Cutting box section

[RHS]

Of late I have made a few frames for home projects (BBQ & a forge) out of box section up to 60x60x3, and have been using my 4.5" grinder with a 1mm cutting wheel to cut all the pieces to length. I always seem to struggle to get decent straight cuts all the way round, can anyone give me some advice on how to do this better?

Cheers,
RHS

 

[the snooper]

unless you buy a cut off saw its just down to marking with a square and getting the grinder in the right place and angle

 

[cumbriasteve]

It's one of those practice makes perfect tasks, you do need to be comfortable and well balanced whilst cutting, have a very clearly marked cut line illuminated by a light and don't force the machine.

Many people try cutting whilst standing on rubbish, in partial light and with a pair of goggles so dirty or misted up they are nearly blind.

 

[the snooper]

you can always add masking tape so you cut to the edge of the tape and whilst making the first cut always go through the corner for the next flat to be cut before rotating the box then you are not guessing if the cuts will meet up

 

[dan.taylor.1]

As above, its a practice thing, i had a lot of 80mm 10mm wall box to do and by the end i had my 9" grinder making bandsaw straight cuts!

Dan

 

[RHS]

Thanks guys, I'll be doing a fair amount more practice soon when making a workbench. I'll try the masking tape idea out too as I think that might really help me on the corners.

 

[the snooper]

Thanks guys, I'll be doing a fair amount more practice soon when making a workbench. I'll try the masking tape idea out too as I think that might really help me on the corners.

gives you a line very easy to follow although it does sometimes burn a little

 

[fixerupper]

Yep I agree with all of the above , If you use nine inch grinder you can cut through quite big box without having to turn the steel over ,I use a bit of old scaff board with a bit of 2x1 screwed to it to cut on ...jeff

 

[rich r]

Masking tape really does help when cutting anything like this. Same goes for cutting wood or things like plastic pipe. It just gives you that extra reference to help you aim the cut.

 

[fixerupper]

Yes the masking tape thing is great ,when I was instaling wood stoves for a living ,it was the best way of cutting flue pipe neatly with the minimum of waste....jeff...

 

[Mr shiney]

I bought a Rage saw for about £60 and it's been brilliant for cutting box.

 

[Kent]

use a saw perhaps? this is too much like hard work and lacks accuracy besides I feel doing a lot of cutting tends to shorten the life of a grinder- cutting big box with a 4 1/2" grinder is going to ruin the grinder and eat discs, I only use cutting discs in a 4 1/2" for very small cutting jobs, it just don't have the muscle

 

[DanielW]

An essential item for cutting straight or 45 degrees cuts
http://www.spiritburner.com/fusion/fbbuploads/1299584980-Grinderstand.jpg

 

[Anguz]

9" is the way to go far easier to cut straight

 

[dan.taylor.1]

Kent, my Bosch grinders are at least 5 if not 10 years old and both (4.5" and 9") have cut a LOT of box section and other steel from 20mm thick plate to 1.2mm galv sheet and neither looks or sounds like they are worn in any way, as long as i blow the dust out and replace brushes when needed that's what they are designed to do so I can't see it wearing them out!

Dan

 

[Kent]

so your basically into rebuilding grinders then. No way should I start chopping 20mm plate with a 9" and like I say small cuts only with a 41/2" . Then I cant contemplate having a grinder last ten years. The question is however why? there are better tools for the job.

1.2 Galv sheet and its not a bad tool 9" long cuts 4 1/2" lil uns, it appears my take is somewhat different than yours on this. Then again I was doing a load of 5mm plate cuts in the side of a boat yesterday with a 9" and thinking I need to get a plasma

A guy tunnelled out of Alcatraz with a spoon but that's all he could lay his hands on

 

[dan.taylor.1]

i agree there are better tools, plasma being one, but i havent the money for one,and ive never had to rebuild a grinder, i said i blow them out, which if i remember right the manual said to do once in a while.

 

[Bill Edwards]

I've cut plenty of 25mm plate with a 9" grinder - get a thin disc and don't work it too hard and you manage. They are built for it, don't be a wimp.

 

[Kent]

I just plain disagree on cutting thick plate
you guys should feel how hot the mechanism gets on a 9" after a reasonable cut. You just cant cut much with a 4 1/2" before the disc is all used up anyhow.

I am wondering actually why anyone should need to cut 20mm plate with a grinder? sure you might need to put a chamfer on it or take a corner off here and there with a grinding wheel but actually put a cut in, nah that's got to be bad measuring Order it the right size to begin with next time

 

[Bill Edwards]

Well it depends what you're doing. When you are working on a digger bucket for over 20t of dozer that can break just about anything but the guy you are working for only has bits of inch plate in a certain size with no plasma or oxy fuel you find that the 9" grinder is a brilliant approach, unless you are a fan of the hacksaw.

Yes they do get hot but if you don't rag the hell out of them (more harm tends to be done while grinding, at least for me) and take it steady with a slitting disc they take it just fine.