Precision cutting 2x1 tube on a waterjet?

We got our OMAX GlobalMax 1508 waterjet right before last year’s season, and we made decent use of it for a last-minute major tool add. (Thanks CTE manager & budget!)

We only cut aluminum and polycarb sheet last year, and one thing I’d like to be able to do is precision cut tube on it like people do on their Omios. However, reading this past thread, it seems like that could be a bit of a production. Is anyone routinely precision cutting 2x1 tube on their waterjet? If so, I assume there is some method/jig for repeatedly locating the tube end on the table (like the Omio tube jig). And I assume there is some way to deal with (avoid) the imprecise exit cuts on the far side of the tube. Wondering if people might just submerge the far side of the tube and use a piece of waste steel inside (instead of wood as the thread above suggests… not that easy to make a bunch of 1.75x.75 or 1.875x.875 pieces of wood). Thanks.

A positioning fixture for the tube will certainly help make more repeatable cuts. Even just two fences would be sufficient.

My own opinion is that cutting wood to size is far easier than cutting steel. But will the wood prevent a waterjet from penetrating? Dunno, but I suspect not.

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That sounds like a ton of wasted steel.

I’ve never tried to locate waterjet cut features to the stock metal exterior dimensions, and definitely not to within 0.005" repeatability (easy on a router).

Do you have an indicator attachment for the waterjet head? Or I guess you could clamp down fixture stock, cut the fixture with the jet, then clamp part stock into the fixture?

I’ve never used waterjet cut features as final bore diameters either, just as locations for finishing passes with other tools.

I don’t see how using this tool for tubing saves you time or money or even gains you precision.

Why do you want to cut tubing on it?

You can do really cool sheet metal style work with the waterjet tool - investing in a press brake for bending 0.060-0.100 5052 aluminum will get you a much longer way to productive work than figuring out how to cut tubes on the jet. Look at 95’s build thread for design language ideas.

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Back when I used to run a WaterJet for a local shop, we would clamp a large piece of metal on the bed, cut along the X and Y axis to make essentially a large carpenter square, and set the machine home to be at the exact corner of the newly cut square corner. You would need to recut the square edge/corner of your machine ever lost home, but allowed for an accurate (don’t know specifically how accurate), repeatable home/start location.

All that being said, I’d agree with others above that cutting 2x1 aluminum tube on your water seems like more effort than it’s worth. But I could be totally wrong. Submerging half your tube under water with a steel plate inside the tube may be enough to not pierce/damage the far side of the tube. If your steel plate came out relatively undamaged so that you can reuse it for multiple pieces of tubes, that could be relatively sustainable. If you need a new piece for every length of tubing you cut, that sounds a lot less sustainable/practical.

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When I needed tube rotary waterjet… the trick was to put a carbide bar inside it. A very loose fit. This would break up the beam/stream before it hit the opposite side.
No direct experience, just what the supplier told me about the process.

yep, I was thinking of maybe putting several pieces of 3/8" (#3) diameter rebar in the tube or something like that, sort of as you described

I haven’t used water-jet since college, but from my memory of the surface finish would need reaming for bearing fits anyway, so if your aiming to put the same hole pattern in each side, hand reaming might take care of any finish/ tolerance issues, but putting different hole patterns in each side might not be practical. My water jet experience is limited so who knows.