How to Sharpen Lathe Chisels

Anyone who has had a lathe for more than a week knows that you need to sharpen your chisels and sharpen then often.  Nothing dulls tool steel like a 3000rpm spinning chunk of wood.  I have recently gotten back into wood turning after a ten year break from it so I am revisiting my sharpening techniques and questioning them so what you see here is a combination of my old tradition with a few changes.

A quick google search will yield about ten million hits on jigs, techniques, systems, and machines for lathe tool sharpening.  The popular questions seem to be dry grinder vs slow speed water grinder, jigs vs free hand, and whether to use tools straight from the grinder or honing them a little.  It really comes down to the fact that there is no right or wrong way to sharpen your chisels and what works for a production turner might not be best for a hobbyist.  I used to be a run to the grinder and then straight back to the turning, it was quick enough for most chisels and seemed to work find.  The problem occurred when trying to use a jig for a fingernail grind gouge, it was just slow to change from a flat tool rest to the jigs needed for the gouge so I went searching for something else.

So what do you need....  Well you can start with sharpening stones, they are slow and you simply cannot regrind a profile on a bench stone, it is just too slow.  Other options are a bench grinder or belt sander, I currently have a bench grinder which works fine but takes up a lot of room in my small shop and takes forever to change to a different grit stone.  I am seriously considering getting rid of the grinder and using a small 1" X 30" belt sander but for now the grinder works fine.

My setup is:
1725 rpm 6" Baldor Grinder with 120 grit pink wheel
Wolvering Basic Grinding Jig  
Two sided diamond stone (course and fine)

Step 1: Sharpening the Skew Chisel

We will start talking a little bit about the flat chisels, the skew and scrapers.  These chisels will be sharpened using a flat tool rest.

Skew Chisel - The skew is used to produce a very fine finish on spindle turnings.  It is also a great too for creating beads on a spindle.  The skew is also a tough tool to master, it can produce some really impressive catches so be careful and spend some time practicing, it will be worth it.  I have included an image with the proper angles for the skew chisel.  The first step to getting a good edge is to establish your initial grind and we will do this on the grinder.  I start by putting my flat platform in front of the wheel and adjust the angle with the skew on it until I get that skew on the wheel near 25 degrees.  You can place marks on the platform at 70 degrees as a reference and to help you hold it straight.  You want to grind at this angle until you have reached both ends of your bevel.  You want the edge to meet in the middle of the tool thickness so this might take a little trial and error to get there.

Step 2: Sharpening the Scraper

The scraper is one of the easiest tools to sharpen, the only technical part is the angle, most literature suggests using a 70 degree angle. So once gain adjust the angle of your tool rest to where the angle will be around 70 degrees and start grinding.  For round nose scrapers you sweep the end of the tool back and forth in a smooth manner to make a nice smooth rounded edge.  Once again grind until you have the full bevel ground and you are done.

There are many types of scrapers in all different shapes but they are all sharpened in the same manner.

Step 3: Sharpening the Gouge

Wow, you could write a book on the gouge but trust me I will not.  What I will explain is the types of gouges:
1.  Roughing Gouge - This is a large gouge with high sides used for rouging stock into a round shape.  This gouge is typically ground straight across.
2.  Continental Gouge - This is the gouge usually included in cheap tool sets, it is similar to a roughing gouge but has much lower sides.  Expect to find this gouge shoved in a corner with a straight grind, this is a shame because I find the continental gouge with a mild fingernail grind to be an incredible forgiving chisel capable of producing a finish almost as good as a skew.
3.  Spindle gouge - This is usually ground from a solid bar of steel with a wide shallow grind.  These work great with all kinds of grinds for different situations.
4.  Bowl gouge - These beasts are ground from a solid bar steel and can be found with all kinds of grinds on them, I have models with straight grinds, fingernail grinds, and aggressive swept back designs. Different areas and bowl types call for different grinds, I find a swept back design great for hogging out a bowl but too aggressive for finishing cuts and usually switch to a milder grind.

Those are the gouges so let's talk about the grinds.

For most all gouges around 60 to 70 degrees is a good starting angle to grind, as you get more comfortable or just want a more aggressive chisel you can go below 60 degrees but be careful these things can take a lot of wood off fast and you need a lathe with some good horsepower to hog off that find of wood.

The most basic and simple way to grind a gouge is to set the angle on the flat tool rest right and then roll the tool back and forth until sharpened, this creates a tool with a straight cutting edge and high wings.

Every other grind takes either experience of a good jig, there are many brands of jigs to choose from or you can do like me and make your own jig.  Just do a quick google search for "homemade fingernail grinding jig" without the quotes for plenty of ideas.  As you can see in the pictures of my jig I have marks for the angle of the arm, basically the further forward the arm is the more swept back the grind.  So for a basic continental gouge I will have the arm all the way back for a basic almost straight fingernail grind, for a swept back bowl gouge I will have the arm all the way forward and in between those two extremes is everything else.

As you can see I have a block of wood mounted on the grinder platform, this is my gauge on how far the tool extends from the jig, I use 2" for everything, it just keeps things simple.  

So once you have your tool in the jig and the arm of the jig adjusted to where you want it, adjust the v-arm of the grinder rest in our out to get the right front angle on the grinding wheel.  Then  you simply start grinding swinging that tool handle side to side in a nice slow and smooth manner.  As you can see going back to the grinder every time you need to touch a tool up can be a pain which is going to lead into the next step. 

