CNC and clock building

[bill z]

[bill z]

I do have a 1/8 cullet that I can use. This morning I sent an email to a router bit company asking about smaller than 1/8 router bits. I'll be getting some soon.

From here on out, I will spot the arbor holes with the Shark.

Just a few more questions.

How do I print from a DXF to the right size so I can cut and paste on the wood to use my scroll saw?

How about using a smaller than 1/8 end mill and cutting as far down the ½ plywood that the bit will allow and then cut the rest using the scroll saw? The scroll saw will not be working as hard and I can use the CNC cut as a pattern.

What order should I be cutting the gears in?

Looks to me all of the pinion gears are 1/2 and should be cut first at one time.
cut all spacers
Escape wheel
3rd Wheel
Center Wheel
Intermediate Wheel
Hour Wheel

[cjablonski]

That's a great idea regarding using the smaller end mill and finishing up with the scroll saw! I never thought of that....hmm..I might even do it, saves tons of time. As far as printing the dxf's, I have a way that will make both you and the wife happy . Google Deltacad. It's free initially for 45 days, then it's a small fee (I think 20 bucks) for a copy. Clayton tipped me off to it, and I use it all the time now. If you decide to get Deltacad, PM me I I will forward the directions how to print to scale for you . Additionally, make sure if you decide to cut the pinions all at once, be absolutely certain you label each one. Sometimes there are slight variations in each ( an extra tooth, slightly smaller size, different pitch diameters ECT). It's real easy to attach the wrong pinion to the wrong wheel. Lastly, do you have a disc sander or a belt sander? Making the spacers is easier and faster with them. Simply rough cut the spacer size (even square if you want!) And round them off to size at the sander. Quick and dirty. .....and old school lol.
Glad to be of service, and hope to continue to help throughout!



PS- be advised something about the escape wheel. Cut the contact areas where it will touch the pallets a little heavy if you can. This will allow you some "fudge " room once you assemble the clock. Since the escape is the most sensitive in the entire train, cutting it heavy allows you to sand a little off if you need to later. Keep in mind, once that Volkswagen of weight is transferred through all those wheels, the escape is left with only a few grams of force, so it's important to tread lightly with it. I usually cut that one last, allowing me to "get into a groove " with the shark and know it will turn out perfect.

[bill z]

Got a Craftsman table belt and disk sander. I was thinking the spacers should not be real critical and I could use the sander.

[cjablonski]

You are correct. They are only there for thier thickness. Want em perfectly round? . Use the arbor hole in the center, drill the same size hole as the arbor in some scrap, and use the arbor to pin the spacer to the scrap. Bring it up to the sander and gently spin the spacer and, whala, a perfectly round spacer, no programming required.

[bill z]

Back to the hard stuff, cutting gears.

Has anyone been successful in cutting the gears using a CNC? If so, I would like to know the bit information (diameter, depth, number of flutes…) and the software specifications (Step Over, Pass Depth, Feed Rate, RPMs…), maybe bit manufacturer.

Not blaming anyone, just stating some facts in hope that I can help the next guy. I have not found much information about CNC cutting of these clocks. I have looked at a bunch of videos on these clocks. Only found one and it looked like he was showing off his home made CNC. Nothing about the bit information.

My calculations may be off somewhat, but zooming in on the small gears, I calculate there is a gap of 3/25 of an inch between each tooth near the bottom of the teeth (narrowest point, diameter of the bottom semicircle). Theoretically, a 1/8 router bit will NOT fit but a 3/32 or 1/16 would with room to spare (OK, a small amount of room).
I don’t have ether a 1/32 or 1/16 router bit yet. Some are on the way.

It is strange but previewing the cut in Aspire v8.007 doesn’t show problems, at least to the new guy in the CNC hobby. See 3D picture.

The cut on the left represents a cut made with a 1/8 end mill bit that is somewhat too large but NOT noticeable in the previews, looking at the resultant gear teeth. The one in the right is made using a 1/6 end mill that will fit but the gear teeth show no significant difference in any gear tooth.

For the new guy, remember that the gear in the pictures below will be less than an inch wide, so these small amounts do count.

In the 2D JPG, again, it looks like it would work using ether bit.

[cjablonski]

I have used the cnc for cutting gears, just not the smallest pinions, as I don't own the collet reducer and 1/16 bits. The issue with the model is related to an algorithm within aspire regarding bit contact point and model generation. This works 99 percent of the time, but the smaller the part, the more the algorithm shows it sores. It can be solved to view a 3d image more accurately but not cheaply (in my experience ). The solution involves the purchase of commercial software ( again my own experience with Solid Works ) and ends several thousand dollars later. It isn't worth the cost, as experience interpreting softwares virtual reality to the real world is much cheaper.
With regard to flutes, feed rates pass depths and rpm. All are related. Flutes=cutter contact to material and waste removal. More flutes =faster feed rates (but minimal in regards to your question, as choice is usually limited to 2 or 3. Basically statistically zero). Rpm is related to bit diameter. Simply, the smaller the diameter, the faster the RPM. 1/8"= 24000 rpm. 3" shaping bit = 14000 rpm. Physics is Mass x velocity =force. Pass depth should be 1/2 the diameter of the bit max. Feed rate to me is more complicated, as I have not really done the calculations, I have solely relied on my own experience with routers. Lastly, I truly believe the 1/16 bits you have ordered should be the solution to your issue.

[rungemach]

Hello Bill

I have cut wooden gears with good success using an 1/8 th inch bit. straight sided 1 or two flutes.

pass depth of .125 feed rate 10 inches / minute.
stepover is 20% but doesn't really matter for this type of cut.

for your 1/2 inch pinions you would do 4 passes to get the full .5 depth.

If your machine is working correctly and does not have abnormal free play, you should be able to get the precision you need for Clayton's clock gears.

A critical gear is the escapement gear as it needs to be uniform for every tooth to give you an even beat from second to second. If the individual teeth are off, the consistency of each beat will suffer.
The rest of the gears can have a loose mesh in that they are not involved in the actual timing. The gears that carry the force to the escapement from the weight need to be smooth and run without hanging up, so here again, no pinching.

The 1/8 th inch did bit is fine for all of this as the only thing that is affected by the bit size is the shape of the very bottom of each gear tooth. The gears do not mesh tightly in this area anyway.

Also attached is a picture of a pinion from my extra parts box, it is as cut on the cnc with no sanding done. You should be able to duplicate this result without having to cut anything on a scroll saw or by hand.
also attached is a picture of a very small pinion made for a toothed belt assembly. also done on the cnc.

I hope this answers your question regarding settings.

Bob

[bill z]

Thanks for all of the encouragement here guys.

I’m going to try some things.

Yesterday, I tried out my new 1/16 single flute router bit that chucks into my ¼ cullet. It is a straight blade and cuts real well. I was surprised how well it cut. Check out the picture. Like a razor.

I had been using a 2 flute spiral and it caused some raising and fluffing of the grain. It only cuts 5/16 inch deep but I can work with that since most of the cuts for a clock gear are ½ to 1/4.

Now that I know I can cut these gears, I can work on what settings are needed to use my 1/8 end mill like Bob does. I’m impressed with how his came out.

[cjablonski]

Thanks runge. My past experience with gear cutting went poorly for me ( a Rube Goldberg device ) and hadn't tried since (nearly 4 years ago ). Based solely on you settings written above and currently working on a boyer design, I decided to give it a whirl. Worked flawlessly. Saved me a ton of time, putting it a week or so ahead of schedule. The beauty of this forum. ....and the reason for this post. ....multiple heads are better than one.