Seeking advice on cutting many slots in a tube

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May 2, 2017
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The attached picture is part of a larger project, a kinetic sculpture. The aluminum tube is just under 2 inches OD and 1.5 inches ID. I need to cut a series of slots as indicated by the wide lines. I will not be able to spin the tube during the cutting operation, because it will be 30 inches long. The slots will be nearly half way around the tube and offset by 90 degrees from one to the next. Each slot is 0.25 inches wide and they 1 inch apart on center.

What's the best method to accomplish this task?

Thanks in advance for all replies.



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Depends how precision they need to be and what their purpose is, so a bit more info would be helpful.

But if their function is purely aesthetic or non-precision, you could simply cut the slots using a friction disc cut-off saw aka drop saw. Mark out the slots, clamp tube in vice and lower the disc to cut slot. If doing multiples, you can usually set a depth stop on those machines.

If more precision is needed, a wide slitting saw or even a round side and face cutter in the milling machine would work. Horizontal mill would be easier to set up than vertical if the slots go all the way along the tube. Which not sure of from your description.

You could even mount such a cutter in the lathe on an arbor and clamp the tube to the cross slide and machine the slots that way.
I would have to ask what the end of the slot has to look like? Is the end of the slot rounded or square? Is the end of the slot parallel to a chord line or must the end of the slot be parallel to the line drawn on the radius of the tube? To me this makes a lot of difference on the setup and the cutter used..

no neat sig line
The wall thickness is 1/4", so fairly sturdy.

If you have a vertical mill, mount the tube along the table and cut all the first direction slots from the top using a long series end mill. Once the first set of slots have been machined, turn the tube 90 degrees and proceed as previously.

lg questioned about the end shape of the slot. If the ends of the slots are square, a normal end mill can be used; if rounded ends are required, then a ball end mill will be used.

I would make up two close fitting 'bungs' to go inside the tube where the clamps go so that the tube is not crushed.

The Emerald Isle
If "many" means lots and lots, then it would seem a template and/or a fixture could be made to simplify the layout and indexing tasks. I'm thinking of a tubular or part-of-a-tube with ID to mach the OD of your part that would fit over your tube for help in positioning the stock for layout or machining.