New indicator

The dealer in the next town had a magnetic base and an indicator combo on sale for $30. So I decided to make like a real machinist and bought one to
see what my various turning implements are doing.
First of all, I do not have a clue about differing qualities of indicators. However, all the tests were done with this one, so hopefully if not accurate, at least repeatable. I understand that using an indicator is not straightforward but I tried to be careful to have everything clamped down tight, the arm at 90 degrees to the surface etc. and I even tried different positions of the indicator with similar results.
I tried my new drill press first. I put the indicator on the outside of the chuck first and there was no more than 0.001-0.002" runout. Then I chucked my biggest and bestest drill bit (3/4") and tried again. This time I got as much as 0.015" runout. I tried rotating the drill in the chuck a quarter turn at a time (re-chucking by tightening all three holes but not excessively). The run-out varied between 0.010 and 0.015". I tried differrent drill bits with very similar results, down to 1/8". I should say that I tested by rotating the spindle manually holding the pulley.
I found I could bend the chuck 0.007" ether way without any tremendous effort on my part.
I then tried the same but abbreviated test in my old cheap drill press - the runouts were of the order of 0.007".
The reason I tried the drill bits is that I do not have anything round that I am confident is machined to a close tolerance.
So a number of questions:
1) What is the expected stiffness of a drill press spindle? Is bending arc of 0.014" to be expected? What would you expect in a mill? Or a lathe? 2) What are the expected tolerances of drill bits? Is 0.010" out of round usual? 3) What are the expected tolerances of Jacobs 5/8" chucks? Is 0.010-0.015" reasonable? I understand that 3-jaw chucks on lathes are not as good at centering as manually adjusted 4-jaw chucks. Is this about the order of things? 4) Given that the runout was of the same order throughout the testing would you say that it is predominantly due to the chuck rather than the drill bits being out of round?
Thanks,
--
Michael Koblic,
Campbell River, BC
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This seems to be a part of the answer:
http://www.jacobschuck.com/images/products/Pro%20Keyed%20Updated%20 (ENG)-1.pdf
The question is if the runout would be cured by buying a "name" chuck to replace the existing People's Liberation Army one...At a cost which almost equals the drill press as a whole.
BTW has anyone tried the hitting-it-with-the hammer adjustment (as recommended on a couple of forums)?
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Drill bits are probably good to a thousandth. Dowel pins are cheap and very accurate.
The better Jacobs chucks are worth it on a milling machine, probably not on a cheap drill press. Twist drills are flexible anyway and center themselves on the punch mark, so runout in the chuck doesn't matter all that much.
The one Enco keyless chuck I have is pretty good, too, although it's on the tailstock of my lathe where I can't quickly measure the runout. For small holes they are handier than keyed chucks, for larger ones they have a problem with slipping.
A good chuck isn't really wasted on the drill press, you can move it to a better machine later.
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    Agreed.
    Well ... that depends. Yes, a typical half-inch Jacobs chuck can't *directly* hold a drill bit much below 1/16th of an inch, and 0.007" runout is probably tolerable with a 1/16" drill bit. However, if you are using one of the sensitive drill adaptors, and a #70 or #80 drill bit, your runout is going to be on the order of the drill diameter, and that is likely to break the drill bit once it gets deep enough into the workpiece. Even more so if you are using solid carbide bits for drilling printed circuit boards. They are very brittle when exposed to side loads.

    Hmm ... a real Albrecht is good at self tightening, so it tends not so slip.

    Agreed -- and if the drill press and the lathe tailstock have the same Morse taper (or the lathe tailstock is larger so you can use an adaptor sleeve), you can move the same chuck back and forth at need. (Granted, it is nicer to have them each have its own good chuck. My lathe currently has a Polish clone of the Albrecht in the 5/8" size, my drill press has a Jacobs (close of the Albrecht, though looks a little different), and my little Compact-5/CNC lathe has three chucks -- a 1/8" Albrecht, a 1/4" Albrecht, and a 3/8" Rohm, which is a good clone of the Albrecht.
    A worn Albrecht with a large bit can self-tighten to the point where you need a strap wrench to loosen it.
    Enjoy,         DoN.
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"Drill bits are probably good to a thousandth. Dowel pins are cheap and very accurate.
The better Jacobs chucks are worth it on a milling machine, probably not on a cheap drill press. Twist drills are flexible anyway and center themselves on the punch mark, so runout in the chuck doesn't matter all that much.
The one Enco keyless chuck I have is pretty good, too, although it's on the tailstock of my lathe where I can't quickly measure the runout. For small holes they are handier than keyed chucks, for larger ones they have a problem with slipping.
A good chuck isn't really wasted on the drill press, you can move it to a better machine later."
***I was thinking along the same lines. I have actually found a real Jacobs chuck in my possession. I think it is this one:
http://www.jacobschuck.com/images/products/JC-003%20Multicraft%20Series%20No%20Crops.pdf
Cost less than $20, but the specs are about the same I am getting now. And it is, of course, smaller. It was just an interesting exercise.
BTW what TIR would you expect on a, say, 3-inch 3-jaw chuck in a lathe? What sort of improvement do you expect going to 4-jaw chuck? When you are mounting a chuck, are most of the mounts self-centering (The Advanced Machine Work says they just screw on to the spindle but that is surely not the case in every instance)? Can you center the chuck by using the indicator on the periphery of the chuck or do you need to chuck something demonstrably round and center on that?
--
Michael Koblic,
Campbell River, BC
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    [ ... ]

