Welding

Post by **Lukey** » Wed Jan 21, 2009 5:37 pm

I have recently bought an ARC welder and a MIG Welder, for the last week I've been cutting and welding different thicknesses of metal, making little things, just generally practicing.

My welding is up to an acceptable level now but my metal cutting is atrocious! I'm going in to town to order a books on metal forming and welding tomorrow but I'm curious as to how it's done properly.

I want to cut the repair that was done to my foot well out and do it properly. It's just a bit of plate slapped over the hole from underneath and welded on with masses of spatter. How would I cut this out tidily? Any time I have ever attempted to be precise with my angle grinder it goes very wrong.

Post by **Alec** » Wed Jan 21, 2009 6:05 pm

HelloLukey,

angle grinders are normally pretty accurate as long as you have room. Better still with the very thin cutting discs now available, about 1mm thick. Ensure that you have a steel cutting disc, not stone.

Alec

Post by **alex_holden** » Wed Jan 21, 2009 6:08 pm

What I do is:
* Clean the paint and rust off the area with a rotary wire brush until I get back to clean solid shiny metal.
* Use a black Sharpie marker pen and a ruler/square to mark out where I want to cut.
* Cut along the lines with an ordinary metal cutting disc (the width of the cut is about the same as the width of the line). You don't want to let the disc go a long way through; you can control the cut most accurately if it's only just cutting right through the thickness of the metal. I don't worry if I cut slightly too far along a line because I can always weld the gap back together when I weld the new panel in.
* Tidy up the rough cut edges with a coarse flat file.

Sometimes there are tight corners you can't quite reach with a grinder. I usually use a padsaw on those (the type that holds a hacksaw blade).

Pay attention to what is on the other side of the panel you are about to cut through (make sure you're clear of brake lines and wiring etc.). If the grinder sparks are going anywhere near the windows, cover them up with something otherwise the sparks melt into the glass and leave ugly black marks that can't be removed.

Post by **Lukey** » Wed Jan 21, 2009 7:20 pm

Oh OK, I'll have to practice. Is that how most metal is cut on a car for repair work? Extra thanks for the tip about glass, I can guaranty I would have done that.

Post by **Dean** » Wed Jan 21, 2009 8:10 pm

I don't think you can cut through metal and get a tidy clean finish with ARC or MIG, GAS is usually the one for cutting. Use the cutting suggestions above, it'll be so much more successful.

Post by **alzax3** » Wed Jan 21, 2009 8:10 pm

It depends who's doing the cutting and how much they have to do. A good jigsaw with a metal blade and slow speed (essential or the blade will melt) will cut neatly in single thickness. A plasma cutter will slice through pretty much any sheet, painted or not - like butter, and with little distortion. It sounds like a grinder with a thin cutting blade is probably the easiest solution for you.

Post by **bmcecosse** » Wed Jan 21, 2009 8:48 pm

The sparks from angle grinder will also burn into the paintwork and the chrome, and any interior trim if you are working inside the car - it ALL needs to be covered! Oh - and your skin too - and of course your eyes, and protect your ears from the noise! Good idea to drill a small hole at the end of each cut line before you start cutting! You can also use hand snips - and of course there are specialist cutters (Monodex eg) that take out a thin strip of metal - some can be air powered to save your hands the effort. http://www.pvrdirect.co.uk/productinfo. ... ma-EDM0101 There will be other suppliers - I have never used this one - it's just to show the tool.

Post by **Lukey** » Wed Jan 21, 2009 9:31 pm

Ah OK, I've have a gas cutting torch donated to me but I've never used it. Under what circumstances would I used a gas torch?

Post by **Alec** » Wed Jan 21, 2009 10:09 pm

Hello Lukey,

if you are talking about an oxy\acetylene cutter it will not cut very thin steel cleanly. 1\8" is about the thinnest and that requires a special nozzle.
I use many different tools to cut sheet metal, air chisels are quick and neat, but don't work well on rusty\thin metal, angle grinder in some circumstances, aviation snips for accurate cutting, air reciprocating saw in tight places and occasionally an oxy\acetylene welding torch if access is very limited but it is not particularly clean or accurate.

Alec

Post by **stag36587** » Wed Jan 21, 2009 10:17 pm

I agree with Alec and I've found the reciprocating saw excellent for tight spaces

Post by **alainmoran** » Wed Jan 21, 2009 11:06 pm

Alec wrote:HelloLukey,

angle grinders are normally pretty accurate as long as you have room. Better still with the very thin cutting discs now available, about 1mm thick. Ensure that you have a steel cutting disc, not stone.

Alec

EEEEK nooo ... those 1mm cutting discs are great with modern steel, but with the thicker stuff you get on a minor then you will burn your way through LOADS of them just getting through a small bit ... get yourself some of the cheap ones from machine mart or wilko's - they will last a LOT longer!

Post by **ADO16** » Thu Jan 22, 2009 3:46 pm

Hello Lukey,

One of the most important items when welding, grinding, etc. is the all important pair of gloves!!! I've learned this lesson the hard way. I hope this didn't kill the tread, but I needed to drop in my 2cents.

Steve

Post by **Alec** » Thu Jan 22, 2009 4:29 pm

Hello Alain,

The original post was to do with accuracy not consumables' life.
I didn't say they were long lasting, however, a lot depends on how you use them, maximise the life by only having the disc just through the metal, too deep and that really consumes them.
I don't consider that the steel on a Morris is thick, most of my cutting with these discs is stainless steel of 1.6mm to 3mm and they are excellent for that.

Alec

Post by **Lukey** » Thu Jan 22, 2009 4:37 pm

ADO16 wrote:Hello Lukey,

One of the most important items when welding, grinding, etc. is the all important pair of gloves!!! I've learned this lesson the hard way. I hope this didn't kill the tread, but I needed to drop in my 2cents.

Steve

Not to worry, I always wear ear defenders, goggles and a fat pair of gauntlets.

Post by **grumpygrandad** » Thu Jan 22, 2009 5:07 pm

hello let the disc do the cutting only with gentle pressure from you then they will last, my mate always puts his 16 stone on the end of his power tools just breaks every thing, no he doesnt use mine if i can help it, treat your tools with respect and they will respect you,,,,grandad

Post by **Steve_PFJ** » Thu Jan 22, 2009 6:16 pm

I can thoroughly recomend plasma cutters.

Cutting bodywork steel thicknesses is like a knife through butter and the cut is clean. I'm not very steady handed with it yet so use straight edges to guide it. If I don't then, because the cut is so precise, you can see every little twitch i make. There's minimal chance of distortion as it's so quick and the heat so concentrated.

Steve

Post by **paulk** » Thu Jan 22, 2009 6:25 pm

As Grandad said let the speed in the blade do the work, don't try and force the Grinder blade through the metal.
Plasmas are great tools and possibly the most fun you can have whilst wearing goggles but not really DIY ...Yet.

Post by **Steve_PFJ** » Thu Jan 22, 2009 6:44 pm

Not sure I'd agree. The initial cost is quite high, particuarly if you don't already have a compressor, but prices on both machines have fallen dramatically.

Consumables work out cheaper than an equivalent amount of cutting using discs. The setup is similar to that of mig welding and no more dangerous than mig welding or oxy/acetylene cutting.

This is, of course, just my opinion.

Post by **stag36587** » Fri Jan 23, 2009 12:28 am

Just on the cost of 1mm discs. I got a set of 40 at the NEC in November for £7 which I thought was excellent value.

Post by **chanyboi** » Mon Nov 02, 2009 10:13 pm

wow.. im new here and have just got myself a morris, whats NEC??