I can see a plastic-covered cheat-sheet in my future: based on the diameter, what's the modulo-0.125 dial reading to match it? 0.1 dials would skip that step, but the travel isn't so big that it will be problem.
Do you ever indicate your compound parallel to the spindle? I would think that to be essential if you ever plan to transfer the dial readings to another point on the part, or does something else prevent doing so?
Something tells me it is the nut on the dials that matters ;)
Knowing what I sometimes go through to get setups right now, I can only imagine that CNC would be a HUGE time sink for me.
Same here. My idea of "big run" is >5 of any given part ;)
That seems to be the evolving story, most work is measure/remove. I will look around one more time, but I will probably end up keeping the machine sitting in my garage.
Exactly what I do on a mill, but the difference is that "caring" usually means matching the dial to the last two digits on the drawing. If those walked every revolution, I'd go nuts. If most work "take another
I've never seen a system that does but that doesn't mean they don't exist. All the DROs I've seen on a lathe have just been for carriage and cross slide position.
Great thing about a DRO on a mill is you don't need to think about backslash, you can just move it to where you want from either direction. They also can provide useful addition features to make life easier such as n holes equi-spaced on a PCD, centre line calc.
However, if I take what you say, is that the dial indicates a movement of .125" at .001" increments of the crosslide, then that means the dial is reading radial movement and a cut of .001 will result in .002" being removed from the diameter.
Is that what you mean?
The dial for a 8 tpi cross-slide feedscrew, in normal circumstances, would have 250 graduations, each graduation representing .001" off the diameter of the workpiece. Whereas the compound dial would have 125 graduations for the same tpi.
So what do you have? :-) The former is to be avoided, the latter is the norm.
The cross I can understand, as that is a precision movement. The only way I can see (the carriage) a 0.020/div (not rev) dial with a worm gear and rack being precise is with a DRO or indicator to guide it, and even at that, I would much rather fine tune position with the compound as it is made to be a precision movement. Aside from helping with long parts where measuring would be cumbersome (a 36 inch rule appears to go for about $60 - $150 for Starrett), I really don't see the use of it. In fact, I submit that I would be hindered from doing the right thing for fear of moving beyond its capability.
I reserve the right to change my tune after I actually learn something about _using_ a lathe vs. studying the machine itself :)
With respect, I do not buy it. Backlash is a symptom of slack in the machine, and it is not difficult to tame once the process becomes largely sub-conscious. It strikes me that the table movements that allow me to work despite backlash are precisely what one needs to remove the slack. I cannot help but think that will result in better accuracy and finish. The exception might be Harold's described "float" on the final cut to clean up a window.
Granted. There are situations when that type of help would save me some time, though most of the time, I just go to the location based on a scale and dial readings off the drawing.
Indeed. If you want precision in longitudinal motion, you clamp either a turret bed stop or a dial indicator to the bed parallel to the ways. You could do with a micrometer bed stop and a set of spacers if you don't need it very often.
Yes -- except that the inexpensive ones are likely to use the leadscrew's threads for feeds too -- requiring more changing of speeds to get to a fine enough feed. As examples:
1) The Atlas/Craftsman 6x18 lathe (long out of production) -- had only the leadscrew and a basket of change gears. You used the half-nuts for both feed and threading, and if the change gears were set up for threading they would be too fast for practical feed if you are after a nice finish. So -- you could not even get away with a "good enough" and leave the gears set as they were.
2) My 12x24" Clausing (also long out of production) has both a quick-change gearbox making it easier to change feeds and speeds (and less messy -- you wind up with rather black hands changing gears frequently if you keep them properly lubed), and separate feed controls on the apron. This machine used the same leadscrew to power the feeds, but not the threads on the leadscrew. Instead, it had a keyway milled in the side of the leadscrew the full length. The apron had a sleeve in bearings which surrounded the leadscrew with a key engaging the keyway, and a worm gear on the OD of the sleeve. Gears in the apron picked up the rotation of the leadscrew through the worm and were carried to either the handwheel to move the carriage via the rack and pinion (and much slower than the half-nuts would at the same speed so you don't need to change feed gears as much), or to the cross-feed (even slower for fine finish when facing off.
