How Sharp do Lathe Chisels Have to Be?

[Steve H Graham]

I know nothing about lathe chisels, so I decided to get a relatively cheap NOS set of HSS chisels off Ebay. I figure I can replace them with better ones as needed, and until I do, at least I won't be doing without.

Here is my question, and it's probably not that easy to answer: how sharp do lathe chisels have to be? It's my understanding that they're not like bench chisels, which have to be insanely sharp.

The chisels I got are sharp enough to cut wood, but in order to shave hairs, they would need some work.

[allen thunem]

shaving hair isn't what you are after

[Peter Dougenik]

My turning chisels are nowhere near as sharp as my bench chisels, nor do they have to be. That said I highly recommend a nice 8" low speed grinder and a way to create repeatable angles be it freehand if you have the skill, the default little table, or a jig if you're doing fancy grinds

[Michael Mills]

For most turners, tools are used as they come from the grinder. The main reason is the amount of wood being cut. As an example, a small bowl of 6.5" diameter and fairly slow speed of 600 rpm would still have 200 inches of wood passing the tip per second.
Many/most do hone the skew because with some cuts you are trying to put the pressure towards the head/tail stock instead of against the wood perpendicular and to leave a surface which does not need sanding around sharp details. I also hone my parting tool because it gets so little use it is quicker to hone than to go back to the grinder.

[Steve H Graham]

Geez. Sounds like you can use them out of the box.

[John Keeton]

Geez. Sounds like you can use them out of the box.The edge "out of the box" may or may not be sufficient, but the grind on the tools usually is not sufficient unless you buy from one of the known manufacturers. Additionally, while the tools may be sharp enough, they won't stay that way long.

[Steve H Graham]

I am hoping to get my tool rest put together tomorrow or the next day so I can give these things a try. I guess once I'm actually turning things I will understand what is required.

I'm really looking forward to this. I saw a guy on Youtube say that turning was woodworking for people with ADD. I completely understood that. It takes me forever to get anything done with saws and planes and so on. It would be neat to do something a little freer and faster.

[Thomas Canfield]

Here is my question, and it's probably not that easy to answer: how sharp do lathe chisels have to be? It's my understanding that they're not like bench chisels, which have to be insanely sharp.

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Lathe tools need to be sharp enough to cut and not tear the wood. Depending on the stage of the cutting process, you can get by with duller tools for roughing, but the finishing cuts pretty well demand a sharp tool. Good sharpening practice will greatly enhance your turning skill and enjoyment with less finish sanding required. The sharp edge does not last too long, so get ready to do a lot of sharpening, but it does go quickly when all you are doing is touch up the edge.

[Thom Sturgill]

And this is where the modern 'crucible' steels come in. Also called 'Powder metal', they wear better and hold an edge longer. Carbon steel gets a sharper edge perhaps, but does not have the wear resistance provided by the cobalt or vanadium carbides produced in crucible steels. The other side of the coin is that they are harder to get sharp as the carbides are harder than an Aluminium Oxide wheel.

These steels do benefit from a light honing with either diamond or CBN hones, but HSS not as much except for skews and gouges used for skew-like cuts. Even then the honed edge wears off quickly.

[Prashun Patel]

The chief difference is that you don't have to HONE lathe tools for them to be effective. A lot of people (me) use a bench grinder with an ~80 grit wheel and take it straight to the wood. There are times when you may benefit from a honed edge, but most of the time, my main concern is speed. With flatwork blades, I may sharpen once a session. With lathe tools, I may sharpen 10 times in a single session. HSS lathe tools are designed to take abuse and to be resharpened fast on a grinder and to marginally better resist heat damage than other types of steel.

What tools did you purchase? The way you sharpen skews and scrapers is different from the way you sharpen gouges. You may want to get a jig for the latter.

While I have rarely honed my lathe tools, I'm willing to bet they would perform marginally better for longer than my 80 grit ground blades. However, this would require at least 2 grinders and wheels or changeover costs. This would slow things down. By not honing, the sharpening process with jig and dedicated wheel takes about 30 seconds. It's just more efficient for me.

[David Walser]

...

While I have rarely honed my lathe tools, I'm willing to bet they would perform marginally better for longer than my 80 grit ground blades. However, this would require at least 2 grinders and wheels or changeover costs. This would slow things down. By not honing, the sharpening process with jig and dedicated wheel takes about 30 seconds. It's just more efficient for me.

Those of us who use a Tormek or the new CBN wheels would note that it only takes about 30 seconds to refresh the edge using our method. And, you're correct: the sharper edge lasts longer. Not only that, it cuts better. Where your 80 grit wheel out performs a Tormek is when the edge has been nicked and needs more than just a touch up. If you don't drop your tool or aren't turning wood with embeded nails, this isn't an issue.

[Reed Gray]

The debate goes on.... The finer honed edge has fewer teeth to wear down so it stays sharp longer. The more serrated edge cuts better and lasts longer..... I have tried the Tormek and CBN wheels, and I don't notice any difference. Like the old Miller Beer commercial, 'Tastes Great/Less filling'. Probably not some thing you can measure. I don't play with the skew enough to have any feed back, but I do know a local spindle master who uses her skew straight from the 6 inch grinding wheel...

robo hippy

[Brian Kent]

The only exception I make to the above wisdom is with an almost flat nose scraper (very slight convex arc) has been giving a cleaner finish when I hone it with a diamond card. When I finish with that, I can start sanding at 220 or 320 instead of 80 or 150.

