Staight Cutting Sheet Materials

[SteveF]

I have a steel plate I want to cut relatively square 2'
I have an angle grinder and suitable discs
it is only about 3mm thick
is there a trick to getting a neat cut
It's not like I can put it against the fence of my table saw
would clamping a length of mdf help
or will i end up with a fire and chewed up mdf?

Steve

 

[t8hants]

I assume you have a 9" grinder and a thin slitting disc.
I don't think you will find MDF will be any help at all, the trick of cutting with a slitting disc is practice.
Get a good scribed line so you can see where your cutting, let the machine do the work, don't fight it and don't push it.
Hold it firmly, but not excessively so. most mistakes happen when you get out of line and start bending the disc to correct your cut.
if you have enough spare material have a couple of trial cuts.

 

[graduate_owner]

I find it really difficult to see the line because of the sparks, espcially with the safety goggles causing my specs to misr up.

K

 

[Nelsun]

If you have the cash to throw at the problem there's assorted gizmos you can fit a grinder in to run on a track saw rail. I have one and cut some slate to size and rebated the edges with relative ease. Metabo and Festool do them and possibly Bosch.

 

[TFrench]

Find a local metal shop with a guillotine, it'll take seconds, cost you a fiver and look much better than you can do with a grinder. If you were round this way I'd happily do it!

If you do have to do it with a grinder, I've found the best way is to make a light cut the full length then go over it again, but the initial cut stops too much wandering. Top tip - make sure you're careful of where the sparks are going - guess who managed to burn through a new set of overall the other day doing just this? (metal was too thick for our guillotine)

 

[Hitch]

I assume you have a 9" grinder and a thin slitting disc.
I don't think you will find MDF will be any help at all, the trick of cutting with a slitting disc is practice.
Get a good scribed line so you can see where your cutting, let the machine do the work, don't fight it and don't push it.
Hold it firmly, but not excessively so. most mistakes happen when you get out of line and start bending the disc to correct your cut.
if you have enough spare material have a couple of trial cuts.

Spot on there... a 4.5/5" grinder would happily cut 3mm all day long with a quality disc, and is much easier to control for accurate cuts.

 

[Hitch]

Find a local metal shop with a guillotine, it'll take seconds, cost you a fiver and look much better than you can do with a grinder. If you were round this way I'd happily do it!

Absoloutely, takes seconds... or spend the same on a pack of discs :lol:

 

[graduate_owner]

TFrench - get yourself a leather apron. Mine has done the job of saving my pullovers etc really well. Before I bought one my pullovers used to disintegrate around the midriff. Mine cost about £18 from Axminster.
One modification - I was fed up of tying the 'apron strings' every time I went to put it on so I replaced them with a bungee cord. One hook is bent tight so permanently attached, and the other just hooks on, quick and easy with no knots.
Comes in handy when welding too.

K

 

[SteveF]

Thankyou everyone for your help
I will go with the 5" disc cutter..I want to do during the break and I won't find anyone then
I can hide the edge with some angle if it is too hideous

have a good xmas

Steve

 

[Inspector]

Know anyone with a plasma cutter?

Pete

 

[Beau]

I have used a wooden batten as a guide and does help.

 

[ColeyS1]

TFrench - get yourself a leather apron. Mine has done the job of saving my pullovers etc really well. Before I bought one my pullovers used to disintegrate around the midriff. Mine cost about £18 from Axminster.
One modification - I was fed up of tying the 'apron strings' every time I went to put it on so I replaced them with a bungee cord. One hook is bent tight so permanently attached, and the other just hooks on, quick and easy with no knots.
Comes in handy when welding too.

K

I wish I'd known this a few weeks ago.

Cotton apron caught well alight from grinding. Perhaps the apron being a little dusty didn't help. It nearly burnt my balls off :lol:
Cheers

Coley

 

[dickm]

Oddly enough, I spent the afternoon of the original post cutting roofing sheets with a Bosch 4.5" angle grinder in dim Aberdeenshire daylight and asking myself the same questions as the OP. Would definitely second the comments about sparks! But still wonder - does anyone make some sort of fence/datum surface for angle grinders? And if not, is there a reason why not?

 

[t8hants]

Cutting a sheet with an angle grinder is a bit like using a hand saw, if you start in the right place, and go in the right direction then the width of the blade acts as your guide.
As far as I am aware it isn't regular practice to cut a sheet with a hand saw by following a straight edge you only follow a straight line using the width of the saw plate as your guide.
Sheet cutting by a grinder is the same principle, and that is why I think it better to use a 9" over a 4-1/2 " because of the greater width of the blade available to guide you, and like a hand saw the tool must do the work. You mustn't force things.

 

[Inspector]

You can mount an abrasive cutoff wheel in a circular saw and run it along a clamped piece of angle iron. If you plan on cutting often dedicate the saw to it instead of switching back and forth between the two. It's hard on them. With the right sawblade you can cut aluminium sheet and plate too.

Pete

 

[TFrench]

Oddly enough, I spent the afternoon of the original post cutting roofing sheets with a Bosch 4.5" angle grinder in dim Aberdeenshire daylight and asking myself the same questions as the OP. Would definitely second the comments about sparks! But still wonder - does anyone make some sort of fence/datum surface for angle grinders? And if not, is there a reason why not?

We use a makita steel saw for roofing sheets, I guess its similar to the evolution ones that are slower spinning than a usual circular saw.

 

[pops92]

Use to cut 2 and 3 mm all the time with a 4" slitting disc. When I required an accurate cut I would scribe the final cut line,then with a auto or manual centre dot punch do the whole scribed line with dots.
Then cut on the waste side by a 1mm or 2mm. All the dots are visible through the sparks.
Then sanding disc to the dots all along.
Centre dotting all your cut lines use to be common practice where you on had basic cutting tools to work with.
Merry Xmas

Sent from my SM-T310 using Tapatalk

 

[Robbo3]

Bosch do a cutting guide for 4-1/2" grinders
Part number: 2605510292
EAN code: 3165140498432
- https://www.bosch-do-it.com/gb/en/diy/a ... -59717.jsp

Ebay - £32 upwards
- http://www.ebay.co.uk/sch/i.html?_from= ... de&_sop=15

 

[Bod]

Shetack saw.
No sparks.

Bod

 

[dickm]

Bosch do a cutting guide for 4-1/2" grinders
Part number: 2605510292
EAN code: 3165140498432
- https://www.bosch-do-it.com/gb/en/diy/a ... -59717.jsp

Ebay - £32 upwards
- http://www.ebay.co.uk/sch/i.html?_from= ... de&_sop=15

Thanks, mate. Seems an obvious addition when you think about it. If you've got a lot of straught line cuts, it's probably well worth the 'bay price. All the sheets are cut now, so probably won' t be getting one, but will remember it in case the need arises.
One suggestion for the OP that hasn't come up is jigsaw with metal cutting blade. Have cut 3mm sheet with one, slow but pretty precise.