Making Round forms on a metal lathe

snip---


Hey Eric,
Yep--been there---done that. If you have a large enough machine, most of the problems seem to evaporate. I recall with fondness my first job outside the missile industry. I was assigned to a 17" Axelson on which we turned some cast steel pulleys for C size belts. It was a job that repeated, a part of the product produced by the corporation. We'd cut one side of the groove, then the other, using a form tool. Believe it or not, no chatter, but you had to know when to get out of the cut. I never mastered it as well as old Ozzie Gallagher, who had been employed there for years. His grooves were masterful, a great finish and no chatter. On a scale of 1-10, I'd rate those old Axelsons about 11. Wonderful machines.
Harold
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Harold and Susan Vordos wrote:

*****GLOOM***** - thanks Harold. I still dont understand much of what you are saying, but will dig out the textbooks and try and figure it out (dont speak Engineering fluently yet, its a new language to me...)
I am doing a trades course, but its a weird way of teaching - (showing my age, again) - you are given a heap of theory prac. books to fill in by finding the answer in the text book. This may work for some, but not me - I need to "see" whats being taught, in front of me, and then ask "Why is it done this way" - at the moment, trying to tie in theory with practice. And yes, the instructor (when you can get him) will answer questions, but sometimes I dont know the questions to ask...(yes, I know, that doesnt make much sense.)
My school text book is big and thick with Lots of Pictures of Big Industrial Machines - theres an assumption you have a basic knowledge of the trade - which is reasonable, its an apprentice course. Thank God the kids in my class are tolerant and helpful of the token " Old Fart".....actually,its been a real eye opener - a good bunch of people who will go on to be decent citizens, - we are so accustomed to seeing the stuff-ups and disasters on the evening news.
The only time there is a group lesson is when someone does something wrong and we get a lesson on how NOT to do it.....and a lecture on how much the broken tool cost....or how close someone came to serious injury....
But I will get there, - thanks Harold for answering my questions (and the other people as well - much appreciated). Was it Gunner a few days ago said that this is a truly infuriating occupation - so much effort needed to get some basic competence in the field?
And I am getting there, albeit slowly - understanding more of whats being discussed here, texts are starting to make more sense. And, starting to be able to work to tolerance consistently most of the time (oh, ok - 4 out of five times, better than a few months ago..)
Andrew VK3BFA.
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On 29 Sep 2006 02:57:11 -0700, "Andrew VK3BFA"

===================What you are describing is the result of administration efforts to "get by on the cheap," stressing efficiency over effectiveness, with the primary goal of meeting standardized [paper] test requirements.
It has been known at least from the work of John Dewey in the early 20's [American educator 1859-1952] and possibly as far back as John Amos Comenius (1592-1670) that most people learn far more/better from observation and imitation [AKA "monkey see-monkey do"] than they do from any form of the traditional academic/lecture format [AKA "sage on the stage"] which was originally developed before the advent of the printing press, because the handwritten books were too expensive for student use.
While it is a truism, it is never the less true that:     I hear and I forget;     I see and I remember;     I do and I understand.
I have instructed beginning and intermediate machining classes, and have found that the best combination from both an effectiveness [students can actually do machining] and efficiency [amount of material covered and number of students instructed] is video tapes of actual machining operations that the students can watch at home, class discussion of the tapes including the "why" as well as the "how," and as much hands-on chip-making time as possible in class, preferably on student selected projects, or simple tools they can use, such as pump staffs.
These video tape series tend to be a somewhat expensive for the individual but in the United States there are companies that rent the tapes. Most likely there will be similar companies in Australia. Another possibility is to get the school to buy the set, or to get several of your friends to share the cost.
The series that I like are from the American Gunsmithing Institute cover general turret [Bridgeport] milling and typical engine lathe operation. They also have a number of firearms specific videos on action tuning, specific weapon disassembly/maintenance, etc. which most likely will be of little use in Australia.
See: http://www.americangunsmith.com/view.php?idX http://www.americangunsmith.com/view.php?idX {turret mill} http://www.americangunsmith.com/view.php?id ` {general shop info} http://www.americangunsmith.com/view.php?idb {package deal all three} http://www.americangunsmith.com/view.php?ida {videos only no books}
Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (17431826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor
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Interesting observations! I teach at a dental school and I get the students when they are beginning to learn how to use high and low speed drills. At the same time they are indoctrinated into the intellectual side of anatomy physiology and material sciences. The big learning curve is training the eye to see and the brain to control the hand and to vizualize. Any suggestions on what teaching methods are "foolproof" would be appreciated.
Charles Friedman DDS Ventura by the Sea Woodturner Deep drawer on the press Metal spinner 6th childhood
. This may work for some, but not

