Source for small precision shafting

I don't think that's really needed. An adjustable reamer could be tweaked with a couple of setup pieces to get the correct press without knurling the shaft. It would be one more additional step that really does not make the final product any better.

There's already little enough surface area in the design as is, knurling would tend to reduce that even more.

Jim

I should be surprised?

You and Eric have

Had someone posted that message to you, how would you have interpreted it?

How many readers do you know that read anything Cliff has to say? Certainly I do not, not even a glance, although I don't have him bonked. What's the point? He's not worth the effort for me to do so, and for you to suggest I enter into dialogue with him on a subject about which he likely knows less than even you do is absurd. Further, I'm not interested in anyone that spends their time tearing to shreds the likes of Gunner. Gunner is what he is, and I accept him that way. He has some wonderful qualities, qualities that many others could use to better themselves as human beings. Gunner posts many things that don't interest me, but rarely are they unimportant to at least a few readers. I haven't noticed him spending his time tearing others down, not that he isn't capable. Having established that, should you have need to challenge something I have to say in the future, follow your own advice and bring it to me directly, not through innuendo or snide comments.

How the bearings fit a shaft have little to nothing to do with the capabilities of any given grinder. How a centerless grinder performs is up to the operator. If you make mistakes setting it up, it will pay you back with poor performance. For that reason it wasn't prudent for me to suggest that the parts he requires might be held to any specific tolerance. I would have no control over the job and how it might be run, so my suggestion may not turn out as it should and I'd be the one that lead someone down the wrong path. By suggesting a centerless was more than qualified for such a job was all one need know to pursue a project, just as it would be proper to suggest a lathe for a round object with external threads as opposed to suggesting a drop spindle mill. How hard can that be to grasp when I'm speaking to a person that is already somewhat familiar with machine tools (the OP had mentioned he had at his disposal a small lathe). The mere suggestion that the machine is capable when properly operated, after your comment that they can't provide round work, was more than adequate to eliminate any question about a course one *could* follow.

You haven't learned anything yet, apparently. Read what I said above, and do it until it makes sense to you.

I spent considerable time running a 251 Heald internal grinder processing bearing housings for the guidance system of the Sergeant Missile. We had but +.0002"/0000" tolerance on a 1.6250" bore. Using a Federal air gage, we could measure to millionths, and would often find a bore bordering on minimum tolerance. Inspection occurred at the machine, so any anomalies could be dealt with appropriately. While the Heald was built to work to tenths, it was a simple matter to take out .000020" millionths to bring the part in, *if you knew how*,and it was never accomplished with the feed, which would risk scrapping a part. In essence, what I'm saying is that nothing replaces skill and experience. In the hands of a fool, it might be difficult for the operator to hold a half thou, and in fact I'd suggest it would be, plus getting a good finish could be challenging. One must know and understand how a centerless works, and have a machine that is in good condition before expecting any particular level of quality------so----once again, I hesitate to reply. The machine is likely capable, the operator may not be. I can't answer that, no more than you can tell me that you'd be good at grinding. You may think you would be, but it may not be true. Not many make a good grinder.

Slander? Chuckle! I call 'em as I see them. You want me to have a different opinion of you, show me something different than you've been showing me. If you want my respect, try showing some. You could have chosen a dozen ways to make your comment (that you claim was a question) and have it be one instead of a left handed compliment. I don't think you're clever, and I don't think you're cute. If you want to discuss an issue, stand up like a man and ask a question so it appears to be one. In case you haven't noticed, I tend to have fairly friendly conversations with people that show respect, which I gladly return. I share with them, to the best of my ability, that which I have learned through the years. Sometimes I'm even wrong. You want in on some of my questionable knowledge, act like it.

Harold

leadframe-die

Good point, Ed. I've personally never been around a Swiss screw machine, but the idea conjures some wonderful visions.

Regards the shaft, when I read he was using Loc-Tite for the bearings, and was fighting the press fit for the hub, I had this terrible vision of shafts that were a couple thou under being glued inside bearings in gawd knows where, rendering them off center. I was concentrating on that. Truth be known, what Jim had to say ring dead true. What prevents this entire assembly from being made form commercially available precision ground 303 stock (PIC has it on the shelf, or at least they used to) and press the stamped housing in place *after* opening it with a reamer. Nice suggestion, Jim. That could all be accomplished with nothing more than a simple lathe and drill press.

Harold

Perhaps with some numbers? What are the metaltrades without tolerances?

I don't really know anyone here. Nor do I now who they think knows somthing, and who is full of bs.

Why? You discuss processes here with people who know virtually nothing about them...

Where did Gunner come from?

My comments were neither.

You're making assumptions about the original poster. Does he understand that grinders are typically capable of exceptional accuracy? What if I told him to do it with an angle grinder, or a die grinder? Would he know the difference? Why should he believe you? What if he had believed me?

Show me a machine in which this is not the case.

Why not? We do that in industry all the time. A process's capability is precisely how we select them.

By suggesting *any* process, and not actually performing it, you cannot guarentee anything at all. Why is centerless grinding any different?

