Accurising an RCBS 5.0.5 set of scales

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by Campbell, Sep 5, 2017.

  1. Campbell

    Campbell

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    I own the above-mentioned scales.

    I have fitted a zoom web-cam and can detect as little as 1/2 of a kernel of Vit. 140 difference.

    My problem is that my scales sometimes does not re-zero by as much as 3 kernels of the above-mentioned powder.

    Please, have any of you got knowledge on how to increase the consistency?
     
  2. Mulligan

    Mulligan Silver $$ Contributor

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    I had a similar issue.
    Went through the "tune up" process again completely, still had it.
    Wipe a little graffite on the blades and to the extent you can do not let beam bounce off the top or bottom of travel limiter. When the beam is allowed to bounce (when the pan is removed) it can force the blades to resettle in another location in the agates. A tiny piece of mole skin works as a cushion......hey it's what I had on hand.

    @BoydAllen was a huge help, he has an incredible grasp on this.
    CW
     
  3. 47WillysGuy

    47WillysGuy

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    Changed my 505 out for a Ohaus 1010 because I was having the same problems. Great starter scale IMHO!
     
  4. Campbell

    Campbell

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    Hi CW

    Many thanks! Tah

    I use a piece of polystyrene foam at the bottom of the scales, but until now I had not considered a top stop.

    Would using some Redding Imperial Dry Neck Lube on agates be appropriate?

    I will study what Mr BoydAllen has to say. I remember reading something ages ago, did not take notice of the author, got distracted, and lost the link. It was Mr BA on recollection.

    Thanks again.

    Cam
     
  5. Mulligan

    Mulligan Silver $$ Contributor

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    Yes the dry lube will work.
     
  6. swadiver

    swadiver Silver $$ Contributor

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    I second the use of pencil lead on the blades. I have a vintage Ohaus 10-0-5 (same a a Lyman M5) accurized by Sparker. adding the pencil lead made a HUGE difference in repeatability
     
  7. BoydAllen

    BoydAllen Gold $$ Contributor

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    IMO the main thing is to get the knife edges and the agates and their holders, the sockets that they sit in perfectly clean and dry (assuming that you have carefully sharpened the edges with an equal number of strokes on both sides of both edges so that there are no shiny spots as you look straight at the edges) . When I have that right things work well for me. When I did the pencil lead it was simply rubbing the side of the lead point of a sharpened pencil along the edges a couple of times. I did not want to have granules of graphite in the bearings. I recommend that you experiment a little. Padding the beam swing stops seems to help. I think that the reason is that when the beam bangs on a hard surface it shifts the edges in the agates slightly. Another thing that I have found to affect consistency are the wire loops on the secondary edges. I carefully remove that from the beam and spread them ever so slightly, put them back on and then carefully squeeze them together to the point where they cannot shift from side to side, but are not pushing against the outer ends of the knife edges. Also as a last step when setting up each time. I pick up the pan assembly slightly by grasping the pan holder hook between thumb and finger so that the wire loops are taken off of the edges a bit and then set them down so that the contact is exactly at 12 o'clock in the inside of the loops.
     
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  8. Campbell

    Campbell

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    Many thanks to all of you, especially BoydAllen. He certainly knows and understands how to accurize a set of beam scales!

    My scales appear to be re-zeroing bob-on.

    One day, I hope to be able to help others.

    Cam
     
    Mulligan likes this.
  9. brians356

    brians356 Gold $$ Contributor

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    Sorry, but I keep coming back to what S. Parker wrote about the 5-0-5's fatal flaw:

    " ... the middle poise rests on a folded flat section and also on the top portion of the slot that is cut in it. The issue is that there some variability in how that poise positions itself as the beam moves. This causes a lack of repeatability. Moreover, that poise is easily dislodged. That poise adjusts in whole grain increments! Yikes!"
    -
     
  10. Ledd Slinger

    Ledd Slinger Gold $$ Contributor

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    I introduced my 505 to the garbage can. Problem solved ;)
     
  11. Campbell

    Campbell

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    I have never (since 1985) had the middle poise move without user intervention.

    I have, however, had the 1/10gr poise move when I have had cause to remove the pan handler.
     
  12. 47WillysGuy

    47WillysGuy

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    Friction is not a friend to the scale. I overhauled the wire connector from the 505 beam to the pan wire hoop. The connector was shaped in a V shape. I rebent the wire into a U shape so the connector wire loops are square to the beam pivot ends. No friction and the scale works a whole lot better.

    Also cleaned the pivot points (2ea) with a solvent.

    These changes made it into a lot better scale.
     

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