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  1. #1
    Join Date
    Mar 2010
    Location
    UK
    Posts
    16

    Default help me work out if my spindle is 'true'?

    Hello!

    On my other post I was advised to get a dial gauge of sorts to see if there is any variation as I turn things around. Apparently i need such a thing for the small rings I'm making anyway, but I was advised to use it on the chuck/face plate.

    I must say, I'm a complete newbie to lathe work so excuse my ignorance!

    If I get a dial gauge, I can see the variations and if things are running true or not, I will have a measurement for that. However, how do i actually adjust things by a fraction of mm when they've mounted on the chuck? That's what's got me confused. To me, if I mount things correctly on the chuck, push it flat, it should run true. Having worked on it a bit, I've been able to get some jobs done.

    The jobs I have done have been with very thin rings of metal. When i mount anything that comes out further away from the chuck, it wobbles all over the place. For example I put the 'pin' out of the tailstock in the chuck and instead or turning on it's central point it drew a circle around, wobbling everywhere. This can't be right, can it?

    I took the chuck and faceplate off and took a look down the spindle. To my eye, it is not running true, you can physically see it appear to not run centrally. But i don't have any way of measuring it.

    It's a frustrating point. Because I can actually do most of the work I need to do with it, but if i ever want to turn a bar or work from rings from a solid rod I just can't see it being able to cope. It wasn't an inexpensive purchase for me. I realise it's not a great brand (Axminster Sieg C1) but i'd still like to know I'm getting what I can from it.

    Sorry for my rambling post.. Just not sure what to do :/

  2. #2
    Join Date
    Aug 2008
    Location
    Charlestown NSW
    Age
    65
    Posts
    1,669

    Default

    DJ

    A real good idea for you would be to look around and get hold of some trade school text books on machining. You should be able to get some used cheaply I would think.
    There is also some good info on the net.
    eg
    [ame=http://www.youtube.com/watch?v=2KMhx4DbyDg]YouTube - Easy centering 4 jaw chuck[/ame]

    In this vid he mentions a special clamp for the dial indicator. That is nice but not essential. A good indicator on a good mag base will do, as will just 1 chuck key. Setting up in a 4 jaw gets easier the more you do it. I'm assuming you are using a 4 Jaw chuck? If you want accurate setups you really need to use a 4 jaw.

    You mentioned looking inside the lathe spindle and it not running true. That would be right as all the spindles on the lathes I've used are just drilled through. It doesn't have to be super accurate on the inside except at the front where they usually have a taper machined in. This is for fitting a centre into the spindle. The rest of the hole is just so you can stick a long work piece through.

    regards
    bollie7

  3. #3
    Dave J Guest

    Default

    Hi,I see you haven't got it sorted yet.
    Do you have some pictures of your set up, we might be able to help more if you show us what your turning and the setup your using.
    Dave

  4. #4
    Join Date
    Oct 2007
    Location
    Alexandra Vic
    Age
    69
    Posts
    654

    Default

    Hi David, it seems that you are one the steep end of the learning curve at the moment.

    There are three general families of chuck for lathe use. These are collet (highly accurate), independant (can be accurate but depends on users job setting capability), and self centering (not overly accurate). Depending on manufacturer and price most lathes will will be supplied standard with a self centering chuck, some higher end ones will also come with an independant chuck as standard. Collet chucks and collets are almost always optional, if available.

    Self centering chucks have the jaws geared together by a scroll wheel in the chuck body so that the jaws move more or less in unison with each other. They come in 3 and 4 jaw versions but the standard ones supplied are normally 3 jaw.
    The primary difference is that 3 jaws work with rounds and hexagonal materials while the 4 jaws work with rounds, square and octagonal materials. Because the basic standard chuck supplied with with a machine is most likely to be a 3 jaw self centering unit, many people assume that refering to a 3 jaw chuck implies is a self centering one, but this is not exclusively so. Depending on build quality and hence price, self centering chucks can range from awfull to quite accurate, but generally lack the ability to cater for fine tuning the setup of a work piece.

    Independant chucks have the jaws positioned by individual worm screws adjusted by the user to position and grip the work. Therefore the user, their dial guage or other setup indicator, and their ability substantially control the accuracy of material setup in the lathe, The video above shows the setup procedure. I have come accross 2, 3, 4 and 6 jaw independant chucks, but the more common form is the 4 jaw version. Again, because of their predominance, many people assume that a reference to a 4 jaw chuck implies an independant one but this not exclusively so.

    If you buy a dial guage now, you can use it to help diagnose the faceplate/chuck issues that you are reporting, but it will not particularly help set your work up as you have a self centering chuck, and cannot adjust the jaws independantly to position the work more accurately. To get a more accurate setup, you would also need to move to an independant chuck.

    Re your comment about chucking the tailstock dead centre (pin) and the centre wobbling, this is an invalid test as for the C1 lathe which I believe you eventually purchased, this centre is machined with a 1 Morse Taper shank. Because the sides are not parallel, it will not directly chuck accurately in any form of jaw chuck, so centre wobble will occur.
    .
    The standard test for lathe alignment is to mount a length of material between headstock and tailstock centres and machine it over it's lengthwith uniform cuts, then compare the diameter at various points along its length. If the bed is perfectly straight and true and the headstock and tailstock are perfectly aligned, the measured diameter should be identical at all points along the length of the cut. An even taper indicates that the head and tail are out of allignment or the bed has a twist, while a non straight cut indicates that the bed is bowed. However this test is not viable for your machine as standard because it is not supplied with a headstock centre or a means to drive the workpiece.

    To check the spindle for runout, the usual method is to set a dial guage on the reference mounting faces for the chuck/faceplate, manually rotate the spindle and observe the runout on the guage. By locating the guage probe onto the ground surface of the spindle internal taper at various depths in the taper, the taper an also be checked.

    The faceplate can be checked near the rim and the centre in the areas free of slots, and then checked accross the balance of the face with a straightedge and feeler guages.

    It is difficult to check the chuck directly, but by chucking accurately machined material in the jaws and checking with the dial guage, you should be able to check the runout at various jaw positions, works for internal or externally gripped test pieces but beware of deflecting hollow material as you tighten the jaws, this will telegragh into the guage readings.

    Hope this long post helps a little.

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