Grinding stainless

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Spuddy

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Had a Google but nowt specific I can find on whether an angle grinder work hardens SS. I understand that heat is the factor that causes work hardening and I'll be splashing lubricant about but even so....
Need to follow up with hacksaw and file so staying softest is important.
Material is 3mm thick angle.
Anyone know the gospel?
 
I have certainly cut stainless with cutting discs specifically for stainless steel, on a 115mm grinder. As long as you do it fairly slowly I've never had a problem, and it cleans up ok with a file. I've never used any coolant.
 
Spuddy said:
Had a Google but nowt specific I can find on whether an angle grinder work hardens SS. I understand that heat is the factor that causes work hardening and I'll be splashing lubricant about but even so....
Need to follow up with hacksaw and file so staying softest is important.
Material is 3mm thick angle.
Anyone know the gospel?
Click to expand...

With stainless steel work hardening begins after the steel has 'yielded' and begins to plastically deform. Grinding does not plastically deform the material so no real work hardening will take place.

plastically deform will only occur with bending, stamping pressing or any clod forming but not cutting . When drilling it only when the drill rubs and does not cut that working can take place if at all.
 
Spuddy said:
Had a Google but nowt specific I can find on whether an angle grinder work hardens SS. I understand that heat is the factor that causes work hardening and I'll be splashing lubricant about but even so....
Need to follow up with hacksaw and file so staying softest is important.
Material is 3mm thick angle.
Anyone know the gospel?
Click to expand...
Why use a grinder anyway? A good hi speed hacksaw blade will go through it and less messy.
Stu
 
Using grinder because lots to chop off first followed by more precision stuff with hand tools. That's why
 
Spuddy said:
Using grinder because lots to chop off first followed by more precision stuff with hand tools. That's why
Click to expand...

Beg, borrow, or steal a Chop Saw. That way you'll cut it accurately right away. By the way, you would be astonished at what some of us, working in potentially gassy conditions, have had to cut with hacksaws.
 
I use 1mm discs in an angle grinder, followed up by flap discs. They give a much better finish than grinding discs. Tip, I mark the discs with felt tip 'SS', so as not to use them on steel, as the contamination will give rust stains.
Never had problems with hardening, unless using blunt drills, when I deserved it...
 
Rogershaw said:
With stainless steel work hardening begins after the steel has 'yielded' and begins to plastically deform. Grinding does not plastically deform the material so no real work hardening will take place.

plastically deform will only occur with bending, stamping pressing or any clod forming but not cutting . When drilling it only when the drill rubs and does not cut that working can take place if at all.
Click to expand...

I would be grateful for information about working with/grinding, cutting etc Stainless Steel.
I have very little experience of the tasks/outcomes, other than blunting drill-bits. :o
Please don't get too scientifically technical, but more along the lines of what happens to the SS and how it might affect its strength/properties.

Much appreciated in anticipation
 
Robert Wilson said:
I would be grateful for information about working with/grinding, cutting etc Stainless Steel.
I have very little experience of the tasks/outcomes, other than blunting drill-bits. :o
Please don't get too scientifically technical, but more along the lines of what happens to the SS and how it might affect its strength/properties.

Much appreciated in anticipation
Click to expand...

There's a thread on this every few months.
The main issue with stainless, as this thread attests, is work-hardening - caused by plastic deformation (i.e. a permanent change in shape, such as occurs with pipe-bending). Drilling without cutting can also cause it, such that a 'failed' attempt to drill a hole makes it the devil's own job to drill a hole in the same place.

The key to drilling is keep the job cool (almost any lubricant is OK), use a slow cutting speed, apply plenty of force with a sharp bit. Someone will be along to tell you the bit has to be cobalt, but a sharp HSS bit is fine. The required force is easiest to generate in a drill press. If you're drilling thin stuff, mount it on a flat wooden or plastic board, otherwise you'll deform it with the force you need to apply. The aim is to keep generating swarf: if the bit's not cutting, it's work-hardening the piece.

