[4]

Curta Calculator Scale Replica

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

ttabbal

Brass
Registered
Joined
Jun 12, 2017
Messages
904
I'm not sure those can be CNC milled. Inside corners and the only radius spec is 0.1mm max on the key. That's a pretty small endmill.. Punching is probably the best option outside of laser, or EDM. Maybe broaching the corners, but that could be tricky too. And tedious.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
I agree. In fact, I don't even know if we can punch these out to within acceptable tolerances. This whole adventure is new territory. I'm going to challenge Racer to study up on punch and die and let us know if he can build tooling that will meet the required tolerances. :grin:

If nothing else he will have learned quite a bit about about punch and die stamping, perforating pressures, die clearances, and other important information conerning this manufacturing technique. He may even discover that he can't meet the tolerances he requires, and have to reject the punch and die method. I'm just proposing lessons. :grin:

It's up to Racer to do the "homework".

A Note on Tolerances:

I'm thinking that, although we should strive to meet the tolerances called out on these drawings, in reality, we can probably loosen up on the tolerances a bit. The reason I say this is because we are building this as a handcrafted item. Therefore we can work with looser tolerances via the assembly of a one-off handcrafted item.

Keep in mind that the tolerances called out on these drawings are for manufacturing to assure that all these parts will fit on any Curta Calculator even as replacement parts. If our parts are slightly off on some dimensions, we can probably take care of that during the handcrafted assembly. For example, my handcrafted gears may not fit your replica of the Curta Calulator, and your gears may not fit directly into mine. But as long as they work in the calculator they were handcrafted into that's all that matters for our purposes.

So we have a little more room for error in tolerances than are called out on these drawings simply because we are building a handcrafted replica,.

~~~~~

None the less, Racer is going to need to design a punch and die that is going to punch out gears as close to the drawing tolerances as possible. This is going to require that he gains a really good understanding of the punch and die processes, especially concerning clearance issues. He may need to consider shearing angles of the punch and die edges as well.

He'll no doubt need to do some preliminary trial and error work. I would (and will) suggest in future homework lessons to begin by making a simple circular punch and die. Get the brass sheeting that will be used. And punch out some circles. And see what you get. Try different clearance tolerances, etc.

Hey, I never said this was going to be EASY!

I'm not claiming to know how to build these things. All I plan on doing is teaching Racer how to go about figuring out how to build it. He'll need to overcome all the obstacles. I'm just an innocent by-stander. Honest. :grin:
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
I was actually planning on having you build something more like this one. Only one that runs at a higher speed and has a guard on it so you can't stick your fingers into the punch press.


The punch and die will be a lot more complicated too. Although when you first build the punch press you will want to try it out with just punching circles out first.

But that wasn't the homework assignment I gave you. You're supposed to be learning about the process of stamping metals. And learning the formula for calculating perforating pressure.

You'll need to be able to calculate how much pressure you'll need to punch out the gears you want to make. And that will change as you design the dies and choose the material you'll make the gears from.

The final punch and die you'll need to make will look a lot like the compound die on page 3 of the booklet I asked you to read.

And the final punch press I'll have you build (assuming you ever get access to a lathe), will be more like the one in the video I posted above. Except it will have a much faster punch speed and more safety guards around the actual punch.

I might be expecting too much.

If you tried to punch the gears out using a hydraulic jack like in the video you posted it would take you a week to punch out 20 gears. :grin:

You want to be able to punch out 100 gears in a few minutes. So you'll need a fast press like the one in the video I posted only even faster.

Besides a faster punching speed actually produces a far better finished product. So you don't want to be pushing the punch through slow with a hydraulic jack. You want it to just punch the part out in a split second. That will make a much cleaner punch.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
A Sneak Preview

I ran across this video animation. This is a bit advanced as I haven't addressed all the design considerations for the punch and die. But this animation is almost precisely what we need to build. It's a simplified version of our compound punch and die.

The animation is great. The narration not so hot. Kind of robotic sounding.