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On Fri, 29 Sep 2006 17:19:07 GMT, "Charles Friedman"

===================I can see at least half a dozen dissertations, 10 or more books, and a ton of monographs/journal articles in your question.
If I had an answer to this (and not even a "good" answer, or *THE* answer) I would be on my way to Stockholm to pick-up my special Nobel Prize. ASAIK there are no "foolproof" or even "fool resistant" methods. Even Harvard Medical produces a few duds that somehow manage to slip through the final performance test called "internship."
I do have some observations limited to your particular area.
First, you need to determine what characteristics your students must have to be good dentists, other than they want to make a lot of money and have Mondays off. Then you need to prioritize these traits. While some minimum IQ or "smarts" is necessary, given that most dentists do not do research work, ultra-high academic [as you may be aware, there are other IQs] IQs are not particularly important, and in fact may be counter productive.
From my understanding of Dentistry, (having had my teeth worked on occasionally) outstanding hand-eye coordination is an essential requirement, as is an exceptional micro-kinesthetic sense that allows micromanipulation with minimal visual clues/feedback.
A separate but co-equal requirement is an excellent spatial sense of how various small 3D objects/surfaces will relate when rotated and translated.
These are psychomotor skills that can and must be developed, but to be developed, an underlying talent or capacity must pre-exist.
If you do not currently use the existing tests for these characteristics/abilities for screening applicants, it would be helpful. Indeed, you may find it helpful to develop additional tests stressing micromanipulation.
Assuming that you have weeded out the totally maladroit and the spastic, then the key is practice, practice, practice.
Because there is only 24 hours in the day, overemphasis on intellectual/academic topics and GPA may well interfere with acquiring, improving and retaining the necessary foundational psychomotor skills. It is at this point an unusually high academic IQ may be a problem, in that there is little intellectual challenge in practice, practice, practice.
It can be helpful to use the practice time to create items of interest to the students, and to engage the students in friendly competition, such as who can grind the smallest "DDS" on a simulated tooth hidden from view in a simulated mouth.
Do you have milestones established, for example that at the end of week three the student will demonstrate their ability to drill a hole in, or polish, a simulated tooth with limited access/visibility.
Are your students encouraged to stop by the lab and use the equipment outside of class time, possibly on their own projects? These might include a charm for their girlfriend's bracelet, or tie tack for their boy friend.
Some of the finest home shop machinists and model makers I have seen have been dentists.
Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (17431826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor
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My dental school is one of those that is research based. The students are very bright and they are motivated by the good life style. They intellectually get it most of the time, but the link from the mind to the hand needs lots of practice to function well.

There is as much feedback as there is in working on a manual machine and stopping for measurements periodically. Not as satisfying as a DRO.

I am open to any interesting ideas on developing a feeling for 3-D.

I agree, there is no substitute.

I think that the problem here is one of frustration. But I thought that all of those hours spent mastering video games would come in handy here. Or does that only work for fighter pilots?

There is plenty of free access to to the lab and faculty.

My own experience is that sometimes an instructor can help you with a set up or introduce you to a tool or hold down device that you did not know about. Otherwise I play with feed speed and nature of cutting tool. Go with what works, but try to understand it.
Charles Friedman DDS Ventura by the Sea
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F. George McDuffee wrote: <snip>

<snip>
A similar phrase got used a lot in some of the circles I hung with.
See one, Do one, Show one.
You see it to get the idea, you do it to learn it, and you show it to the next person, thus fulfilling the first step for him or her and firmly planting the knowledge in yourself.
Cheers Trevor Jones
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s
snip------

Do not despair. Some of us don't grasp the concept initially----but unless you're hopeless, the light will come on and things will make sense. Cutting tools, in particular, are very simple to grind, but you must first understand why they cut. Once that's entrenched in your head, and you understand how clearance and rake affect performance, it's dead easy to design tools for specific chores.
snip great report of class, methods, people and progress----

That's a common complaint I have----along with the related lack of respect for those that have paid dues to achieve a level of competence by a select few that don't understand that making chips isn't the same as making parts. Nothing sorts them out quicker than building a part to prints specs, which will be inspected by an unbiased inspector that's looking for nothing more than good and proper work. Some folks can't put it together.

