Bench grinder – wheel grit

[colin hamiltonParticipant @colinhamilton16803]

I've recently been given a 6 inch bench grinder which I'm hoping to mainly use for making HSS lathe tools. The wheels are in poor shape so I'm looking to replace them. I was thinking of getting a couple of white aluminium oxide ones (roughing &polish finish). What's the consensus on appropriate grits? Also looking at some of the adverts for the wheels they state for dry cutting only. Does this mean I would need to dry the steel after dipping it in a cup of water to cool?

[colin hamiltonParticipant @colinhamilton16803]

[Clive Brown 1Participant @clivebrown1]

For HSS grinding in my home workshop, toolbits say 3/16" to 3/8" and drills, I mostly use a 60 grit wheel. 80 grit would also be OK I'd think. The finish can always be improved with a slip-stone if necessary.

IIRC, my coarse wheel is 30 or 40 grit. It's used a lot less than the finer wheel, but useful for initial shaping.

No need to dry the steel after cooling.

Edited By Clive Brown 1 on 06/09/2021 15:58:55

[Rod RenshawParticipant @rodrenshaw28584]

There is a theory that if you let the steel get too hot then dipping in water creates cracks in the steel? Better to let the steel cool more slowly. Work on several tools in turn letting the "resting" tools lie on a metal surface to aid cooling.

Rod

[Anonymous]

I use an 80 grit Alox wheel on one end of my small bench grinder for HSS tooling. The other end has an 80 grit 'green' wheel, mainly for TIG electrodes. I also have a larger bench grinder with a 220 grit wheel, but that's really too fine to be useful. After grinding I use a diamond hone to clean up the edges after grinding, and bring to size if needed. If a lot of material needs to be removed I use the mill and a carbide cutter.

Dry cutting only refers to the use of flood coolant, not a toolbit that's been dunked in water to cool it.

Andrew

Edited By Andrew Johnston on 06/09/2021 16:49:27

[Dave SParticipant @daves59043]

46 grit and 60 grit would be a reasonable pair. If you want a polished finish grab a resin bonded diamond wheel.

Yes they are theoretically no good for HSS, but in practice mine is still sharpening HSS, Carbide and the odd bit of silver steel just fine after years of use (and the tools are also fine)

Why are you dipping HSS?

Hold the blank in a pair of mole grips and grind it.
You will not draw the temper – that’s why it’s called High Speed Steel. It has enough red hardness to cut metal…

Dave

[colin hamiltonParticipant @colinhamilton16803]

Thanks everyone. I've bought an 80 grit so I think I go for something around the 40 grit to pair with it.

[colin hamiltonParticipant @colinhamilton16803]

Posted by Dave S on 06/09/2021 17:24:53:

46 grit and 60 grit would be a reasonable pair. If you want a polished finish grab a resin bonded diamond wheel.

Yes they are theoretically no good for HSS, but in practice mine is still sharpening HSS, Carbide and the odd bit of silver steel just fine after years of use (and the tools are also fine)

Why are you dipping HSS?

Simply to save burning my fingers. I think I would find the mole grips too cumbersome. I would end up picking it up and burning myself so I think better to keep the temp down as I go.

Hold the blank in a pair of mole grips and grind it.
You will not draw the temper – that’s why it’s called High Speed Steel. It has enough red hardness to cut metal…

Dave

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