RFQ - What am I doing wrong?

I still do not understand the reasoning behind these tolerances. It sounds to me like you came up with these tolerances just because you learned the highest accuracy specs on the machine you think this part should be made with. Put down the tolerances you need for your part. If these dimples are for set screws, the tolerance can be as wide as the slop from the set screw with its tapped hole. With a proper tolerance on the angle, this part can be made on a swiss lathe. It can even be made on a vertical mill with proper part supports. I don't know why you have to be so concerned about what machine the shop will use to make the part and inspect the part. If they can hit the tolerances with a mill instead of EDM, what is the problem? If they want to inspect the part with their CMM and still stay within budget, what would be the problem?

Ok. It’s long but I feel it’s valuable

Tolerance aside, the approach to design is what would have me walk away.
This kind of customer could go 2 ways
Dimple it with a hand drill and they are happy.
Or use the most advanced “magic machine” and the customer still comes back mad because it “does not work”
What a headache. And for what? 20-30 parts at $150 each?
Or they charge proper for these parts at the requested tolerance (anyone care to place a number here for me?) and the design still does not work..
then what? Mad customer? Lawsuit? Any headache is unpaid time and stress.

That’s the real problem with this rfq.
And thinking about it for more than 5 min. Pass, better things to do.

Imagine thinking of a process to make. To measure. Price it all about. $3000 a part (my random number) This will be a good job, customer must know what he wants to be calling out THAT kind of precision….
*rams set screw in*
It is out of balance/time! “Wtf magic machine shop? I’m not paying”

All a$$hole ness aside.

Have you thought about this design completely before using others people time quoting?
Is your shaft straight. Will it remain straight, how are you timing the elements your placing on it to the level of accuracy you are asking(perfect dimples do not mean perfect set screw placement)? How are you balancing the assembly?(“perfect parts” won’t make perfectly balances assembly’s”)
Have you considered vibration resonance of the assembly and rolling elements and it’s effect on your output measurement?
What class of bearing are you choosing, what internal clearances, what cage design? (there will be more clearance in the bearing than your allowing for dimple depth.)

The point is someone calling out a wild spec then telling me I must not know/understand the positional/repeatability tolorance of my equipment and process “cuz they talked to a salesmen about these kinda things” is arrogance at best.
Remember that same salesmen told you a $500 rotory was gonna do the trick but someone’s $300,000 Swiss won’t?

All food for thought my friend.
I’ve had too many potential customers add decimal points for no reason.
You add a decimal. So will the shop quoting it. $$ now it’s “too expensive” then they do down the road and have it made with Joe hand drill and call me a prick.
Communication is essential but also takes time. Time many won’t waste on a one off customer who wants to make something cheap so it never pans out anyways.
Cheap and quality meany it’s up to you to eliminate wasted time from hello to finished part.

I give people 10 min before I explain that we can discuss a retainer and hourly fee for consultation services.

(Now I give people on practical machinist more than 10m because in return so many have helped me here. Thanks all!!)

Comatose said:

Erm, no...

The thermal growth doesn't just impact the overall length. It also impacts everything... along... the length, all of which are toleranced +-.0004.

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I added a note there I think before you replied. edit: hmmm but features will move too....have to think about that...

