Turning speeds re-visited

DoN. Nichols wrote:


Clearly I need *two* lathes. A serious one and a comedy one...

In the end the answer will: Get hold of one and see how it fits. Not a simple proposition locally, but not insoluble. At least now I have much clearer idea of a) what I expect it to do b) what it can do and c) what to look for

I do not think so. I am pretty sure all the bad noise came from the workpiece. I know what the gear grinding sounds like - before I discovered the trick of changing the speeds :-)

1/2" - 5/8" end mill? Now here is a thing I do not remember from the DVDs: Clearly, if one has a 3x3" surface and only 1/2" mill (for arguments sake) one has to do this in several different mill positions. Each position may require several passess. So to get to an even depth, do you a) mill each position in turn, change depth and do subsequent passes in the same order or b) do you mill each position to the required depth by however many passes it takes and then move to a different position and repeat? I can see how easy it would be to get it wrong and have "steps" on the surface of the work instead of perfectly flat finish. Of course a fly cutter or a bigger indexing mill would solve the problem, but let's say "if"...

That is the sort of experience I am trying to minimize by doing due dilligence.

2 shillings was 10 pence. Half a crown (2/6) was 12.5 pence Sixpence was 2.5 *new* pence. And so on. Years of therapy...

http://www.brainyquote.com/quotes/authors/f/friedrich_nietzsche.html
Most of them. The one applicable here I think is the bit about what does not make your head explode makes you stronger, or something to that effect.
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Michael Koblic,
Campbell River, BC
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    There is some doubt as to the necessity of the comedy one. :-)

    At least you can make a cardboard layout of the table and the column at their closest approach to see whether things line up before carrying something home.
    At least you don't have a large enough mill to have to beware the other end of the rotary table spectrum -- one which is too heavy to lift to your machine's table. :-)
    [ ... ]

    O.K.
    With the workpiece held down by double-sided tape, I would consider 3/8" to be the maximum size for cutting the OD to shape. Perhaps 1/4" if you are going to be cutting a circular slot in a larger piece of metal.
    For a slot -- you want a 2-flute cutter. For simply cleaning up the edge of the workpiece, the more flutes the better as you cut less material per flute, thus keeping the forces lower.

    Plunge to a certain shallow depth, then cut the whole surface, then increase the depth and repeat. With the backlash in your Z-axis feed, I doubt that you could even come close to repeating the depth.
    For a rectangular workpiece, cut along one edge, then shift axes to cut the edge at right angles to it, repeat until you return to your starting point, then move X and Y in to the next path (say 1/2 to at minimum 1/4 overlap with the previous, and repeat.
    For circular, cut around the edge by rotating the table, then move in radially and repeat -- with similar overlaps. The 1/2 overlap will probably produce a nicer finish than the 1/4 overlap.

    If the fly cutter is large enough to do it all in one pass. Otherwise, it increases the chance that a very slight out of-tram will produce noticeable steps in either the X or Y axis -- depending on where it is out of tram.
    [ ... ]

    Ouch! The old system I can remember (other than the common names for the various units other than the basic Pence, Shillings, Pounds, and Guineas.

    Lots of duplications there -- including two adjacent with appear identical. I could see how various translations through time could produce some of the variations at least.

    O.K. I had heard that (somewhat differently worded) many times, but not with attribution. :-)
    Enjoy,         DoN.
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DoN. Nichols wrote:

I saw that in the MIT clips and was suitably impressed. It brings out all kinds of differrent issues.

Just so I understand: You have covered the whole surface at one depth. Then you increase the depth and do it all over again until result satisfactory?

The surfaces on the same piece I saw looked much better done with a flycutter than with an end mill.

I am pretty sure it was him. Could have been Joseph Stalin. Or Hamlet.
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    :-)
    There are hydraulic lift tables to get it to the height of the machine's table to slide it on or off. :-)
    The six station bed turret for my 12x24" Clausing lathe is too heavy for me to lift with tools in the stations, so I made a table just the right height o slide it onto which lives off the tailstock end of my lathe, since for most things, I use a standard tailstock, but for certain projects the turret is a great timesaver.

    Yes. The "until satisfactory" could be in a single pass if you don't need to reduce the thickness itself, but are just after finish, or perhaps two passes if the original surface is rough (e.g. hot-rolled steel (HRS). Or -- it can be a lot of passes if you need to significantly reduce the thickness, given the limitations of your machine.

