Some additional references: The Museum of Woodworking Tools has an excellent Guide to Honing and Sharpening available on their web site. Much of the information below is similar to what you will find there, with the only real difference being that I am sharpening a gouge, rather than a chisel. Also, the Norton Abrasives company has a consumer web site available that addresses many questions.
Of course, and as always, there's a lengthy stretch of reading before you get to the good stuff - but it's important! If you want to skip this part and go directly to the sharpening the gouge section, click HERE.
The sharpening tools I will be using include (starting from just left of the chisels and going clockwise) a hard arkansas oil stone (ultra fine), a medium India stone, a Tormek, a soft arkansas set of slip stones, a hard arkansas set of slip stones, and a medium India slip stone.
This is exciting for me - these are new, high quality stones recently purchased after having saved my money for a good long while. I used to have a similar setup, but those stones were destroyed beyond recognition during a move about 10 years ago, and since then I've been using sandpaper and inexpensive water stones, all the time saving up for a new set of oil stones. A couple nights of using these reminded me why I was so fond of my old setup. All of the oil stones pictured were purchased and are available from Tools for Working Wood, for whom I have nothing but high praise.
Depending on what shape the gouge is in, it might be easiest (though certainly not necessary) to use a powered grinder of some sort to re-establish the bevel on the gouge. Higher end versions of these tools include the Mark II sharpening system available through Lee Valley, or the Tormek sharpening system. Mid priced versions include the 2 wet grinders used by Delta, model numbers 23-710 and 23-700. Lower end versions can be anything from a 1" belt sander to a cheap grinder - It's not too important what type of grinder; it can be a belt sander, a regular 6" grinder, a $40 cheapie - really, all it has to do is move something abrasive that you can grind or sand metal with.
I use a Tormek wet grinder in this example; before I bought that, my favorite method was using a 3"x24" Craftsman belt sander I happen to own. I made a jig out of some scrap pine to hold it in place upside down on my bench, which also allowed me to run a bar over the sanding belt that I could register the tools I was sharpening against. To tell the truth, it was just about as effective, though the wet stone the Tormek has helps to keep the tool cool while grinding.
That's important to know when grinding the edge of a tool - don't let the steel overheat as you grind it, which could result in it losing its temper. Temper refers the hardness of the steel in the tool - this hardness is achieved through a sequence of heating and cooling metal in a specific way, and mucking about and overheating the steel using a grinder and the steel can lose it's ability to hold an edge. It becomes either brittle or soft, and will no longer function adequately for your needs. If you aren't using a water cooled grinder, have a container of water near your grinder that you can dunk the tool in frequently to keep it cool.
Why Oil Stones?
I should mention that while I am using oil stones, there are other methods that can be just as effective. Sandpaper on glass (aka Scary Sharp) or water stones can also be used to achieve the same goals - my preference, especially for gouges and curved edges, is to use oil stones. Why?
I tired of the expense of sandpaper. Not that it was a great deal, mind you - but the bi-monthly $5 or $10 trip to the hardware store adds up in both dollars and inconvenience.
I always seem to rip sandpaper when sharpening a gouge on it.
The water stones I've had experience with need flattening too often when sharpening curved tools. It's not a big issue with flat chisels and plane blades, but with gouges I always either hollowed them out too quickly or accidentally scratched the surface with the gouge. Good oil stones aren't as susceptible to this kind of damage, and good ones can stay dead flat for years...
I could go into diamond, water, or ceramic stones - there are fine examples of each. But I was trained using oil stones, and I find I am most comfortable with them - and I think that is what could be the most important issue for the sharpener - confidence in the method chosen.
Types of Oil Stones
A Note on Arkansas and Natural Stones. Because they are a natural product, the quality of arkansas stones (hard or soft) can vary greatly, even within a single stone. For example, one of my old stones had a real soft spot in one corner that wore down faster than the rest of the stone, but also cut faster... It is a case where it can honestly be said that when buying new, you get what you pay for. I have noticed a great deal of difference between the different grades of stones, with some that simply wouldn't cut worth squat. It should also be noted that the quantity of remaining high quality arkansas stone is finite, and dwindling - which also serves to drive the price on some of the more premium stones.