I never said I was a mech-e professionally, just that I am for this project I'm a software engineer professionally, and I have been working on this project since before college, so I took more physics than I needed for my degree to have some shot at being able to make this work. Physics wasn't enough to get me through mechanical design, so I've had to learn a lot along the way. I graduated college in 2004 to give you an idea of how long I've been working on this, and how much I've had to learn to make this a reality. That is to say, if my mechanical design is stupid, I do lack formal training, but here's what I'm thinking in terms of the design. First off, I made this thing as small as I felt comfortable making it. Why? Many parts of this system will be rotating at 5000-7200 RPM. If that doesn't scare you, well, I don't know what to say There's a lot of mechanical energy there even in light parts with a small diameter. Unfortunately, as the size shrinks, so too do tolerances. Its why I bought multi-ton machines to make parts that are, at the biggest, a couple inches in any direction. To be able to get that 0.0002" tolerance where needed. The biggest factor in the design was this part, and the collars around it. How do you make a part with varying diameter, but make it so that parts can be assembled and then constrained onto the shaft...accurately? Well, the answer is, you can't as far as I can tell, but you do what you can! For me, this was start of with locating pins. However, the axle diameter is quite thin, so locating pins have to be just that, locating pins. They will not be able to take much force. So how do you add strength in the axial direction to the Collars? My idea was conical point set screws. However, "talking it out" helps a bit....In software, we call this phenomenon "Rubber Duck Debugging - tell your problem to a rubber duck and you'll get the answer...turns out its helpful in mechanical design as well, thanks for being my rubber duck!) Perhaps set screws are entirely stupid for this, when what I'm trying to accomplish with them is basically bigger alignment pins that don't go through the shaft to not weaken the shaft too much, distributing the contact area across the axial direction and the radial direction to achieve the necessary cross sectional area to resist the forces applied. Why not just skip straight to bigger pins? The only problem with pins alone is fixation. Which is why I went with set screws in the first place. The idea being self affixing locating pins...but you're right, they aren't good locating pins, conical or not. However, I could just stick a collar around the collar to hold the pins in, and set screw that collar in place. That collar won't be experiencing any force, and its accuracy requirements will be quite low.

That doesn't obviate the accuracy requirements for the now squared dimples in the shaft. So the shaft requirements haven't really changed...the one thing that might have changed is maybe I don't need the holes all the way through the shaft, since the set screws are gone and are all accurate locating pins with enough strength to hold the part in place.

Why not make it on a swiss machine - The main problem I see is tool deflection. Maybe a 3/4" spot drill won't flex and won't walk on the round surface..maybe. But if we're talking 0.0002", will it not walk that much? I don't know. Maybe I'll try one on the rotary and see if it is all able to be assembled. I think if I do though, I'll see about getting some precision ground fixtures....though again, I may try my own...if nothing else, for the learning experience of it all. Its not fun to waste maraging 300 steel, but I bought way more than I needed expecting to make some waste.

Now, just to finish the thought on the set screws that got interrupted by my rubber duck debugging, and even though I think I'm convinced to change them to locating pins with a retaining collar, my original thought was the alignment pin would get it as close to perfect as was possible, and the set screws would stress and slightly flex the pin, but then move only minimally as the axial force was applied. They wouldn't be perfect, like in any accuracy stackup (It applies to setup for machining as well as final machine assembly, but the accuracy of the final assembly would be a function of the accuracy of the individual parts. Buying commodity set screws, sure, their accuracy isn't going to be 0.0002", but if the axle dimples were 0.0002", the collar threaded holes were 0.0002", and the set screws 0.005" (generous, probably), then the induced error from my parts is at worse 0.0004", so the total error is 0.00054, vs if I put them out there as 0.005", then my total error would be 0.015". I had figured if worse came to worse, I could machine my own set screws that were 0.001" or better. Rolled screws certainly wouldn't be 0.001, but a machined screw with the collar having a tight thread, and the screw having a tight thread, could probably get that number down....that was the thought process anyhow. A collar for retaining locating pins is far better than "self retaining locating pins" though So I thank you for making me think about my design! In software engineering, I really know what I'm doing...I've been doing it since I was 8. Mechanical engineering on the other hand, well, I kind of suck at it, and I'm not too proud to admit it!

Stirling said:

Ok. It’s long but I feel it’s valuable

Tolerance aside, the approach to design is what would have me walk away.
This kind of customer could go 2 ways
Dimple it with a hand drill and they are happy.
Or use the most advanced “magic machine” and the customer still comes back mad because it “does not work”
What a headache. And for what? 20-30 parts at $150 each?
Or they charge proper for these parts at the requested tolerance (anyone care to place a number here for me?) and the design still does not work..
then what? Mad customer? Lawsuit? Any headache is unpaid time and stress.

That’s the real problem with this rfq.
And thinking about it for more than 5 min. Pass, better things to do.

