Newbie question

[ClockMaster]

I have read alot in this forum and am very impressed with what I have seen. I build wodden clocks for my hobby and am very interested in creating a CNC cutter. I have been cutting gears on a scroll saw for a few years and its such a pain. It would be nice to have a 99.9% perfect gear the first cut, especially when your cutting 100+ teeth. Mostly I use hard woods and acrylic. I have seen the JGRO DIY plans and some stuff on hobbyCNC.com. The largest gear I cut is about 12 inches and thats rare. I just want some basic info on what would best suit my needs and be the most cost effective. Thank you.

[sp00k1e]

Like this, my first cut on my Jgro machine. This was from a DXF from Garys wooden clocks site Garys 2003 clock took about 10 minutes to cut in 1/4 ply, unfortunately a 3mm cutter is too big and the bottoms of the small gear were not cut properly.
When I build another driver I may try again, My homebuilt X axis just blew up :frown:

[ClockMaster]

Something I have tried....Use a small drill bit and SLOW movement for little cuts. A finishing nail filed to a sharp edge will work too. Used both methods with my drill press to clean up small corners.

[ynneb]

Hey Clockmaster, I recently met this guy who sells his hand made clocks for many thousands of dollars. He told me that he makes the gears using a gear cutting machine.
He cuts 10 or more gears at a time. He uses a high desity compressed timber compound for the gears, and puts a thin laminate on the front of them. Essentially you see only the teeth. He tells me that these gears could go for a 100 years without wearing. Unfortunately I can only find a small picture of the process he uses. In this case it is much better than the CNC option you are thinking about, and also cheaper.
His process is to stack the gears together and cut along the stack, and then rotate the stack by a notch, until he has cut all the teeth. He has a guide that calibrates each partial rotaion, this make his gears very accurate.
I hope you can understsnd my poor description. Study the small picture and see if you can work out what i mean.

EDIT: see the hands on those clocks, well apparently they are made from Austalian gum tree that has been imersed in water for 100,000 years. The timber is stained by all the minerails and salts of the earth over that time.
I dont know if little things like that are his speil to justify the high price of his clocks, but he is getting orders all around the world. I must say he has found a niche that people are not afraid to spend money on. Who would have thought hey!

I happened to mention to him that I am thinking about making a clock on my CNC machine, he asked what material I would be using. You should have seen the look of horror on his face when I said MDF

[Splint]

The process Ynneb is describing is called gear hobbing, it is the most efficient method of producing gears.

[Splint]

When I say the most efficient method of producing gears I am talking in the context of an industrial manufacturing opperation. Using a cnc router would probably be the way to go for the hobbiest.

[ger21]

In an old Fine Woodworking magazine, there is an article on making wood clocks. He cuts the gears with an indexing head on a lathe, with a router with custom ground cutters. The article is also in a FW compilation book, called Small Projects, or something like that.

[sp00k1e]

Originally Posted by ynneb snip He uses a high desity compressed timber compound for the gears snip I happened to mention to him that I am thinking about making a clock on my CNC machine, he asked what material I would be using. You should have seen the look of horror on his face when I said MDF

What is high density compressed timber compound material, would it be HDF?

[ger21]

That's what I was thinking, High Density Fiberboard.

[jcc3inc]

Sir,

Probably the best method of cutting gears would be to use a GEAR HOB; these are designed to produce the ideal tooth form which has a rolling action. The hobs are expensive but are the optimum solution.

If you were to use CNC for the cutting, you would need a program to generate the proper tooth form. IF you had the Program AND you needed a sample cut, I could cut out a gear or two for you as my CNC router is 3 axis and should do the job OK. If you were satisfied with the end product, then you could go ahead and get your own machine. I do not know of a program to cut gear teeth as I have not looked for one!

Maybe other members know of a gear cutting program and would respond.

Let me know what you'd like to do.

Regards,
Jack C.

[ClockMaster]

I like the way he cuts his gears but they are very limited in style. Depending on the clock. I cut the gears in many different sizes and styles. I have different spoke patterns that I use. I draw all my gears in CAD even though its a pain..I get good results.

[ynneb]

They might be limited in style but you can precut the spokes via CNC and then cut the teeth via the "gear hobbing". That way you get the best of both worlds. Speed, accuracy, and lots of variance in design styles.

EDIT: I guess thats what he meant, HDF high density fibreboard. I just dont remember exactly what it was called.