Ok my, friend, lets see what we can do here....(funny the timing, I was just working the CMCO in my DXFS exactly when I was notified of your post lol,). Ok, to start....
The Small Gears
This may not be due to the machine being used or the number of hours at all ( Whew, a relief I'm sure). There are more likely scenarios at play here. First, and most likely a contributing factor is the diameter of the bit itself. Although you may have done everything perfect ( chose what you believed was the right tool, set it to cut "outside the line", cut to the correct depth) the sheer small size of the gears doesn't allow enough room for clearance of the bit to not chew through the backside of the teeth. The end result will be gears that appear to look too small ( because they are
. As the tool progresses through the cut, it will not recognize that it is cutting through the backside of the prior tooth, causing it to shrink its size. Basically, "That tool is too big". Found that out myself. Remember, the entire diameter of the tool must be smaller than the smallest diameter at the inside of the tooth, or it won't fit, and shrink the gear. Check the preview image of what the part will look like in Aspire before cutting the material. If it doesn't look the same, the diameter is too big.
How do I make the part then? Well, a couple of ways....
1 way is to purchase a collet adaptor to use smaller bits. Rockler sells a 1/4" to 1/8" collet adaptor which would allow you to use 1/16" end mills. This will provide you the bit diameter you need to fit in between the teeth and not deform the smaller gears.
The Plus-It fits into smaller gears ( pitch diameter is small enough)
The Minus- due to the flute lengths, the bits are only recommended to cut material small than 3/16" thick. Most of claytons gears are 1/2" inch + material. It can be done, but risk breaking bits and tearing up material.
The Second way ( which is how I cut gears mosty) is.........not to use my shark for it.
Surprised? You would think its the best application for it. In most cases, it is. There are plenty of critical parts in a clock I do use my CNC for, just not gears. "Well, then how in H... do you cut them?". Believe it or not....I scroll saw them.....old school. I find that their is a balancing act when deciding what to use the CNC for and what not to. Simply put, I follow this montra...Can I cut it just as well yet faster than programming the shark? If so, old school. If not-Shark. Is it something that absolutely needs to be perfect? Default-shark, but only if I am sure that it is capable ( Example, the frame, pendulum, pallets, escape if I have the bits). If not, old school.
Some tips about drilling, or what I've found successful for clocks. If the hole size is EXACTLY the same size as the bit I am using, I will drill with it. If it isn't I do the following-
The Bit is Too Big( say that's the only bit I have)- I use the shark to "touch off" where the hole is, but don't drill it through. EX- If I need a 1/16" hole but only have a 1/8" bit, I have the shark drill down a tiny amount ( say 1/16" on 1/2" material) and then drill through will my drill press. That way the shark marks the EXACT location of where the hole goes, so I cant go wrong.
The Bit is Too Small( for the hole I want to drill)- I drill through where the hole is going to be, but don't use it to make the final hole size (similar to above). EX- I have a 1/8" bit but need a 1/4" hole-I will have the CNC drill the
center location of the 1/4" hole, but use the 1/8" bit. Now that I have the location hole, its off to the drill press to drill the correct size hole.
I have found that the tolerances for the CNC are just too big to make the hole the right size with the wrong bit, and in clockmaking, tolerances for arbor holes is way to critical to have slop.
Some other items you might want to try...
Set your origin (Home location of X,Y, and Z) to the lower left or right corner of your material rather than center. The reason? Convenient. The gantry will come all the way forward for you for bit changes. Additionally, the corner of the material, I find, gives you a perfect place to center your bit. You can "sight down" the X and Y axis of the material to the bit, even jogging the shark just above both axis to see if your material is square to the bit. Lastly, no need to mark the center of your material, the corner brings you home
The stepper motors in the shark are "Dumb". I mean that in a kind way. They have no software to "know" the limits of the machine size. These steppers assume that the machine is infinitely long and infinitely wide. It doesn't know the shark is 24 x 24, so they will continue to travel past that and think " Im still moving", and it will try. That was what you heard when it reached the machines limit, it trying to continue to move, all the while the software thinking obliviously that it is, when you can see it isn't. That is why it was 2 1/2 inches off. Rather than automatically assuming you have done harm to the shark, try this. Use aspire to draw a 2" circle and a 2" square. Create a toolpath that cuts outside the line and run the program on some scrap. Measure the actual size of the parts. If they are close, machine is fine ( and I would be surprised if it wasn't). Only if they are extremely different would I be concerned. I have done the overtravel thing in the past, and haven't had to replace a single part.
Almost done here, 2 more things. Unfortunately I do not use aspire, so I cannot help on that end (sorry). I still use v-carve, which for most things I do is fine ( and fine for clock making). I'm sure you would find tons of help with aspire in the forums, and in particular tonydude is a wiz. Look em up, he can answer those
And finally ( thankfully I am sure lol), the order of the build. I would try to follow the plans in the order they were written, but sometimes it makes sense to vary. In general, I cut the frame first. That allows me to have a place to house finished parts and try them as I go along. If something doesn't work right, I catch it right away and can adjust immediately and accordingly, saving me time later. I then cut all the arbors and spacers. What good is having a frame to house parts but no way to hold em in place, eh? lol. Then I proceed with the clock gears themselves, in order they are placed in the frame, back to front. As I get a pair done, I can then check them to see if they mesh well.
That's just my order to the chaos of clock making, your results may vary
. Trust me, it does become fun. Just keep this in mind. "Your sense of achievement is directly correlated to the height of the mountains climbed....."