Hacksawing stainless is fairly straightforward. Again, if it's actually cutting, it's not work-hardening. A 1mm cutting disc in an angle grinder is a lot less effort.

Fairing and polishing is also easy enough, granted that stainless is harder than mild steel. As said above, going down the grades with a flapwheel is the usual approach, finishing by doing the same with buffing mops. Flapwheels specifically made for stainless are available. Polishing kits are available for £15 or so on Amazon/e-Bay. It's fairly laborious (and dirty) but strangely rewarding.
 
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Robert Wilson said:
Thank you, macd.
That puts my mind at rest knowing I have followed all the advice. I was wondering if the heat from grinding/cutting/drilling changed the properties of the metal, e.g. weakened it or reduced its stainless property.

Much appreciated.
R
Click to expand...

Heating stainless (welding, rather than correctly grinding/drilling) will stop it being stainless for a while, as will exposing a new surface. A fresh weld, a newly drilled hole, a hacksaw cut, filed edge etc on a boat will go rusty over night.

It needs to be passivated. It will naturally passivate in time (keep it inside, out of salty air, for a day or three), or it can be pickled or polished. Plenty of additional info on the 'net about passivation.
 
I had to lop a piece off my wind gen pole at the weekend, so my experience is less than 24hrs old.

A thin cutting disc for your angle grinder from toolstation cuts through stainless like butter. I filed off the rest.

I needed to drill 2 10mm holes, which took some time. Use a punch to mark the spot. I started with a 3.5mm drill piece and worked my way up 0.5 at a time. Slow and steady as others have said.
 
PaulRainbow said:
Heating stainless (welding, rather than correctly grinding/drilling) will stop it being stainless for a while, as will exposing a new surface. A fresh weld, a newly drilled hole, a hacksaw cut, filed edge etc on a boat will go rusty over night.

It needs to be passivated. It will naturally passivate in time (keep it inside, out of salty air, for a day or three), or it can be pickled or polished. Plenty of additional info on the 'net about passivation.
Click to expand...

Welding stainless causes chrome migration at the weld site. This is where the chrome content lose to the weld is reduced thus changing the properties of the stainless steel.

Its the chrome oxide that protects the iron in the stainless steel from rusting so as you say cutting or polishing the surface tends to remove the chrome oxide thus the protective layer but in an oxygen rich environment the oxide layer forms quickly so would not form much rust. Do note rust spots that can form on stainless could be due to atmospheric contaminates from industrial processes nearby.

Further reading

http://www.bssa.org.uk/topics.php?article=107
 
timmygobang said:
I tried this after scouring the internet for advice and got nowhere very slowly. Try with a 5mm and if you're still struggling follow my advice. :encouragement:
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Perhaps your scour failed to show up the recent thread on here on the very subject of drilling stainless by increments? Plenty of hands-on practical advice (pretty much confirming Graham's view: increments, yes; tiny ones, no).
 
macd said:
Perhaps your scour failed to show up the recent thread on here on the very subject of drilling stainless by increments? Plenty of hands-on practical advice (pretty much confirming Graham's view: increments, yes; tiny ones, no).
Click to expand...

I disagree and know what worked for me. I tried drilling the holes following the advice on the forum with no success. Bare in mind, this with a regular drill on tubular ss, and not with a pillar drill in a workshop.

Anyhow I'm not going to get into any tit for tat with other forum users. That was my first hand experience.
 
timmygobang said:
I disagree and know what worked for me. I tried drilling the holes following the advice on the forum with no success. Bare in mind, this with a regular drill on tubular ss, and not with a pillar drill in a workshop.

Anyhow I'm not going to get into any tit for tat with other forum users. That was my first hand experience.
Click to expand...

With a hand-drill on the thin-wall tube found on most boats, which is prone to deformation, it can indeed be different. Glad it worked for you.
 
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