Re-hardened inexpensive chisels vs "good" chisels

[John C Cox]

Hey guys. New guy here.

My primary wood hobby is building acoustic guitars - so I primarily use chisels for paring sort of things, not pounding sort of things. And hard exotic woods are commonly used...

As such - I generally feel like my chisels are too soft, not too hard...

I have recently chased down the rat hole of re-hardening chisels... Without too much preamble here - I found that the Buck Brothers chisels found at the local BORG harden fabulously by heating a smidge past nonmagnetic and then quenching in olive oil. My older Footprint chisel did as well.. They are made of some sort of oil hardening good steel...

(Narex, some sort of German chisel (probably W1), and Harbor Freight wood chisels require water quench.. After making a bunch of banana chisels and cracked chisels - I have decided that water quench is too much trouble)

I decided I liked them much better when not crumbly hard - so I tempered them back at 375F to 400F to get a nice hard edge that doesn't chip immediately.. They are certainly harder now than out of the box - I can easily scratch a box chisel with one of mine now.. And the standard chisels don't mark mine.

But... This whole thing has me thinking..

Is the performance of these re-hardened chisels any better than "Good" chisels? Is Quenched and Tempered $10 Buck Brothers chisel steel anywhere close to that of Veritas O1 or Hirsch steel right out of the box?

I know I am not the only one who has ever tried this out... I know that several of you guys here have done this... Is this something worthwhile...

Thanks

[Jim Koepke]

Howdy John and welcome to the Creek.

I have no idea about comparing the modern soft chisels to harder modern chisels.

I have very few new chisels. Only a few of my older chisels have any problems with edge retention. They tend to get set aside and not used.

Most of the 'hardware store' chisels may be soft for a reason. It has been suggested there may be legal aspects involved. The makers do not want to get sued if some nimno ends up injured because a chisel shattered when he used it to open a paint can.

There is also the idea of some customers, without knowing prefer the easier to sharpen soft chisels since they are only using them to install a couple of hinges and edge retention isn't as important to their work.

For my use my old high carbon blades are fine. They may need a honing or two during a project, that doesn't bother me as much as it seems to bother others. A few minutes on the stones is like a quick breather for me.

jtk

[Larry Frank]

I think rehardening those chisels is a shot in the dark. For Veritas, when they heat treat something like O-1, they know the grade of steel and exactly what heat treatment is needed. In addition, their control of times and temperatures are much better.

When you just reharden the chisels you bought, you really do not have any idea what grade of steel it is. I am glad that your heat treatment works for you. Be careful you do not get them too hard or they could fracture.

[Frederick Skelly]

I can't answer your question, other than to say that if they work - use them.

But I wanted to say 'Welcome John!' And that we're glad to have you join us!
Fred

[John C Cox]

Yes - the hardware store chisels do seem to be tempered soft out of the package... For all the reasons listed.

I tried out the Harbor Freight wood chisels - they won't oil harden - even in warm canola. They will water harden - but they crack and warp badly. Narex will water and warm canola quench.. Water takes them harder. They warp badly if you harden any more than about the first 3/4". Unfortunately - doing that looses all the benefits of isothermal tempering...

The Buck Brothers chisels are very well behaved. They will quench to really hard in room temperature oil. They warp a little - but it's nothing they can't be flattened back out on the stones.

What works best for me is to only harden the last 3/4" to 1" of the chisel. That reduces the amount of warp you have to deal with. They all warp...

If if any of you guys are interested in trying it out - I can post a brief write up with pix. It takes longer to write it up than to actually do it start to finish.

[Warren Mickley]

For a beginner there is a narrow window between too hard and too soft. Too hard and the chisel is liable to chip and too soft and the chisel tends to fold at the edge. An experienced worker has a much larger window because with cleaner technique he can avoid the inadvertent abuses that cause these failures.

I have some chisels that are lightly tempered like yours and I use them but I prefer 19th century chisels because they are so nice to sharpen. I get good sharpness and retention.

It would not surprise me if your chisels were a bit more like the Japanese chisels and harder than many of the premium chisels. So you might be disappointed in some of the brands you mention.