There are two top punches. One (in blue in the video). This will punch the outer profile of the gear. The second punch is the center punch wrapped in a spring. That punches out the center hole of the gear. The pink block (held down by the spring around the top center punch) holds the gear blank in place during the punching operation.

The bottom die is the reddish part in the center of the bottom. It has both a center profile to accept the top center punch, and the outer profile of the gear teeth to match up with the outer blue punch on the top.

The spring-loaded yellow stage is used to hold the feed material flush with the top of the bottom die.

In this animation they are just punching out round washers with a hole in the center.

In our case the finished product will be a profiled gear with a center hole that has the wedge key we need.

This is a very complex punch and die set up. Making this alone will be a masterpiece of machining. So this punch and die setup is not something we want to rush though. How well this is made will determine how nice the gears are that it punches out.

But this is the idea. I'm really glad I was able to find this animation. This animation saves a lot of explaining. :grin:

Key issues of importance will be the clearance between the punches and dies. I've done punch press work before and I can tell you that another factor of how well things go will be determined by the speed of the operation. This tends to be something we find by trial and error once it's all up and running.

There will be two perforating forces. Each one being applied at different points in the punch stroke. In this animation the Blue top punch cuts the outer profile first. Then the center punch punches through the center hole. Because of this staggered operation the punch press only needs to be rated for one of these two operations. Obviously it will need to be rated for the higher pressure operation which will be the outside profile.

In any case, there you have it. It's almost designed for us. All we need to do is calculate the clearances we need for our material and the exact dimensions of the two top punches and the two cutting edges on the bottom die.

As soon as we get this made we can start punching out gears.

Of course, we need to build the punch press itself too. But let's not get too bogged down in the details. :grin:

Let's take it one step at a time.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Good work.

I've been off in this thread, A Lawnmower Punch Press, preparing to design a punch press for us to build.

I even got a lawnmower to use. :grin:

I was going to take you though building the compound die one step at a time, but perhaps you can design the compound die on your own now?

From what I've learned in the Lawnmower Punch Press thread from Jim Dawson, using half-hard 260 brass should work well for this purpose.

The shear stress for half-hard 260 brass is about 52400 psi.

Have you learned enough from those videos to take a stab and calculating the clearances we'll need?

You could probably start simple with just the center hole punch and die.

See if you can figure out what size the punch and die need to be. We can deal with the more complex outer gear profile later.

The center punch will be extremely simple to make. It's just a rod with a v-groove in it.

The die will be a round hole with the triangular key sticking out of it.

Personally I would make the die in two pieces by just drilling and reaming a round hole. And then cutting a keyway slot to accept an insert we can slide into it from the bottom to stick out as the triangular groove cutter.

Don't worry about actually making the punch and die. Just calculate the clearance. And then see if you can figure out what size the punch and die should be to produce the correct size hole.

Tip: In real life engineers often cheat by doing things trial and error to some degree. You can make a round punch, a round hole die, set up a way to keep them lined up. Then put some brass material between them and whack the punch with a nice heavy hammer. This should produce the hole and the a piece that comes out of the hole.

You can then measure the hole and the piece that came out of the hole and see if you get the results you are expecting. If not, back to the drawing board. Adjust the sizes of the punch and die and try again. :grin:

You can use this same method for the larger circle on the outside diameter of the gear. You want to make sure you can punch out a nice blank that has the precise diameter you are hoping to punch out.

Note: If this proves to be too difficult to produce a perfect gear we can move forward to option #2 which I haven't yet mentioned. Option #2 still requires that we punch out round washers. So we'll still need the punch press and compound die to punch out are washer blanks. We can then machine those blanks to finial precise profile dimensions by stacking them all on a transmission shaft arbor and machining them all at once in a batch milling operation.

So we'll need to make these round brass washers either way. And we'll still need to punch out the center hole with the wedge key. So this is the path forward. Unless you have better ideas.

