Hello,

I'm looking to get a bench grinder to sharpen some chisels. I see some
have discs six inches wide, others are eight inches; is one any better
than the other?

Is there anything else to look for? Should the power be a certain
number of Watts for example?

I see most grinders have two discs: a coarse and a fine one but a few
are wet and dry. Is there any advantage to a wet and dry one, and if
so, why aren't they more prevalent? Why is the wet disc always at
right angles to the body?

Thanks,
Stephen.

On 22 Sep, 15:20, Stephen wrote:
Hello,

I'm looking to get a bench grinder to sharpen some chisels. I see some
have discs six inches wide, others are eight inches; is one any better
than the other?

Bigger is vaguely better, as the resultant grind has less of a hollow
to it. However this is a very minor point.

I see most grinders have two discs: a coarse and a fine one but a few
are wet and dry. Is there any advantage to a wet and dry one,

I'd strongly recommend the sort with a 10" slow water cooled wheel.

Double-ended coarse/fine fast grinders with small wheels are OK for
most metalworking applications, such as cold chisels and HSS lathe
tools. However we now have angle grinders for many other tasks and
there just aren't that many things for which is the best sort of
grinder.

For woodworking tools, these grinders are much too fast, too hot and
rather too coarse too. They're better than nothing if you want poor
results on HSS woodworking tools in a hurry, but that's about it. I
wouldn't even use them for woodturning tools (which are generally more
robust to abuse in grinding). In particular, they'll ruin good edges
in good steels by overheating them.

If you do see a woodworking grinder, then it's usually slow-speed,
large wheel diameter and water cooled. I've a Record one (rebadged
Scan) that's quite cheap, the popular Tormek is 200 quid+ and there
are some Creusen grinders that are very similar to the typical
metalworking grinder, except for running at half the speed (1425, not
3450).

A useful compromise for the DIY workshop is a cheap (I've seen 30
quid) double-ended grinder with a worm drive to a 10" wet wheel.
They're noisy, the wheels are a bit too coarse and the dry wheel is on
the small side, but they're 30 quid... These are useful for
woodworking tools, the wet end at least. I use mine for the
woodturning tools and for initial shaping of newly forged tools or
refurbishing and reshaping of old damaged S/H chisels. Then it's the
Record for rough grinding, then hand stones for actual sharpening.

On Tue, 22 Sep 2009 07:50:11 -0700 (PDT), Andy Dingley
wrote:

Double-ended coarse/fine fast grinders with small wheels are OK for
most metalworking applications, such as cold chisels

Cold chisels and sds chisel bits were what I had in mind. It sounds as
though for these types of chisel a dry grinder is ok but if I wanted
to sharpen wood chisels I would need a water cooled one?

Stephen formulated on Wednesday :
On Tue, 22 Sep 2009 07:50:11 -0700 (PDT), Andy Dingley
wrote:

Double-ended coarse/fine fast grinders with small wheels are OK for
most metalworking applications, such as cold chisels

Cold chisels and sds chisel bits were what I had in mind. It sounds as
though for these types of chisel a dry grinder is ok but if I wanted
to sharpen wood chisels I would need a water cooled one?

Probably you could get away with a fine wheel, gentle grinding and
dipping frequently in a water bath.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Stephen wrote:
On Tue, 22 Sep 2009 07:50:11 -0700 (PDT), Andy Dingley
wrote:

Double-ended coarse/fine fast grinders with small wheels are OK for
most metalworking applications, such as cold chisels

Cold chisels and sds chisel bits were what I had in mind. It sounds as
though for these types of chisel a dry grinder is ok but if I wanted
to sharpen wood chisels I would need a water cooled one?

Cold and SDS chisels will be OK as they are tempered differently from a
wood chisel.

Cold and SDS chisels have a much greater mass to absorb the heat
generated as well. However, they don't need heavy pressure on the wheel.
Blueing them is not a crime, as that is what colour they are tempered to
in manufacture.

Grinding anything is not about loading the grindstone wheel, but about
getting a feel of grinding. If you want to grind something quickly,
revert to the DIY favourite, the angle grinder.

In fact, what would the group's opinion be on that?

Wood chisels are tempered to a lower temperature of straw coloured. That
gives them a much harder edge, but much more liable to chipping that
edge. Blue one of those and you have 2 ways out.

Through it away, or start the hardening and tempering process all over
again.

Not

Dave

Dave explained :
Grinding anything is not about loading the grindstone wheel, but about
getting a feel of grinding. If you want to grind something quickly, revert to
the DIY favourite, the angle grinder.