Crystolon/Carborundum Stones. If you don't have a powered grinder, not to worry - a coarse Crystolon stone removes metal quickly - more quickly than you might realize, using proper techniques. Crystolon stones are the dark gray colored manmade stones you see so often at the hardware store. They do wear over time, but are excellent stones for coarse work. I'm not as sold on the finer versions of this particular type of stone, and if you have a grinder, you might find having a coarse stone unnecessary. I have an old Crystolon combination stone that was broken in half that I use now for stoning saws, and for mundane tasks such as lawn mower blades and axes - but I prefer to use a grinder or belt sander for the coarse work on most of my hand tools, its much quicker.
I can think of one very special use for a Crystolon stone: I have a couple incannel (bevel on the inside curve) patternmakers gouges that are almost sharp enough to cut butter, and a Crystolon slip stone would make reshaping the bevel much easier. Of course, I might also use some sandpaper on a dowel, as re-shaping incannel gouges isn't going to be an every day occurrence for me.
However - if you are going for a completely electron free method of sharpening, a coarse Crystolon stone is a great addition to your arsenal. They are economical, easy to find, and handy to have around. Crystolon stones are a good option if you need a fast cutting stone.
India Stones are also available in a coarse grit, but I don't seem to see them as often - it may be just my experience, or maybe they just aren't big sellers. If I was to choose between an India stone and a Crystolon stone, I would choose the India personally - unless the only requirement was they be fast cutting. They leave a finer edge, stay flatter longer... all in all, a good, all purpose stone.
There is some confusion about the differences between Carborundum, Crystolon, and India stones... They are all manmade stones - Crystolon is a brand name Norton uses for their Carborundum stones, so those two are the same - a silicon carbide. The red India stones are aluminum oxide, so are different - and the term "India" stone is a trademark of Norton's as well. I have read that some of the earlier version of Carborundum were, or were considered to be, India stones. That is not the case now and may be a source of some of the confusion between them.
India Stones. Today's India stones are great general purpose stones, period. They are made much better today than the ones my dad had when I was growing up. Properly cared for, they also have the added benefit of being long lasting as well as being economical. India stones come in three easy to remember grits - coarse, medium, and fine, though most of what you will find will be of the medium or fine varieties. India stones come presoaked with oil from the factory, so soaking them is not necessary - a few drops of honing oil will suffice. A medium India stone will do minor re-shaping of the bevel, as when it's angle has blunted itself over time as a result of many repeated honings using a finer stone. They also stay flat longer than most other stones.
"Lily White" Washita Stones. A Washita stone is just variety of a soft arkansas stone, but I want to make a separate case for this particular variety here. I used to have a Lily White Washita soft arkansas stone, and it worked well - that is to say it cut fast and left a fine edge - but did dish a bit over time. I find India stones cut very close to as fast as the old Washita, and are cheaper. However, there are some that prefer the old Washita stones, and with good reason - they are very fast cutting and leave a fine edge - I remember using only the Washita stone, even for a final finish just short of stropping - and being very satisfied with the results. Sharpening past this stage is often only necessary for the finest chisel work, and let's admit it - not all of the work we are all doing is all that. If I could have only one bench stone - it would be a Lily White Washita.
- Joel from Tools for Working Wood has informed me that the original old style Norton Lily White Washita stones are available again ... That's good to know. I absolutely loved my old one... Now to save up for one! UPDATE: The Lily Whites are no longer available. I was able to snag one, thankfully!
No. 1 Washita Stones. The #1 Washita is a less expensive Washita stone that was a popular stone for carpenters because of it's relatively low cost. While it cuts more slowly than a Lily White, it is a better quality stone than many other soft arkansas stones. In grit, it's somewhere between a medium India and a translucent arkansas - somewhere in the 600-800 grit range would be my best guess. Some use it as a step between the two stones...
