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  1. #271
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    Nov 2017
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    I’d have to have a look back a bit at your drawing, but don’t you need a bigger through hole anyway - for a spacer sleeve between inner bearings?

    Steve

  2. #272
    Join Date
    Sep 2012
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    York, North Yorkshire UK
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    Hi Steve,

    Yes that's true, the other end is going to be bored out as a mirror image of the first one. I suppose that 3 thou isn't going to make any real difference. I can clock either the bore or the outer and get one or the other true.

    I just didn't want the runout to cause me any future problem !

    Thanks.
    Best Regards:
    Baron J.

  3. #273
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    Sep 2012
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    York, North Yorkshire UK
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    Thumbs up Spindle machining !

    Hi Guys,

    I've machined one end of the spindle today, I found a length of hard chromed 1/2" diameter rod that is suitable for this job. I've turned it down to a shade under 12 mm for a distance of 80 mm, so the bearing just pushes on and slides down to the shoulder. I've also drilled and threaded the end to take an M6 cap screw to hold the wheel arbour.

    I'll do the other end after I have finished the spindle housing.

    27-04-2020-003.JPG 27-04-2020-001.JPG 27-04-2020-002.JPG

    This is the end of the spindle that I have machined and threaded. I started the tap in the lathe before taking the work out of the chuck and finished tapping it using a tapping handle and held it in the bench vise.

    I need to find some suitable material to make some spacers now so that I can install the bearings on the spindle. Somewhere kicking about I have some brass tube that might be OK for those.

    Thanks for looking Guys.
    Best Regards:
    Baron J.

  4. #274
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    Nov 2017
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    Quote Originally Posted by BaronJ View Post
    Hi Steve,

    Yes that's true, the other end is going to be bored out as a mirror image of the first one. I suppose that 3 thou isn't going to make any real difference. I can clock either the bore or the outer and get one or the other true.

    I just didn't want the runout to cause me any future problem !

    Thanks.
    Just clock the outer and since the bore is just clearance it becomes a non-issue.
    Thats my logical thinking and minimal experience talking though. YMMV

    Steve

  5. #275
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    Thumbs up Not forgotten !

    Hi Guys,

    Nothing really to add at the moment !

    I had discovered an issue with the jaws of the slim body Myford lathe chuck. The jaws after much measuring and checking have turned out not to have faces that are square to the chuck face or follow the line of the lathe bed.

    Whilst I have no difficulty in truing up the spindle body at the end it means that there is about 20 thou maximum offset at the chuck. So whilst I sort this problem out, the job is on hold.

    Sorting the problem out on what is basically a 40 year old unused chuck shouldn't be necessary. Turning the jaws round shows that the small end is actually almost perfectly true. The suggested way to sort this problem is to grind the jaws true insitu on the lathe using a toolpost grinder.


    17-05-2020-011.jpg 17-05-2020-010.jpg

    17-05-2020-012.jpg 17-05-2020-013.jpg

    These are pictures of the four jaws. I've stood them on a sheet of white copy paper so that the gap can be seen more easily. Using feeler gauges that gap varies between 5 and 20 thou.

    Before I start grinding them I am open to any advice or suggestions.

    Thanks for your understanding.
    Best Regards:
    Baron J.

  6. #276
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    574

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    Thats a tough one, I've seen videos on youtube where it was done with something like a Dremel on smaller chucks, Dremels don't have a great deal of reach and it might be a problem on larger chucks where you need a longer reach, I'm assuming it is 4 independent jaws which I have heard isn't as critical as a 3 jaw. Pity you don't have your spindle and motor assembly finished you might have been able to set that up for the job.

  7. #277
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    Sep 2012
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    York, North Yorkshire UK
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    Hi FamilyGuy,

    Thankyou for your post.

    At the moment a dremal grinder is all I've got ! I've spoken to a guy at 600 group who own PB and is going to come back to me at some point. In the meantime all I can do is wait.

    A friend of mine who is the foreman of an engineering company and has given me a great deal of help and advice has suggested that I can grind them myself without too much difficulty and has suggested a way of doing it. He said that he would be happy to grind them for me but because of this Covid19 issue that most of his staff are not in and they are pulled out with work that is late and wanted urgently.

    So I'm on Honey Do at the moment...
    Best Regards:
    Baron J.

  8. #278
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    Dec 2007
    Location
    Adelaide
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    As it is a 4 jaw and the jaws don't move in unison is it possible to tidy them up in the mill one jaw at a time, clamp the jaw to the mill table in the same position as shown in you photos and mount a grinding wheel in the spindle, you should have enough travel in the quill to traverse the full length of the jaw, as long as you are certain the the spindle if perfectly perpendicular to the table then the clamping surface of the jaw should turn out perpendicular as well, a thou or two at a time - it is doable, you'll need to run the spindle at full speed, I trued up the jaws of my chinese mill vice this way, using a small mounted stone, I have 3 phase VFD and the max spindle speed is 4K.
    I would though check something first (and maybe you have already done this) with reference to the photos of the jaws, I assume they are sitting on a surface plate, run a test indicator along the the groove that the jaw slides in and make sure it is parallel to the surface plate, on my 4 jaw it is that groove that is the reference for checking, just a thought.

  9. #279
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    Sep 2012
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    York, North Yorkshire UK
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    Hi FamilyGuy,

    Thanks for your suggestions.

    The way It was said that I could grind the jaws true was to do it in the chuck itself, one jaw at a time. Lock the chuck at 90 degrees to the bed and put two opposing jaws in, set the left hand jaw so that it was far enough past the bore so the grinding wheel could clear it. Then to use a clamp across the outside of the two jaws to hold them so they couldn't move.

