Steel Prep

[rorie]

Quick question…. how do you guys prepare steel for welding? Currently i am using knotted wire to remove rust and paint, then flappy pads (40 grit).

However, i am going through SOOO many flappy pads and at £2 each, this is costing me a small fortune! So am i missing something? What do you guys use?

Thanks!

 

[Bill Edwards]

Mostly grinding disks, what sort of thickness is the metal you're working with?

 

[Richard.]

Grinding discs are cheaper last longer and cut through scale and rust better than flap discs. A flap disc is more of a finishing tool or if a ground finish is too rough/harsh. It's a waste to use good flap discs on scale.

 

[rorie]

Ah ok - its only 1.6mm and 2mm steel i'm using….is a grinding disc not a bit harsh? Or would you still suggest its best? I guess i just need to try and get it as flat as possible on the steel?

 

[Richard.]

Well if grinding marks are acceptable then should be fine I grind thin metal. Some discs are less harsh.

 

[Shedendman]

get yourself some backing pads
http://www.ebay.co.uk/itm/115mm-Rub...203?pt=LH_DefaultDomain_3&hash=item3aaccb36fb

http://www.ebay.co.uk/itm/FLEXIPAD-...t=LH_DefaultDomain_3&var=&hash=item51cce34d22

My advice it to get both the nylon and rubber ones
Then shop around for different grades of discs,forget those crap brown ones go for the blue zirconia
http://www.ebay.co.uk/itm/20x-115mm...t=LH_DefaultDomain_3&var=&hash=item27c38d6a36

then you can swop what disc for what needs

 

[Bill Edwards]

I tend to use a grinding disk for that sort of thickness, just don't get carried away or press hard. At the end of the day, you've still got to remove the rust and paint, and done carefully a grinding disk makes a good job quickly and cheaply.

 

[anto44]

The edges of thin steel like the can destroy a flap disc very quickly if your not carefull. Keep the disc as flat to the sheet as possible when at the edge, if you go over the edge with the disc at a big angle it'll tear the disc to bits.

 

[rorie]

Thanks very much for the replies. I will have a go with the grinding disc tonight and see how i get on!

Thanks for the links to the backing pads - i never knew of that option before. Though they still aint that cheap, assuming they run down at the same sort of rate as a flappy?

What about the shape of the grinding disc? I have seen some which are flat, and some that have a slight cone in the middle. I assume this is just personal preference?

 

[Richard.]

Thanks very much for the replies. I will have a go with the grinding disc tonight and see how i get on!

Thanks for the links to the backing pads - i never knew of that option before. Though they still aint that cheap, assuming they run down at the same sort of rate as a flappy?

What about the shape of the grinding disc? I have seen some which are flat, and some that have a slight cone in the middle. I assume this is just personal preference?

Most metal grinding discs have a depressed centre so they will only go on one way because the reinforcement is at the back. Cutting discs are usually (not always) flat. Some cutting discs do have depressed centres but I don't believe you will find many flat grinding discs. Could be wrong mind

 

[langy]

I use a poly disc as it don't remove metal, only rust and millscale

 

[sapperb]

I use grinding disks like the ones Stalwart posted, then clean it up more with a mild wire wheel on my bench grinder..Metal prep is everything..IMO.

 

[zx9]

I use a poly disc as it don't remove metal, only rust and millscale

And remember to run the disc off an edge, run it onto an edge will destroy the disc in no time.

 

[wortgames]

Why are you using the flap discs after the knotted wire for prepping? I find the knotted wire cleans things up nicely, before and after the weld. I only use flap discs when I need to try and blend an ugly weld.

I bought a stainless knotted wire wheel for cleaning up a beer keg years ago, and I have only just replaced it after several years of odd jobs and almost completing a tandem trailer rebuild. I don't know how well the carbon steel wheels last, but I reckon the stainless one has been excellent value so I just got another one the same.

 

[Maker]

And remember to run the disc off an edge, run it onto an edge will destroy the disc in no time.

I keep making this mistake with the Velcro backed sanding discs on my grinder, go into an edge and the sandpaper disintegrates.

 

[Kent]

I dislike flap discs they are too dear for
thier lifespan.
I use std grinding discs for tough stuff. Wire wheels for thick paint and rust and backing pads with various grades of sanding discs for Polish.
I also but rarely use those thick sort of rubbery fleece types if I need to remove midscale on the flat only!
If I was working non ferrous I should do differently as lots of these newer products have advantages there but on std mild Steels no not cost effective

 

[Bede]

Never used flap disks, as said above, too expensive for lifespan. Grinder for scale, 36 grit zirconia sanding pad for rust and wire wheel for cleaning welds.