Soft Arkansas Stones. Other soft arkansas stones are generally a little finer cutting than a Lily White, will probably wear faster, and cut a bit slower. These are by far the most common arkansas stones on the market, and is sold at prices and qualities that range a great deal. Most modern soft arkansas stones are of fair quality, and as long as they are kept reasonably clean will perform well - if you get a good one. There are some lemons out there - so the buyer must beware and buy only from a reputable source. The low quality soft arkansas stones are probably many people's first experience with oil stones, and a big reason why they are turned off by them afterwards. There's little more frustrating than using a poor stone.
It's recommended by manufacturers that new soft arkansas stones be soaked in oil for a couple days when you first get them, to let the oil soak into the stone without bringing metal with it to clog the pores. Then you can use them as you would normally. If you don't pre-oil the stones, the oil you use to sharpen with will soak into the stone bringing those metal filings with it, clogging the stone - reducing it's effectiveness.
Fine Grit Stones
There are different varieties of Hard Arkansas Stones, including White, Black, and Translucent White. Color is not always a constant, either, so the term "White" or "Black" might be a bit of a misnomer, though the black arkansas stone is generally darker. Colors can range from white, to gray, to black - even pink.
Hard arkansas stone do not require pre-oiling like soft arkansas stones - they are too fine for oil to soak into - so you can start using them right out of the box.
White Arkansas Stones. These are the Fine or Extra fine grade stones, and are the most common of the hard variety and are used for polishing. These are the most economical of the hard stones, and do wear more than the harder varieties below. They make for a good economical stone when used in unison with an India or Soft Arkansas stone and a strop... or for use as a lower cost stone as a step between an India or Washita stone and a translucent or black stone.
Black and Translucent White Arkansas Stones. Ultra-fine stones - used expressly for polishing the edges of cutting tools. I don't know if there is any real noticeable difference between the Black and Translucent White stones - it may be mostly marketing, or it may be there is a noticeable difference. I've not tried the Black enough to know if there is one, but Norton themselves equate the relevant grits as approximately equal, as attested to in the table below, which was gleaned mostly from their information. The black is usually more expensive, and considered rarer, if that means anything. In any case, I don't think you can go wrong by getting either variety.
Going Beyond the Arkansas'
I personally chose the translucent white, ultra-fine stone (HB-8) as the polishing stone of choice for myself, and can honestly say it is the single best sharpening stone that I have ever used, though my experience is somewhat more limited than many others. I decided to follow the advice given by the Museum of Woodworking Tools' Guide to Honing and Sharpening I mentioned above because it basically reflects my own experiences - that you only really need 2 oil bench stones, a medium India and a hard white arkansas stone, followed by a leather strop. There are those who believe you should take it further, using an intermediate grit between the two and then use an 8,000 or higher stone after the arkansas, but I've always thought of that as following the law of diminishing returns. That's your call, though...
Stropping is a very important part of sharpening and in maintaining the edge of your cutting tools. I believe my definition of sharp was upgraded the most when I discovered using a powered strop - I found I could more evenly apply pressure across the cutting edge. More control meant a sharper edge, and also makes maintaining the edge much easier in my opinion. I currently use leather wheels on the Tormek, but previously I've used cardboard and MDF wheels attached to a drill, as well as leather from an old jacket both attached to a small board and folded to get into the concave surface of a gouge.
I've use a stropping compound on my Tormek's wheel... others recommend stropping on clean, undressed leather, and while I've found I prefer using a compound, I am slowly converting to going without. Lately I've been keeping a cut-off from a belt handy and polishing edge up on it I would suggest you experiment to see what you prefer. I know I will be giving it some more thought and experimenting a bit more, myself.
You don't need to spend a great deal of time stropping. In fact, over-doing can actually begin to blunt the cutting edge. Just a few seconds on the wheel, or a few strokes by hand will do.