[Geoff Whaling]

"How sharp is sharp" is a relative concept. Roughing out bowls does not require a razor edge but a honed razor sharp edge does make a huge difference on delicate spindle turnings.

Many new turners get into all sorts of difficulties primarily due to the shape of the edge they are trying to use and due to how poorly the tool is sharpened. Being able to replicate the shape of a cutting edge is as important as how sharp the tool is.

"Blunt tools" also encourage poor turning practices such as forcing the tool which then creates other issues from that force such as spirals, torn grain, uneven cut surface, distorting the shape of the spinning bowl leading to unexpected catches etc.

A sharp tool permits the timber to come onto the tools edge, cuts smoothly, requires less force and depending upon who you listen to lasts longer.

[Scott Hackler]

Sharp tools are a big pet peeve of mine. I don't know how many times a turner will show up at our local club meeting workshops and ask me to sharpen their gouges because it's been a few MONTHS! Those tools are just about as sharp at a butter knife and they were turning with them. Soooo, I preach to get the tools sharp and keep them sharp. Let the tools do the work and stop fighting the wood. You will need to refresh the edge regularly. Remember that the difference between a flat plane and a bowl gouge and their edge holding ability is directly related to the feet of wood the tool actually cuts. I can plane a couple doors and still have a very sharp hand plane, but during one 10" bowl, I will have "traveled" the tool across the wood the equivalent of 50 doors. i.e. will need to re-sharpen more often to maintain a clean cut.

And like mentioned before, a very sharp tool and good technique allows you to start with a higher grit sanding paper (220).

I sharpen on a 180 grit CBN and will refresh 2-3 times during a bowl rough out.

[Ron Rutter]

Steve. A simple demonstration for yourself. Work on a bowl for 10-15 minutes then sharpen your gouge. I think you will find it cuts much better & is far less stressful!

[Jon Shank]

Steve, first the woodworking for people with ADD? Totally true! I have really limited time in the shop like alot of the folks on this or any other woodworking forum(heck I have limited time in town, shop time is like gold!). With flat woodworking a project can take me months. I still enjoy it and gave up on hurrying a long time ago. But with turning I can do a fun turning, say a mushroom or simple bowl/platter in an afternoon with dry wood. That still amazes me! Comparatively instant gratification and spinny stuff is just cool and fun. If that sounds a little silly I'm fine with it, turning reminds me of why I love wood, just turning out a piece that I look at and I'm happy with and getting that I made that! rush. Turning can be like a drug that way. Just putting a tree branch on the lathe and making a fat dowel is really addicting(serious cathartic fun, still one of my favorite things about turning), making it into something pretty is icing on the cake. Your gonna love it!

Ok, so the sharpness thing you asked about. Everybody who already posted is pretty much on the money. You need to have sharp tools to cut wood, but off the grinder with a 120 grit wheel(generally a white or blue wheel) is plenty sharp enough for all the roughing in and shaping work. For a clean finish cut that shortens sanding time, sometimes really by a huge margin, you will want at the very least a freshly sharpened tool and probably a honed tool. Some tools like honing more than others, the skew for instance really does better with a smooth honed edge, again, not really needed for roughing but the edge will last longer if it is smooth for roughing. And the difference is night and day for a finishing cut. A grinder sharp bowl gouge will do the job all day long for hogging out material, but for that cleanup cut that cuts an hour off your sanding regimen, a honed edge(and a good practiced technique) is the cats meow. A sharper, cleaner grind will never hurt you but for alot of the grunt work the grinder edge is really fine. And keeps you cutting spinning wood. I think the balance is in finding the happy medium between a good edge is better and I wanna cut the spinny thing. You can get away with a ground edge to start cutting the spinning thing no problem, then just find your happy medium while you figure out the whole turning thing. The figuring it out is part of the fun.

Jon

[Thomas Canfield]

Steve - I am a big advocate for using 2x6 lumber for practice turning bowls to see difference in a sharp tool, higher speed, different technique, etc. The grain pattern of most construction 2x6 has both hard and soft grain, and tear out of the end grain is very apparent with dull tools. Give it a try and you will improve your sharpening and other habits.

[Keith Westfall]

If you have a lathe, you need a sharpening device. And it needs to be close to the lathe, so you can quickly touch up your tool. If you keep them sharp, you will never have to "grind" them, (unless you hit something in the wood). Use a lite touch, and they should never heat when you sharpen.

Some may differ, but I use (have because it came with my lathe) an 8 inch high speed grinder, but do have the white wheels on it. I can turn it on, and when almost up to speed I can turn it off and still touch up quite well, as it only takes a quick touch.

If you don't have one, get some kind of device for sharpening unit, and learn how to use it. But do a bit of planning, because if you go a grinder and will sometime add a jig/tool for holding the tool (wolverine type perhaps), many of them work with a 8" wheel. Something to think about. And a low speed one (1750 RPM) will do quite well.

As many have said, turning will be a LOT more fun with sharp tools....