Others have been suggesting using EDM, but that requires sending the brass out and having someone else make the gears. That would kind of defeat our whole purpose right? Another suggestion was to have someone else make the compound punch and die tools. And then we just punch them out. But again, doesn't that defeat our purpose? That would also be extremely EXPENSIVE.

My suggestions have been within the scope of what we might actually be able to do.

If these parts were 10 times bigger this would be a lot easier to do. But they aren't. They're tiny. So that's what we're stuck with.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Racer,

What I'm proposing may even be physically impossible. It's up to you do find out. :grin:

The hole we want to punch in the center is only 2.3 mm in diameter.

The material we hope to punch the hole into is 0.6 mm thick.

That means our hole diameter is only about 3.8 times larger than the thickness of the material.

We must be dangerously close (if not already exceeding) what a punch and die can even do.

See if you can find out what the limits are for the smallest hole you can punch in a given thickness of material.

We may need to give up on the punch press idea entirely.

I honestly don't know the answer. I've never worked with such small parts before. This is new territory for me.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
I found this on this web page: Design Tips

Minimum Hole Diameters

Holes can be punched most economically when the hole diameter is 1 1/2 times greater than the stock thickness. Minimum diameter is related to the shear strength of the material. In softer materials this can be equal to or less than stock thickness. Stainless steel, on the other hand, would normally require a hole diameter equal to 2 times stock thickness. If the hole diameter is less than material thickness (or less than .032 dia.), it must normally be drilled and the burr removed.


Based on this "Design Tip" it looks like we might be ok. We're 3.8 times larger than the stock size. That should be ok according to this shop tip.

See, I'm even doing your homework for you. :grin:
 

rwm

Active User
H-M Supporter - Gold Member ($25)
Joined
Mar 25, 2013
Messages
1,697
Maybe I missed it but does anybody know how these parts were originally made?
Robert
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
I haven't seen any information on that. Would love to see it if anyone knows where it can be found. I doubt the original gears were punch pressed. The outside profile can easily be machined. But I'd like to know how they did the center hole with the wedge key. They could have had a special broach for that. The broach idea was my first idea, but for various reasons I chose to abandon the broach idea in favor of punch press.

We haven't made a gear yet, or even a punch and die. So we're certainly open to alternative options. :grin:

I'm looking into building a small punch press from a lawnmower crankshaft. But I've always wanted to have a small punch press anyway. So I'll probably build that in any case. This Curta Project was just the spark that ignited the flame of my old desire to build a punch press. I've had that dream for a very long time.

But yeah, if there is any original manufacturing information to be had, I would love to see it.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
A Public Service Announcement

Just for the record. I've been doing most of the posting in this thread. But it was never my intent to hijack this project. I'm simply offering my potential solutions. They may or may not even work. Obviously I feel strongly that they have potential or I wouldn't be suggesting them. But that's no guarantee that they will actually work.

If anyone else has another approach they would like to share, please feel more than welcome to chime in and share your ideas.

Obviously things like EDM and farming out machining to other sources kind of defeats the purpose of this project. We already know that we could do that at great expense. So that's not an idea we haven't already considered.

Buy yeah, if anyone has any alternative methods to approach this project, by all means chime in.

The first one to produce a set of Curta gears WINS a FREE "Congradulations!". :grin:
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Alternative Curta Designs.

I just joined a Curta Forum. I can't post until I've been approved. I'll ask there for any information concerning how the original calculators were manufactured. That would be extremely valuable information to be sure.

In the meantime I searched through some of their posts and found a picture of this early Curta made in 1938, Notice that his one is quite different from the later model that Racer has the drawings for.




Notice that the numbers for the setting levers are just stamped onto the body. There are no number dials for the setting numbers. The only dials appear to be on the top for showing the results of calculations.

Note also in the slots of the setting levers you can see the setting dimples are all in a straight line. That too is quite different from the one Racer gave us the drawings for. The model Racer is trying to build has spiral setting arms and those dimples follow the spiral.

