Bench grinder wheels for sharpening tools?

[johncee1945]

Hi I have a 8inch bench grinder that runs at 3000 revs and seek advice and recommendations for a finer wheel more suitable for sharpening plane blades, chisels, knives etc., At the moment I have the standard rough and fine wheels that come normally supplied with a grinder - probably suited to grinding rough steel down. These wheels soon produce heated bluing when sharpening an axe.
I understand the revs being high must be a significant factor. Can the revs be slowed down using a device, like a sewing machine foot pedal or something else?
In anticipation, many thanks for all suggestions.

[BobL]

Hi I have a 8inch bench grinder that runs at 3000 revs and seek advice and recommendations for a finer wheel more suitable for sharpening plane blades, chisels, knives etc., At the moment I have the standard rough and fine wheels that come normally supplied with a grinder - probably suited to grinding rough steel down. These wheels soon produce heated bluing when sharpening an axe.
I understand the revs being high must be a significant factor. Can the revs be slowed down using a device, like a sewing machine foot pedal or something else?
In anticipation, many thanks for all suggestions.

Revs you can't do anything about on a basic grinder, they are what they are. What you can do something about are the grinding wheels. Contrary to what you might think a coarse soft wheel is better for (re)forming the basic bevel on plane blades, chisels, knives. Something like a coarse white Alox wheel is much better than a fine hard wheel. I don't know if you can even get fine soft wheels.

[Jim Carroll]

John you are unable to slow the speed of a standard 240v motor due to the way they are wired etc.

One option is to buy a slow grinder they run about 1700 rpm.

Another option is to get aluminium oxide wheels as they are softer than the standard grey wheels that come with the grinder and they come in 60-80 or 120g.

The next option is to get a Tormek wet grinder with the right attatchments to do the job even better.

[Bob38S]

I run the "Blue Max" wheel which is wide, coarse and quite soft. With the grinder turned on it actually produces a blast of air which assists in the cooling. It's not foolporoof but it does help.

[rsser]

Yes.

Better still is a coarse grit with a soft bond. Most of the bonds I see are K; J would be better. The surface breaks down quicker.

The Blue Max is a fairly hard bond but coarse grit and has a honeycomb structure to help it keep cool. A good choice for high carbon steel.

But whatever you get, the risk of bluing is high when your passes cover the entire bevel. At that stage, one light pass followed by cooling allowing the tool to cool might get you through.

[seanz]

John you are unable to slow the speed of a standard 240v motor due to the way they are wired etc.

One option is to buy a slow grinder they run about 1700 rpm.

Another option is to get aluminium oxide wheels as they are softer than the standard grey wheels that come with the grinder and they come in 60-80 or 120g.

The next option is to get a Tormek wet grinder with the right attatchments to do the job even better.

Shame, really as the pedal idea sounds like a good one. Wonder how a floor mounted rocker type switch would work? Ahh...maybe not..........

Johncee1945;
How's your toolrest set-up?
I found that I got a lot more control of everything including heat build up after I purchased one of the Carba-tec ones.
Carba-Tec Chisel Grinding Jig : CARBA-TEC

And I now sharpen axes with a file.
Still do the first bit of re-hab work on them with a grinder though...

[gerhard]

Hi Sean,

it's not so much the rpm, it's the circumference speed and friction. Much speed has the same effect as much working pressure: a lot of friction heat, which has to be avoided. The grain hardness is comparable to steel hardness of a tool. Soft grains get dull or get blocked "pores"between them, hard grains rather break or chip of, to reveal new sharp edges. The bonding grade dictates the regime of breaking-off, either of grain sections or entire grains from the wheel. Wheels op to 200 mms diameter often have 2-pole motors (2800-3000 rpm) and bigger wheels are often powered by three phase 4-pole motors (1400-1500 rpm). Relying on cooling air as generated by the wheel, is not enough. With tool sharpening you often need water. Whereas cooling water for metal cutting processes is often mixed with vegetable oil into a milky suspension (to prevent rust and to prolong standing time of cutting edges), such additions to cooling water must not be used for bench grinders. The oil will soil and spoil the wheels and may even deteriorate the bonding agent (cracked-off bits flying around!).

Regulating the rpm of a brushless induction motor is a technical nightmare. A sewing machine foot pedal is either a large wire wound resistor with a sliding contact, or a version of an electronic light dimmer. These devices regulate the mains power voltage-wise, whereas an induction motor also needs a regulation frequency-wise. Without the regulated frequency-component, the efficiency in the lower rpm regions is very poor, there will be hardly any torque left to get any decent amount of work out of the machine. So it is customary to rather adapt the working pressure and "friction dosage" instead of the rpm.