In fact, what would the group's opinion be on that?

No problem, I do it all the time.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Harry Bloomfield wrote:
Dave explained :
Grinding anything is not about loading the grindstone wheel, but about
getting a feel of grinding. If you want to grind something quickly,
revert to the DIY favourite, the angle grinder.

In fact, what would the group's opinion be on that?

No problem, I do it all the time.

Well, that is one comment :-)

Dave

On 23 Sep, 23:02, Stephen wrote:

Cold chisels and sds chisel bits were what I had in mind.

How many of these are you realistically planning on sharpening?

I have several "old style" grinders and rarely use them (lathe tools
only). On the rare cases when I do need to sharpen a cold chisel, I'm
usually on-site, up to my ears in plaster dust and have an angle
grinder with me but not a bench grinder. You can imagine the rest...

to sharpen wood chisels I would need a water cooled one?

Yes. This depends somewhat on the steel used and the quality of both
chisel and the work you're planning for it, but broadly yes.

You'll see woodworking tools, particularly Stanley plane irons,
advertised as using chrome molybdenum vanadium steels. This is a _bad_
thing in a plane iron - the steels are softer, "gummy" to sharpen and
you can't get a good edge on them (my notion of "good" is pretty high
here). These HSS-like alloys are used because they increase the
softening temperature of the steel, thus allowing them to be ground in
factories on fast, dry air-blast wheels, thus reducing costs. Note
that you can't have a grinder like this yourself - you won't get the
cooling air jet (serious HSE issues involving dust extraction), so
you're going to be running even hotter.

The best chisels around are 50+ year old Sheffield-made chisels with
very simple alloys of high carbon steel, particularly if you can find
laminated ones. These are fairly easy to sharpen, but do need to be
kept cool if they're not to draw the temper. Any powered grinding
needs to be wet. For another thing, the angles are more acute, so an
edge has much less "body" behind it to distribute heat by conduction.
Then their final grinding (bevel & honing) really needs to be done by
hand (only takes moments) because a mechanical wheel would have to
have very expensive bearings to give the necessary stability.

I'd strongly recommend a starter sharpening kit for woodworking of a
cheap powered wet wheel for resurrecting car-boot sale chisels, a
cheap combination waterstone (1000 / 4000 grit on each side) and a
read of Leonard Lee's "Sharpening" book. You might find Scary Sharp
worth a look too (silicon carbide wet & dry paper stuck to glass).
Oilstones are a pain, diamond and ceramic are expensive for good
quality.

In article , "Stephen"
wrote:

Hello,

I'm looking to get a bench grinder to sharpen some chisels. I see some
have discs six inches wide, others are eight inches; is one any better
than the other?

By wide I assume you mean diameter? It's easier to use larger diameter
wheels on most materials - but that may have been because the large ones
were used professionally so were always well dressed. (I must get round
to doing mine...)

Is there anything else to look for? Should the power be a certain
number of Watts for example?

Not usually a problem unless you intend to grind thick stock.

I see most grinders have two discs: a coarse and a fine one but a few
are wet and dry. Is there any advantage to a wet and dry one, and if
so, why aren't they more prevalent? Why is the wet disc always at
right angles to the body?

Yes, for chisels and other hardened and tempered tools a slow, wet wheel
is practically mandatory as you'll probably draw the temper using a
fast, dry wheel, ruining the item being ground.

The wet wheel is usually at right angles to the high speed shaft to
accommodate the gearing slowing it down considerably from the dry wheel
speed, connected directly to the motor shaft.


Thanks,
Stephen.



--
John W
I you really want to mail me, replace the obvious with co.uk twice

On Tue, 22 Sep 2009 15:59:45 +0100, John Weston
wrote:

The wet wheel is usually at right angles to the high speed shaft to
accommodate the gearing slowing it down considerably from the dry wheel
speed, connected directly to the motor shaft.

That explains it. Thanks.

Stephen formulated on Tuesday :
Hello,

I'm looking to get a bench grinder to sharpen some chisels.

Wood chisels, or some other type of chisel?

I see some
have discs six inches wide, others are eight inches; is one any better
than the other?

Diameter, rather than wide?

The greater the diameter, the wider will be the edge face of the wheel
and probably the more powerful it will be for grinding heavy materials.

Is there anything else to look for? Should the power be a certain
number of Watts for example?

No - the larger and heavier the wheels, the more power will be needed
to make them turn and grind (see above).


I see most grinders have two discs: a coarse and a fine one but a few
are wet and dry. Is there any advantage to a wet and dry one, and if
so, why aren't they more prevalent? Why is the wet disc always at
right angles to the body?

