Bench grinders

[t121anf]

We are doing a large amount out of work on the house and my cold chisels keep getting blunted in the process.

My dad has a bench grinder which I sharpen them on but he lives 30miles away so it’s a pain.

Thinking about getting a cheap bench grinder, but it’s 150w, would that be powerful enough?

No idea what power my dads is, no markings and if I ask I’ll get a load of “just use mine” which doesn’t help.

[MarJay]

Don't get hung up on numbers with stuff like this. I honestly can't see a 150w bench grinder being bad at sharpening tools. I got a free bench grinder from my Dad, and it's an ancient Clarke one. It sharpened my mates shears up like a razor blade, so meh. The key to a bench grinder is that a) it bolts to a bench making repeatability and bracing easier and b) it grinds stuff. Everything else is a bonus. If you're interested, I just went to the garage to check, and it's 200W and if anything it's a bit too much for the stuff I use it for, so 150w will be absolutely fine I think.
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[Pete.]

The little 150w bench grinder will sharpen your chisels but there are 2 other things to consider:

1, It will blunt pretty quickly, so buy a dressing tool.
2, Chisels when sharpened will lose their temper is you let the chisel edge go blue even once, so don't grind that chisel edge at too shallow an angle (60 degrees or more is OK) and dip it in water often.

If you don't follow 1, nothing will stop that chisel edge going soft.
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[stinkwheel]

I bought a bench grinder, then realised I should have bought a belt grinder.

I would sharpen a cold chisel with a file. Don't forget to dress the top too if it's looking like a badly hammered fencepost top so you don't learn about spalling the hard way.
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[t121anf]

Thanks Marjay, the next step is 400w and double the cost so I’ll give the 150w a try.

Pete, does that apply to cold chisels or just woodwork chisels? Only taking cold here, I sharpen woodwork ones on a whetstone.

Stinkwheel, fortunately my chisels haven’t got to that point yet, good tip though.

[stinkwheel]

They are still hardened steel. Once hardened, the hotter the temper temperature, the softer the steel lands up. For tool steel, it'll be tempered at temperatures you'd bake a cake at. Get it hotter than that and you'll be making the steel softer.

I'm shit at metalwork and an engineer once told me that power tools don't do a job better, only faster. Hence why I use files a lot, then I can spot when I'm making a cock and balls of it before it gets unsaveable.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MCN]

I've used 'cold' chisels for years and anytime I tried to use a file to repair the edge it's been a time consuming phaph.

A big grinder with a quenching pot near it works perfectly. And the edge lasts as long as it did when new.

Once you have ground down a few mm though you will be into different material properties.

I can re harden and temper a chisel though.

As Stinkers said, grind off your mushrooms too.

And buy good chisels. You cannot make a sow's ear from a silk purse.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Pete.]

[Robby]

You haven't said what the chisels are being used for. Is it woodwork, or is it levering tiles off the wall?

If it's the latter, a battery SDS drill with a chisel attachment makes it much easier. Then when all the decorating is done and you're fixing things to the wall, you can drill holes without making as much mess as a hammer drill.

It's another of those tools that I don't need, but I'm very glad I have.

[MCN]

Hardening and tempering:

Heat in a hearth or with a blow torch until the top of the chisel is 'cherry-red'.

Cool it immediately in cold water. Cooling in oil will make a ton of thick smoke and might result in a bit of fire.

Clean off the blackened surface using emery cloth, wet and dry, sand paper etc. to a shiny finish. Heat the chisel again with a blow torch and watch the shiny surface change colour as the metal reaches each tempering stage.
It's a bit like a rainbow (but not ghey).

The heat creeps along the metal so it is easier to heat the shaft and watch the colour move up to the tip.
If you heat it up too quick you risk missing the temperature range and the tempering will not be correct.

For a cold chisel you want the tip to be at the straw colour.
Then dip in the water again to stop the tempering process.

You can phaph about with the sand paper to clean up, heat the whole thing up for a bit then drop it in oil. That will give the surface a burned oil finish which helps prevent corrosion for a while.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[MCN]

[Pete.]

[Polarbear]

If you use a rotary grinder to sharpen cold chisels. don't get them too hot or you'll fcuk up the heat treatment.

I have a cheap and nasty wet grindstone that does way better than my bench grinder.

https://cdn.aws.toolstation.com/images/141020-UK/800/30131.jpg

£60 from toolstation. Nothing special but way more versatile than a bog standard bench grinder.
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[MCN]

[t121anf]

Currently removing pebble dash from my walls to get them back to brick to get it rendered, otherwise smashing through bricks to make holes for pipes etc.

Got a bit of a point with a file but not had a chance to use it in anger yet, got to be better than a rounded tip.