[John C Cox]

When I first quenched them and left them full hard - they would slice right through anything and still be shaving sharp. Bubinga, Jatoba, White oak, rosewood - and then shave transparent shavings of spruce with no hairs of torn grain.

The problem was that the edges would chip if your technique wasn't perfect. If you twisted or levered even a tiny bit - they would chip out. And after going round and round - back to the coarse stones to get the chips out, I decided to temper them back a bit.

[Mike Henderson]

Yes - the hardware store chisels do seem to be tempered soft out of the package... For all the reasons listed.

I tried out the Harbor Freight wood chisels - they won't oil harden - even in warm canola. They will water harden - but they crack and warp badly. Narex will water and warm canola quench.. Water takes them harder. They warp badly if you harden any more than about the first 3/4". Unfortunately - doing that looses all the benefits of isothermal tempering...

The Buck Brothers chisels are very well behaved. They will quench to really hard in room temperature oil. They warp a little - but it's nothing they can't be flattened back out on the stones.

What works best for me is to only harden the last 3/4" to 1" of the chisel. That reduces the amount of warp you have to deal with. They all warp...

If if any of you guys are interested in trying it out - I can post a brief write up with pix. It takes longer to write it up than to actually do it start to finish.

Sure, post pictures. It's a lot easier to see and understand with pictures.

My understanding of hardening steel is that you trade off between hardness and toughness. Too hard and the edge chips, as you discovered. You have to go a bit softer to get the toughness in the edge.

I suspect most commercial chisels are tempered a bit on the soft side to make sure they won't break in half in use. If you're willing to go a bit harder and understand the tradeoffs, you can get a longer lasting edge.

Japanese chisels go to the hard side with one layer and then use a layer of very low carbon steel to provide some toughness - to keep the chisel from breaking in half.

Mike

[Jim Koepke]

Yes to pictures. Doesn't everyone love pictures?

jtk

[george wilson]

The problems with trying to re harden chisels and plane irons are these:

1. You don't know the type of steel they may be made of. There is air hardening, oil hardening, and water hardening.

2. Steel starts doing strange things when repeatedly re hardened. It needs to be NORMALIZED before re hardening. GOOGLE "normalizing steel" and proceed from there.

3. If your chisels have beveled edges, or a plane iron has its beveled cutting edge, it will WARP. This is because those bevels make different amounts of surface area on either side of the tool. Wider bevel edge chisels will warp more than narrower ones. Plane irons need the BEVEL EDGE GROUND SQUARE, totally eliminating the bevel before you go quenching it.

4.You cannot go using quenched but not tempered steel. It has NO mechanical strength, and will shatter like glass. That's WHY it is TEMPERED!! I had just hardened a plane iron years ago, and it was laying on the bench. I was as yet too young to know better, and the plane iron had not been TEMPERED. I noticed a FLY had landed on the bevel of the blade, and was walking along it when:PING!!!!! The bevel shattered into several pieces. The fly was killed by the concussion!!!! O.K.,I made up that last story but,you will soon find out WHY you should have tempered that tool!

5. You do not know the hardening medium, and neither do you know the tempering color. (And,the use of tempering colors is NOT the most accurate means of tempering tools as the steel's chemistry makes those colors a different temperature for different steels).( It works well enough for simple steels like W1 or 01.) For most ordinary quality tools though, it should be sanded bright,and carefully heated SLOWLY to a medium brown color. There are many steels that this will not apply to,but it is a decent guess for most tools. High Speed Steel will not respond to that color,but FEW ordinary wood worker's tools are made from HSS. The only ones I am aware of off hand, are some WOOD TURNING chisels. And,believe it or not,some cheap CHINESE chisels,














Sorry,my little dog laid her head on the keyboard!! She always manages to push some key that messes up a posting!





with crudely brazed on tips. (I do not refer to metal turning lathe tools. I mean wood cutting chisels) Even Sears Craftsman offered a set of HSS wood turning tools.