Step 4: Honing the Edge Between Grinding

Now this step is were I deviate from conventional wisdom.  I hear people say it is so quick to put the gouge back into the fingernail jig and put it back on the grinder, perfect identical results every time.  I am calling shenanigans!  My take is you will never get the same exact angle of everything, but who cares about 1/2 degree, well that is more time spent grinding which means it is not so quick.

I hate the grinder personally, it is so much quicker and easier is to take out my diamond hone and ten seconds later I have a tool way sharper than one straight off the grinder.  This becomes very evident when working with the skew or continental gouge, a few swipes on the diamond stone and I just saved myself five minutes of sanding.

I usually just hone the edge until I have completely flattened out the hollow grind from the grinder, and that is a lot of turning.

You may have noticed I left out the parting tool, well that is one tool you will probably never had to re-grind, just a few swipes with a hone and you are back in business.  Also with a parting tool, I get horrible cuts no matter how sharp it is, but maybe that is just me.

I hope this instructable has helped someone out there, remember, sharp tools make working much more pleasant.

Comments

[DewiK1]

I'm beginner in wood lathe, I'm from central java- indonesia
I'm going to turn teak wood tobe a bowl, but I face a problem that the chissel I used was always dull or sometimes broken (I used tct plat)
What is the solution for this problem
Thanks,
Hartanto

[pfred2]

I have yet another reason for you to hate grinders.

You may not be aware of it but every time you mount a circular grinding wheel you should dress the wheel to true it up. They never quite run the same after being dismounted then remounted.

If you want your edges to last longer you should strop them. That stops the wire edge from bending over. If you can strop a wire off a sharpened edge then you know what you have is really sharp. I use leather charged with red rouge polish.

Another tip: put some super cleaner on your diamond hones for lubrication. Stuff like Super Clean by Castrol or Purple Power a knock off that is basically the same thing.

My sharpening routine goes grinder, synthetic diamonds, 4 grits, medium, then hard Arkansas stones, then stropping. Though once I have the geometry correct I don't usually grind anymore. I have Japanese water stones too but I don't use those for everything.

[JoshS59]

Thanks! This response alone was worth reading the article!

[Mindmapper1]

Mounting circular grinding stones is something you should only do if you know what you are doing. They can explode when spinning due to overtightening and the like.

BTW I think there is a lot of confusion in these comments between grinding and sharpening, the two are not the same! Pfred is correct turing tools should be stropped to remove the wire edge and then it is really sharp. making the face of the tool shiny makes a HUGE difference.

Personally I prepare my tools on a Sorby belt linisher and then polish. Been doing this for years and have been turning professionally for years.

Friger: grinding a turning chisel.... mmmm bet your tools dont last that long then ;)

[friger]

Did you know that when turning the wire edge is what is doing the cutting? You don't need to strop a lathe chisel, the grinder is all you need. Call me wrong but I've spent too much time standing in wood curls to be mistaken about this. What you are doing is a fine job of making a carving chisel, and I would think you are an expert carver.

[jskingry]

Thanks for the comment friger. Those oysters you smoked look great too, gonna have to try that myself! Down here on the west coast of Florida we smoke a lot of a fish called mullet to make dips or just eat straight, maybe I will grab some oysters next time I fire up the smoker.

[pfred2]

When I lived in Florida we netted mullet for bait. I never knew you could eat the things!

[jskingry]

They make great bait, but some of us brave folk on the west coast eat them too.

[pfred2]

Yeah I lived on the east coast on the Indian River Drive so I had the Indian River in my front yard. Was nice, I had crabs for lunch just about every day. I used the mullet to bait the crab trap.

[pfred2]

I guess you like to scrape then.

[jskingry]

pfred,

I have the solution for dressing the wheel, I just don't remove it from the grinder ever. I do have a diamond dresser that I use from time to time to keep the face flat. I just didn't want to broach that subject since it is not directly related to the topic of lathe chisels and not being a metal worker I will leave grinder setup and maintenance to the true experts.

One of these days I might get around to stropping but the diamond is just so quick and easy and the edge the fine side leaves will not shave but it will pop hairs.For cleaning my diamond I just used dawn from time to time to clean it, seems to work ok and I like the stone dry so I can keep it in my pocket. I have water stones and oil stones too but I like the simplicity of this routine since I never have to leave the lathe I just pull the diamond stone out of my pocket a few quick swipes and I am ready to do my finishing cuts on the piece.

Now if I am sharpening a plane iron or a bench chisel I will go all the way to my 8000 grit water stone to make it shine, but that is another instructable.

Thanks for feedback.

[HapHazzard]

I have a question concerning the radius of a round-nosed scraper. I recently bought a set of Hurricane round-nosed scrapers that included a 1 1/2", 1", 3/4" and 1/2" scraper. The nose radii are 15/16", 5/8", 1 1/4" and 3/8", respectively, so the ratio of radius to blade width is the same for the two largest scrapers, slightly larger for the smallest, and insanely larger for the 3/4" scraper. The 3/4" blade is also significantly shorter than the other three. (See picture.)

Should I regrind the 3/4" scraper's nose to something more in line with that of the other scrapers (about 7/16"–1/2") or is there a reason for why it was made this way?

[mdawson3]

As to whether you need to more than just grind turning tools, it's not as simple as you should just grind them or you should hone them till they shine.

This article discusses this.

http://woodturninglearn.net/articles/honingturningtools.htm

[Somethingtotallyrandom]

Wait. What... You mean I'm supposed to sharpen those lathe tools? Oh, man....



Just kidding. Nice instructable. Perhaps you could add a couple links to sites that expand on the subject so that beginners can learn some more. When I started, I was so taken up with producing perfect edges that I didn't do any turning for close to six months ;-)