Exactly! One does not eat an elephant in one gulp----it's done a bite at a time----and suddenly the elephant is gone. You'll do fine, Andrew. Have patience, and do your best. What's important is your attitude. If you care, and choose to learn good and proper procedures, you will. If, on the other hand, you choose to use every dodge one can fathom to avoid the learning curve, that's likely to be the outcome as well. You have a choice of becoming a good machinist, or a good bullshit artist that claims he can, but can't.
You mentioned being an old fart, Andrew. How old? I believe I mentioned somewhere that I turned 67 in July. I feel every one of those years.
Harold
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Greetings Brent, It all depends on what kind of tools you have. But I'll describe two different methods you can use. For concave curves you can make a too,that cuts on the tangent. See this link for good pictures and descriptions: http://www.frets.com/FRETSPages/Machining/QuickTricks/ToolPostFile/toolpostfile.html Another way is to make form cutters out of either mild steel or tool steel. File, drill, grind, etc. the desired profile mirror image into the steel. Then, if using mild steel it can be case hardened with some stuff called "Kasenit". If using tool steel then follow the directions that come with the steel. The heat treating can all be done with a propane torch. Since it's brass you are machining the tools don't need to be super hard. This makes the heat treating more forgiving. When making the form tool clearance must be provided so that the tool doesn't rub. A way to visualize this is to imagine a hole going through a plate. If you pushed something through this hole it would rub the sides all the way. But if the hole is conical with the smaller diameter at the top then something pushed through would only contact the hole at the edge. When making the form tool you should file or grind this into the tool. A third method is to make a template out of something easy to shape, like sheet metal, and then file each part to fit the template. ERS
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Hi Brent. Besides the suggestions already put forth, you might also want to look up profile tracers. I dont know what machine you have but I have seen plans for small simple tracers that can be adapted to various machines ( I *think* I have one from ME and authored by Westbury IIRC-). It would allow you to do non elliptical curved segments on your pieces. regards, Art
Brent wrote:

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Brent wrote:

There's a number of different ways of doing this, form tools are one way. Grind a tool to the concave/convex radius you want and feed it straight in. If you don't have a tool and cutter grinder, it'll take some skill to get the tool ground to the right radius. On a chess set, the tolerances probably aren't going to be that tight, though. Bigger radii call for wider tools and a more rigid machine to avoid chatter.
Guy Lautard wrote a set of books called the Machinist's Bedside Readers, one of them has directions for doing manual coordinate turning, basically generating a table of X-Y coordinates for cutting spherical surface of a desired radius. After cutting a set of stepped cuts, you then smooth off with a file or abrasive cloth.
Here's one sort of radius cutting attachment: http://www.littlemachineshop.com/products/product_view.php?ProductID70 The company has other types for more money. This is a perennial home shop project, back issues of Model Engineer, Home Shop Machinist and others have basically the same idea with more or less complication. Some are manual, some have worm drive to turn the cutter around the axis. Accurately setting cutter protrusion can be a problem, most designs have a socket for a setup spud located right on the pivot axis, you then measure protrusion from the point of the spud.
If you have no particular requirements other than the end be rounded off, you can rough it out with the cross-slide movements, then file it by eye to shape in the lathe. If you do this, make absolutely sure you have a handle on the file, you can get some serious injuries from bare file tangs if the file gets loose with the workpiece under power.
Stan
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wrote:

===================called radius turning attachments and ball turning attachments.
For bolt and go solutions see: http://www.littlemachineshop.com/products/product_view.php?ProductID70 http://littlemachineshop.com/products/product_view.php?ProductID%69 http://littlemachineshop.com/products/product_view.php?ProductID%68
Ball turning attachments, knurl tool holders and rear mounted cut-off tool holders are traditional home shop machining projects. If you want to roll your own see http://www.homemetalshopclub.org/news/oct03/oct03.html (about 1/2 down page) http://www.nucleus.com/~harlan/ball.html http://www.bedair.org/Ball/ball.html http://tabletopmachinewiki.com/wiki/Ball_Turning_Tool
For your purposes and skill level a simple unit like the first one listed [LMS#1970] should be more than adequate.
Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (17431826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor
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I've always wanted to try this from a different approach. Get someone with a CNC lathe to cut out maybe as few as four types/blanks out of brass and aluminum and then modify them each at home with a shaper , lathe, mill, files, ect... That way they would at least be close to the same size as the rest without taking forever.
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    Look on eBay for "lathe radius turn*" and you will find the following auction (among others): # 260035622642
    Sometimes, commercial radius turning fixtures show up, sometimes things like this which can be scaled to the size of your machine.
    Another trick is to mount the stock in a chuck on an index head, set it to an angle from the table on a mill, and hold a reversed boring bar in a boring head in the spindle. Lower the rotating boring head until the boring bar is cutting around the end of the stock, and then start cranking the index head to rotate the workpiece. This will make something similar to the ball on a bolt handle on a rifle. You'll need to bring it to the lathe and use a file to finish up the center if you want it to look like a ball all the way through the axis.

    Indeed so.
    Enjoy,         DoN.
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