Plasma cut kerf width?

[hooblah]

I'm hacking the tunnel out of my car and I'll be welding it back in after a few modifications. I don't want to get grinding sparks all over the place. Especially on the glass!
I was thinking about using a plasma cutter to cut it out instead, as the sparks will be directed to the outside, but is the kerf going to be too wide that it will be difficult to weld the panel back in without adding metal?

 

[Barking Mat]

Grind it back with a grinder post plasma, and for God's sake watch out for glass and sparks, wish someone had told me that many years ago. D'oh.

Kerf shouldn't be a problem.

And watch out for general fire issues.

 

[hotponyshoes]

The cut width on car thickness material is less than a slim cutting disc and you can follow curves with plasma so actually less to weld up afterwards.
I'd still cover the glass though!

 

[Hood]

The kerf width will depend on how steady you are as well as the nozzle size/current used.
On my CNC plasma the kerf width with a 1.4mm nozzle is 2mm so with a smaller nozzle and lower current it could be as little as 1mm. As said however that is on a CNC that is steady, cutting by hand you will be wavering about so...

 

[hooblah]

Ok now hood's post contradicts hot pony's post.
A 1.4mm nozzle that has a 2.0mm kerf is not going to be suitable. What's the smallest nozzle/kerf that can be achieved?

 

[chunkolini]

If you are calm, collected and focussed working by hand it can be around 2mm.
But chill out first and watch the Karate Kid films first. There is a lot to breathing right and being in the Zone
Also practice plenty first. Do several dry runs before committing yourself. its a bugger getting to the end of a run and having to adjust your posture

 

[Hood]

Ok now hood's post contradicts hot pony's post.
A 1.4mm nozzle that has a 2.0mm kerf is not going to be suitable. What's the smallest nozzle/kerf that can be achieved?

A 1.4mm nozzle is for 80-90Amps on my torch/plasma so if you are using a lower current then you would be using a smaller nozzle, for example if I use 30Amps I would use a 0.9mm nozzle which, on the CNC, would probably be just over 1mm kerf.

 

[tigdlo]

Plasma or cutting disc, are these the only 2 options?

Jigsaw, padsaw, sabresaw, air hacksaw?

 

[Erie Fred]

Tack a strip on the outside, to bridge between the patch and the main body ?
Maybe 1" (25mm) wide, same thickness as the patch.

 

[hooblah]

Plasma or cutting disc, are these the only 2 options?

Jigsaw, padsaw, sabresaw, air hacksaw?

You're right. I have a recip saw but I find their accuracy to be somewhat lacking.

 

[MattF]

You're right. I have a recip saw but I find their accuracy to be somewhat lacking.

That's it. Blame the tool.

 

[daedalusminos]

You're right. I have a recip saw but I find their accuracy to be somewhat lacking.

I'd forget the plasma then!

 

[zeppelin builder]

You're right. I have a recip saw but I find their accuracy to be somewhat lacking.

Air panel saw cost about £20
use cut down hacksaw blades if you have a hand shear

 

[hooblah]

No air unfortunately.

 

[hotponyshoes]

No air unfortunately.

You'd normally need air for a plasma cutter.
Unless you get one with an inbuilt compressor

 

[tigdlo]

No air unfortunately.

Arm operated version, if you don't already have one. https://www.ebay.co.uk/itm/125840528952 It's a usefull tool to have even if you aren't going to cut a full tunnel out with it, somethimes you cant get anything better in or want to cut through 1 layer of a multi layer flange like the bottom of a sill.

 

[skotl]

That's it. Blame the tool.

Mattf: "Hmmm... I blame the tool"

...
...
time passes
...
...
Mattf reads the mig-welding forum
...
...

Mattf: "I need a better tool!"

 

[Morrisman]

Ok now hood's post contradicts hot pony's post.
A 1.4mm nozzle that has a 2.0mm kerf is not going to be suitable. What's the smallest nozzle/kerf that can be achieved?

My r-tech cut30 takes 1mm out cutting thin sheet. Or a y sheet up to 6mm or so. To take 2mm you'd need a brute of a plasma cutter.

 

[James1979]

It’s all a bit irrelevant to be fair as you’ll be grinding it back for welding anyway.

Plasma cut edges weld like crap. Full of porosity. You only need to take the hard edge off with a flap disk but you’ll still be +0.5mm on the kerf at best I would think.