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  1. #1
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    Apr 2009
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    Default BXY QCTP Height Setting Nut Out-of-square

    I recently purchased a BXY QCTP set plus extra holders from CDCO.
    The items supplied are generally OK, except the holder height setting nuts are not square to the thread.
    (Also an incorrect supply of too many boring bar holders (got the V). Anyone who wants to swap holders please PM me.)

    I knocked up a prototype proposed new nut with an extra 10 mm of thread below the original setting nut.
    I can do this because the subject lathe is a Harrison M250 with an unusually deep topslide, so the holders all set quite low down.

    I used a piece of scap MS, a Chinese drill size U (9.3 mm) and a Chinese taper tap in a tailstock holder to form the M10x1.0 mm thread by hand in the lathe.
    The result was spectacularly unacceptable - far too loose.

    My plan is to get some new 1214 bar, new quality drill, new quality taps (Bordo is common in Penrith/Windsor), and to power cut the thread in the lathe.
    My situation cannot be unique, others must have made nuts previously.

    Can any Forum Member confirm that standard taps provide an acceptable nut fit to the supplied holder M10x1.0 mm setting stud ?
    What size tapping drill ?
    What lathe speed and lubricant to cut the thread in 1214 ?

    John.

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  3. #2
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    Feb 2013
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    Laidley, SE Qld
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    Default

    The required drill is 9.0mm, I use Rocol RTD for tapping etc, others will use different products.

  4. #3
    Join Date
    Aug 2012
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    Australia
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    Default

    Quote Originally Posted by electrosteam View Post
    The result was spectacularly unacceptable - far too loose.

    new quality taps (Bordo is common in Penrith/Windsor), and to power cut the thread in the lathe.
    My situation cannot be unique, others must have made nuts previously.
    John.
    John, I do not have the answers to your questions. But one thing I would say is that Bordo are not "quality" taps, or at least quality in my eyes. I have only seen Carbon Steel Bordo taps and I have broken a bunch of them. Get HSS such as Goliath or Dormer.

    Loose threads is not all that uncommon. Even using a quality 3 tap (taper, intermediate, bottom) set I have seen some play. If you want a tight fit you could try drilling undersized, although that does not always work out well. I do know of a guaranteed tight fit - Time sert. If you use one you will have a very tight perfect thread. That said they are like all good things - expensive..

    Stuart might chime in here, as he knows a lot more than I do about thread depth and getting a good thread cut..

    PS: I also sometimes use Rocol, but most often Tap Magic.

  5. #4
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    Default

    Does it really matter if either the knurled height adjuster or locking nut are loose or not square.

    Once you have set the correct height and locked it in place with the locking nut it wont move.

    You will be able to remove and replace the holder and the centre height of the tool should remain the same.

    If you are using HSS tool then after re sharpening you would have to readjust your height anyway.

  6. #5
    Join Date
    Jul 2010
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    Melbourne
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    Quote Originally Posted by variant22 View Post
    Stuart might chime in here, as he knows a lot more than I do about thread depth and getting a good thread cut..
    If I'm the Stuart you're talking about I'm not so sure about that........... I didnt even fully understand the problem to start with

    I'm not sure what the problem is with the thread being "to loose".(a picture might help)

    Is the nut as loose on a good M10 bolt?

    I'm not sure a 9.0mm hole will help much..... but its certainly cheap enough to try.(until you break the tap lol)

    I dont think power cutting the thread is a good idea either.

    While the Chinese taps I have "sort of work" I wouldn't use them for work I was going to get fussy about(ok I wouldnt use them at all unless I didn't have the size I needed in the good taps draw, they really are pretty bad, but then I paid for the full set M3 to M12 the same price as 1 M12 Sutton tap down the road)

    A better tap might be your answer.

    You could not run the taper tap all the way through. With a bit of playing about that would make the thread tighter one end and might suit your needs.

    Failing that and special taps I think that leaves you with either single point cutting the nuts or making new studs.

    Stuart

  7. #6
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    Kingswood
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    Attached is a photo showing an original height setting nut on the left and my prototype on the right.
    The extra thread depth possible should assist in keeping the new setting nut square.



    Bob,
    There is always a bit of lee-way on selecting tapping drill sizes depending on the material, manufacturing method, tolerances and the desired fit.
    Just hoping someone had done this before and could provide some advice.

    Stuart,
    This a very fine metric thread and I have no representative nuts to check against.
    The supplied locking nut appears to be a commercial one and it fits like a commercial nut should.
    My original post was to see if anyone else had found that the studs were a bit different to the nominal M10x1.0 size, and to get suggestions on the best way to get a relatively firm fit.

    Pipeclay,
    The problem is that as you get close to setting the correct height, a small rotation of the setting nut may move the holder in either direction, up or down.
    The correct position is arrived at eventually, after learning the particular idiosyncrasies of that nut at that rotation point - arghhh !