A wet wheel will prevent the material being ground heating up and
loosing it's temper. You can get the same by grinding gently and
dipping the tool tip frequently in a water bath to keep it cool during
grinding.

The important thing to remember is that the RPM of the grinder means
little, what matters is the speed that the edge of the wheel will pass
a tool which is being ground. The faster it moves and the more course
it is, the hotter the tool tip will become.

For gentle grinding of wood chisels, the Plasplugs 4 in 1 unit is quite
good for these and also does various types of drill bits and helps make
sure you get the correct angles. The go for around £50, but I recently
saw one in a shop for just under £25, special offer. I have one of
these, a 6" and an 8" grinder.




Thanks,
Stephen.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Tue, 22 Sep 2009 18:36:03 +0100, Harry Bloomfield
wrote:

Wood chisels, or some other type of chisel?

Diameter, rather than wide?

Sorry, I was not very clear in my OP. I was talking about cold
chisels, bolster chisels and sds chisel bits, and you and the other
poster are quite right, I meant diameter.

the larger and heavier the wheels, the more power will be needed
to make them turn and grind.

Are they all induction motors, and if not, is induction preferable?

I have one of these, a 6" and an 8" grinder.

Why do you need both a 6" and an 8"? Is one more suited to one task
than another?

Thanks.

Stephen has brought this to us :
On Tue, 22 Sep 2009 18:36:03 +0100, Harry Bloomfield
wrote:

Wood chisels, or some other type of chisel?

Diameter, rather than wide?

Sorry, I was not very clear in my OP. I was talking about cold
chisels, bolster chisels and sds chisel bits, and you and the other
poster are quite right, I meant diameter.

The bigger the better then, if you intend to do many. 8" as a minimum.

The SDS is a different beast. Probably a 6" would do for that, but it
will need a special wheel called a green grit wheel. The normal
blue/grey will not even mark the carbide edge.

the larger and heavier the wheels, the more power will be needed
to make them turn and grind.

Are they all induction motors, and if not, is induction preferable?

Yes, certainly for this size of grinder.


I have one of these, a 6" and an 8" grinder.

Why do you need both a 6" and an 8"? Is one more suited to one task
than another?

The 6" is better suited for drill bits and HSS lathe bits. The 8" does
the courser and heavier work and is twice the power.


Thanks.

No problem.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Tue, 22 Sep 2009 18:36:03 +0100, Harry Bloomfield
wrote:

a 6" and an 8" grinder.

I have been browsing a few online shops and it occurs to me you may
have one machine with a 6" wet wheel and an 8" dry wheel. Is this
right?

Stephen formulated on Wednesday :
I have been browsing a few online shops and it occurs to me you may
have one machine with a 6" wet wheel and an 8" dry wheel. Is this
right?

I have never heard of one, but there is no reason why not. Probably the
best of both worlds - but you still need a means to grind the SDS.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Stephen wrote:
On Tue, 22 Sep 2009 18:36:03 +0100, Harry Bloomfield
wrote:

a 6" and an 8" grinder.

I have been browsing a few online shops and it occurs to me you may
have one machine with a 6" wet wheel and an 8" dry wheel. Is this
right?

Go to your local 'shed' and look for one. If you find one, spin the
smaller wheel with you finger and see how fast the other wheel spins. It
must be slower, otherwise. you have got the wheels mixed up.

Wet wheels are usually larger and wider.

Dave

"Stephen" wrote in message
...
Hello,

I'm looking to get a bench grinder to sharpen some chisels. I see some
have discs six inches wide, others are eight inches; is one any better
than the other?

Is there anything else to look for? Should the power be a certain
number of Watts for example?

I see most grinders have two discs: a coarse and a fine one but a few
are wet and dry. Is there any advantage to a wet and dry one, and if
so, why aren't they more prevalent? Why is the wet disc always at
right angles to the body?

Thanks,
Stephen.


If its wood chisels .. then just use an oil stone (or diamond if you have
money to burn) ... a grinder will be too fast & too coarse, and probably
take temper out of chisel as well.

I bought a record plane & chisel guide for use on oilstones ... at least 25
years ago ... stills works perfect.

Mostly agree with the above, although I was taught to grind chisels
and plane irons on a fast dry wheel - but go gently and be really
vigilant about overheating.

Possibly where a fast wheel is better is when you chip a tool and have
to remove a bit of material - again being ultra-careful about
overheating.

Oh and make sure the tool rests/jigs are to your liking and cover all
the tools you're likely to want to grand.