What if his local centerless shop was incapable (as Eric's first vendor was) of holding an appropirate tolerance for that process? How would the original poster know what he was supposed to get?

I'm not sure what a drop spindle mill is, but I can certainly make a round part with external threads on a mill, and it is not uncommon to do so.

The OP said he couldn't turn the shaft down to a tolerance of less than .004". How familiar is he?

True. I was wrong, and I admit it. Now I know better (with your help, and I thank you for it).

Machines have a certain capability. While there is some change depending on the operator/company/machine, one can make certain generalizations about a machine. If not, how would anyone select one process from another?

No one has suggested otherwise. While I've never run a centerless (or internal) grinder, I do have to work with other people, and you're certainly right about skill and experience.

So the OP has no idea what to expect. He may believe that +/-.0005 is pretty damn good.

I don't understand that conneciton. Why such over-complication?

Well, life is full of choices. You chose your words (as we all do) and you certainly had choices.

I was *asking* you to explain the specific nature of centerless grinders and the parts they produce.

I don't want your respect.

And you could have chosen a dozen ways to say what you did.

Harold, why do I care about what you think of me? Why do you care what anyone here thinks of you?

I asked for numbers. Sorry if I'm slightly blunt - perhaps I've been in a shop for too long?

Yes, I can remember specific instances myself.

I don't appologize for what I said (nor do I think I was out of line to ask it as I did), but it is unfortunate that you were so offended by my question.

Regards,

Robin

Just wanted to clear up the bearing / pressed fit clearence issue. When the shaft is the correct size, 3.08mm, it is an excellent fit in the bearings, almost press fit, as well as a good press fit into the pressed endbell. The major problem is finding/making shafts that are 3.08mm in diameter, pretty hard (to resist bending under load and crashes) and corrosion resistant to weather.

The two options I have explored so far are: Supposedly 3mm drill rod which turned out to be 1/8" (3.18mm) and the shafts out of junk CDRom drives. The CDRom shafts work perfect. They are hard, corrosion resistant, easy to machine and the perfect size (probably centerless ground) but I only have enough for 8 more shafts with no reliable and cheap source. I tried the drill rod and found it didn't machine very well, was not round and does corrode.

Yesterday I got a quote back from a company that they could supply shafts > Hi,

A couple of minor, but potentially important points: When you say "resist bending," I hope you mean "permanent deformation" in bending. Hard steel and soft steel have the same stiffness; hard steel does not resist bending any more than soft steel does. But, once bent, the hard steel will spring back, while the soft steel may stay permanently bent, depending on how far you bent it in the first place.

That's not exactly the correct explanation but I hope you get the picture. You're probably aware of that already, but, just in case...

The other thing is the "25 micron finish." More likely you mean 25 microinch finish. That's a fairly fine finish. 25 microns would be almost 40 times coarser (around 980 microinches) which is extremely rough. Finicky people will further point out that a roughness measurement requires both the units (microinches or microns) and the measurement method (Ra, which is roughness average, is most common). So a surface roughness measurement would be specified, for example, as 25 µin. Ra (or Rt, or RMS, etc., etc.). Ra used to be called "AA," for "arithmetic average, and some people still use that term.

All of these may be important if real money is on the line and you make a specification for some material. It probably doesn't matter at all for this job.

I've never turned 416 but supposedly it machines pretty easily, as stainless goes. It sounds like the right material for your application.

-- Ed Huntress

Ah, one more thing. You're paying roughly $1/shaft for the material, which you have to cut off and turn on the end. If you're going to do 200 or so at a time, you should look into having them fully turned and cut to length by a small screw-machine shop. I'm taking a WAG here but I think you'll be right around $2/each to have them done.

Also, your motor mount looks like another screw-machine job. Both parts are very simple for screw-machining and are just the kind of thing that screw-machine shops do every day.

You could go to alt.machines.cnc and ask for a quote. You want the guy called "Dobie Dave," who uses the name "Why" on the "From" line. He's there once or twice a week. This is exactly what he does, and he's very good with short runs like this. I can get his email address if you want; he may use his real on in the NG, I don't remember. And, since I interviewed him for an article one time, I could tell you his real name if you need it.

I don't hang out there anymore or I'd check with him myself.

-- Ed Huntress

Well Robin, it sure sounded like you were equating Harold with Cliff, as if they had something in common. Because of the way I read your message I replied a little tongue in cheek. The parts were measured with micrometers and vee blocks and an indicator with .00002" resolution. The mike was plenty good enough for the .0002 tolerance O.D. measurement. The indicator was used with the vee block to check for roundness. Oh yeah, a dial bore gauge was used for the I.D.. ERS

Harold, I don't think I would go so far as calling Robin a punk assed kid. You oughta cut him a little slack. ERS

jim rozen wrote in news: snipped-for-privacy@drn.newsguy.com:

True enough. After thinking about just that (small surface area), staking the end cap on to the shaft might be the better way to go. Or use heat.