Fancier systems would have a separate rod with the keyway for the feed, and sometimes a second leadscrew and half-nut set for metric threading instead of Imperial threading. I would like to have this capability. Metric threading really should have a metric thread leadscrew to allow the threading dial to be useful.
O.K. I have made mistakes using the 0.125"/rotation handwheels on the machine at work before I retired. I prefer the 0.100"/rotation on my Clausing. But I do have an inexpensive DRO (The Shooting Star) which I plan to eventually mount on the Clausing. Among the advantages are accurate position even when leadscrews are badly worn, and the ability to switch the readout between reading diameter removed and reading radius removed depending on what you need to do. As it is, I keep a digital caliper and an HP-15C calculator handy for keeping track of what dimension I am sneaking up on. I tend to zero the calipers at the target diameter so my readings tell me how much needs to be removed, and the divide the reading by two to get the necessary dial reading change.
Just which model of Jet did you have problems with? The lathe which I used was essentially the brother of yours -- same castings and features, and those had a pretty good reputation compared to the 9" and
7" ones, which were very limited.
Note that an 8 TPI thread works out to precisely 3.1750 mm thread pitch -- not exactly the most convenient value, but precise. :-)
At this point -- why not keep it? I don't think that you will find anything with a 10 TPI cross-slide leadscrew which is not made in the USA -- which mostly means older machines like my 12x24" Clausing, which was made in 1957.
Since the DRO scales measure the position of the saddle or cross slide, whatever actually MOVES said pieces makes no difference as it's not looking at the screw or rack at all.
And the compound rest is meant to cut and move on an angle, not for positioning.
As I said, if only one DRO, I'd put it on the mill, but that doesn't mean I don't want one on the lathe, too.
And I"m not sure what you mean by "be hindered from doing the right thing...". Could you please explain that one?
I don't want to sound like an ass here, but you just said that you are basing your opinions on looking at a machine rather than USING that machine. On the other hand, I and many others who have tried to help you and to explain things do this for a living and have for many years.
You don't have to "buy it"...the fact is that you CAN work around backlash, but with a DRO, you largely don't need for positioning. For milling and cutting, yes, you need to deal with it, but why bother if you don't need to?
All the systems I have seen have the DRO position sensor fixed to the carriage and bed, and saddle and cross slide so the position reading is only relative to the position and not reliant on the carriage/cross slide transport such as rack and pinion or lead screw. In this way the DRO doesn't care if the carriage move 0.020/div or 0.50/div it just reads the amount moved regardless of how far you rotate the hand wheel. Regarding compound use, with the DRO most of the time my compound stays locked so it can't move and throw the DRO settings out. Once the DRO has been set to the diameter and end of the workpiece for instance, I can then take a known amount off the piece on diameter and length. Usual start procedure for me is to take a test cut and measure the piece then punch the number into the DRO to set the diameter and maybe touch on the end of the piece and zero it or set the current length so the readout shows the length when the carriage is moved. My Newall unit has the provision for multiple tool offsets also so one can swap tools and select that tool in the DRO so that the readout values are correct for the chosen tool.
These days I wouldn't have a mill without a DRO but it is more of a luxury on a lathe. I used my M300 for a few years without a DRO but am very happy I now have one as for many operation it does save quite a bit of time.
Well when I used machines with backlash and no DRO you had to compensate and approach the point from the same direction in order to account for it. Approaching points from one direction then the other could leave the points out by the backlash. Also the DRO isn't troubled by wear in the leadscrews, my Bridgeport has worn screws but that doesn't bother me as I have a DRO which is independant of the leadscrews. If you tried to do accurate work on a machine with worn leadscrews based on the dial settings you could easily fail due to the inaccuracy produced due to the wear as the dials don't compensate.
Why do you think that I don't adjust the toolpost once I have started? Remember that I suggested that it (a quick-change toolpost) should be with one dovetail parallel to the workpiece and the other parallel to the face of the chuck or the faceplate. (Or was this in another thread dealing with a different lathe and a choice of toolpost style?). Anyway -- a good quick-change toolpost will repeat the position of a tool quite accurately when it is removed and replaced many times. It is this capability (or tool turrets on a CNC machine) which make carbide inserts so desirable compared to hand-sharpened HSS tools. The inserts repeat quite accurately, so the ability of the quick-change toolpost to repeat makes it possible to write down your needed dial readings when producing more than one of something.
