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  1. #11
    I have just sent the picture for the Z axis screw machining to Gary and ordered a girt lump of aluminium.

    The spindle doesn't like running at 5000 rpm which is top whack, 2500 rpm of the pulleys and 100Hz from the inverter, the bearings run hot. I would actually like twice that so I can run tiny ball end mills.

    The plan is a false spindle set inside a 3MT soft end arbor and a lay shaft with two timing belts. That way the false spindle with it's ER11 collet can turn at 9 times the main spindle speed.
    Give me something to do while I wait for the Z screw
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  2. #12
    Quote Originally Posted by Kip View Post
    I tried a micro grinder in a 20mm collet...it works well at 60.000RPM
    Sounds tempting, I'm having a slight alignment problems with the double axial race on my tiny collet gizmo. Going to have to bolt a boring bar to the mill bed, cut the seat oversize in situ then fit a sleeve.

    To do that I need to make a 1/2" BSW drawbar. Can't make the drawbar because my 1 1/2" die holder has gone walkabout. Can't make the Z axis bottom plate 'til I know if I need to fit the layshaft etc.

    However the Z axis screw has arrived and fits inside it's sleeve okay.

    More soon

    Robin
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  3. Quote Originally Posted by Robin Hewitt View Post
    To do that I need to make a 1/2" BSW drawbar.
    Do what I did and buy a 36" length of 1/2" BSW threaded rod and 4 matching nuts. Cut rod in half, screw into tool (through quill), place 1/2 washer, screw on 1 nut till tool retained, then a second nut and lock together. Remove bar and nuts together as one assembly, weld up the nuts, repeat and hey presto two draw bars! (one for mill, one for lathe as they share the same MT3 taper and tooling).

  4. #14
    Quote Originally Posted by irving2008 View Post
    Do what I did and buy a 36" length of 1/2" BSW threaded rod and 4 matching nuts.

    Where did you manage to buy archaic studding in an ISO world? Enquiring minds need to know

  5. Quote Originally Posted by Kip View Post
    I got mine from Sowerby Bridge (on recommendation from RDG) Archaic.....are you incinerating it's bent :naughty: :D
    RDG got it for me, think it was from the same place Kip.

    Or here: http://www.thesitebox.com/Product/12...-12-x-3ft.aspx

    or here: http://www.fastfixdirect.co.uk/code/navigation.asp?Diameter=1%2F2*&Thread=BSW&Length=a ll&Filtered=True&PageID=1&MainCategoryID=4&Product CategoryID=129

  6. Quote Originally Posted by Kip View Post
    Have you seen these on ebay Robin? Looks like a plan :)
    Interesting but I wonder about backlash... aircraft positional control doesnt need high spec in terms of backlash and since it has a 'mechanical detach' I suspect the backlash could be problematic

  7. These are for the First class chair control, i helped design one for a company a few years ago.
    Backlash will be a problem.
    Also they normally have a long lead so it can be back driven if the power fails.
    Quote Originally Posted by irving2008 View Post
    Interesting but I wonder about backlash... aircraft positional control doesnt need high spec in terms of backlash and since it has a 'mechanical detach' I suspect the backlash could be problematic

  8. #18
    Quote Originally Posted by Kip View Post
    A honking big lump of Al mixed with a tube and a 20mm NSK

    Great minds think alike

    The honking plate holds the screw square to the quill with minimum flex, I was thinking two 8mm pinch bolts at the back.

    One vital feature missing in your picture though, probably early days and not forgot but still worth mentioning, you have to be able to release it before you hammer the chuck out of it's taper

    I don't have any convenient flat to bolt a plummer type bearing mount to so I have to extend the sides of the quill housing forwards. This is almost convenient because it ain't easy to get a precise measurement for the separation 'twixt spindle and screw, I thought a bit of slack before I drilled the fixing bolts wouldn't be a bad thing.

  9. #19
    Back again and cutting metal...

    Going for the larger stepper motor this time with half the pulley reduction to put me in the power band. 1 rev = 4mm, half step = 10 microns.

    Same pair of angular contact races with the Belleville washers holding it in tension as before.

    The front of the mill is to extend forwards with bolt on cheeks. The bearings are set in a 16mm plate which fits into grooves in the cheeks to hold it square and rigid.

    The ball nut is enclosed a la Kip, the bottom of the housing is wider to take a pair of 8mm set screws which tie it to the spindle, or not, as the case may be.

    Next job, fitting the cheeks so they wedge tight in the ironwork
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  10. #20
    I don't really do 'excited' anymore

    I think I have to fit this top section then fudge to connect it to the quill.

    Once it's all bolted together and moving I can measure the fudge and get precise dimensions for the honking plate.

    Robin

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