Imagine thinking of a process to make. To measure. Price it all about. $3000 a part (my random number) This will be a good job, customer must know what he wants to be calling out THAT kind of precision….
*rams set screw in*
It is out of balance/time! “Wtf magic machine shop? I’m not paying”

All a$$hole ness aside.

Have you thought about this design completely before using others people time quoting?
Is your shaft straight. Will it remain straight, how are you timing the elements your placing on it to the level of accuracy you are asking(perfect dimples do not mean perfect set screw placement)? How are you balancing the assembly?(“perfect parts” won’t make perfectly balances assembly’s”)
Have you considered vibration resonance of the assembly and rolling elements and it’s effect on your output measurement?
What class of bearing are you choosing, what internal clearances, what cage design? (there will be more clearance in the bearing than your allowing for dimple depth.)

The point is someone calling out a wild spec then telling me I must not know/understand the positional/repeatability tolorance of my equipment and process “cuz they talked to a salesmen about these kinda things” is arrogance at best.
Remember that same salesmen told you a $500 rotory was gonna do the trick but someone’s $300,000 Swiss won’t?

All food for thought my friend.
I’ve had too many potential customers add decimal points for no reason.
You add a decimal. So will the shop quoting it. $$ now it’s “too expensive” then they do down the road and have it made with Joe hand drill and call me a prick.
Communication is essential but also takes time. Time many won’t waste on a one off customer who wants to make something cheap so it never pans out anyways.
Cheap and quality meany it’s up to you to eliminate wasted time from hello to finished part.

I give people 10 min before I explain that we can discuss a retainer and hourly fee for consultation services.

(Now I give people on practical machinist more than 10m because in return so many have helped me here. Thanks all!!)

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I do appreciate the candor, and see my previous reply about what I was thinking with the set screws.

As for accuracy, again, I just don't see it being an issue with an edm. 0.00002" stepping on position accuracy, and no tool pressure. I thought there were two reasons to go EDM, hardness of materials, and accuracy. All the "perfect fit" "videos" on the internet. (I realize those are wire edm).

As for balance, yes, I have thought a lot about balance, and have made parts specifically to be able to balance the system to ridiculous levels. I've thought about resonance as well. As I said before, I've shrunk this to as small as I can think to make it for safety. Tolerances shrink too. I self-admit to sucking at mechanical engineering, but that isn't to say I haven't thought about the basics. Remember the cost quoted on the bearings? Yeah....I've thought about it, an awful lot unfortunately. I'm self-funded here and spent close to $500,000 so far. For a large company, this is chump change. And they certainly wouldn't quibble about $50k for a part. But I'm on a shoestring compared to that. For a self funded, one man research shop, I'm probably spending at the upper tier.

I really do enjoy the discussion, and don't mind people calling out stupid stuff as stupid, and hell, you don't know the whole design, or even what the project is, so you're right to make sure I've checked other aspects! It all helps. I'd hope someone who came this far would have done so, but you never know. The internet is full of insanity. I

Corry said:

I do appreciate the candor, and see my previous reply about what I was thinking with the set screws.

As for accuracy, again, I just don't see it being an issue with an edm. 0.00002" stepping on position accuracy, and no tool pressure. I thought there were two reasons to go EDM, hardness of materials, and accuracy. All the "perfect fit" "videos" on the internet. (I realize those are wire edm).

As for balance, yes, I have thought a lot about balance, and have made parts specifically to be able to balance the system to ridiculous levels. I've thought about resonance as well. As I said before, I've shrunk this to as small as I can think to make it for safety. Tolerances shrink too. I self-admit to sucking at mechanical engineering, but that isn't to say I haven't thought about the basics. Remember the cost quoted on the bearings? Yeah....I've thought about it, an awful lot unfortunately. I'm self-funded here and spent close to $500,000 so far. For a large company, this is chump change. And they certainly wouldn't quibble about $50k for a part. But I'm on a shoestring compared to that. For a self funded, one man research shop, I'm probably spending at the upper tier.

I really do enjoy the discussion, and don't mind people calling out stupid stuff as stupid, and hell, you don't know the whole design, or even what the project is, so you're right to make sure I've checked other aspects! It all helps. I'd hope someone who came this far would have done so, but you never know. The internet is full of insanity. I

Click to expand...

