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C-Beam Assembly issue

Discussion in 'CNC Mills/Routers' started by dezignit, Aug 24, 2021.

  1. dezignit

    dezignit New
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    Hi, I'm rebuilding a workbee C-Beam machine that I bought from a friend. The assembly instructions call for one and sometimes two spacers to be placed between the acme block and the plate that it is attached to. So, my question - are the spacers meant to locate in the recessed holes as in Dia 9.00 below? If they are, there is a problem in that the spacers are 10mm OD and will not fit in the recess. In this case the nuts then stand proud and cause a slight bow in the lead screw at either travel ends. It would make sense that the spacer should sit in the recess - yes????
    upload_2021-8-24_20-0-17.png
     
  2. Rob Taylor

    Rob Taylor Master
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    Standard M5 washer OD is 10mm.

    upload_2021-8-24_7-18-59.png

    Mark should probably have a "Must fit low-profile M5 screw head" callout like the one for the nut, especially since M5 socket head size standard is 9.5mm.
     
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    No the recess is for other applications where a bolt head fits into the recess. In a configuration where they are used as spacers, they sit outside, acting as "spacers," to drop centerline of the nut into the leadscrew path - without spacers, or with recessed spacers, it would bend the leadscrew.

    Thus bolt head > plate > spacer > leadnut > hex nut into recess.
     
    Rick 2.0 likes this.
  4. dezignit

    dezignit New
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    Gentlemen, thank you for you prompt replies. If I can let the mechanical engineer in me come out, if the recess has an OD of 9mm and the spacer 10mm, this results in a landing on only 0.5mm which is very little given this is a plastic device. Indeed when I was stripping the achine down the fastening screws were quite loose and the spacer had "bitten" into the plastic by about 0.5mm in depth. As a solution I am going to open the recess diameter to 10mm so that the spacers fit flush with the bottom and then add an extra spacer to make up the difference in height. Thanks again for the response.
     
    Peter Van Der Walt likes this.
  5. Christian James

    Christian James Journeyman
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    I highlighted this problem a couple of years ago - and yes there is very little "meat" on the washers to sit against the counterbores of the nut blocks. No need to bore out though, just make some 3D printed spaces instead. nut block spacer.jpg
     
    Peter Van Der Walt likes this.
  6. dezignit

    dezignit New
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    Hi Christian, thank you, that's a great idea and much easier to work with on installation given that I have not stripped down the Y axis roller cage! Cheers!
     

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