This 1938 model might be easier to build. But we don't have the drawings for it.

We could probably spend a full year just studying this antique calculator. :grin:

I think I'd almost rather build this 1938 model. But unfortunately we don't have the drawings for it. So we're stuck with having to build the more advanced version.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Another photo of the 1938 prototype Curta



Apparently this was the original prototype. There probably aren't any reliable drawings for it.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
There's a guy on the Curta Forum from Switzerland who designed a Curta Watch. The following picture is a rendering from his CAD model. He's looking for a watchmaker who might be interested in making it for him. Not sure if he has the internal mechanism worked out or just wants this face put onto an existing mechanical watch. The numbers in the little windows don't move. It's just 1 thru 9 then 0 = 10:00, 1 = 11:00 and 2 = 12:00.

Kind of a cool idea for Curta Enthusiasts. Others on the forum say they would like to have one too. A person could probably buy an inexpensive quartz watch and try to put that mechanism in a case like this with a face like this.

Apparently there's quite a large Curta following.

If you stick with this project Racer and build a Curta Calculator to completion you could potentially set yourself up for a lifetime career just making replacement parts, doing repairs, and selling replicas. There appears to be a potentially large enough following out there. People who repair Curta Calculators are reporting as much as a year backlog. So apparently there's no shortage of interest in these calculators. And from what I hear repair parts bring a fortune if you can make them. So this is definitely a worthwhile project to follow up on.



curta_watch.jpg
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Don't mind me I'm posting up a storm here:

I just looked up information on ordering replacement parts for a Curta Calculator. The Gears we are talking about making cost $40 EACH as replacement parts.

Let's see, there are 42 gears, that's 42 times $40,, . . . $1,680 worth of gears we're about to make. And that's if we only make 42 of them. :grin:
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Something is Terribly Wrong!

The gears in the drawings we have don't look anything at all like the gears in this assembly video!

Why is that? Which gears are we making?

The gears we have drawings for are just flat gears. The gears on the transmission shafts in this assembly video have extended brass collars above and below the gears. You can clearly see this starting at 0:44 on the video.


I was going to just start making parts based on the Solidworks drawings we have. But there seems to be a difference between those drawings and this assembly video.

Which one is correct?

I'm working with the Solidworks drawings. But now I'm not convinced the drawings can be trusted. The gears shown in the video cannot be produced via a punch and die method.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
First photo I was able to find of a Curta manufacturing facility.



Can't tell from this photo what anyone is working on, but it sure looks like they had some pretty crude tools to work with.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Solved the temporary panic over the gear design

The drawings we have are correct. The video just doesn't show enough detail. In the video this looked like a one-piece gear, but it's actually an assembly of 3 parts. A ferrule, gear, and sleeve. I'm not sure what holds them all together, but it's three pieces. So the drawings we have of the gears are correct after all.



gear assembly.JPG
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
This is becoming a nightmare Racer

After we manufacture all these gears, we need to make a whole lot of sleeves and ferrules. Far easier to make than the gears to be sure, but still require quite a bit of manufacturing processes.

Then when we get the sleeves, gears, and ferrules all made they need to be assembled as sub-units.

Here's the assembly drawing:


A complex sleeve, part number 410360 slips down through the center of the gear and through a ferrule, part number 410347, and then the whole assembly is crimped together as a unit at the bottom. Then you finally have an entire gear assembly that can be slipped onto a transmission shaft which you also have yet to make. :grin:

It's probably this 3-piece gear assembly that cost $40.

What do you think?

We need to build setting shafts and all their related parts.

Counter dials with all their gears, etc.

Let's not forget the pinion gear that goes on top of the transmission shafts too.