For my own sharpening work i have several bench grinders, dedicated solely to specific tasks. For wood chisels i have a 350 Watts 3000 rpm Creusen grinder with a wider white 150 mm diameter wheel. No other tools are allowed on that machine, i use it for chisels only. Carefully touching the stone, moving the chisel left and right with the handle remaining in perfect vertical downward direction to achieve one single curved edge of the fold. With a tray of cooling water at the ready. Grinding for 10 seconds, dip the chisel in the tray, grind for another 10 seconds, dip again, etc. The water may not sizzle during the dip and as long as it doesn't, the chisel will not have any chance of getting blued. Just a lot of care and patience until you're done and finish the job with a few slides along the whetstone. Perfect chisels and edges that stay sharp for a long time.

Another (bigger) Creusen bench grinder has slightly coarser stones and is used for simpler tool like drill bits or paint scrapers. And for larger objects i use a three phase 900 Watts Metabo grinder. Axes i start off with a small angle grinder. First with a well worn in disc (a new one bites too much into the depth) and finish with a flap disc. The actual touching up and sharpening is then done on the large Metabo or on the bigger Creusen.

Creusen will be a totally unknown brand in Australia, it is a Dutch manufacturer from the southern city of Roermond. Its product quality can be compared to that of Elektra Beckum (merged with Metabo).

Below is a pic of the grinder i use for chisels. It isn't even a full-pro version. Creusen also makes those, but i had its 250 Watts "DIY" predecessor for more than 30 years now, with only one ball bearing grease session and not even a bearing change. So i stuck to this version, it proved good enough for me. It goes to show that power tools can go a very long way if you don't use them up to their red line limits. The DS7150TS has a 40 mm wide aluminium oxide wheel on the left, which is 100-grain. The siliciumcarbide wheel on the right is 80-grain, both wheels have 150 mms diameter. The leanrests have adjustable angles. You set them one time for the right chisel fold angle and -with the machine reserved exclusive for chisels afterwards- you can rely on the fold having the same angle at all times, which saves a lot of adjustment hassle which arises during different settings for different tools. Furthermore, with the fold staying exactly the same every time, there is less material loss in every chisel at every sharpening occasion.

A slow-speed Tormek with a water bath is of course a far more brilliant and professional solution, but i'd rather recommend a precise enough and well-balanced budget bench grinder to keep for chisels only, and some other grinder model for other jobs. That should be affordable for nearly everyone.

regards

gerhard

[gerhard]

here are some hints about grinding wheel selection:

http://www.grindwellnorton.co.in/Gri...tSelection.pdf

[johncee1945]

Hi and thank you all. Every comment has clarified and helped. I will get an additional grinder with the white or pink wheel for exclusively sharpening chisels and plane blades. And a decent jig for keeping tools square and aligned precisely to the grinding wheel. Warmest regards to all.

[Heavansabove]

There are some very basic factors in wheel selection – note this is for chisels and plane irons, not HSS turning gouges, and a Norton wheel illustrates:

Norton 38A46JVBE

“38A” is the type of AlO, 32A is better but hard to get. “SG” is seeded gel, as in the Blu-Max, which has no code on it, but is something like 3SG54J. The Norton 3X SG wheels are not available in Australia as far as I know, Derek imported one from the US I seem to remember. However Norton (or rather the French company that owns them) are closing/have closed manufacturing in the US, and wheels are coming from Mexico.

"46" is the grit you need - for sharpening you want as coarse as possible for a number of reasons:
1. to grind as quick as possible
2. to avoid heat buildup
3. to reduce the frequency of wheel dressing

Remember you are not sharpening the chisel/iron, you are creating the bevel.

“J” is the hardness of the wheel. Most wheels sold are “L” or “M”, “K” is the hardest you want. A hard wheel has more bond and less grit, and tends to polish the chisel and buildup heat quickly.

“VBE” is not important.

After “J” there used to be a number, 1-10, representing density. This is no longer shown on these wheels, generally we want an open density (low number), so the wheel continuously breaks down exposing new grit. The 38A wheel is probably on the medium/high density end, unlike the Blu-Max which is very open.

Do not put any hot tool in water; all steel fractures (however microscopically) as it cools, and the quicker the cooling the greater the effect. There is some disagreement as to how deleterious the effect is, but I prefer to not potentially damage tools

Do dress the wheel regularly; during a 30 minute grinding session worthwhile dressing the wheel a couple of times. You will notice the difference.

As you are in Sydney try Abraquip at Seven Hills, they are most likely to have the correct wheel; forget the hardware stores like Bunnings.


Life is too short to use the Tormek.


Cheers
Peter

[Bob38S]

Great information [I certainly was not aware of].

Without hijacking the thread any chance of the responders and or others adding what they use to dress their stones?

Regards,
Bob

[Heavansabove]

I use a diamond point for truing wheels, and a carbide stick for dressing. Cheap diamonds are probably a waste of money, and in any case need to be used carefully to avoid damaging the diamond tip. The carbide sticks should be available at any hardware shop, I have not bought one for some time.