The turret toolpost which usually comes with that style of lathe does need to be replaced with a quick-change toolpost -- and my preference is for the wedge style, not the less expensive piston style, because the wedged design offers greater rigidity.
That depends on the maker. My 12x24" Clausing (from 1957) has a dial which is calibrated 0.000-0.100 on a 10 TPI leadscrew. It was a light industrial machine in its day, not a hobby toy. I suspect that the dials reading in direct diameter change are more recent machines. And perhaps yours is a metric machine as well, since you are in .nz?
What you want it to. There is typically a button (labeled something like "2X" to multiply the direct reading of radius to get the diameter difference instead.
And there are times when the radial reading is more useful -- for example when cutting a groove for an O-ring or an e-clip you need to cut it to a specific depth, not to a diameter.
It does not have a sensor for the compound slide or angle, so it has no way to deal with that. (Or at least, I have never seen one which did.) They normally have two sensors -- cross-slide motion, and motion of the carriage along the bed. They have the option to multiply the cross-slide reading by two so you get the diameter removed instead of the radius.
Well ... the sensors on the mill are not being confused by backlash in the leadscrew and nut, which the dials progressively are. And depending on the amount you have spent on the mill's DRO, you can have it do things like calculate bolt circles for you. You tell it where the center of the circle is, where the first bolt goes, and the number of bolts (or the number of degrees between bolts) and it guides you to drill all of the holes without you having to first calculate their locations in X-Y coordinates. If you don't need to do anything like this, go for a cheaper model.
Or...the amount remaining if you zeroed on the OD, particulaly if your DRO has "offset" features.
Indeed.
People also flew around the world in Ford Trimotors for a long time. They also used semaphores to communicate information.
Bill...an inexpensive DRO will allow you to work faster, far more accurately and do a number of operations that would take you hours to do, in just a few minutes
They also work very well on lathes
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
That seems like an obvious solution to the problem. The lathe of the hour has a separate shaft with keyway to drive the feeds.
No question about that.
The big example is an H/V bandsaw. My real gripe is their reaction to my pointing out a serious design flaw in the emergency cutoff. They really showed their colors on it, and it did fail as I predicted. Prior to that, I bought one of their woodworking jigs. Never again.
I am leaning toward keeping it. I would have preferred to hash this out pre-purchase, but this has been a helpful discussion, and if I do keep it, it won't be because I made foolish assumptions about how I will use the dials. It sounds like the primary deficiency will be in setting dials to agree after a witness cut, but I can create a chart for converting diameter to dial readings to simplify it.
Fair enough, but it sure looks like, bumped parallel to the spindle, like a great way to position with precision.
The carriage motion is quite course; the compound is on precision dials. With the freedom that comes for ignorance, I would choose to move left or right 0.001 using the compound.
Which is why I asked for advice: to avoid _being_ an ass.
Call me a throw-back, but running a mill "the hard way" has saved me a LOT of money and allowed me to build a gadget that would have been out of my reach had I relied on a DRO for the easy stuff. Sadly it is under non-disclosure right now. I will crow about it when possible.
As I said, the slack is there unless you do what the manual process requires.
Understood, but it seems that for small movements, it would be far easier to use an spindle-parallel compound than the courser carriage movement.
It looks a little too useful to be in that state, but understood.
That's nice.
Your choice of course, but two DROs would buy my next mill.
But understanding that, I sometimes come in from the backlash-compensated direction, deliberately overshooting by decreasing amounts for rough on down to finish cuts. Frequently though, I work from measurements when going against the dials. It's not hard.
Very true.
I will probably outgrow my mill long before it gets to that point. If it or its successor is lucky enough to see that much use, replacement screws would probably be in order. No argument about the independent measurement though.
I didn't assume one way or the other, but I was starting to wonder about toolposts...
... and meant to ask the question you just answered. I am sad to report that Enco has the style you suggest on sale currently, and that I am going to pass for my wallet's sake. The sale runs through early June IIRC, by which time I will probably see my way clear to buying it.
Good to know.
You have made the case well. I will get one, but I need to slow down the financial bleeding, at least for a month. I can defend every expense in the last quarter, but there have been quite a few of them :(
The good news is that I got very nice prices on a few things I was hoping to buy this year; it just happened closer together than I had expected.
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