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Thread: Turret Troubles

  1. #1
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    Default Turret Troubles

    A while back I picked up on Ebay a turret to suit my 9 inch Hercus. Bruce "Abratool" mentioned that he had acquired one for his 260 Hercus, in Joe Hovel's buried treasure thread. Others may also be familiar with these accessories and their fine tuning on this forum. One issue that I have concerns the sping loaded detent that indexes the turret. The detent occupies a slot in the casting along with a screw adjusted gib. The adjustment of the gib is tricky. To positively lock the turret in place without any rotation requires very fine adjustment of the screws. A tiny bit too tight prevents the movement of the detent. A fraction loose enables the turret to rotate maybe 1 degree.

    I don't kow if the latter 260 turret had the same detent and gib setup. I am interested to find out if anyone else has encountered this sensitivity.

    The other issue I have is the non alignment of the tool holder bores with the lathe spindle centreline. The bores are presently 3/4" in diameter. I would need to rebore the holes to maybe 13/16 to rectify the problem. My intention would be to use a boring head mounted in the lathe spindle.

    Has anyone done this and if so, how did they go about it?

    Bob.


  2. #2
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    Hi BT,

    I'm not sure I can be much help to you, nice looking turret however.

    The only thing I can think of to fix your problem (without major surgery) is to install a stronger spring. Lock up the gib to the degree of tighteness that stops the unwanted rotation, and then see how much force is required to move the pin.

    I would have thought the adjustment screws on the front edge would allow you to adjust the tool holder bore to align with spindle center.

    Regards
    Ray

  3. #3
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    Hello Ray,

    The six screws are for the main slide gib adjustment. There is no provision for realignment of the turret bore centrelines other than remachining. If the attachment was sold separately and not factory fitted, the bores were undersize, allowing for insitu boring on the lathe it was to be used on.

    That shiny spring is a longer than standard replacement.

    Bob.

  4. #4
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    Hi BT,

    If you can't make the spring stronger to overcome the friction, then maybe you can reduce the friction with some well placed ball bearings or rollers. That would involve making a new gib however...

    Regards
    Ray

  5. #5
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    Or how about a ball or needle thrust bearing under the nut? I put one on my shaper vise screw and it made quite a difference to the handle force required. I know it's a different situation but my feeling is that it largely isolated the axial and rotational forces.

  6. #6
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    Default

    BT, is the plunger worn on the non-gib side? As I understand it, the plunger goes into the turret tightly, but is loose in its slot without gib ultra-tuning?

    Can you blue the gib and plunger to see what kind of contact they have? This might be a case of a poor bearing making gradual adjustment impossible.

    GQ

    ** My only tool in use this week is my scraper, hence all of my problems look that way ;-)
    It's all part of the service here at The House of Pain™

  7. #7
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    I had fooled around with the adjustment of the turret stud locknuts on the weekend. Overtightening them appeared to have the effect of removing the rotational play. An illusion in reality. I just slipped up to the shed for another look. The overtightening just makes it diffucult to turn the turret. I can turn it using the leverage of the handle but not by holding the turret and twisting. That tight and any play going to look like it has disappeared

    GQ, the attachment appeared to have had little use when I bought it. There could be wear that was not apparent. I will daub a little bearing blue on the sliding parts and report my findings.

    Bob.

  8. #8
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    Bob I guess the fit is the most important thing. But just in case I wasn't clear, by nut I meant the locking handle. Looking again at your pics I don't know if you would find one (a thrust bearing) the right shape & size.

  9. #9
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    Bryan,

    Not much force is required when tightening the handle to lock the turret rigidly in place. My problem seems to be with the detent and gib.

    Bob.

  10. #10
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    Bob I have no clue regarding the gib, but with the bore misalignement I take it that's because it's been taken off another lathe? Are the bores low or high? Rather than reboring them oversize (and maybe inserting bushings to bring back to size), I was wondering if you could either shim or scrape some other component of the turret to bring the centrelines back on axis? I had a mismatched tailstock that I shimmed up this way. There is quite a lot of information on realigning tailstocks on the net if that's of help.

    Pete

  11. #11
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    Hi BT,

    Just a question, in the picture of the turret lock, it shows the detent fully inserted into the slot



    The other picture showing the detent, it has a bevelled end, producing a wedge type locking action. The picture above the wedge is fully inserted.

    Ok, now the question, is it possible that the detent isn't fully engaging the slot when fully extended? and leaving enough play for the turret to rotate slightly..

    I hope I'm explaining that clearly enough.. to my mind, the little bit of side play in the detent and gib, would be irrelevant if the detent wasn't going in far enough.

    Regards
    Ray

  12. #12
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    Ray,

    I understand exactly. I think some careful blueing should reveal the depth of detent engagement. As you point out, if the detent is not properly seated, the turret will rotate.


    Pete,

    When I purchased the turret, it sat 15 thou too high. I machined a corresponding amount off the bottom face of the turret. A problem with reboring the the tool sockets is that the cotters will require remaching to suit the over size bore. I will have to make a jig to facilitate that task.

    (An aside. The tailstock of Hercus lathe No.1 is mounted on lathe No. 2. I used a selection of brass shim material to raise the tailstock the match the No.2 centreline.)

    Thank you both for your suggestions.

    Bob.

  13. #13
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    Sorry Bob, I don't quite understand. In your first post you mentioned that the bores didn't align with the headstock spindle. Presumably because of that you machined 15 thou off (that was lucky in it being high rather than needing to shim!). Having done that, does it still not align with the headstock?

    Pete

  14. #14
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    Pete,

    The bores are ever so slightly rotated out of alignment on the vertical axis. There should have been clarity in my initial post. I'm starting to slip up all too often! Even my spelling is flawed.

    Hopefully I'll sharpen up.

    BT

  15. #15
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    Quote Originally Posted by Anorak Bob View Post
    Pete,

    The bores are ever so slightly rotated out of alignment on the vertical axis. There should have been clarity in my initial post. I'm starting to slip up all too often! Even my spelling is flawed.

    Hopefully I'll sharpen up.

    BT
    Ok, I think I understand now. So when they're indexed the bore is angled slightly up or down? If that's the case is it possible to scrape the surface you machined to tilt the bores back to alignment? ie if the bore was tilted down, then scrape the rear of the surface to tilt it back up etc.

    Pete

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