So you ignoring all that advice that was given above.....

7000 rpm is not that fast. A 4 1/2 inch grinder goes faster, has a somewhat balance nut on almost certainly unbalanced wheel with a semi sloppy fit all on a threaded shaft that has been used as a hammer at least three times a day.
You are looking for smooth 7000. Shaft split collars can be balanced and will clamp into axle. This allows axle to be stronger (no dimple weak points), cheaper (no dimples to millionths of a inch), and more versatile (you can move collars in case you forgot to carry a one in maths).
You can even super glue rings on a clean shaft and remove with a heat gun.

DDoug said:

So you ignoring all that advice that was given above.....

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Seems that way. At first it looked like he was willing to listen and learn, and having had no formal training some pointers from seasoned engineers who deal with this kind of stuff daily should be just the ticket. Still, the key points have not yet been absorbed.

Corry said:

Why not make it on a swiss machine - The main problem I see is tool deflection. Maybe a 3/4" spot drill won't flex and won't walk on the round surface..maybe. But if we're talking 0.0002", will it not walk that much? I don't know. Maybe I'll try one on the rotary and see if it is all able to be assembled. I think if I do though, I'll see about getting some precision ground fixtures....though again, I may try my own...if nothing else, for the learning experience of it all. Its not fun to waste maraging 300 steel, but I bought way more than I needed expecting to make some waste.

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Now you are just making things up. No one is running a 3/4" spot drill in a swiss. There are tons of options for spot drills, even ones designed to cut on a slope. The web on most spot drill is way too big and a bigger drill isn't going to help things. Just use the correct drill. Fancy option are available here: https://www.mikrontool.com/en/Products/Crazy-tools

Whatever rotary and mill you have has very little in common with a modern sliding headstock lathe. Just have someone run these on a swiss. This part won't be the problem.

I still have no idea what you are trying to do really. If it is just locate collars axially along a shaft, use split collars and a fixture to assist locking them into place. Most shaft assemblies just use steps to locate parts. If you need super accurate location, you lap the registration face of the mating part.

You're obviously way more invested and passionate about this project than anyone else ever will be. Just buy the equipment and build it in house if that's an option as you stated. This way you can make and tweak it however you see fit and you'll probably learn a bunch along the way. I can't see a shop with these capabilities getting involved for less than $10k. Good luck, I hope whatever you're making works. Regardless...post updates.

DDoug said:

So you ignoring all that advice that was given above.....

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I'm not sure I see it that way. The advice seemed to be, don't use set screws if you want that kind of accuracy. (the worst comment to that effect was telling me he was offended that I would try such a thing...now, if that's what you call friendly advise, I'd like you definition of friendly.) I am trying to read things not in the nastiest of tones as is common when people read things on the internet, but some of you are making that a bit difficult. So unless you think the advice was to not go for accuracy, I am not sure how I am "ignoring all previous advise". If you do, well, I do not consider that to be an option, good advise or not. Also, make sure you're up to date on reading the entire thread of long posts before making assumptions. Many things I already did take, so its a pretty bold statement to say I'm ignoring all previous advise.

Collar placement/affixation: Its, unfortunately, not just axial placement. Its radial placement as well. If you know of some way to clock the parts to miniscule tolerances, I'm all ears. I'm far from married to the design. Its just the best way I could think of to get what I need. I did many searches, but nothing really came up. I probably don't have the right search terms, but having never worked in that industry, I'm at a disadvantage to search. The way typical responses on here go, I have to get pretty desperate before subjecting myself to the ridicule, so no, I didn't post here about clocking parts on a shaft and locating them axially at the same time. Sadly, mech-e forums aren't much better in terms of ridicule, and Linus Torvalds is a prime example of how software engineering isn't much better (the exception being stack overflow. People there are usually quite helpful without the snark). Now that I've chosen to subject myself to the ridicule, and it did come is droves, I'm still more than willing to take my lashes and listen. I just have some requirements that I do not think I can budge on. If there is no other way I will have to go back to try to see if I can find ways in the parts already made to increase my signal level since I can't get the noise down...but for me, that's absolute last resort. Chances are, a lot of parts will need to be remade.

