I have unreasonable sentimentality about Stanley Model 40 chisels. I started buying them about 30 years ago just as they were being discontinued. They seem to sharpen easily and hold a good edge. I was always missing the one inch chisel and recently was lucky enough to find one on eBay.
Step 1: Beat up chisel handle
When I received it, I noticed that the back of the handle had been hit pretty hard over the years.
Step 2: Badly sharpened bevel
When you saw the bevel, it was no surprise that someone had hit it that hard. It looks like it had been sharpened multiple times but each sharpening had only added another facet to the bevel.
All chisels, whether new from the factory or used, need tuning before they work well.
All chisels, whether new from the factory or used, need tuning before they work well.
Step 3: Reason #1 for sharpening
The primary reason to sharpen a chisel is shown in this photograph. You can see how poorly the chisel cut a piece of softwood and all I was trying to do was pare a small piece off the corner. The chisel crushes the fibers until they break rather than cutting them.
Step 4: Reason #2 for sharpening
And there’s a second less obvious reason. For 35 years, I have carried a reminder on my left palm of the dangers of working with a dull chisel.
Step 5: The back of the chisel
Ideally, you want to have two perfectly smooth surfaces, the bevel and the back, meet to form the cutting edge. Any imperfections in either will reduce the sharpness of the chisel.
Here’s the chisel back when I received it. You can still see the machine grinding marks left from the factory.
Here’s the chisel back when I received it. You can still see the machine grinding marks left from the factory.
Step 6: Flattening the back
The most overlooked part of tuning a chisel is flattening and polishing the back. The easiest way I’ve found to do this uses sandpaper and a piece of plate glass. Using a spray bottle, I spray water on the back of a sheet off sandpaper which usually creates enough suction to have it adhere to the glass. Depending on the condition of the chisel, I’ll choose the appropriate grit but generally I start with 80 grit open coat silicon carbide sandpaper. I move the chisel back and forth (along the long axis of the chisel), keeping the back, flat against the paper, until the marks on the back are consistent across the surface.
Step 7: Refining the back
I usually use 80, 120, 150 and 220 sandpaper. After all, I only have to do this the first time I sharpen a chisel. Use each grit moving the chisel until you get a consistent pattern
Step 8: Polishing the back
After using sandpaper, I polish the back with a set of Japanese water stones.
I end with an 8000 grit waterstone or when I run out of time or patience
I end with an 8000 grit waterstone or when I run out of time or patience
Step 9: Hollow grinding the bevel
After flattening and polishing the back, I grind the bevel. My favorite tool for doing it is a water cooled large diameter grindstone. It turns slowly and leaves a beautiful finish. You can also do it on a regular grinder but you have to be very careful not to overheat the tool and lose the temper of the steel.
I apply pressure very close to the edge of the tool and use a jig to ensure that the edge of the blade stays square
I apply pressure very close to the edge of the tool and use a jig to ensure that the edge of the blade stays square
Step 10: Honing the bevel
I use a 4000 grit water stone to hone the bevel. I apply pressure close to the edge and use my other fingers to support the weight of the chisel. I start by setting the back of the bevel on the stone and slowly rocking it forward until the tip of the chisel touches the stone. One of the primary advantages of the hollow grind is that the chisel almost locks into place because there are only two points of contact
I gently pull back on the chisel four or five times and look for the small bevel forming at the two points of contact. Once I’m happy with the bevel, I finish up with an 8000 grit stone to polish the bevel.
I’ve tried various jigs over the years to hone the bevel but I find most of them way too fussy for me. If you have trouble doing it by hand, there are some good jigs commercially available.
I gently pull back on the chisel four or five times and look for the small bevel forming at the two points of contact. Once I’m happy with the bevel, I finish up with an 8000 grit stone to polish the bevel.
I’ve tried various jigs over the years to hone the bevel but I find most of them way too fussy for me. If you have trouble doing it by hand, there are some good jigs commercially available.
Step 11: Testing for sharpness
There are many ways to test for sharpness. You can gently use the chisel on your fingernail, try to cut a piece of paper or if you have the means, try shaving the hair on your arms.
