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  1. #11
    This is a view of the mill with all the remachining and scraping done as well as the start of a vertical spindle thing
    Click image for larger version. 

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    This is a shot of one of the bearing blocks being centred. I find the easiest way to centre a dot punced block is to use a more taper centre with a spring cntre as a wiggler. This does rely on accurate centre puching thought. I have recently invested in an optical centre punch which makes life a bit easier. this is on the larger harrison lathe.

    Click image for larger version. 

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  2. #12
    the next few shots show the first knee raising method. this was replaced later as I was not happy with it. It also shows a spindle that was later replaced with one with less run out and larger bearing centres. With this knee raising method the force is off centre and so the knee crabbed slightly and required a lot more force to raise the knee.
    Click image for larger version. 

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    you can see the original handle at the back of the mill that was used to raise and lower the knee. If you look at some of the previous posts you can see the rack on the knee. The handle is connected to a pinion that meshes with the rack. I replaced the handle with a bike chain wheel and a bike chain with weight attached is used to counterbalance the knee. I have just realised that I do not have any pics of this so I will ahve to go and take some.

  3. #13
    brrr its cold out there! Here are some pics of the counter balance assembly.

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    Click image for larger version. 

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    a weight is fitted to the end of the chain

  4. #14
    Jonathan,
    here are some close ups of the y axis nut
    Click image for larger version. 

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    Click image for larger version. 

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  5. #15
    Andy keep up the good work and nice to see old being brought into the modern age.
    If the nagging gets really bad......Get a bigger shed:naughty:

  6. #16
    cheers 2e0poz (callsign?)

    I replaced the side acting z screw with a screw that acted below the approx c of g of the knee. This resulted in a much smoother action. The stepper is geared 2:1 and as stated before the knee is counterbalanced using the original rack and pinion system using a chain wheel, chain and mass (the wiring is just a lash up to test it)
    Click image for larger version. 

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    the stepper turns the nut rather than the screw. The nut is supported using two largish AC bearings. No anti backlash nut is required as long as the counterbalanced force is less than the weight of the knee. This improves the raising action significantly and it is smooth with no evidence of the crabbing action seen with the first method.
    The only issue is that the screw protrudes below the base of the mill when the knee is lowered so the bench has to have a hole in it! Not too much of a comprimise for a simpler system without the mass of the stepper on the knee.
    Click image for larger version. 

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    The electronics are also shown in the box next to the machine. I may add a post about this later.

  7. #17
    2e0poz I am m1cws (I think, it is a long time since I used my radio!)

  8. #18
    QSL Andy seems half off 'G' land is into CNC these days and it's been over 15 months since i used mine.

    As an idea could you not mount the nut into the base of the knee and use a belt to turn the screw in the configuration you have now? a bearing block could be placed under the plate you have the motor mounted to. a couple of pneumatic rams like used on hatchbacks would help with the weight if you use them upside down and a light spring over the ram section?
    If the nagging gets really bad......Get a bigger shed:naughty:

  9. #19
    Quote Originally Posted by 2e0poz View Post
    As an idea could you not mount the nut into the base of the knee and use a belt to turn the screw in the configuration you have now? a bearing block could be placed under the plate you have the motor mounted to. a couple of pneumatic rams like used on hatchbacks would help with the weight if you use them upside down and a light spring over the ram section?
    I think Andrew has the best solution now as maybe he maybe would need a hole in the table to do as you suggest.

    I went through 4 different Z builds on my mill so i know the frustration after a lot of effort it is all in vain.

    Like the amp meters in the control box, i would like to see an Estop placed on the machine when the wiring is finished, in case the worst happens.

    Phil

  10. #20
    on with the mechanical build:

    new gibs machined, teflon glued on then remachined. I prefer using the shaper rather than the manual mill.



    Spindle started. Spindle rough machined and drilled



    taper set on the top slide (female centre drilled)



    taper set using existing more 2 centre



    taper in the end of the spindle was finished with a mores 2 reamer. TIR was less than 0.0002.

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