I don't know how long I'll be able to help with this project. I have a life to live. :grin:

I'd kind of like to see the gears made and maybe take a shot at figuring out how to make a setting shaft which I think is the most difficult piece on the whole calculator. If we actually did that much you should be able to take on the rest of the project by yourself. You will have already learned how to tackle the most difficult parts. Everything from there on out should be a piece of cake, at least in terms of how to make the rest of the parts. It won't necessarily be a piece of cake to actually make them though.

As you can see, even to make these gears requires quite a bit of external tooling and engineering skills. The same will be true for the setting shafts. And probably every other part on this calculator. Most of your time will be spent designing and building the necessary tools to make the parts. Making the actual parts will be a "secondary operation". :grin:

It's going to be this way the whole way through this project.
 

rwm

Active User
H-M Supporter - Gold Member ($25)
Joined
Mar 25, 2013
Messages
1,697
I feel like the 1938 prototype would be a lot easier to make. The spiral shafts add a lot of complexity just to add numerals at the top. I would start there. For those small gears it would be easy to machine a log bar to make the outside contour and then you could part off individual gears. I am just not sure how to make the center holes. I would consider soldering the gears to the ferule.
Robert
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
I am in total agreement with EVERYTHING you said Robert. :grin:

I feel like the 1938 prototype would be a lot easier to make
I would rather build the 1938 prototype too. The problem there is that we don't have the drawings for that. We could probably figure it out. But we'd surely need to spend a lot of time doing that before we even begin.

If we knew where we could get the drawings for the prototype that would be cool.

The spiral shafts add a lot of complexity just to add numerals at the top.
Agreed. The one we have the drawings for is a monster to be sure.

For those small gears it would be easy to machine a log bar to make the outside contour and then you could part off individual gears. I am just not sure how to make the center holes.
Well, I do have an idea to go in reverse order for perfect gears. In other words, punch out a bunch of round washers with the correct shaped center hole. Then stack them all together on a transmission shaft arbor, and machine the outside profile that way using a forming tool bit maybe even on a flycutter? That would be hobby-machinist friendly. We'd only need to make 5 milling passes to cut the five complex teeth. This would ensure that the outer profile of the gears was well machined and in perfect tolerances too.

I would consider soldering the gears to the ferule.
Yeah I like that idea too, but we'd still need to make the sleeves and ferrules anyway. So soldering rather than crimping wouldn't save much, if anything. And then there's always the possibility that solder could interfere with the fit on the transmission shaft. These gears need to slide up and down the transmission shafts effortlessly.

The whole thing is going to take quite a bit of handcrafted care during assembly no matter what.

I mean, if we currently had a whole box full of parts that we just made, putting them all together would not be easy. Each and every part would need to be checked to be sure it slid over every place it needs to go without binding. It also couldn't be too loose either lest it might get jammed up from being crooked.

This is almost as bad as building a watch. Maybe not quite that bad, but pretty darn close to it.
 

rwm

Active User
H-M Supporter - Gold Member ($25)
Joined
Mar 25, 2013
Messages
1,697
"Well, I do have an idea to go in reverse order for perfect gears. In other words, punch out a bunch of round washers with the correct shaped center hole. Then stack them all together on a transmission shaft arbor, and machine the outside profile that way using a forming tool bit maybe even on a flycutter? That would be hobby-machinist friendly. We'd only need to make 5 milling passes to cut the five complex teeth. This would ensure that the outer profile of the gears was well machined and in perfect tolerances too. "

That is a great idea.

I think you could use the diagram you have and modify the shafts and eliminate the numeral dials without changing much else, no?

Robert
 

RJSakowski

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 1, 2015
Messages
4,123
How determined are you to make exact replicas of parts? Parts are designed with ease of manufacturing in mind. The purpose of the vee shaped protrusion in the bore of the gear is to follow the keyway on the shaft. A conically pointed pin inserted through the bushing and brazed in place could accomplish the same goal.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
I think you could use the diagram you have and modify the shafts and eliminate the numeral dials without changing much else, no?