http://www.jacobschuck.com/images/products/JC-003%20Multicraft%20Series%20No%20Crops.pdf
    I note that those are chucks with threaded mounts, not Jacobs Taper mounts. I don't expect as good a runout on the threaded back chucks.

    That depends on who made the chuck, how old it is, and how it has been cared for.
    For the 3-jaw for my Emco-Maier Compact-5/CNC (which I bought new) I would expect less than 0.001" runout at the present stage in its life -- assuming the jaws were clean before clamping on the workpiece. This was made in Austria, and mounts to a flat spindle nose with through bolts clamping it to the spindle. The mounting surface is a surface ground plate inside the back of the chuck.
    For a cheap Chinese one, still new, perhaps 0.003" (more for a larger chuck).

    What kind of patience do you have? How much resolution on the indicator being used to center the workpiece? How good a finish on the workpiece? Assuming a ground finish on a dowel pin, and a tenths reading indicator I would expect perhaps to be able to tune to 0.0001" -- if I had the patience at that particular time.
    With a rougher finish on the workpiece, it would get in the way of measuring, and result in poorer concentricity.

    The lathes which I have which currently have a threaded spindle nose are the Unimat SL-1000, the Taig, and the Atlas-Clausing 6x18" which I no longer use.
    I've described the Emco-Maier above -- with the exception of forgetting to mention that the OD of the spindle nose is cylindrical, and slides into a pocket on the back of the chuck. This gives quite repeatable concentricity.
    The 12x24" Clausing came with a 2-1/4x8 threaded spindle nose, but I fairly soon replaced it with a L-00 (long taper) spindle nose which is quite self centering.

    You can't depend on the chuck's body to be concentric with its grip. On a good one, it will be fairly close, but what really matters is the faces of the jaws, not the OD of the chuck. There is not even a certainty that the register turning inside the back of the chuck is truly concentric with the OD of the chuck -- but it *should* be concentric with the grip of the jaws.

    Yes -- and if you are checking the chuck, you need to check multiple diameters of workpiece, because the centering of the jaws will be controlled by imperfections in the thread of the scroll plate.
    In a chuck with three sockets for the chuck key, one of them *should* be (but is not always) be marked with a stamped "0" or something similar to indicate the one which gives the best centering. (Yes, it does make a difference which key socket you use to tighten it. Those others are convenient for releasing the workpiece when it is finished, but should not be used for the final stages of tightening.
    Note that there are chucks available with a feature called "set-tru" by one manufacturer, and lots of other (trademarked) names by others. The chuck body is mounted to the backplate by screws which are accessible from the front, and there are four radial screws near the back which bear on a projection from the backplate. These screws can be used like a 4-jaw chuck to adjust so a single diameter of workpiece runs true in the jaws. Other diameters are a different thing, and if you care about them you'll have to re-adjust at the different diameter.
    Also -- you can use two-piece jaws in your larger chucks, and bolt soft jaws onto the master jaws and turn them to perfectly fit your workpiece for precise centering of that one diameter -- and while about it to provide a step to set how deep into the chuck the workpiece sits for predictable facing to length. (Actually, the little Taig comes with two-piece jaws, with the soft jaws being made of aluminum.) I have soft jaws for many (but not all) of my lathe chucks.
    Enjoy,         DoN.
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Thank you. I just knew it was going to be simple...:-)
So the bottom line is you need a set of perfect cylinders of varying diameters to get your chuck right on. This made perfect common sense to me but oddly enough I could not find any reference to this in any literature I perused. Are such sets being sold for this very purpose?
--
Michael Koblic,
Campbell River, BC
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You are asking the wrong questions. The blank doesn't have to be accurately centered in the chuck. As long as it is large enough to clean up all the way around the cutting tool will generate a true concentric cylinder. When you plan the job, assume that you will lose some concentricity if you remove the work from the chuck no matter what type of chuck the lathe has, even collets. If you need to remove and replace it, turn it between centers.
Otherwise turn all surfaces that -must- be concentric at one chucking. Plan how you will chuck it when reversed to turn the other end, and if necessary leave extra material with enough room to hold it in a 4-jaw and indicate it true enough.
You can rough the part close to size all over in a 3-jaw chuck, hone the tool and finish the non-critical surfaces, then change to another more accurate setup and dial it in carefully to finish the critical dimensions without unclamping it.
Here's a good example. I just made a 17mm mandrel with center holes to fit the 6203Z bearings in the HF 1 Ton I-beam trolley so I could turn down the rollers to fit into 3 [ 5 channel iron. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber392
I chucked the rollers by the outer rim in a 3-jaw to rough them close to size, then put them on the mandrel between centers and drove them with a hose clamp to finish the rolling surfaces true with the bores of the bearings. They were out about 0.020" - 0.035" from the first chucking, mostly because the outer rims weren't machined true with the bearing recess. I suspect the castings were machined on the two sides in two different operations.
The 3-jaw is a new Bison Set-Tru good within about 0.001". I don't know how they hold up in production but for hobby use it's a very good chuck.
The roughing setup was solid and I could cut 0.025" deep without chatter from that particular round-nosed HSS bit. The finish setup was rather fragile, driven by a long 1/4" bolt pushing the hose clamp screw, and only allowed 0.005" per pass. This is typical of ad hoc faceplate driving schemes, so plan ahead.
When I spin the rollers only the rim that was about 0.035" off wobbles visibly. The ~ 0.020" ones look OK. That should give you an idea of how much accuracy you really need for art work.
As for the perfect setting cylinders, just use the part itself. Turn the end slightly oversize with a good finish, reverse it and adjust it to run true. Once you have a lathe the paradigm shifts from buying to making the parts you need.
Jim Wilkins
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    [ ... ]

