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  1. #61
    Join Date
    Sep 2007
    Posts
    359
    Quote Originally Posted by Khalid View Post
    Hi Phil,
    I have checked the Gib Tighteness... Following were my observations:

    The Screw has some spring action inside.. The wheel is turned first upto a limit with the screw and then screw nut takes the load and further after quarter turn the slide was moving...
    Khalid,

    I think the next thing to fix as i seem to remember you are now using ball screws is that the slightest turn on the pulley will move the table, once you have overcome any backlash there should be no spring action

    Phil

  2. #62
    Join Date
    Apr 2006
    Posts
    3498
    Quote Originally Posted by M250cnc View Post
    Khalid,

    I think the next thing to fix as i seem to remember you are now using ball screws is that the slightest turn on the pulley will move the table, once you have overcome any backlash there should be no spring action

    Phil
    Yes, I have to recalibrate all the axis again for the new adjustment... The slides are very free moving..It seems that i have installed the linear rails
    I am planning to make the new spindle with AISI 4140...Today I have hardened 03 different cylindrical pieces( dia: 1inch, length 1.5") of AISI 4140..
    Each piece was heated to 850C and then one piece was Oil Quenched, One was Normal water Quench whereas the last one was quenched in the chilled water...
    I have observed the longitudinal crack in the normal water quenched workpiece...

    Tomorrow i will check it for Rockwell hardness.. For a good spindle the hardness must be in the range of 50~57HRC..
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/

  3. #63
    Join Date
    Apr 2006
    Posts
    3498
    Actually the pully rotate the ball screw and their is no lag between pully and ballscrew... However i am having backlash in the screw and the ballnut... I am using second-hand non-preloaded ballscrew...

    I don't know what will be the affect when the actual cutting forces work on the table and the screw...What you guess?
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/

  4. #64
    Join Date
    Apr 2006
    Posts
    3498
    Following are the hardness results of 4140..

    A) Oil Quenched: 38.8HRC
    B) Normal Water (Amb. temp): 54.1 HRC
    C) Chilled Water: 49.8HRC

    I cut half the option B, material and again taken the readings at the centre. I got 50HRC...That is excellent for spindle...
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/

  5. #65
    Join Date
    Apr 2006
    Posts
    3498
    Today i recalibrated X and Y axes as i have loosen the gibs.. I Did some real drilling on the SS-316 tube sheet of one of the exchanger we are fabricating... You can see the centre drills and two 8mm deep drills... The OTL (Outer Tube limit)is under 0.03mm... I also measure 14holes across and the commulative length is under 0.02mm...Now, I can drill SS-316 upto 33mm deep ...

    The Spindle is roughly machined out of AISI4140... I am going to Quench it on monday..
    Attached Thumbnails Attached Thumbnails two holes 8mm.JPG   DSC05185.JPG   DSC05186.JPG   final centre drill.JPG  

    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/

  6. #66
    Join Date
    Jun 2013
    Posts
    5

    Re: Milling Cast Iron

    You CNC guys crack me up! You ought to learn how to cut on a manual machine before you do things with a computer. You're always picking the wrong machine, wrong tooling, too fast spindle speeds, too fast feed rates, or climb when you should be conventional milling. This is a radial drill. It is meant to be quickly positioned for plunge cutting, not locked rigidly for side milling. The spindle can't be locked tight enough to resist the pull of a milling cutter with a helix. You don't know the material. I'd bet dollars to doughnuts that it's NOT cast iron, but ductile or malleable iron, which is a whole different animal. And a HSCO cutter with only 2 flutes? Any form of iron has a matrix of carbides in it. The stuff will dull a HSS or HSCO cutter really quick. You should be using carbide. And you're further hurting yourself by trying to cut with only 2 edges. Because it's CNC, you have no feel for how fast the cutter is dulling and how much side load is put on the cutter. You could feel it in the hand wheels if you were doing this on a manual machine. Climb milling is what you do to get a nice finish, not make progress. It is very hard on setups that aren't rigid, so you probably had a lot of chatter too. So the shank broke. Not surprising.

  7. #67
    Join Date
    Jun 2007
    Posts
    3757

    Re: Milling Cast Iron

    And that was almost 8 years ago. Did they figure it out, or die after retirement?
    Note my signature!
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.

  8. #68
    Join Date
    Jun 2013
    Posts
    5

    Re: Milling Cast Iron

    Quote Originally Posted by neilw20 View Post
    And that was almost 8 years ago. Did they figure it out, or die after retirement?
    Note my signature!
    I couldn't resist replying, even if it is an ancient thread. Not even sure how I stumbled across the forum. I go to youtube looking for solutions to machining problems and see novices put a $100 cutter in a $50,000 CNC machine, and turn the cutter red hot.... I'm not privileged to have a CNC machine here at work. I'm 64 and stuck with a tired, worn out '64 manual Bridgeport.

  9. #69
    Join Date
    Jun 2007
    Posts
    3757

    Re: Milling Cast Iron

    I got my first CNC when I was 58, and second when 64.
    There is hope for you yet? or buy some ballscrews and retrofit your Bridgeport. Nothing a scrape of the ways and gibs won't fix.
    Stepper motors good enough if you don't ask for stupid feed rates.
    And then I built myself a 3D printer, because I could, and a control system for 12M x 5M x 2M X,Y,Z monster, someone else built.
    Life begins at 60. Where in the world are you?
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.

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