I used to make steel spinning chucks for all the major golf trophies. I would rough them out as much as possible. I made a drawing of the spinning chuck,accurately drawing in "Stair steps" along the curved bodies. Then,I turned the stair steps as drawn(this HAS to be drawn ACCURATELY!!!!! After I had stepped in the body shape,I'd use carbon steel,or High Speed Steel wood lathe chisels to smooth away the steps. The HSS tools lasted longer between sharpenings,but men used carbon steel for centuries . Thousands of years, even! So,a decent carbon steel chisel would work. Especially if I was making the chuck out of LEADED STEEL. Turns wonderfully, but keep it off your skin, and wash your arms afterwards.

Why did I throw in that story? I tend to wander into a related story. But,save that tidbit. If your lathe will run SLOW enough, you can turn steel freehand perfectly well, to make missing bits and pieces you need.

Leave out SORBY lathe tools. They are disgustingly SOFT!!!(That's my opinion anyway,and they can't SUE me for my stated OPINION!! I HAVE re hardened Sorby lathe tools(who knows WHAT they are made of?) and did make them better at least.

[Pat Barry]

4.You cannot go using quenched but not tempered steel. It has NO mechanical strength, and will shatter like glass. That's WHY it is TEMPERED!! I had just hardened a plane iron years ago, and it was laying on the bench. I was as yet too young to know better, and the plane iron had not been TEMPERED. I noticed a FLY had landed on the bevel of the blade, and was walking along it when:PING!!!!! The bevel shattered into several pieces. The fly was killed by the concussion!!!!

Thanks George!

[Ryan Mooney]

First, interesting to know that the Buck Bros retemper fairly easily, thanks for taking the plunge and passing the info along!

As for comparison the only way to really know for sure is to take them head to head, you know what you have to do Practically speaking though if what you have is working well why look further unless its for abstract knowledge (worthwhile if that's the goal)?

My first pass guess is that you're leaving yours somewhat harder than most of the commercial ones. Assuming the steel is O1 you would be in the Rc60-63 hardness, but whether its O1 (and indeed where in the O1 line it falls as there is a substantial variation) is anyones guess (so you may well be harder or softer).
http://www.buffaloprecision.com/data.../DSO1TSbpp.pdf
The veritas O1 are claimed Rc58-60 and the PMv11 are claimed Rc61-63 (but that's a completely different type of steel so apples to apples its not). Hirsch claims Rc61 but again may not be apples to apples..

I suspect you might get slightly better results on the warping issue annealing the chisels first and then re-hardening but you'd have to trade that off against the risk of slightly more decarburization from the repeated heating.

[Jim Koepke]

Leave out SORBY lathe tools. They are disgustingly SOFT!!!(That's my opinion anyway,and they can't SUE me for my stated OPINION!!

I will be a material witness on your behalf. My Sorby lathe tools seem to be challenged at holding an edge.

jtk

[george wilson]

I forgot to mention that just leaving hardened, but un tempered steel, parts laying about,is that they have been well known to suddenly pop into two or more pieces. Fully hardened steel is just full of high stresses. So, always temper your hardened tools ! I made up the bit about the fly,but it was based on the fact that fully hardened parts can ,sometimes violently go POP. You don't want your eyes near them when they suddenly blow up.

Jim: it is just too bad that Sorby tools,with their nice London Pattern boxwood handles lack in the performance of their blades. The OLD Sorby tools of the 19th. C., with their figure of Punch stamped upon their blades, were among the finest English tools.

[John C Cox]

mI suspect you might get slightly better results on the warping issue annealing the chisels first and then re-hardening but you'd have to trade that off against the risk of slightly more decarburization from the repeated heating.

George covers this pretty well - but the issue is the bevel edges on the sides and tip. About 100% of the chisels warp towards the back. And the reason is that there's more steel on that side. But - this outcome is preferable (to me at least) to the chisel taking a belly.

2 things seem to make for less clean up work subsequent...
1. Prep the back of the chisel prior to hardening. They almost always come out of the box warped a bit towards the back/tip. This clean up doesn't reduce the warpage - but it's easier to grind a softer chisel than a harder one. And so the subsequent cleanup effort is less than if you just heat straight out of the package.

2. Only harden the last 3/4" to 1". Don't get greedy and try to harden 2+ inches of chisel - that is almost guaranteed to leave you a hard steel banana that's going to take hours and hours and hours to clean up (if possible).