Robert
I imagine this could be done fairly easily. That would not only eliminate the numerical dials, but it would eliminate the need for the pinion gears on the top end of the transmission shafts as well. It would also eliminate the need for the "Spider Spring" and all the steel balls that hold the numerical dials in place.

But if you look on the first page of this thread at the video on how this thing works, you might take note that it's important to have the balls and spider spring holding the numerical dials in place, which in turn, hold the transmission shafts in place, when they aren't being locked in by the locking gear. :grin:

In other words, changing anything on this design could potentially have cascading effects that could result in other problems. For all we know the original prototype model had these problems and was prone to jamming up? Maybe that's part of the reason they redesigned it?

Changing things without being clear on what the consequences are could result in trouble down the road.

How determined are you to make exact replicas of parts? Parts are designed with ease of manufacturing in mind. The purpose of the vee shaped protrusion in the bore of the gear is to follow the keyway on the shaft. A conically pointed pin inserted through the bushing and brazed in place could accomplish the same goal.
I agree, there is a lot of opportunity here for some design changes that would make things much easier for a hobby machinist to be sure.

I don't know what Racer's full purpose is. Nor am convinced of his conviction to the project at this point. :grin:

I'm thinking that anyone who takes this project on would probably do well to stick to the original design. Unless they are only interested in building a single unique hand-made calculator for their own personal accomplishment and satisfaction.

Seems to me the latter would be a terrible waste of effort. For just a little more effort making it correctly could result in a potential for some real profit down the road. Apparently there are people willing to pay good money to have their repaired. If a machinist put in the effort to do this project by the book it could result in a potential pay off in the long haul.

Let's face it, no matter how we approach this project it's going to be at least a year long (if we're LUCKY!) Maybe longer than that.

This isn't a project you're going to want to look back on and say, "Darn I wish I would have taken the time to do it right".

Probably better off just doing it right from the get go.

Forty dollars a gear? Once you are set up to make them, it could potentially pan out. :grin:

Just say'in.

Especially for someone just starting out in life like Racer. This is an opportunity he really shouldn't pass up. He won't have time to do this after he graduates and starts working full-time. And if he does it now, he could get himself set up in a Curta Calculator repair business and even sell the "Replicas" that he makes. This could turn out to be a full time career if someone takes it seriously.

Look around. I just came from a web site where people are selling Curta Calculators for as much as $5,000. A working replica will easily bring in a grand. In fact, it's hard to find even used beat up one for much under $1000.

Although some people do get lucky. I just read a post on the Curta forum where a guy just picked one up at an antique store for $10. No kidding! Apparently the owner of the shop had no clue what it was worth. And the photo of the one he got appears to be immaculate.
 

rgray

Active User
H-M Supporter - Gold Member ($25)
Joined
Nov 26, 2012
Messages
1,193
Have you seen the Reddit post and the github files on the Curta?
Someone started an effort 4 years ago.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
Have you seen the Reddit post and the github files on the Curta?
Someone started an effort 4 years ago.
Are you talking about this one ReCurta

Or is there another one?

Edited to add:

It looks like the ReCurta project was started (or possibly last updated) in 2015.
It also appears that their goal was to post all the drawings and parts lists, etc. Which they appear to have completed.
I don't think it as ever their intention to actually build one. Just make the plans available for someone else to build one.

Ah,... I think that's supposed to be us? :grin:

It's fate. We're supposed to be building this thing.
 
Last edited:

tcarrington

Making miscellaneous parts for years now
H-M Platinum Supporter ($50)
Joined
Dec 27, 2013
Messages
78
I have worried less about the gears and assembly thereof than how you are going to make the shaft with the spiral groove.
 

Robo_Pi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 18, 2016
Messages
451
I have worried less about the gears and assembly thereof than how you are going to make the shaft with the spiral groove.
That's next in line. :grin:

I have a dividing head so I'm prepared for that one.



I didn't want to scare Racer off with more expensive tools. :grin:

Although I think there are tricks that can be used to cut a spiral without using expensive equipment.
 
[5] [7]
Top