    John.
    Attached Images Attached Images

  8. #7
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    I still dont see a problem with the setting up of the holders,but thats just me.

    You may find if you purchase the M10x1 screws from somewhere other than China that they may be a slightly different tolerance.

    Are you only using HSS in the holders or are you placing your HSS in a tool holder and then placing that holder into the QC.

    If you are only using HSS in the QC and it is less than 1/4"/6mm square you may run into a problem with the VEE in the bottom of the QC.

    If its larger than the above sizes there really shouldnt be any problem.

    If you are using indexable or cemented carbide tooling to fit your QC holders there also shouldnt be any problem with the VEE in the bottom.

  9. #8
    Join Date
    Jun 2011
    Location
    Australia east coast
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    1,469

    Default

    Quote Originally Posted by electrosteam View Post
    Attached is a photo showing an original height setting nut on the left and my prototype on the right.
    The extra thread depth possible should assist in keeping the new setting nut square.



    Bob,
    There is always a bit of lee-way on selecting tapping drill sizes depending on the material, manufacturing method, tolerances and the desired fit.
    Just hoping someone had done this before and could provide some advice.

    Stuart,
    This a very fine metric thread and I have no representative nuts to check against.
    The supplied locking nut appears to be a commercial one and it fits like a commercial nut should.
    My original post was to see if anyone else had found that the studs were a bit different to the nominal M10x1.0 size, and to get suggestions on the best way to get a relatively firm fit.
    As others have said, use a 9.0mm drill bit and a good sharp tap.

    There are a whole series of thread class fits depending on what you want to achieve. If you want better than a 'commercial' fit, you need to make both parts or buy both threaded portion and nuts to a specified close tolerance thread class. Good luck with that....

    I think you're worrying over nothing frankly. The fit of the adjusting nuts & studs on my very expensive Dickson QCTP isn't what I'd consider close tolerance, and I've never had an issue with it in the last 15+ years of use. Set it, lock it, forget it......

    PDW

  10. #9
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    Jul 2010
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    Melbourne
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    Ok I'm still not really seeing looseness of the thread being an issue except when tightening the lock nut. But then the only QCTP I have had much to do with was a Multiflex.

    First thing I would do is go and buy some new studs and see what that does for you.

    You could try making a sleeve with no thread that's a nice sliding fit on the stud. See how that goes with a single nut above it. If you're happy with that then add a lock nut or change the standard nut for a self-locking nut of some kind(hacksaw and a vice?. nyloc, make your own etc ).

    If you really want to get excited you could try finding some close fitting nuts, taps etc

    Stuart

    p.s. Thats twice. A guy doesn't get time to have a cup of coffee around here

  11. #10
    Join Date
    Jun 2013
    Location
    Tasmania
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    Default

    I have the same problem on my QCTP from CDCO in the states. Its just annoying that they are wonky when trying to adjust them and you do wonder how the hell they got them so off line. But anyway.

    I'm going to make some replacements for mine when I get the time (just another on the list of projects), but I will be changing out all the set screws for better ones and I might as well change out that height adjustment stud at the same time. I'll make a larger diameter adjustment disk and just run the die in like you have done. Guess I'll see if its loose or not but it shouldn't really matter with the locking nut on top.

    Whatever I do I figure it will be better than the crap that came on it.

  12. #11
    Join Date
    Apr 2009
    Location
    Kingswood
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    Default

    I have made 21 new nuts.
    The photos show the sequence.
    Nuts have larger knurled diameter to assist manual grip, but the same diameter in contact with the QCTP body.
    Machining sequence aimed at producing best accuracy between the thread and the nut bottom surface.

    Blanks sawn from grade 1214 Dia 28.4 bar.
    3-jaw used to hold each blank to face both ends with first end marked with centrepop to designate as not true to thread.
    Drill 9.0 with new P&N drill, power tap at 16 RPM with tap hand restrained in tailstock tap holder, M10x1.0 with a Bordo chrome steel taper tap.
    A tailstock supported threaded mandrel with accurate shoulder machined from 1214 bar held in collet chuck and screwcut with carbide tip.
    Each tapped blank loaded onto mandrel with non centrepop end against the shoulder and nut shape machined.
    Each shaped blank loaded onto mandrel and knurling added, then some minor filing to remove burrs.
    (Knurling step separated from the machining step in case the forces involved disturbed the mandrel)

    Very satisfying watching the nuts spin onto the mandrel without a hint of wobble and snap tight against the accurate shoulder.

    A new lock-nut T-spanner was made from a 6-sided socket tapered by hand against a linisher with epoxy glued shaft and handle.

    QCTP New Nuts 6.jpgQCTP New Nuts 1.jpgQCTP New Nuts 2.jpgQCTP New Nuts 3.jpgQCTP New Nuts 4.jpgQCTP New Nuts 5.jpg

    I can recommend the method.
    John

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