Use Epoxy for a reference straight line

[feldah]

I have one piece of aluminum 1500mm milled to a precision of 0.004mm. but everybody says aluminum will be too much affected by temperature. Would you say the same?

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[routercnc]

How much accuracy do you need on the final machine? Somewhere between 0.01 - 0.05 for general hobby might be OK and was the range I was aiming for on my latest machine.

If you look at my YouTube video around episode 16 you can see my experiences using epoxy to level rails directly (channel is routercnc)
I found it set level to at least 0.05 mm and probably more but I couldn’t be sure as my reference surface is not a proper calibrated one. Just be aware of the problem with bubbles and ways to get rid of them.

If you want to level rails you can also use shims and an engineers precision level. The 300mm square level was around £100 but measures down to 0.02mm over 1000 mm. I must have paid ~£80 for 2 sets of epoxy mix so actually the level is good value as it can be reused !

[feldah]

How much accuracy do you need on the final machine? Somewhere between 0.01 - 0.05 for general hobby might be OK and was the range I was aiming for on my latest machine.

If you look at my YouTube video around episode 16 you can see my experiences using epoxy to level rails directly (channel is routercnc)
I found it set level to at least 0.05 mm and probably more but I couldn’t be sure as my reference surface is not a proper calibrated one. Just be aware of the problem with bubbles and ways to get rid of them.

If you want to level rails you can also use shims and an engineers precision level. The 300mm square level was around £100 but measures down to 0.02mm over 1000 mm. I must have paid ~£80 for 2 sets of epoxy mix so actually the level is good value as it can be reused !

Yes your opinion sounds reasonable. I didn't have a specific precision in mind. I just like to know what options there are. My idea with the epoxy was to pour it on a piece of metal or maybe even granite. And use that as a reusable reference. I think I get the Westcoast Epoxy for around 20$. I also have a vacuum chamber to get rid of the bubbles. It would be a nice try. But without a super precision reference I will never know if it worked :-)


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[mekanik]

I have one piece of aluminum 1500mm milled to a precision of 0.004mm. but everybody says aluminum will be too much affected by temperature. Would you say the same?

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If your Ally is of reasonable cross section so it doesn't bend then temprature is not a problem it's still going to be flat and that tolerance over 1500mm is as good as any precision straight edge you can buy. as routercnc has stated you can't get it perfect but with time and patience it's going to be fit for purpose.
Regards
Mike