X Rail Material


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    Default X Rail Material

    I've been trying to figure out why my cut depth when engraving varies about 006" from one side of my table to the other. I have machined my spoil board a couple of times, but that didn't help. I found that the X rail on the right side is worn where the top bearings run. Other rails are OK. So I blame this on overtightening the bearings. The rails were ground O-1 tool steel tight precision flat stock from McMaster-Carr. They were used in as bought state and not hardened after maching. The bearings are the normal skate bearings. Does anyone know of a better material to make the rails out of or should I have hardened the rails? If I go back with the same material, I'll pay more attention to the bearing adjustment and try not to get them so tight.

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    I don't make mistakes ... I make 'unintended engineering design changes'.


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    Default Re: X Rail Material

    I was engraving some 3/8 plexi and it varies .010 in 12 inches measured in different places.



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    Default Re: X Rail Material

    I have a hard time believing you really wore .006" off your tool steel rails with the skateboard wheels. Unevenness in the material (as pointed out above) makes more sense, or maybe some chips underneath it you didn't notice.

    Andrew Werby
    https://computersculpture.com/


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    Default Re: X Rail Material

    I was not expecting that either. But that is what it measured with a micrometer. No stray chips or uneven material. There was even a sharp edge on the top of the rail (where the bearings spend a lot of their time) just a few thousands wide that was outside of the bearing path. It looked like displaced metal, but was the orginal thickness. The rail had actually worn down that much. This machine does get a workout and has been very dependable. The far ends of the rail did not show this wear. I did find that the bearings were adjusted really tight. so I am very confident that this was wear. I mounted a dial indicator to the router mount and checked the spoilboard before and after it was surfaced. Before it was surfaced, the dial indicator reflected the dip in the rail on the right side and the error decreased as it moved toward the left side. After the spoilboard was surfaced, the error was reduced significantly, but was still present but acceptable. I might explore hardening the rail when it is replaced. Sparkness-- I use only cast cell acrylic for engraving. It seems much more uniform in thickness and machines much better than extruded plexiglass. After I resurfaced the spoilboard, I engraved an acrylic edge lit sign that was 15" x 15" at .012" deep with a 10 degree V bit. The cut depth seemed uniform from side to side. So, I guess I'll carry on and replace the rail with the same material.

    I don't make mistakes ... I make 'unintended engineering design changes'.


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    Default Re: X Rail Material

    Could you share a photograph of your setup, with a close-up showing how the skateboard wheels are bearing on those rails? I'm not doubting your word, just having a hard time imagining them removing that much steel. It's easier to conceive of the bearings getting loose or deflecting by that amount.

    Andrew Werby
    https://computersculpture.com/


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    Default Re: X Rail Material

    Ref772 & Andrew,

    O1 Tool Steel is relatively soft in its native as shipped state before a hardening process is performed, a 10 Rockwell is slightly tougher than a wet noodle or a soft grape.

    Jeff...

    Quote Originally Posted by ref772 View Post
    I've been trying to figure out why my cut depth when engraving varies about 006" from one side of my table to the other. I have machined my spoil board a couple of times, but that didn't help. I found that the X rail on the right side is worn where the top bearings run. Other rails are OK. So I blame this on overtightening the bearings. The rails were ground O-1 tool steel tight precision flat stock from McMaster-Carr. They were used in as bought state and not hardened after maching. The bearings are the normal skate bearings. Does anyone know of a better material to make the rails out of or should I have hardened the rails? If I go back with the same material, I'll pay more attention to the bearing adjustment and try not to get them so tight.


    Patience and perseverance have a magical effect before which difficulties disappear and obstacles vanish.


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    Default Re: X Rail Material

    Well that pretty well 'splains' it. Any suggestions on a tougher alloy? or just have it hardened after drilling. I've hardened small things like punches, pins, and such - but never a large item. I need to find a knife maker around here. If I go that route, it will probably have to be ground after heat treatment. Or just replace it for another few years of use. After all, it has made 400+ car show plaques (all the same size) since I built it. So that same spot on the rail got a lot of use.

    I don't make mistakes ... I make 'unintended engineering design changes'.


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    Post Re: X Rail Material

    Ref772,

    O1 is super, SUPER TOUGH once its hardened (60 Rockwell )

    4142 precision ground flat stock is available pre-hardened to 27-32 Rockwell

    https://store.diesupplies.com/4142-p...2-pm-p106.aspx

    Jeff...


    Quote Originally Posted by ref772 View Post
    Well that pretty well 'splains' it. Any suggestions on a tougher alloy? or just have it hardened after drilling. I've hardened small things like punches, pins, and such - but never a large item. I need to find a knife maker around here. If I go that route, it will probably have to be ground after heat treatment. Or just replace it for another few years of use. After all, it has made 400+ car show plaques (all the same size) since I built it. So that same spot on the rail got a lot of use.


    Patience and perseverance have a magical effect before which difficulties disappear and obstacles vanish.


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    Default Re: X Rail Material

    It is useful to keep in mind that these system are built using components that were never intended for long term professional results. I have some of the same parts, but they are skate bearings and soft steel, so "achieving a result" after meticulous tuning is not the same as "regularly achieving a result over a long period of time".

    If you are going to need long term reliable precision (sub +/- 0.010 inch) it might be time to look at more professional type rails, example PBC linear, etc.



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