    Not exactly -- you need them to see how much the off-center behavior *varies* with diameter. You aren't going to find a 3-jaw (or a universal 4-jaw or 6-jaw) chuck which is truly on center at all diameters -- though if it has the adjust-tru feature, you can make it very close at any given diameter, while it is off a bit more at other diameters until you re-adjust it. Think of zeroing an adjust-tru for a given diameter as similar to zeroing a 4-jaw chuck. That can be pretty good for more workpieces of the same diameter, but worse than useless for other diameters until you re-adjust it.

    That is because it is not a permanent fix -- just a way of checking how bad things are to decide whether it is time to purchase a new chuck.
    Note that if you check at a number of diameters (perhaps those which cover a range representing one full turn of the scroll plate in the back of the chuck) and find out that you have close to the same runout through the range of testing, and much more runout than the range which you measure from min to max, you can perhaps improve things by grinding the tips of the hard jaws while the chuck is closed on some spacers between the faces of the jaws) using a toolpost grinder. (Be sure to protect the bed and ways from the grinding grit while you do this.) This won't be perfect, but it will deal with worn jaw tips and make things significantly better.

    Not as such -- for the reasons suggested above. But if you want a set which could be used for such testing -- consider buying an index of hardened and ground drill blanks. (They are also called "reamer blanks". Here is an example at MSC's web site.
    <http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO 44515&PMT4NOQ073658>
It is on page 64 of their current "Big Book" catalog, if you have that. Be warned that they are expensive.
    O.K. I've found a set:
    <http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO80286&PMT4NOQ074150>
for only $29.52. That is metric sizes, nine of them from 1mm to 6mm by 0.5mm steps. That makes the biggest just a little under 1/4" which might be too small to cover the full range of a scroll plate rotation. Pull a jaw, and measure from the start of one tooth to the start of the next tooth. This is the range of sizes which you will need. You'll probably need a fractional inch set, which is noticeably more expensive.
Try: <http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO76488&PMT4NOQ074150>
    $135.49 import quality MSC part number 01105295
    1/16" to 1/2" by 1/64" steps.
    But you probably don't really need to do this. Just learn to live with your 3-jaw chuck, or get a 4-jaw and learn to set it properly when (and only when) you need the accuracy.
    Enjoy,         DoN.
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wrote:
<big snip>

Thank you Don and Jim.
In my case it is more about understanding the concepts than about immediate practical application. I am getting a better grasp.
One final question: Grinding - does it damage a chuck or is it mainly the ways and the bed you have to be careful about? I was thinking it was almost inevitable for the grinding dust to get inside the chuck and causing mischief there. I am talking about grinding things clamped in the chuck rather than doing the chuck itself as Don suggested.
--
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Campbell River, BC
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wrote:

Aluminum foil, newspaper and masking tape, vaseline and motor oil are your friends if you grind in a lathe. The grit can get anywhere, including the chuck.
I make temporary vacuum devices out of gallon milk bottles cut with a pocketknife to fit over the wheel and the work as much as possible. Then I tape the opening to a vacuum cleaner hose. It helps a lot. But I still use aluminum foil, vaseline, and newspaper soaked in motor oil.
-- Ed Huntress
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    Good! :-)

    O.K.
    Yes -- the grit can damage the chuck too. If you can, wrap newspaper (or plastic sheeting) around it and tape to the workpiece and the chuck body behind the jaws (and ideally covering the sockets for the chuck key as well. Better, if you can, is to turn between centers for the grinding, as it allows greater precision of removing and replacing the workpiece. Since you would normally be grinding something which has been hardened after turning, you will need to remove and replace the workpiece. (And turn it a little oversized, as it can grow slightly in the hardening -- maybe 0.001" per inch of diameter.)
    If you have been truing the hardened (not soft) chuck jaws by grinding, plan to strip the chuck down completely, wash it out with kerosene or some similar solvent, blow out with compressed air (if you have that available), and then relube as you reassemble. If you leave the grit in there, it will both grind the teeth (interrupted threads) in the jaws, the threads in the scroll plate, and the fit of the jaws to the body, resulting in looser jaws which will introduce greater error when chucking.
    Probably the more significant reason to grind true the chuck jaws is for jaws which have developed "bellmouth" -- that is they grip firmly at the back, but are worn near the front allowing the workpiece to tilt in the chuck under turning forces. This is typically only found in very well used chucks.
    As has already been mentioned, usually a little runout is no problem, because you are turning off the skin of the original stock anyway so everything turned in a single setup should be concentric. If you expect to reverse the workpiece in the chuck after this stage, perhaps you want soft jaws turned to precisely receive the reversed piece, which should give you better concentricity.
    Enjoy,         DoN.
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Opinions vary on lathe grinding. The dealer I bought mine from warned never to grind on it because it has hardened ways. I haven't need to anyway because I bought new chucks for it and have another small lathe that is easily disassembled for thorough cleaning, plus a surface grinder with a tool grinding swivel table. The small lathe and the surface grinder each cost less than a new chuck.
Ground shafting is easy to find cheap or surplus if you can adapt to whatever diameter you find. Old dot-matrix printers have some and you can salvage it from hydraulic cylinders or car shock absorbers. In my experience hydraulic cylinder rods are good steel that turns and threads well once the chrome has been removed with a carbide bit.
If you need to improve on a lathe-turned finish you can lap it with fine loose abrasive like Clover compound in a home-made cast lead lap. This doesn't spread abrasive grit all over like dry grinding with a high speed wheel.
I've been able to finish bearing surfaces to a few ten-thousandths and a near mirror polish with fine single-cut files and black SiC sandpaper, using the tool marks as a guide to file evenly.
Jim Wilkins
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wrote:

Hard or soft, grinding grit is hell on the ways of a lathe, and anything else it gets into. Old timers avoided grinding on a good lathe if at all possible, because even the best precautions sometimes let you down. That grit wants to get everywhere.

Hand lapping is becoming a lost art. There are lots of lapping tools and tips available in the really old books and the MAP booklets from the UK. They really ought to be re-promoted for hobby machinists, because lapping is easy and versatile, and it can save a lathe if the alternative is grinding.
However, it's important to keep in mind what lapping will and will not do. It can produce better roundness than grinding. But it does not improve concentricity. In other words, a lapped shaft may measure excellent roundness but the concentricity at one spot may not agree with that 1/2 inch further along the shaft. Another way to look at it is that the center of the lapped shaft at any point may not be in line with the center at another point. Lapping tends to follow the mean center of the shaft, at any given point. If you start with a badly turned shaft you'll wind up with a badly lapped shaft, even if you have a mirror finish and the roundness at any point is near perfect.
In practice, this hardly matters. The differences are on the order of a few millionths of an inch, if you use good technique throughout. But it could matter in extreme circumstances.
-- Ed Huntress
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Filing and sanding can also degrade roundness and add a taper, but they are quick and easy, all you need is a good "hand" or "pillar" file. That's why I mentioned using the remaining tool marks as a guide. You don't need to try to leave them, cut as close to size as you can, filing shouldn't take off more than a few ten-thousandths and sanding is barely measurable. At the hobbyist level a few remaining fine marks don't harm a bearing surface. They may even help by carrying oil.
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Don't count on drill bits as gages, Jim. They're tapered, as much as 0.003" toward the butt end. That's true of even the highest quality ones.
Put a mike on a few bits to see.
-- Ed Huntress
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I should have written -round- to a thousandth, for indicating runout. The dowel pins are -accurate- to perhaps 0.0002".
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