Care and Maintenance
One of the great things about oil stones is the ease of maintaining them. Keep them dust free, and oil them before each use. Keep a good skim of oil on the stone while using, then wipe as much of the oil and swarf off when your finished sharpening. When you are switching between different grit stones, make sure you wipe off the tool so you don't cross-contaminate the stone with the swarf. I keep a rag handy for each stone I'm using, and use only that rag for cleaning that stone. Do it religiously! Do not allow the oil and swarf to dry on the stone, as it will clog the stone and reduce its cutting ability.
Proper care should keep the stone cutting well for many years... I found that laying the stones in the window sill on a warm summer day can sometimes "float" some of the stuck particle out of the stone... If you do have a stone that gets glazed over or otherwise contaminated past what a simple rag will wipe away, try cleaning it using a stiff bristle brush and some kerosene or mineral spirits, then re-oil the stone in order to "charge" it back up again.
If it becomes hopelessly clogged, you can use sandpaper on a piece of glass or some other flat surface - the same procedures you would used to flatten the stone. Flattening can be done with a concrete block, sandpaper on glass, or using another similar oil stone and rubbing the two together. Softer stones obviously require flattening more often than harder ones... I've read you can go a lifetime and not have to flatten the hardest arkansas stones, and the same is supposed to be true with India stones, too. I did have to flatten the soft arkansas stones I owned previously - once when I first got them, and again about 5 years later. Crystolon/Carborundum stones require flattening more regularly - I used to flatten the one I had once a year or so.
An important part of oil stones is obvious in the name - oil. A few drops to cover the surface of the stone as you're sharpening should be enough. Wipe the excess swarf away occasionally when it gets too thick with metal shavings with a clean rag, and apply a few more drops. It doesn't have to be messy, though you should separate your sharpening area from your woodworking area. Always wipe down the tool and wash your hands before returning to woodworking.
Days past saw names such as neatsfoot, sperm oil - I can't say that I've ever used those older varieties of oil. I always just used a lightweight oil - mineral oil mixed 50/50 with kerosene or mineral spirits, or something similar - usually just the honing oil sold at the local hardware store.. Don't use motor or other heavyweight oils as it's too thick to carry the swarf away properly, and will clog the stone. The opposite is true for WD-40 or other aerosol born lubricants - they are too lightweight to carry away the swarf effectively and the stone will wear prematurely. That in the end is all the oil is for - if you don't use oil, or use the wrong type, the stone can either wear too quickly and require flattening, or plug up and require cleaning too frequently, or both. If you're in doubt, just get Norton's honing oil - I'm sure it's quality is top notch. Another recommended brand is "Smith Advanced Formula Honing Oil" which could also be available in your local hardware store.
If you are going to be using an oil stone for sharpening your knives in the kitchen, make sure it's a food safe oil. Norton's honing oil is food safe - I don't know about the others.
- Note - one thing I've noticed is colder weather thickens the oil - so if you are working in a colder shop, you may need to cut the oil with some turpentine or mineral spirits so it isn't too thick. You will be able to tell by the feel and sound of the stone as you work the edge whether or not it is cutting or the edge is simply riding on a film of oil.
Please note this is just a guide - the grit size does not necessarily equate to the sharpness of the edge you will get using the type of stone indicated. A good example of this would be my old Lily White stone - which gave a much finer edge than the 340 grit indicated on this scale:
|Type of Stone||Sandpaper (US)||Water Stone||Microns (Diamond)|
|Extra Fine India||450||600||22|
|Hard White Arkansas||1200||1200||11|
|Hard Black Arkansas||2000||4000||6|
|Hard Translucent Arkansas||2000||4000||6|
While most of this table is from the Norton company, the most trustworthy source I can think of, I found variations of this table all over the place, with wildly varying numbers. I think you can only truly tell the differences when actually using the stones. The document mentioned above is available on the Norton companies' web site.