I also realize everyone has some idea in their head about what I'm building, based on their own previous experience, and I'm not being all that forthcoming on the project, or requirements. Sadly, that's intentional. I realize it limits the ability of people to offer design advise, and I could have used a lot along the way. I've reworked and remade a lot of parts already from mistakes that would have been obvious to someone experienced. I also didn't come here for design advise, though I'll take what I can get with the shred of information I offered. There are a bunch of factors involved, and I do mean a bunch, but these factors mean it's pretty much a solo project until its either proven or disproven. Yes, one part is not wanting to share the pie, but that's maybe 15% of the reasons to keep it solo. Don't take it as a personal insult. If it makes you feel better, just think of me as another internet crazy. The chance I give myself of success means you'll have a good chance of being correct!

metal-ica said:

You're obviously way more invested and passionate about this project than anyone else ever will be. Just buy the equipment and build it in house if that's an option as you stated. This way you can make and tweak it however you see fit and you'll probably learn a bunch along the way. I can't see a shop with these capabilities getting involved for less than $10k. Good luck, I hope whatever you're making works. Regardless...post updates.

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Honestly, this is where I started this journey. The only reason I deviated from it was a machinery dealer talking me out of it. Everyone on here seems to think $10k would be cheap for this. If that is honestly the case, and it sure sounds like it is, that's more than 1/4 what the machine will cost. Even adding in the consumables, it would be a significant fraction. One redesign down the road might mean I'm at close to half the cost of the machine. (And that doesn;t include the benefit of learning EDM!) Multiple redesigns and it may be cheaper to have the machine to do it in house. If it were $5K, buying the machine becomes a tough sell. Do I really think I will redesign 10 times? I sure hope not!

Oh man. Before this spirals into another swissmak, I'll spell it out as clearly as I can and then I will leave you to your own devices.

Why aren't you getting quotes? It's because your print is a total mess, and it is a total mess in a way that simultaneously suggests the design is a total mess.

People will happily quote total mess prints, if the design intent is clear in a way that lets them help the new guy out. If you need a spacer or a mount plate for a motor or some identifiable part, then they can make the correct part, knowing that the user will get a usable part.

People will happily quote mystery parts, as long as the print is clear so there is no question about how to measure the parts, what the critical dimensions are and what the acceptance criteria are.

Sometimes people will take a guy with no clue under their wing and point them in the right direction on both. Someone taught everyone here at some point. As a group we may be gruff, but we're genuinely helpful under the grime.

But when someone we are all genuinely trying to help gets combative, well, *shrug.* Machinery dealers are that-a-way.

Corry said:

Honestly, this is where I started this journey. The only reason I deviated from it was a machinery dealer talking me out of it. Everyone on here seems to think $10k would be cheap for this. If that is honestly the case, and it sure sounds like it is, that's more than 1/4 what the machine will cost. Even adding in the consumables, it would be a significant fraction. One redesign down the road might mean I'm at close to half the cost of the machine. (And that doesn;t include the benefit of learning EDM!) Multiple redesigns and it may be cheaper to have the machine to do it in house. If it were $5K, buying the machine becomes a tough sell. Do I really think I will redesign 10 times? I sure hope not

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For 30 pieces on a swiss lathe, you are pretty much just paying for the setup if you are providing the material. You are looking like $1.5-$2.5K with most the shops I work with. You will learn a lot just by trying this approach.

Corry said:

I'm not sure I see it that way. The advice seemed to be, don't use set screws if you want that kind of accuracy. (the worst comment to that effect was telling me he was offended that I would try such a thing...now, if that's what you call friendly advise, I'd like you definition of friendly.) I am trying to read things not in the nastiest of tones as is common when people read things on the internet, but some of you are making that a bit difficult. So unless you think the advice was to not go for accuracy, I am not sure how I am "ignoring all previous advise". If you do, well, I do not consider that to be an option, good advise or not. Also, make sure you're up to date on reading the entire thread of long posts before making assumptions. Many things I already did take, so its a pretty bold statement to say I'm ignoring all previous advise.