[Travis Edwards]

There are some very basic factors in wheel selection – note this is for chisels and plane irons, not HSS turning gouges, and a Norton wheel illustrates:

Norton 38A46JVBE

“38A” is the type of AlO, 32A is better but hard to get. “SG” is seeded gel, as in the Blu-Max, which has no code on it, but is something like 3SG54J. The Norton 3X SG wheels are not available in Australia as far as I know, Derek imported one from the US I seem to remember. However Norton (or rather the French company that owns them) are closing/have closed manufacturing in the US, and wheels are coming from Mexico.

"46" is the grit you need - for sharpening you want as coarse as possible for a number of reasons:
1. to grind as quick as possible
2. to avoid heat buildup
3. to reduce the frequency of wheel dressing

Remember you are not sharpening the chisel/iron, you are creating the bevel.

“J” is the hardness of the wheel. Most wheels sold are “L” or “M”, “K” is the hardest you want. A hard wheel has more bond and less grit, and tends to polish the chisel and buildup heat quickly.

“VBE” is not important.

After “J” there used to be a number, 1-10, representing density. This is no longer shown on these wheels, generally we want an open density (low number), so the wheel continuously breaks down exposing new grit. The 38A wheel is probably on the medium/high density end, unlike the Blu-Max which is very open.

Do not put any hot tool in water; all steel fractures (however microscopically) as it cools, and the quicker the cooling the greater the effect. There is some disagreement as to how deleterious the effect is, but I prefer to not potentially damage tools

Do dress the wheel regularly; during a 30 minute grinding session worthwhile dressing the wheel a couple of times. You will notice the difference.

As you are in Sydney try Abraquip at Seven Hills, they are most likely to have the correct wheel; forget the hardware stores like Bunnings.


Life is too short to use the Tormek.


Cheers
Peter

Good info but I disagree with the 46 grit bit, 60 grit is definetly coarse enough and will leave a bit finer finish which means less time honing a fine edge on the blade. I use a 40 mm wide wheel on my bench grinders 60 grit white aluminium oxide. I find that this retains a nice flat grinding area well and doesn't lose the shoulders like the narrower 25 mm wheels. I cant remember the grade off hand. I use a T-bar diamond dresser for dressing and will do all major grinding then give the wheel a light dress before the finishing grind, This tends to prevent the job from blueing nicely. I also keep a container nearby full of coolant and do a small amount of grinding then cool the blade. However when doing this do not get the tool hot enough to change the colour of the metal prior to quenching. The reasons for this are numerous but probably the most important one is the fact that it changes the temper of the material. Generally I will grind more than one tool at a time and this gives the opportunity to swap the piece you are grinding for another. Also if you maintain your tools regularly you will only grind a small amount each time just to maintain an edge.

[Travis Edwards]

The T-bar diamond dressers are great they will true a wheel and can take out deep gouges very quickly They last very well if treated correctly (probably a lifetime in the home workshop.) and they will dress a wheel beautifully in a matter of seconds. From memory They are made by a company in melbourne or distributed by them any how, But I got the one I have from a company I worked for in Perth called Hughans saw service. Their contact number used to be (08) 9244 1977 I think. they will also be able to help out with grinding wheels.

[derekcohen]

Well I will reinforce the recommendation for 46 grit if we are talking about hand plane bench chisel blades. In fact it is also a consideration to go coarser, say 36 grit. I would not go in the other direction (smoother, that is).

Full speed bench grinders (running at 3400 rpm) and 8" wheels can work very well, but do need a light touch to prevent burning the the steel. It is very easy for a novice to do this. Coarser wheels help here. Coarse, friable wheels help even more. Coarse, friable and freshly dressed wheels work the best.

The absolute "best" wheel for low heat is the Norton 3X. This is a blue wheel but is different from the Blu Max. As far as I am aware, there are no stockists of the 3X in Oz. I bought mine from Tools for Working Wood.

You can cut the heat down by using a 6" wheel since the circumference speed is half that of a 8" wheel. You could also just buy a half-speed 8" grinder (I have one) but these are not cheap in Oz!

The choice of a diamond T-dresser versus a diamond single point will come down to how you grind: do you plan to do this freehand or using a jig (such as the Veritas grinder rest that comes with a sliding holder). The problem with a T-dresser is that you can dress the face of the wheel out-of-square to the rest. Your jig/guide is then out-of-square as well. The preferred dresser is then a single point, which can be run in the jig for optimal alignment.

I use a single point on my Tormek and my bench grinder, but also make use of the T-dresser to lightly freshen up the face of the Tormek (remove glazing).

The width of a grinder wheel is a debatable issue: if you read a FWW article by Joel Moskowitz (the owner of TFWW, by the way), he argues for a 1/2" wheel that is, furthermore, shaped to a rounded face. Essentially he wants to grind on a single point. His argument is a good one (read the article - do a search on FWW website).

My grinder is set up for both a (Tormek) jig and freehand grinding (Blue Norton 3X 46 grit to the left, white Norton 46 grit to the right) ...



My grinding set up is here.

Regards from Perth

Derek