After a while, it’s easy to know whether the chisel is really sharp by just (carefully) running your finger across the edge
After a while, it’s easy to know whether the chisel is really sharp by just (carefully) running your finger across the edge
Step 12: The real test
The real test is whether it cuts wood cleanly. Test it on the edge of a block of wood. A piece of softwood requires a sharper chisel than hardwood to cut cleanly
Step 13: Oil the chisel
Finally, dry the chisel and put a light coat of camellia oil (tea seed oil) on the chisel. It’s an edible non-toxic oil that helps prevent rusting.
When the chisel gets dull, you can just hone and polish the bevel. After five or six times, you’ll have to touch it up on a grinding wheel before honing
When the chisel gets dull, you can just hone and polish the bevel. After five or six times, you’ll have to touch it up on a grinding wheel before honing
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Given the fineness of the mediums you are using I was interested in just how much difference the final polishing of the bevel made so I refinished the bevel on the chisel with stannic oxided slurry on an oiled paper lap. It turns out to be quite significant.[see image] This produces a very slight bull nosing of the bevel. Probably better to use the slurry on a steel lap.
Kind Regards,
DJH.
I was quite pleased with myself that the old chisel [Swedish c. 1910] I was restoring seemed to meet the end grain test till I took a look at my handy work under a microscope.
What appears to the unaided eye as a mirror finish can be deceptive! I still have much to learn. What look like chips out of the edge are in fact tiny corrosion pits on the flat of the blade.
DJH.
Kind regards,
David Hogg.
Any help Please?
In a way it make sense.
Thanks for this instructable that'll be really handy :)
It's funny how sometimes we get used to working with dull tools and don't realize what a difference a sharp blade makes.
For everything else I got used to sharp blades at a very young age. 20 years ago I thought I knew everything there was to know about sharpening too. Since then I've learned a thing or two though.
Today for instance I wouldn't consider a chisel edge fully sharpened unless it was stropped. Wire edges are for scrapers.
http://img.archiexpo.com/images_ae/photo-g/waterproof-rigid-polyisocyanurate-foam-and-bitumen-insulation-panel-for-roof-449951.jpg
A dull knife goes through that stuff like it is hot butter. A sharp knife sucks though. I've used both. I wouldn't have brought it up if it wasn't different.
I never saw anyone ever try to cut the stuff with a hand saw. Mostly because no one had a hand saw, and dull knives worked so well why would we use anything different?
http://www.fine-tools.com/G-applikationsflasche.html
I agree with mikeasaurus it's surprising how people can get used to dull tools.
I recall many years ago spending most of a Sunday getting a workmates chisels up to standard & another Sunday a week or two later teaching him how to keep them like it, he seldom used them but at least when he needed to they did the job properly.
I have always belived that any tool well looked after & maintained is far more useful than the most expensive one mistreated & neglected.
Any chance you will follow this up with one about maintaining your stones & wheel?
It is a long time of experiance and the result of many tries to find what is good or not.
I love to see someone who takes care for his tools and knows how to make them usable.
So far the best steel I've had the pleasure to sharpen is in some kitchen knives I own. Knives made by Henckels for a company named Hoffritz that were cyrogenically treated. I could cut a Japanese waterstone clean in half with one of those knives, and still slice a tomato paper thin after the fact.
Imagine trying to cut a waterstone in half with your knife if it had been left in the bottom of a damp drawer rattlling around with your spanners & hammers for a few years, I doubt you would have much luck.
I have a one inch chisel I bought about twenty years ago for about £1.20, I had left mine at home & needed one to trim around a door frame to fit some cables for an air conditioner, it ihas been well looked after & is still sitting in my workshop now, sure it does not hold it's edge as long as my higher quality ones but it does perform a more than adequate job & I still use it regularly.
The ones I mentioned previously I sharpened for my workmate were if my memory serves me made by Marples, not I will grant you the most supremely high quality available not equally they were not exactly rubbish & many people myself included have enjoyed using their Marples tools for many years; his ones howver had been kept in a plastic bag in the bottom of a tool box, three of then had NEVER been sharpened & the forth had a sloping cutting edge & a CONVEX!!! bevel.
I ask you this, if you had to use one or the other given the choice of using my £1.20 dirt cheap but honed & well maintained chisel or his much better quality & far more expensive but blunt & chipped Marples ones.
"Which would you choose?"
What I really hate about Japanese waterstones is they spall if my shop freezes. Something about water freezing in stones that isn't good you know?
How much is a good set of Japanese water stones?