster Carr's website, they gave the size and tolerance of .190 diameter, plus .002, minus .000. With this information, I should have ordered the ball plungers first, measured them and 'then' ordered the correct size reamer. I tossed the dice here and shot for the middle of the tolerance and bought a .191" reamer. Well that's what I get for guessing so this one's on me. However, I have a solution that should work out just fine that I'll talk about in a minute.

Notice the chamfer on the reamed hole, this was done with the center drill. By going deeper than you normally would, I ended up with a chamfered hole when I'm done reaming (no need to deburr now). This side will be the bottom when I'm done.
 

A keen eye may have noticed I didn't do any counterbores while I was drilling and reaming. Normally you would do this counterbore operation at the same time because once you take a round part out of the vise, it won't go back in the exact same place. But I thought of this before I started drilling and reaming and made a fixture for the counterbore operation.
 

What you see is a small aluminum fixture that I made from some scrap (hence the hole at one end). The reamed hole in the shaft is .191" and by using a .1875" pin (3/16 dowel pin), there will only be a few thousandths difference between the hole and pin. That difference isn't enough to give me a problem and worked out great. I also made the thickness of my fixture at .480". This is under the shaft diameter of .500" so the vise will clamp on the part and not the fixture.
 

Here you can see how the fixture works. By placing the pin just below the depth of the counterbore, I can then machine the part without the cutter hitting the pin and still locate my part. The diameter of the counterbore is .255" X .060 deep and I used an endmill for this. By hanging the shaft over the end of the fixture, I located the part accurately against my mill stop. This operation went pretty quick.
 

Now that I have all the holes and counterbores finished, it's time to deburr them. I used my Dremel with a mounted wheel made from cotton impregnated with grit. This type of wheel works great but it wears away quickly.