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  1. #16
    Join Date
    Apr 2009
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    Update:
    The first photo shows the spindle mounted between centres on my lathe.
    The chuck register end has a MT3 with a soft end provided with a centre, purchased from Arc Eurotrade in the UK.
    The gear end has a purpose made cathead with 3 x M6 cap screws.
    The DTI is 0.01 mm / div, I can easily detect less than 1/4 div by pressing on the spindle.
    The DTI probe was placed on the chuck thread register, undamaged parts of each of the two bearings, and the middle of the pulley mount area.
    Spindle rotation produced no visible movement of the pointer, say less than 1/4 of 0.01 mm - good enough.

    A separate drive dog was made to clamp on the gear teeth form.

    The second photo shows the spindle as ground.
    A typical poor photo from me, but the finish is excellent.
    I did not track the amount of metal removed as I kept going until a good uniform finish was obtained.
    At the gear end, some was taken off the tooth tips.
    Sizes are now 45.98 and 34.64 mm.
    My conversion says these are 1.810 and 1.364 inches.

    As I will have to make the thrust nut, a suggestion was made that I make two - one for final assembly and one to be loaded with lapping paste to clean up all the burrs on the thread so that the bearing shell will slip over without problems.

    Tonight I will do another trial fit of the headstock on the horizontal borer to review the alignment suggestions received.

    John

  2. #17
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    I have done a trial set-up of the headstock on the borer table and done a very light cut just to prove it.

    Alignment was a 12 mm bar clamped to the table and clocked off the boring bar with table movement.
    The headstock V then mounted on the bar and the flat mounting surface shimmed up 8.135 mm to get the headstock flat and parallel.
    (The 8.135 comes from the 12 bar engaged in a 0.5 inch wide 90 degree V)

    The suggestion was made that the spindle centre height from the headstock mounting surface should match that defined by Hercus for a Model 9, just for possible future compatibility.
    But, I do not know what that height is.
    Something like 4.625 inches perhaps.

    Can anyone advise exactly what the centre height is from the headstock mounting surface ?

    Happy machining,
    John.

  3. #18
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    Jun 2007
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    You maybe hard pressed for someone to give you an exact size,due to bed wear.
    I set my tools to 4&5/8".,this could be a few thou out due to wear.

  4. #19
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    Kingswood
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    Thanks pipeclay.
    I will bore at 4 5/8 inches minus 0.010 inches (0.25 mm) to ensure any possible future use has the error such as to allow machining of the tailstock to remove the error.

    John

  5. #20
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    Apr 2009
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    Kingswood
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    Photo below shows the headstock bored.
    Bored sizes will require bearings a bit more than 2 mm thick.
    In front of the headstock is a simple tool setting jig that worked quite well, allowing small increments in tool position to be made with relative ease.
    The bores are set back to miss the clamp bolts and at about 4.62 inches above the mounting surface.
    The eagle-eyed will observe chattering marks, not really a problem at this stage because the bearings will be glued in position.

    Lessons learned:
    Tool setting is critical, and the jig could be improved.
    Chattering is very difficult to avoid and tests will have to be conducted to optimize tool shape.
    The machine needs maintenance to enable the outboard bearing, frozen in place by years of neglect, to be moved closer to the job to help reduce chatter.
    Measuring bore size on the machine is near impossible - need some inspiration to overcome this.

    John

  6. #21
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    Apr 2009
    Location
    Kingswood
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    I have made the two Bronze (LG2) bushes and planning to thoroughly clean the headstock and paint it before gluing in the bushes.

    A couple of aspects prior to gluing not resolved:
    - clamp/not clamp the headstock bearing adjustment bolts,
    - slit/not slit the bushes.

    The headstock was bored with the original, tight fitting, shims in place.
    I don't want to glue the bolt or shims when the bushes go in.

    Not slitting the bushes prior to line boring the bushes helps the rigidity aspects.

    Perhaps best to glue without slits, bolts or shims.
    Then bore with bolts and shims, with shims adjusted to fit the post-glue situation.
    Then slit the bushes.
    Suggestions welcomed.


    I have already started the Sheraton bearing rebuild and ground the chuck end spindle surface the minimum amount to get clean metal, about 0.4 mm diameter (yes, the gouges were that deep).
    The back bearing surface was judged OK to re-use.
    The Cathead used this time to establish a centre at the gear end of the spindle was longer and fitted with two circles of 4 screws, much easier to adjust.

    The photo shows TIR being measured on the Sheraton spindle, the Hercus spindle was done exactly the same way.
    Both spindles have 0.01 mm TIR.
    Exhaustive checks seem to indicate the MT3 soft arbour used for cylindrical grinding contributes most of the error.
    I have reviewed my Bantam lathe set-up with a MT4/MT3 adapter sleeve, and I do not believe I could re-machine the centre any better than that.

    I propose to leave the spindles at 0.01 mm TIR, 0.4 thou.

    John

  7. #22
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    Have you considered what might happen if you slit the bush after machining.
    If you have no intention of useing the shims you maybe better off to clamp the bushes in place with the hold down bolt and the line bore.Once finish bored leave it alone,if the ores ever wear just remachine new bushes.
    Or if you slit the bushes and use the shims you will be able to adjust if needed latter.
    Dosent matter here to much but your indicated figures are showing .01mm and .400",could be a problem with someone trying to interpret drawings or notes at a latter date.