Collar placement/affixation: Its, unfortunately, not just axial placement. Its radial placement as well. If you know of some way to clock the parts to miniscule tolerances, I'm all ears. I'm far from married to the design. Its just the best way I could think of to get what I need. I did many searches, but nothing really came up. I probably don't have the right search terms, but having never worked in that industry, I'm at a disadvantage to search. The way typical responses on here go, I have to get pretty desperate before subjecting myself to the ridicule, so no, I didn't post here about clocking parts on a shaft and locating them axially at the same time. Sadly, mech-e forums aren't much better in terms of ridicule, and Linus Torvalds is a prime example of how software engineering isn't much better (the exception being stack overflow. People there are usually quite helpful without the snark). Now that I've chosen to subject myself to the ridicule, and it did come is droves, I'm still more than willing to take my lashes and listen. I just have some requirements that I do not think I can budge on. If there is no other way I will have to go back to try to see if I can find ways in the parts already made to increase my signal level since I can't get the noise down...but for me, that's absolute last resort. Chances are, a lot of parts will need to be remade.

I also realize everyone has some idea in their head about what I'm building, based on their own previous experience, and I'm not being all that forthcoming on the project, or requirements. Sadly, that's intentional. I realize it limits the ability of people to offer design advise, and I could have used a lot along the way. I've reworked and remade a lot of parts already from mistakes that would have been obvious to someone experienced. I also didn't come here for design advise, though I'll take what I can get with the shred of information I offered. There are a bunch of factors involved, and I do mean a bunch, but these factors mean it's pretty much a solo project until its either proven or disproven. Yes, one part is not wanting to share the pie, but that's maybe 15% of the reasons to keep it solo. Don't take it as a personal insult. If it makes you feel better, just think of me as another internet crazy. The chance I give myself of success means you'll have a good chance of being correct!

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Hirth joint is one very effective way to do this. it was developed specifically for this.

Taper pins?

Did you know that the camshafts in Ford's Triton engines are assembled using shrink fit lobes on a ground tube?

Setscrews seem like a really poor fit even without disclosing what the goal is.

Hey now....Let's not tell the engineer he's wrong.....

Corry said:

Collar placement/affixation: Its, unfortunately, not just axial placement. Its radial placement as well. If you know of some way to clock the parts to miniscule tolerances, I'm all ears. I'm far from married to the design. Its just the best way I could think of to get what I need. I did many searches, but nothing really came up. I probably don't have the right search terms, but having never worked in that industry, I'm at a disadvantage to search. The way typical responses on here go, I have to get pretty desperate before subjecting myself to the ridicule, so no, I didn't post here about clocking parts on a shaft and locating them axially at the same time. Sadly, mech-e forums aren't much better in terms of ridicule, and Linus Torvalds is a prime example of how software engineering isn't much better (the exception being stack overflow. People there are usually quite helpful without the snark). Now that I've chosen to subject myself to the ridicule, and it did come is droves, I'm still more than willing to take my lashes and listen. I just have some requirements that I do not think I can budge on. If there is no other way I will have to go back to try to see if I can find ways in the parts already made to increase my signal level since I can't get the noise down...but for me, that's absolute last resort. Chances are, a lot of parts will need to be remade.

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Knock out a quick mock up of your design. It might not be accurate, but it will let you understand how stable it is when making adjustments. Throw an indicator on the collar, my guess is that will see your collar move axially every time you turn a screw. See if it does what you need.

How about something like this with a jig to locate everything correctly while locking it down? You can always make you own using the same concept.

Corry, does your device generate energy?

Sounds like you’ve got enough money, why not just hire a real MechE to help you design it? In a couple hours a good engineer could fix your precison issues, make you some good drawings, and tell you why you don’t want to edm stress concentrations in a spinning shaft.