Dan

Thank you Ed!! My idea is to prototype them here and get someone to mass produce them so your post is VERY helpful.

Thanks aga>

It's a wonderful experience, especially if your idea of stainless revolves around 304, 316 or 440C. You get the idea. You might compare it as if it's the leadloy of stainless. It's reputed to machine better than 303 S, and I'm inclined to agree, although I'm not sure if it's better than 303 Se, which I like to machine.

Harold

Well, good. Now watch Dave say I'm out of my tree on the price, and they'll be $7/each.

Seriously, I don't think so. Once I went to your site and got a look at your components I realized this is a screw-machine job.

-- Ed Huntress

I have bad memories of machining 304 and 316 back when I worked in a shop, and I've only tried 303 once, giving me little basis for comparison. So I've since found a long list of reasons not to use stainless for my hobby projects.

However, I want to try some 416, since several here and on AMC have said how nice it is to machine.

-- Ed Huntress

"Harold and Susan Vordos" wrote

Ive spent more hours running a centerless than that smart mouthed little bastard has been in the shop. It's plain damned amazing how someone can work in the trade for a couple years and get so knowledgeable that they know all about things they've never touched.

How many readers do you know that read anything Cliff has to say? Certainly I do not, not even a glance, although I don't have him bonked. What's the point? He's not worth the effort for me to do so, and for you to suggest I enter into dialogue with him on a subject about which he likely knows less than even you do is absurd. Further, I'm not interested in anyone that spends their time tearing to shreds the likes of Gunner. Gunner is what he is, and I accept him that way. He has some wonderful qualities, qualities that many others could use to better themselves as human beings. Gunner posts many things that don't interest me, but rarely are they unimportant to at least a few readers. I haven't noticed him spending his time tearing others down, not that he isn't capable. Having established that, should you have need to challenge something I have to say in the future, follow your own advice and bring it to me directly, not through innuendo or snide comments.

Slander? Chuckle! I call 'em as I see them. You want me to have a different opinion of you, show me something different than you've been showing me. If you want my respect, try showing some. You could have chosen a dozen ways to make your comment (that you claim was a question) and have it be one instead of a left handed compliment. I don't think you're clever, and I don't think you're cute. If you want to discuss an issue, stand up like a man and ask a question so it appears to be one. In case you haven't noticed, I tend to have fairly friendly conversations with people that show respect, which I gladly return. I share with them, to the best of my ability, that which I have learned through the years. Sometimes I'm even wrong. You want in on some of my questionable knowledge, act like it.

Harold

Well said, Harold. Robin, you just dig the hole you're in deeper with every post. If you would accept what is being said here rather than arguing every point, you might get some sort of benefit from the conversation. As it is, it looks like these gentlement are wasting their breath and time on you..... they are trying to do you a favor, whether you realize it or not.

Mark

By calling him 'snot-nosed??'

Harold has helped me a *great* deal in the past. It didn't come in that form.

Jim

"smart assed punk kid"

"smart mouthed little bastard"

I haven't cornered the market on defending one's self - and working alongside dozens of toolmakers leaves me with some understanding of the size of a machinist's/toolmaker's ego.

The only favor I was asking for was info on centerless grinding.

This is an idle interest as I am not being trained as a machinist and will probably never touch a centerless grinder. It's certainly no skin off my back.

Regards,

Robin

"Ed Huntress" wrote in news:5n7Td.19822$ snipped-for-privacy@fe08.lga:

I've read the same. I don't see a lot of difference between 303 and 416. I should say "good" 303. Some of the cheap import stuff is pretty bad but overall 303 cuts great. 416 can be run a little faster without burning up your tools, but I don't find that big of a difference over 303. We often run 303 on our demo parts at machine tool shows. It cuts good, looks good, easy to put a 16 Ra or better finish on it. Plus if a guy takes away a demo part it will look good for years. I was just in a shop and saw a demo part I dreamed up and ran about 15 years ago. The guy had it on a shelf with a bunch of other demo parts from shows. It looked like it just came off the machine 10 minutes ago. OTOH, I'm used to cutting it on brand new, rigid, CNC Swiss machines so YMMV. I was on the phone with a customer today. He is quoting a job in Grade 1 Ti. I'm reassuring him that he'll have no problems with it. Titanium cuts great, I tell him, and give him some speeds, feeds, and tool recommendations. He normally cuts Kovar, has never cut brass or steel, so it's all relative.

Dan

I think that my friend Dobie Dave on ACM, who probably has machined miles of the each of those alloys in his Brownies, has said exactly the same thing.

All I need is a stainless steel that has good corrosion resistance (something that makes me hesitate to get into 303) and that I can machine reasonably well on my old lathe. I suppose I could take the time to learn the skills for machining 304 and 316 really well, but I turned one hell of a lot of 304 in a manual turret lathe many years ago, and it took a very careful touch to keep from work-hardening it, particularly when I was end-drilling. You had to behave like a machine yourself, like a servo-motor that just went at it blindly.

What machines are those, Dan?

-- Ed Huntress