Chisel back prep - old vs new alloy steels

[John C Cox]

Hey all,

Finally getting a few good old chisels has been an interesting thing.... They behave "Differently" than the new modern alloy steels I am used to...

For example - back prep....

I have taken it as an article of faith that one must lap the backs of your chisels.... And with my modern alloy steel chisels - they don't sharpen right if you don't lap the backs on a plate when you sharpen to release the feather edge... Wiping them on a pants leg or uncharged leather doesn't really do anything useful for me.... And rubbing the backs on a charged strop can mess up the back geometry bad... A couple years ago - I spent a large amount of time and energy undoing chisel back trouble I had caused through my early zeal on strops....

But I noticed that none of these old chisels have lapped backs... Warren also mentioned this - but never went any further about their use practices and HOW they got around backs that aren't lapped... Steven talks about rubbing chisels on a coarse pants leg or uncharged leather to rejuvenate edges.... None of that works on my modern alloy steel chisels...

But... All that stuff works on the old plain, extra high carbon cast steel chisels of old... Even the really hard ones... You can wipe the feather edge right off the edge on coarse denim or uncharged leather....

Is that why we never find old chisels with lapped backs - but new alloy steel chisels basically have to have lapped backs - so they will sharpen right? Because uncharged leather or cloth really isn't effective on the modern alloy steels in use since the 1950's - so workers had to come up with an alternative practice - aka honing the backs as well as the bevels?

Thanks

[Frederick Skelly]

This should be a really interesting thread. Cant wait to see folks' thoughts.

I speculate - with no data whatsoever - that many oldtimers weren't as utterly fixated on sharpening as we are today. If the feather edge came off with a quick rub, that was good enough.

I for one am DEFINITELY coming to like O1 (Ashley Iles).

Fred

[Jim Koepke]

Back flattening may be a modern phenomenon due to our ability of more accurate measurement.

It is highly doubtful 18th and 19th century workers took a caliper to their shavings.

Many of my planes came to me set up how they were last used. Mostly they were capable of shaving wood from a board. Tuning them up made them able to be regulated to take a chosen thickness of shaving through their full range.

If a chisel could be made to do its work, that was probably good enough.

Now we have multitudes of people who are mostly doing woodworking in their spare time. Two centuries ago, people likely didn't have any concept of "spare time."

jtk

[Derek Cohen]

Hey all,

Finally getting a few good old chisels has been an interesting thing.... They behave "Differently" than the new modern alloy steels I am used to...

For example - back prep....

I have taken it as an article of faith that one must lap the backs of your chisels.... And with my modern alloy steel chisels - they don't sharpen right if you don't lap the backs on a plate when you sharpen to release the feather edge... Wiping them on a pants leg or uncharged leather doesn't really do anything useful for me.... And rubbing the backs on a charged strop can mess up the back geometry bad... A couple years ago - I spent a large amount of time and energy undoing chisel back trouble I had caused through my early zeal on strops....

But I noticed that none of these old chisels have lapped backs... Warren also mentioned this - but never went any further about their use practices and HOW they got around backs that aren't lapped... Steven talks about rubbing chisels on a coarse pants leg or uncharged leather to rejuvenate edges.... None of that works on my modern alloy steel chisels...

But... All that stuff works on the old plain, extra high carbon cast steel chisels of old... Even the really hard ones... You can wipe the feather edge right off the edge on coarse denim or uncharged leather....

Is that why we never find old chisels with lapped backs - but new alloy steel chisels basically have to have lapped backs - so they will sharpen right? Because uncharged leather or cloth really isn't effective on the modern alloy steels in use since the 1950's - so workers had to come up with an alternative practice - aka honing the backs as well as the bevels?

Thanks

John, what do you define as "lap the back"? Does this refer to lapping the entire back, or just the immediate back of the bevel?

I do not subscribe to the "lap the entire back of the blade", although it is a nice touch and I am happy to see it done since it is a sign of a well manufactured chisel. Even flat is unnecessary to make a chisel work, but I would rather have a flat back that one that is curved. I believe that it says much for the skill of past furniture makers, who could produce quality with lesser tools than we have today.

Now are you saying that the rear of the blade is untouched in its entirety? That I could not understand since sharp required two edges meeting equally. Simply wiping a wire away does not say much about the quality of the edge, only about the steel.

Regards from Perth

Derek

[James Pallas]

I needed to get out a really big spoon to stir this pot. If you polish the whole back of a chisel don't you need to polish it every time you sharpen up in order to maintain it. If you just work the last 1/2 inch or so you will soon be out of flat if you use the chisel much.
Jim

[Patrick Chase]

This is a somewhat tricky topic IMO, for a couple reasons.

For starters I strongly disagree with the premise that "new alloys" require working the back with any sort of abrasive. I strop almost all of my tools on uncharged leather and it works perfectly well. I can strop most of them on my bare hand if need be, for that matter. As James says, if the edge is clean to begin with then it will hone without any lapping.

