Retro Tool and Die & Micro Machining questions. Also questions about the forum sections.

[Robo_Pi]

I didn't see a tool & die section on the forum. So I'm not sure where to best post this first question. I'd like to get some ideas and feedback on various approaches to making tool and die fixtures for mass producing a large quantity of small parts.

As one example: I need to make a lot of really small gears. The gears are only 4.4 mm outside diameter and 0.5 mm thick. I can see approaching this problem two different ways. One is to make a long shaft formed to the profile of the gears, and then parting off each gear individually from there. The other method would be to use 0.5 mm sheet stock and make a punch and die to punch them out. I'm looking for a "retro" solution. No CNC or Laser cutting machines, etc.

A large part of this project is to preserve older machining technologies so there's more to the project than just making the parts.

These tiny gears also have a triangular shaped key way tab on the internal surface. That would be easy to make using the punch and die method. But I'm wondering how that would be done using the longer rod method. I'm thinking that a special broach would need to first be made to cut the center hole. Because it couldn't be just drilled out round. I'm thinking a smaller hole would need to be drilled through first, and then run the specialty broach through to finish the final form.

Here's a drawing of the gear. Note the tiny size. All dimensions are mm.



If it wasn't for that blasted keyway tab it would be a piece of cake. I could just drill and ream a round hole through it and be done with it.

Any retro tool and die makers out there?

Also is there a section dedicated to tool and die making on The Hobby Machinists forums? I have more questions concerning tool and die making.

Also is there a section dedicated to machining micro parts? Watch making? Etc.

The extremely small size of these parts is the real problem. If the gear above was say 4 inches in diameter instead of 4.4 mm it would be a piece of cake. Working with such small pieces eliminates a lot of procedures that could be used on larger items.

 

[Latinrascalrg1]

Maybe a two part approach would be beneficial here.....
Parting the gears off of a single rod would probably be the easiest way to get them identical on the outside And then a simple punch setup to extract the center piece while leaving behind the "triangular key" should be no problem once you have the die setup to hold the gears the same way each time.

 

[T Bredehoft]

Beat me to it. Part 'em off, punch 'em out.

 

[Robo_Pi]

Ok, I agree this is the easiest solution. But think of production. After you part them off, you'll need to place each on of these tiny gears in a die individually. And then punch out the center. That's a lot of precision punching. Especially after having parted each one off to boot.

If I'm going the punch press route I'm thinking it would be far quicker to just punch out the whole gear shape in one fell swoop from sheet brass. Then we only have one operation per gear.

What about the broach idea?

I was thinking about drilling an offset hole through the blank rod as large as possible without hitting the triangular key. And then making a special broach to run through the piece to finish the internal machining. Then after the outside diameter gear teeth are cut, parting it off produces a finished gear.

Obviously punching the entire gear out would be the quickest in terms of mass production. But I'm wondering if machining the gears and parting them off might produce a better finished product?

For ultimate manufacturing speed punching out the whole gear would be the quickest. It would need to be a 2-stage punch and die. First punching out the outside profile, and then when it bottoms out in the die the punch continues to punch out the center profile. This is probably the best way to go in the end. I don't know.

I'm thinking for deburring the punched out gears could be put in a tumbler with suitable grit material and just tumbled until they are nicely deburred.

So I'm torn between making a broach for the center profile and just parting off the finished gears, Or punching out the entire gears.

I really don't want to do both. Parting off and then having to punch out would be twice the operations. If I'm going with the punch press may as well just punch out the whole shebang in one fell swoop. That would be the quickest manufacturing process to be sure. One punch and the gear is done (or at least ready for the deburring tumbler).

The two-stage punch press die is looking more attractive the more I think about this.

 

[T Bredehoft]

I don't think a broach would be doable on a length of stock.

A two stage punch press would be easier to make the dies for. The second pass could be located with spring pins to hold it in position. Or a movable jaw to clamp it in place.

Tumble to get rid of burrs, yes.

 

[Robo_Pi]

I think you're right. The custom broach idea is highly problematic.

So I think we've already solved this problem. Just punch the blasted things out with a 2-stage punch and die. Then tumble them home.

Ok, one part solved. Only 599 more parts to go.

 

[pontiac428]

599 parts to go? Might be cheap to hand them off to a shop with EDM. I know it defeats your purpose, but dang.

 

[Robo_Pi]

The 599 was an exaggeration.

Besides, we're building a handcrafted replica of an antique mechanical calculator. So we want this to be handmade, not computer made. Having it computer made would defeat the whole project. Punch pressing the parts is acceptable since it is technology that existed at the time the original calculator was made.

We have self-inflicted restrictions on what we're allowed to do on our project. Consider it as an adventure in the arts. Kind of like trying to rebuild the pyramids by hand.

It's a project to preserve retro machining skills as much as a project to build the final product. We aren't doing this for profit. Trust me on that one.

I know it defeats your purpose, but dang.

Exactly. Our purpose is insane. I'll grant you that much.

I don't know what drives us to do this. Probably a desire to return to by-gone days?

Incurable nostalgia for time immemorial.

 

[hman]

Count gear for a Curta?

I'm totally blown away by the idea of your (and racer8412's) Curta replica project. Recall the ads in Scientific American in the '60s, and drooling mightily over both the Curta and the Questar.

Best of luck to both of you!

 

[astjp2]

.4mm flat sheet, get someone to build you a die, then find someone with a punch press, then punch them out...which is an old school way to make them. Carr Lane for punch parts...