Group Project: Dividing Head - Organization and Design

I started making parts! Sort of...
Here is a pattern for a gear blank.

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I hope to cast one of these in brass so we can see how this machines. I have a bucket of random brasses, mostly yellow brass. I will pick the best stuff and try to get close to C360 or perhaps a little higher Cu content.

I was thinking I could thin the area between the hub and the outer edge to reduce the mass. For the first attempt I just started with a simple doughnut with 5 degree draft.

Robert
 
In a case like this mass may be our friend. More mass will vibrate less during machining of a part.
If this was spinning at high RPM then lightening would help. I think that if you have a real strong arm you might hit 2 RPM on this gear. If the mass reduction is to save material in the casting then go for it. It will not hurt anything, just keep the web at least 1/4 inch thick with a thicker spot for the set screw hole and nice radii in the corners.
 
I thought I might make it, but I ran out of steam, I put in 12 hours today and got all but the last 5 drawings recreated. My poor little brain has turned to peanut butter. It is nap time...........

Once I get these drawing all done again, then I just have to update the BOM with who is making what so that we know what is left to get done. I think I have the actual content of the BOM in good shape.

We are getting close boys.
 
So close i can smell the chips flying. After this round are you wanting to talk to everyone?
 
As soon as I get the drawings finished and posted I will need to talk to everyone before we open the flood gates. Just in case someone needs changes that might have an effect on a part someone else is making. Unless I forgot something, I think I have been able to accommodate all requests so far.
 
Flyinfool said:
In a case like this mass may be our friend. More mass will vibrate less during machining of a part.
If this was spinning at high RPM then lightening would help. I think that if you have a real strong arm you might hit 2 RPM on this gear. If the mass reduction is to save material in the casting then go for it. It will not hurt anything, just keep the web at least 1/4 inch thick with a thicker spot for the set screw hole and nice radii in the corners.
Click to expand...
The main reason to thin the web would be for conservation of material but it would also reduce shrinkage of the casting. This could be an issue with >30% zinc. I could keep it at 3/8" to allow plenty of room for a set screw. Lets see how the first one at a full 3/4" looks and feels.
R
 
So, for stress relief, I just picked up a forge. It's propane and has no automation, but could it be useful for that? I got it more for hardening, but it seems like it would get hot enough. If somewhat tricky to hold at temp for long periods.
 
For stress relieving, you want to be at least 100F below the critical temperature, which is generally 1100F to 1200F. Once reaching temperature, it is only important that you let it cool slowly. Production shops want to rush that part, because they have to make money. We're just looking to make a few quality parts.

My electric furnace is almost done, and it will have temperature control. But , if I were doing it with propane, I'd pack the forge with as much of the steel as I could get in there and heat it to cherry red and hold it there for an hour. Then cover the forge with as much insulation as I could and go to bed.

That is the plan for all the thick parts I'm working on. (The fun part will be case hardening the base, after the machining!!)
 
Is it necessary to case harden the base? Most commercial item bases are probably just cast iron? I would be concerned the part would warp duing hardening?
Robert
 
Stress relief sounds a lot like annealing. Is the difference in the temperature?

Your idea for the propane forge is basically what I was thinking. Just heat and insulate. Online people talk about burying in sand or ashes, about the same thing as leaving them in the firebrick forge.

Still learning about heat treatment. I also fell down the casting rabbit hole reading. :) might have to get some stuff to try that.
 
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