    Did the flycutter have a wide enough swing so it covered the entire width of the part in a single pass? It is when the workpiece is wider than the swing that you risk the significant step from a slight out-of-tram condition.

    At least the web page you pointed me to attributed it to him, along with lots of other things.
    Enjoy,         DoN.
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DoN. Nichols wrote:

I am decrepit. I will probably need one for the Taig. BTW, if you do not mind, what do you think of your Taig? What do you use it for?

Yes, it covered the whole surface in one pass.

What am I thinking! Hamlet was the guy who wanted the kingdom for a horse, then strangled his wife because she kept washing her hands in an obsessive manner.
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    As a small desktop machine, it is pretty rigid thanks to the steel dovetail bolted to an aluminum under-bed filled with concrete to dampen vibrations.
    It has lots of tiny T-slots on both the headstock and tailstock for mounting strange accessories.
    It does *not* have power feed in either axis, nor does it have a gear-driven longitudinal leadscrew for single-pointing threads. The only way to cut threads on it (unless you build a bunch of additions to it) is to use a die in the tailstock mounted sliding holder, which limits you to threads for which dies are available.
    It is significantly more rigid than the Unimat SL-1000 which I had before this (and still have).
    Both of them have available spindles which will handle the WW series watchmaker's collets, but only the Unimat's spindle has the external taper to expand the inverse step collets.
    I've used it for various things, including small milling, but these days I tend to use it for special purposes.
    One was when I was making a large number of adaptors which required both an internal and an external thread, I turned the 3-jaw chuck's soft jaws to hold 3/4" brass rod cut just a bit over length on a horizontal/vertical bandsaw with a stop for repeatability. I faced one end held in the chuck with the workpiece bottomed against steps lefe in the turned jaws for repeatable depth. I then center drilled, through drilled, and tapped to 1/4-20. (The tap was started but not finished in the Taig, because it did not have the power to drive it all the way through. Then the workpiece was transferred to a special arbor which held it by the 1/4-20 internal thread and the faced end, and did quite a bit more work to it using a small CNC lathe.
    As it worked out, it took about as long to do the earlier steps on the manual Taig as to to the others on the CNC, so once I was started, I could just barely keep up with the CNC providing first stage parts to it.
    These days -- that whole job is done in the 12x24" Clausing with the bed turret, and with the 3/4" brass rod fed through the spindle so there is no need for the bandsaw phase.
    However, I also make endbox screws for English system concertinas. This is a long skinny screw with a domed cheese head. The bed turret on the Clausing does the turning to diameter, threading, and parting to just over length. Then the partially complete screws are held in the Taig's WW spindle with the right size of collet, and a form cutter (HSS ground to shape) cuts the dome on the end of the head. The Taig has a nice adjustable carriage stop, so all of the heads are the same height.
    Then the screws with the domed heads go to a clamp fixture in lots of 20 (four rows of five each) and are run under an arbor holding four slitting saws on the Nichols horizontal mill to slot the heads. So -- three machines to make these parts.

    O.K. If you take a micrometer you might see that one side is a little thinner than the other, and if so, then you would have steps if it were wide enough to require more than one pass.
    Enjoy,         DoN.
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On Wed, 10 Dec 2008 11:54:06 -0800, "Michael Koblic"

Now you know how "Monk's" coworkers must feel. I watched a couple episodes, and wanted to put a bullet in his brain to put everyone out of his misery.
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On Thu, 11 Dec 2008 02:40:12 -0800, the infamous Gunner

Hell, I got to that point after seeing 3 commercials for the program a few years ago. I sure as hell _don't_ miss teevee. (Well, OK, the History and movie channels are the exceptions, but I have NetFlix.)
-- At current market valuations (GM is worth less than Mattel) the Chinese government can afford to buy GM with petty cash. --Bertel Shmitt on kencan7 blogspot
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I skipped the meeting, but the Memos showed that Larry Jaques
-0800 in rec.crafts.metalworking :

    I every so often find myself where a TV is showing this. I sometimes want to know "how did this episode turn out" but I rarely care enough to stay.
    I can waste enough time on the computer. At least there is more effort involved in sitting up and typing, than in sitting back and channel surfing. Maybe not much more effort ...
pyotr
-- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!
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Iron knee
--
WB
.........
metalworking projects
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