    This makes a lot of sense because the jaws would then be true to the chuck and the lathe bed. I'll take some pictures of the set up later. At the moment some plastering and painting has to take priority

    Myford-150-mm-Chuck-Jaw.png
    A drawing of the chuck jaws.
    Best Regards:
    Baron J.

  10. #280
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    Sep 2012
    Location
    York, North Yorkshire UK
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    Thumbs up Grinding chuck jaws. Setup.

    Hi Guys,

    I'm not really sure if this shouldn't be in its own thread ! But here goes.

    These are pictures of the setting up to grind the four jaws of an independent four jaw chuck. It was discovered that the jaws on my Myford slim body chuck were tapered towards the back, and that the taper varied on each jaw. I've been in contact with Prat Burnard who are now owned by the 600 group. Someone is supposed to call be back to talk about the issue. Nothing heard for the moment.

    26-05-2020-001.jpg
    This first picture shows the complete set up as suggested by a friend as explained in a previous post. The block of wood under the chuck jaws is only used to set the jaws parallel to the bed and plays no other part.

    26-05-2020-002.jpg
    Once the chuck jaws have been levelled, the wooden wedge is used to lock the spindle and prevent it moving. I did try with engaging the lathe back gear but the chuck could still move a little, hence the wedge. Its now solid and cannot move at all.

    26-05-2020-003.jpg
    My toolpost grinder is a Dremal type grinding tool purchased from Lidl some time ago. As is the grinding stone that is in the collet. The whole thing is secured in the tool post by means of a threaded aluminium bracket and accurately set for centre height. Its also set at an angle of 3 degrees towards the jaw. So the grinding will be on the front edge of the stone. I'm assuming that this is correct and that if not someone will tell me.

    26-05-2020-004.jpg
    Here the grinder is being positioned so that the saddle it will hit the carriage stop without hitting the back of the chuck. Also the tool makers clamp is being used to prevent movement of the jaw being ground by pulling the jaws together against the jaw adjusting screws. The wood block now being removed.

    26-05-2020-005.jpg
    I've now got the chuck squared up to the lathe bed, the chuck locked so it can't move, and the jaws positioned and clamped so they can't move.

    26-05-2020-006.jpg
    Everything is now in position ready for me to start grinding.

    I've stopped at this point to await any advice or comments on this set up before I continue.

    Thanks Guys.
    Best Regards:
    Baron J.

  11. #281
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    Nov 2017
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    Geelong, Australia
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    Hi John,

    I've no personal experience, but have always understood the jaws needed to be loaded in the usual direction before grinding - ie need to be pushed out rather than pulled in like you have them set up there. Obviously easier said that done.
    That said, if the jaws are are a nice fit in the chuck body its probably not going to make much difference, and they will definitely end up better than what they are now!
    I also wonder whether clamping some soft copper or aluminium strip between the jaws afterwards could be used to assess how its come out. Theory being it would be soft enough that normal tightening of the jaws would leave an impression that could be visually checked to see if it was consistent front to back in the jaw.

    Steve

  12. #282
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    Sep 2012
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    York, North Yorkshire UK
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    Hi Steve, Guys,

    Thanks for your post.

    Since its a four jaw chuck it shouldn't matter as long as the jaw cannot migrate one way or the other. If it were a three jaw scroll chuck then I agree with you the jaws need to be tensioned in the direction of use. Actually the same applies to soft jaws. If boring them they need to be restrained on the outside at the approximate diameter that they are going to be used. A ring round the jaws works well for this purpose. Of course the opposite is needed if they are going to be used for inside work. I've seen a clover leaf plate made for this purpose.

    The whole point of the exercise is to get rid of the backwards taper and get the jaw face parallel with the bed.

    I'll post some more pictures when the job is done, then I will re-chuck the grinding spindle body and recheck everything.

    More later.
    Best Regards:
    Baron J.

  13. #283
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    Sep 2012
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    York, North Yorkshire UK
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    Hi Guys,

    Apparently the chuck jaws are ground with a 2 to 3 thou taper towards the back. This is done to allow for the tolerances in the jaw guides. The sort of measurements, 20 thou, that I was getting is far too much. However they can supply a set of new jaws if I have £175 +. I'm sure you all know what my reaction to that was.

    Any way I've just finished grinding mine and they are now done.

    I'll come back when I've checked them out.

    Thanks Guys.
    Best Regards:
    Baron J.

  14. #284
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    Nov 2017
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    My head still thinks that you're going to end up bell mouthed with clamping those jaws on the outside - and the manufacturer saying that the jaws are made with a slight taper to account for clearance in the jaw guides seems to support that.
    I think you're going to end up with that amount of taper going the other way on the jaws (ie more material off the outer end of the jaw), which will then compound into twice that once you load the jaws normally and take up the clearance in the guides.

    Hopefully you've ground them already and can practically say I'm talking through a hole in my tailstock

    Steve

  15. #285
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    Sep 2012
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    Hi Steve,

    Yes I have ground them already and I do agree with you. Fortunately the chuck is essentially new and wear free. The jaws as they were are unacceptable. However the good bit is I've re-chucked the grinding spindle body and there is now less than 2/10th mm difference between the chuck end and the far end 100 mm away.

    The sad thing is that the 3 thou run out that I had before is now more than 5 thou in the bore.

    Thanks Steve, your help is appreciated.
    Best Regards:
    Baron J.

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