Long cuts in steel profiles - prevent bending

[Johan Gunverth]

If you use a regular cut-off wheel and angle grinder to make longitudinal cuts in, for example, a square pipe, it usually ends with the workpiece bending due to thermal expansion. Would some form of water cooling prevent this? Is it possible to use regular ceramic cut-off wheels and water dousing? The machine can handle it, but does the wheel like the water?
Of course, you can use cutting fluid, but it is neither the right tool nor the right environment for this. Machines and tools for proper machining are lacking.
I will, among other things, create a 10 mm wide groove in a 3m 30x30x2 square pipe (equivalent to E220). I tested on a small piece, and the material does not stay straight after the operation. It gets better if you are careful, but it takes the whole day.

 

[Johan Gunverth]

Did a test with the small tile cutter (stationary, water-cooled, 500W) and a 180 mm steel disc and it worked in practice, but far too slowly, about ½ mm/s. It spins at 2800 RPM which is a ¼ of an angle grinder. A magnet in the "drain" picked up all the swarf, which was more like fine dust.

 

[plåtrickard]

How thick cutting disc?
I would have guessed that it's harder to go straight than for it to lose shape.

 

[plåtrickard]

Metal blade in circular saw?

 

[Johan Gunverth]

How thick is the cutting disc?
I would have guessed it was harder to cut straight than for it to lose its shape

2 mm were the only ones I found for 180mm. The cut was completely straight with the guide, but as mentioned unbearably slow with the weak motor and lower rpm.

Metal blade in a circular saw?

The circular saws I have do not handle steel with a toothed blade. However, aluminum. It also sounds a bit unsafe to test in that situation.

 

[RoTe]

How far should you cut? Isn't it easier to just weld together what you need?

 

[Johan Gunverth]

2x 3m. It is for a suspension device with variable hanging points, like a sliding door track. Being frugal, I am using the square tubes that are already on the shelf rather than spending 1500:- on a too-short track with additional special hangers.

 

[Johan Gunverth]

One could indeed run water through the pipe itself and use the large angle grinder. Just a bit of splash protection.

 

[ClasseClas]

I was considering using a nibbler because it probably won't heat up the material too much. The problem is that my hand nibbler can handle a maximum of 1.2 mm, and my nibbler for the drill/screwdriver can handle about 0.8 mm. Check the market further if you think the idea is sensible.

 

[Johan Gunverth]

I was considering using a nibbler because it probably won't heat up the material very much. The problem is that my hand nibbler can handle a maximum of 1.2 mm and my nibbler for a screwdriver/drill can handle about 0.8 mm. Check the market further if you think the idea is reasonable.

Nibblers might work, but won't they leave an uneven edge?

 

[RoTe]

Nibblers might work, but don't they leave an uneven edge?

No, but I don't think they can handle 2mm thick... Nibblers are used for roof sheeting.

 

[Rickard.]

That it bends is probably not due to the heat, or at least not just the heat, but due to tensions in the material from the manufacturing process, similar to how a board can warp when split.

Kind of like this but less extreme 😉
https://www.reddit.com/r/Unexpected/comments/198ehm0/thats_what_experience_looks_like/

 

[ClasseClas]

Nibblers might work, but they probably leave an uneven edge?

Yes, requires some finishing with a file or grinder.

 

[Johan Gunverth]

The fact that it bends is probably not due to the heat, or at least not just the heat, but due to stresses in the material from manufacturing, similar to how a piece of lumber can warp if it's split.

Sort of like this, but less extreme 😉
[link]

That's true. I did some tests a while ago, and there's basically no difference with the cooled slow method and regular dry cutting. The side that got the two cuts (a 10 mm opening in a 30x30x2 square tube swelled to 31 mm for both methods. Fairly easy to bend back to 30 mm with a clamp.

So...I go with the regular "dry method" for the cuts and fine-tune with the wet. Noted that the cutting disc didn't wear at all when it was water-lubricated. At least I've learned something. 🙂