# How do I know when my chisels are sharp enough



## Chris208

A couple months ago I bought a 6 piece set of Marples Splitproof chisels second hand. They were in pretty poor shape when I got them. I spent a ton of time working on them, and now I can shave my arm hair with each of them, but is this really a good indicator that they are sharp enough for woodworking?

What other tests are there for verifying the sharpness of a chisel?

Are my chisels sharp enough?

Thanks,

Chris in Boise


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## Tedstor

If you can shave hair with it, I'll venture to say its sharp enough. 
In all seriousness, try to work some wood with it. That would be the "other" way to verify its sharpness.


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## jmos

Shaving the hair on your arm is a decent indication, and quick to test while sharpening. Try paring end grain; do you get a shaving? Is the surface left smooth and shiny? If so, it's probably sharp enough.


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## rwyoung

You can shave with a dull razor, so the arm hair thing really isn't that indicative of sharpness.

Sharp = two planes (think geometry, not woodworking) coming together at a single intersection.

Ideally, the working end would be one molecule of steel thick. In reality, the best you can do is one grain of steel exposed. In practice, if you cannot see light reflected from the cutting edge, you are likely done. It will look like a black line while the rest of the bevel and back reflect light.

Pairing end grain is a decent enough test, use pine. It should happen nearly effortlessly and create shavings with some body, not dust.

Alternatively, you can hold a sheet of typing paper (copy paper) LOOSELY and push the chisel/blade down through the edge. Don't pinch the paper to form a curve and make it more rigid. This is a cheat and you can push a much duller edge down through a rigid sheet than a "floppy" sheet.

Another simple test is the finger nail test. Carefully try to slide the sharp edge down the length of a thumbnail. It should stick and not slide. If it slides, it is dull. You can also draw your thumbnail across the edge and feel any micro nicks in the blade. Again, it should stick a bit but feel smooth as you draw across. Be careful with this test and don't slice things that shouldn't be sliced. Also, if fingernails on a chalkboard bother you, this test will also make your skin crawl.

Don't spend all your time testing for sharpness. The wood you are working on will tell you if the tool is sharp enough. It should cut and you shouldn't need to fight the tool, just guide it.

Also, invest in a x5 to x7 magnifying glass or eye loupe to inspect the lapping marks. Once you look at these a few times you will learn when you need to lap more (make the marks smaller) on any particular grit regardless of the presence of a burr. The higher the polish, the smoother the steel (in general) and so fewer longitudinal gouges in the steel which form the start of micro-fractures which eventually let a little flake come off and this is how your edge dulls.

Just don't obsess with the steel. Get it sharp and get back to work.


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## rance

They need to be at least sharp enough to shave arm hair with, but not so sharp that you are frustrated with the process of getting them to that point. Somewhere in the middle.


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## Chris208

Thanks for the great info (as always).

I already reached the point of frustration, but I took a break and came back to it after I watched a bunch of youtube vids to make sure I wasn't the problem. As it turned out, the chisels were just beat up, and needed a lot of work.

Thanks!


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## HorizontalMike

IMO, no matter how sharp you think you have them, you should re-strop them frequently while in use. It only takes a couple passes each time but I do find that it really helps keep the edge.


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## Chris208

Assuming I don't have a strop (or know what stropping is, for that matter) can I just touch them up on my high grit stones?


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## rance

No.  Well, you could, but you should read up on making a strop. You can make one from an old leather belt. Google it. I think you'll be happy with your new homemade tool.


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## dkirtley

Just make a strop. It can be as simple as a piece of MDF or nice leather. Something that will hold the stropping compound.


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## Tedstor

I bought a piece of leather off this guy (see below). Glued to a piece of maple. I use it with some green buffing compound. Works boo-tiff-lee.

http://www.ebay.com/itm/3-X-9-inch-Leather-Strop-By-R-Jones-use-as-is-or-on-your-block-/120976436094?pt=LH_DefaultDomain_0&hash=item1c2ac1eb7e


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## HorizontalMike

Mads has the absolute BEST explanation and examples of making and using a strop that I know of. Enjoy:

http://lumberjocks.com/mafe/blog/26468


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## dkirtley

Just be aware that you can strop too much and dub the edge over. There is really no right or wrong. It is a balancing act. Too sharp and the edge doesn't last. Too dull and it doesn't cut as cleanly. There are times you want to change up for what you are doing. Cutting some nasty endgrain? Make it wicked sharp and stop and sharpen it again while you are cutting. Chopping out mortises? The same edge won't last two chops. A soft strop will give you a longer lasting edge. A hard strop will give you a sharper one. That's why barber's stops have different belts (of course most people now days have never seen a barber's strop)


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## waho6o9

Leather + adhesive ( I like 3M 90 high strength adhesive) + Plywood = Stropping board

I charge the leather with oil, my preference, and green honing compound. Once in a while
I mix it up with Autosol for a change of pace.

I like to have the leather close to an edge to hone the back of chisels and blades
as well.

MDF and green honing compound works also.

HTH


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## HorizontalMike

Yeah David, but I sure do remember what that strop felt like! Especially after I misbehaved at home *;-)*


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## vipond33

Take the chisel into a quiet room. Breathe across the edge and then put your ear to it. If really sharp you will hear the germs scream.
gene


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## rblaiklock

you should be able to cleanly slice end-grain in something like oak with minimal effort


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## Earlextech

I've always used the fingernail test, but be careful, if it is sharp you'll know it.


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## HerbC

Vipond33,

If the chisel is REALLY sharp, there will be no noise because the edge was so sharp the germs didn't even feel it when they were bisected. < BIG GRIN >

Herb


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## Cosmicsniper

To me, sharp is when you can take a 1" chisel to a 3/4" square board of pine and chop off the end with a clean cut instead of a compression or tear. It's an over exaggeration of "paring end grain," but it's the type of sharpness you look for when you do it. In other words, if you avoid using chisels when doing end grain paring, you probably are doing so because you've come to expect your chisels to not be able to do the job.

So I like what the guys said above…it the tool is inadequate for doing a job that you know it SHOULD be able to do, then it's not likely sharp enough. I can always shave hairs with my chisels, but those chisels may or may NOT give clean cuts on the wood.


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