  8. #23
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    Apr 2009
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    pipeclay,

    I am concerned about what happens when slitting the bushes post boring.
    The saw would be the same thickness as the existing shim gap.
    Slitting should not put any significant force on the glued bush but, at separation, the rigidity will change significantly.

    I was attempting to leave the arrangement the same as original, adjustable bearings with selectable shims.

    I am not super-confident about getting exact bore size when line boring.
    I was intending to make circular ring Go/Nogo gauges that are slipped onto the boring bar prior to boring.
    The rings can be used to test the bore in-situ.
    I need to do this beacuse the horizontal boring machine is a bit of a problem with butchered adjustments etc and the drive end of the boring bar is clamped rigidly, and the outboard end runs in a parallel bush.
    No way can I extract the bar for measurements and replace it with repeat accuracy.

    Perhaps:
    - slit the bushes before gluing,
    - glue without bolts or shims,
    - fit bolts and shims,
    - line bore.

    The intermittent cut in bronze should not cause significant problems.
    The final job would be to make a V-scraper to apply bevelled edges to the slots in the bushes.

    I don't quite understand what you mean by " interpret drawings".
    I read your .400" as actually 0.0004".

    John.

  9. #24
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    I would be thinking seriously of either splitting prior to boreing or if not just leave as a solid bush.

    If you leave the bushes solid I would look at an interference fit in the headstock bore.

    If you split after boreing there is the chance that they may spring open,making it harder to fit.

    In regards to the way you write your measurements,if you were to send those type of dimensions to someone they would be in contact to confirm what they mean ( .01mm does not equal .4").

  10. #25
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    Kingswood
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    The solid bush option does not sit easy with me.
    I have read the descriptions of shell crushing to get the final spindle fit, but it sounds a bit simplistic.

    The risk of shell opening after slitting should not be too significant as the CI housing is quite stiff.

    If you read my report on sizing, it reads " ... 0.4 thou. ", that is 0.4 of one thousandths of an inch.
    Perhaps the use of "thou" is no longer part of the vernacular.

    A suggestion today was to slit the bush, and soft solder before gluing.
    Post boring, the bush slit could be re-opened using a handsaw of some type.
    This avoids any stressful machining post boring.

    John

  11. #26
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    Are you planing on splitting the bush insitu?
    Reading early posts have you allready machined the OD of the bush?
    If by chance you have machined the OD of the bush I dont think it would be a good idea to sweat the slit.
    Normally when machining split bushes (I understand this is not the case here) you would apply a thin coating of solder to both halves and then sweat the 2 halves together,finish machine and then seperate giving 2 machined halves.
    Not sure of how you interpret dimensions but what you show is .400" not .0004".

  12. #27
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    Apr 2009
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    Kingswood
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    Yes, the original idea was to slit the bush after all machining to ensure the slit was in line with the opening in the housing.
    The bushes have been made as a correct fit for permanent Loctite.
    I note your comment on not slitting before gluing because of the risk of the bush changing size.
    I have no idea of the residual stresses that could be in continuous cast Bronze LG2.

    In the few areas of machining that I have come into contact with, mainly interface integration of American equipment with Australian and European equipment, the use of thousandths of an inch, commonly shortened to "thou" in discussions, was quite normal.
    I will not use "thou" in future.

    As an aside, I found it quite comical that design draftspersons in the US had no end of trouble trying to assimilate just how big a millimetre, or a metre, really was.
    The US may be slowly moving towards metrication for design, but the ordinary person has no idea.

    For reference:
    one thou = one thousandth inch = 0.001"
    0.4 thou = 0.4 of one thousandth = 0.0004".

  13. #28
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    Its a while since I last reported, but progress has been made.
    The Hercus bushes are glued into the headstock, see photo.

    In front are the two plug/ring gauges made to test the bore during boring.
    They will be strung on the bar prior to inserting it into the shells.

    You can see that I have glued the bushes, Loctite preparation 7471 and adhesive 609, without the clamp bolts.
    The bolts will be inserted and firmed up prior to boring.
    Still considering pipeclay's suggestions on not slotting.

    John
    Attached Images Attached Images

  14. #29
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    A mixed bag to report.
    I started to bore out the shells, but managed to oversize the start of the large bore with a bad tool set using the tool previously shown.
    I re-designed the tool set gauge and decided on a rigorous sequence for the boring.
    The new gauge worked a treat and the photo shows the new gauge and the end result.
    The flag on the new gauge allows me to add an engineers clamp to balance the gauge so that it does not fall off the boring bar.
    The large bore still has witness to the accident.

    The large ring gauge engages the large bore without shake, it is +0.04 mm on spindle size.
    The small ring gauge engages the small bore with the first size, exactly spindle size, but does not engage the +0.04 mm size.

    When I tried the spindle, the large end engages a bit too loose for liking, the small end will not enter.
    The problem could be simply burrs left on the thread remnants left after grinding the spindle.

    John
    Attached Images Attached Images

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