It's hard to separate out responses to everyone, Comatose, you've been more helpful than most, and I do appreciate it. I'm sorry you think I was being combative towards you. I'll not call out the offenders by name, but I do get you're trying to help, and I do appreciate it a lot. I do reject the idea that the drawing is reflective of the design, but I do appreciate you getting back on the original topic, why I'm not getting quotes, but I think we beat that to death. I certainly feel that way.

To answer the question asked last, that I should have answered at the beginning, no, it's not a free energy machine. It will use energy. If the concept is proven, ones that can use quite a lot of energy will likely be built. Free Energy, by the way, does violate physics, even that taught at a PhD level. I stated I am not violating any rules of physics. Only apparently bending one to physics plebs like me, and not even bending it to PhDs.

Garwood - Thanks for the names. The Hirth Joint isn't what I am looking for. The parts have precisely one clocking that is valid. But, I think what you're getting at is separating out the axial location from the radial location. Making that 2 separate entities. That is something I hadn't considered, but the part may be too small to accommodate. I'll have to think on this...The taper pins are basically what I was trying to accomplish with set screws, just, not going all the way through the part. a 6mm axle is tiny so a 2mm locating pin is already a point I expect might break. I hadn't thought of tapering to make it less likely to fall out on its own. I'll have to see what it takes for vibration...I fully expect anything not positively captured to shake loose.

cam shafts probably aren't a good example. The opening and closing of the valves, as long as its not trying to open into the piston, just affects the power the engine will make. They can be pretty sloppy and still work. I had considered a shrink fit, but as the axle needs to be heat treated and nitrided. I talked to a mech-e about separating out parts of the axle by diameter. My concern was how the parts actually act together. With a really tight fit, do they act as one part? His answer was yes, mostly. As long as the materials have the same elastic modulus, hardness, etc, so as long as they are as similar as possible. There are a lot of caveats to that statement, and we went over them in depth, but the takeaway was, make the parts as similar as possible, to as tight a tolerance as possible, and the parts will act as one, as closely as possible. So this means the collar is also hardened and nitrided. Maraging 300 was chosen because of its low distortion and shrink. Unfortunately, its heat treat temp is rather low. Meaning, I'm not sure I can get away with a shrink fit without annealing the collar somewhat. Not to mention the first one has to move over, what, 6 inches? Can I get it into position, have the alignment pin through it, before it cools? Maybe someone really skilled could. I don't think I could.

newtons apple - Let me go with the design first since that's how I'm thinking....This is similar I think to what garwood was suggesting, separating out the axial and radial. The screws there wouldn't work, but perhaps pins would. hmmm....I'll have to think about it. One of my "lessons learned" from this, from a design standpoint was make as few parts as possible. Buy as many commodity parts as possible. I made so many freaking bearing spacers, I wanted to rip my hair out. If I never make another bearing spacer, it will be too soon. What a waste of time. So towards the end, I started trying to minimize the number of parts I was making. This concept made the idea of separating out the axial and radial components never cross my mind.

as for the swiss machine - Here's where I am with it. I get that it's a moving headstock. Thats moving support, so it can work long noodles like this one. I get that. What I don't get is how it's going to be any better than my mill with a rotary and custom supports at tool deflection. Its a drill bit pointed at a round surface. It just seems to me that's a recipe for an inaccurate location. I'm more than willing to be corrected on this, but this is where my problem with the idea of using any sort of rotating cutting tool comes from. I can mitigate part deflection with support, but I don't see how to mitigate tool deflection without using a very thick tool. Perhaps there's some wrong think in there.

Jaguar36 - As I said...I have reasons to not bring someone else on board. I don't particularly want to even share those reasons. The shaft won't be spinning. What I have read says the HAZ from EDM is pretty small, and the part will be heat treated after EDM, so too much stress should deform the part and make it useless. One of the reasons I'm making way more than I need.

Comatose said:

People will happily quote total mess prints, if the design intent is clear in a way that lets them help the new guy out. If you need a spacer or a mount plate for a motor or some identifiable part, then they can make the correct part, knowing that the user will get a usable part.

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I'm quite happy to quote and make parts that I know will never have a hope in hell of working. Been doing this for one company the last 18 months. I do what I can to improve their parts, but sometimes some of the designs need to be curtailed at the concept stage.