If I remove a chuck or faceplate with a work in progress attached, when it is returned to the spindle, should it return to center just as when it was removed? My chuck & faceplates do not come back to center when I do this. They do remain square to the centerline. It appears that the only features of the spindle, chuck, & faceplate which would maintain centering are the threads of the parts. Do lathes other than mine have other provisions for returning parts to their original relationship to the spindle center? Incidentally, the chuck tightens against the end of the spindle; the faceplates tighten to a face at the base of the spindle. The workpieces have not come loose or shifted on the faceplate or in the chuck; that is certain.
Thanxx in advance for your input.
Cadiddlehopper
Edited 2/10/2007 5:13 pm ET by cadiddlehopper
Replies
Yes, I would be not best pleased if the hardware did not line up in that situation. However, are you saying that the relationship measured from a fixed point off the Lathe has changed, in other words if you set up beside the centreline of the workpiece but not attached to the Lathe something which will not accidentally move, using a sticky label on which you can make a dot and then measuring the distance from that dot to the centre of your work a few times between dismounting and remounting the assembly, then you will know if there is movement in the headstock assembly.
Of course I do not know your Lathe, but try using a leather or fibre washer between the metal contact points. This will enable the threads themselves over the whole of their length to register the parts and that may solve the problem.
Use the tool rest as a guide for making a mark on the centers, face plate, workpiece and chuck to register everything. Anything that can be adjusted or moved so they all line up needs to be marked.
Also to mufti.
Perhaps I was not totally clear. Here is the situation: a chuck or faceplate is threaded off the lathe spindle with a work piece attached to it. When the faceplate or chuck is threaded back onto the lathe spindle, the work piece is off center. No amount of measuring, etc., can compensate for this inaccuracy. Is this inherent in the design of wood lathes? I have a small metal lathe whose chucks have surfaces which align them to the spindle center every time. The chucks can be removed & installed a dozen times with no loss of centering. Why is this not true with my wood lathe?Apologies for the lack of clarity.Cadiddlehopper
Edited 2/10/2007 5:22 pm ET by cadiddlehopper
There should not be any trouble with removing and relacing faceplates or chucks and returning to exact centre.The problem is either worn threads on the lathe(unlikely) or that the backregister is not making full contact with either the chuck or faceplate.Lathes rely on the accuracy of the fit to the backregister for alignment rather than sloppy threads.However if the thread on the mandrel is bent you might well have problems with the registration.However a little careful observation should determine which of these it is
"Lathes rely on the accuracy of the fit to the backregister for alignment" is exactly as I thought it should be. Since you assure me that it is so, I shall check out how well these features fit to each other. However, as I stated, the chuck does not fit the back. It fits to the front of the spindle. It may actually work better. I have been adding a spacer so that it fits to the back. Perhaps I should not do that.Thanxx again.Cadiddlehopper
Clem, not to be a wise guy but I had this problem and it was dirty morse tapers, clean them up lube them, then I cleaned all threads from the power head out, replaces the teflon washer and all is square. Paddy
Paddy and Philip:The only Morse taper is internal and there is no teflon washer. The threads, etc., are hospital clean. We are having such a deep cold spell that I have trouble handling metal parts in my shop, but when the weather breaks, I will do some precision measuring. My lathe is a Grizzly about 10 years old. One faceplate came with it. I bought the chuck and another faceplate later from Grizzly. I sort of believe that Grizzly overlooked the necessity of matching bores and tapers from spindle to accessories. Many of the older Asian machines came with serious oversights such as this built right in. Thanxx for your interest.Cadiddlehopper
Clem, just a thought that might get you down to the base measure(I could be wrong but worth a try).
Clear the power head and tail stock of all fixtures, clean the MT's (I know you did) insert two fixed MT centers or a live center that you trust and run them nose to nose and see what you have. BTW as Ed McMahon used to say to Johnny Carson "HOW COLD IS IT?*" do you think that it has a bearing on the problem?
* Colder than a brass monkey's "nose" in the straits of Greenland in February.
Paddy, Steve, and ALL:Please read post #11 if you haven't. I believe that the source of my problem is now well known. I really wanted to know if other lathe users had a similar problem. Apparently they do not. I don't know if I can do anything to alleviate it either, unless a new lathe is acquired. I will be asking in person in Springfield eventually.When beginning a turning project, one of my first actions is to align the spindle and tailstock centers. This really does not matter with the faceplate turnings since the tailstock is not being used at the time. The faceplates and chuck do not engage a Morse taper. I am not turning green wood and the part does not slip on the faceplate nor in the chuck. I have encountered distortion due to humidity changes and stress release in the part on occasion, but it is small. The time between removal and reinstallation varies from a few minutes to several days. By releasing and retightening several times, the magnitude of eccentricity can reduced or increased as luck would have it, but it is not under my control. As to how cold it is: I was doing the current project with its problems before it turned cold. To a Minnesotan, it is only mild: the low twenties (F) at night, about 40 daytime.Thanxx again for the interest.Cadiddlehopper
Caddy, the work of the spindle threads is to draw the screwed on fitting (faceplate, chuck etc) onto an accurately machined shoulder on the spindle-which is the crucial item to register against. The threads need to be absolutely clean-grit that you may not see can accumulate in the thread roots and at the meeting shoulders- the chuck or faceplate will not screw on all the way and be out of true.
The spindle nose is not meant to meet any corresponding face in the bottom of the chuck or faceplate in average lathes-this is only for precision stuff.
I suggest you clean all threads with a wire brush and wash out with penetrating oil, especially the beginning of internal threads and the ends of externals. Clean the shoulder on the spindle with steel wool or 400 grit paper just enough to have a uniform shine.
It sounds as if your chuck may have been fitted with a spacer- measure the depth accurately and compare this with length of the spindle from nose end to shoulder-it should be less than the threaded depth of the chuck.
Caddy,
"Incidentally, the chuck tightens against the end of the spindle; the faceplates tighten to a face at the base of the spindle."
The chuck is not as it should be: it is ussual for chucks to register against the spindle shoulder.You may have to have an accurate spacer to get it running true.Naughty Grizzily....
Philip and ALL:I measured spindle and bores with only a dial caliper. I did not want to fight with cold micrometers and bore gauges. The base of the spindle is the same diameter as the major diameter of the threaded shank. There is no precision step or taper for centering. The chuck has no counterbore at the thread entrance. One faceplate bore clears the spindle diameter by ~.013", the other by ~.033". Philip is correct when he writes "naughty Grizzly." I'll be discussing the problem in Springfield several months from now. The consolation is that it did not cost a great deal. However, I did expect something a little better. Thanxx ALL.Cadiddlehopper
You didn't say what the interval was between removal and replacement. While the workpiece may not have loosened wood it could have changed its shape. Turning often unleases internal stresses that can distort the shape, giving the appearance that the faceplace is no longer centered after even an overnight hiatus.
I suddenly remembered(senior moment or BSE must have kicked in ) that the lathe I keep in the UK has a one and a half inch dia 6 tpi thread .that is used by another maker as well but I have to be careful about ordering anything that threads on the spindle as the back register is different.Consequently the wrong one would not seat on the register.So far it hasn't happened as the chuck manufacturer called me with that question.
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