The reason I say "most of my tools" is because while old vs new is completely irrelevant to this topic, tough vs brittle is matters very much. Tough steels can withstand a lot of plastic deformation without breaking, and that leads to tenacious wire edges. As an extreme example, HSS at typical "Western tool hardness" requires more than just bare leather to remove the edge (though my PM-HSS Japanese chisels at Rc64 are sufficiently brittle that they don't).

Another example is austempered steel as in Narex and maybe a couple other brands. Those are on the soft side (Rc59 is just about the limit for lower Bainite) and *very* tough. I can get a clean edge with my Narex chisels on just leather, but it definitely takes more care and double-checking than with otherwise similar conventionally hardened steels that are a couple points harder.

There is nothing magical or unique about old steels, except in nostalgic peoples' overactive imaginations.

[John C Cox]

I am kinda surprised by the responses - as I have since discussed with several woodworker friends in real life... Everybody thinks it is obvious and why "the old guys" don't really talk about it....

One old fellow responded - "Yeah, everybody knows all that... The trouble is that they quit making the stuff like what you are talking about back in the 50's.. So you can't really buy anything like it anyway unless you know somebody with a collection"...

[Derek Cohen]

Hi John

Will you comment on my queries, above.

Regards from Perth

Derek

[steven c newman]

While you are about to flatten a chisel's back...look at your thumbnail....note it's size. That is all you need to work on, just the area the size of your thumbnail...

I use the pants leg as a quickie strop...2-4 swipes on each side...bevel then back....then right back to work....Aldi's or Witherbys...all treated the same way. I want them sharp for the job I need them to do, when I need them....not after a full day at my non-existent "sharpening bench" . I get a chisel...do a full sharpening on it....and expect it to do it's job..nothing more. it is not so much sharpening as it is maintaining the sharpened edges. I might at the end of a project, have a maintenance day....go through and check out the users...if they need a bit of work, that is when I work on the edges. i want them ready to go to work, when next needed..without any fussing around. I really don't care IF I can see myself reflecting from a sharpened edge..have mirrors for that...

Leather strop? yes, but it has been charged up a few time with that "green stick" when needed. Strop was made from an old leather work belt....one that carried my nail bags while I worked building foundations of concrete. The "rig" was finally retired, when I got too old for that work. One of the nail bags supplied the leather face of my leg vise. The belt was cut down a bit, and used as a strop ever since. about..15 years worth? Not too concerned about it...I can get a new one just like it...$3 at the local Borg....

Remember this..you can polish a bevel or a back to a mirror like perfection...and it still will have trouble cutting a warm stick of butter....

[Todd Stock]

I would tend to agree with Patrick on toughness...the 1970's era Two Cherries blades take a bit more to release the wire edge than either the old stuff or the LN A-2 edges...tougher steel or force of habit...not sure which. A strop would give me a faster release, but I want a mirror polish on a good piece of the back in any case (think cutting binding & purfling miters), so the extra couple of strokes is acceptable, and working in abrasive materials occasions the touchups in any case.

[Charles Guest]

Doesn't one end up lapping a goodly part of the back of a chisel or plane iron simply because it's easier to register a good bit of the chisel on whatever media is being used? I mean, how would you actually only register say an eighth or so of the back of a chisel on a honing stone in order to lap only that very small portion? Seems ridiculous to try and with modern, fast abrasives bordering on absurd.

[John C Cox]

Now are you saying that the rear of the blade is untouched in its entirety? That I could not understand since sharp required two edges meeting equally. Simply wiping a wire away does not say much about the quality of the edge, only about the steel.

Warren has mentioned this multiple times... I looked over these "old" tools that I picked up closely to see if I coule find one to refute his position... Not one... I say "old" because I doubt the youngest of them is much older than 20 years old... Then there were a couple from somewhere between the 50's and then.. But the oldest of them looked to be over 100 based on the markings... None of them appear to have had the backs flattened or honed like we talk about on here... Either honing 1/4" to 1/2" at the back of the bevel or flattening the whole back... A few of them had backs which had been abused... But none of them looked like they had been flattened... In fact - the actual old sheffield cast steel still had almost all the "mill black" oxide finish intact on the back...

I never paid this much attention the last time I had a bout with old tools 10 or 15 years ago (and incidentally ended up with a couple chisels with giant humps on their backs)...

I personally find chisels much easier to control when the backs are straight enough... Do they need to be optically flat all the way across the entire back? No.. I just need them flat enough so they don't dive into a cut or push up out of a cut when working... And I do like to hone a good flat across the back of the bevel so I know they have a good edge. So I have picked out my candidates and set out flattened the humps and bumps out of their backs so I could get them to register right on the work...

I agree it's a testimony to their skills that they got good results out of chisels that I would have had trouble with on the wood.. But I suppose it was their day job and it's not mine...

In the process - I got impatient and honed the bevels to see how they would hold up on wood... You know - especially with Sir Paul declaring that Aldi chisels are the match of old quality cast steel (they aren't by a long shot in my hands)... I couldn't bring myself to do the evil "Ruler trick" on a chisel back - so I simply stropped them on dry leather... The feather wiped right off and they came out ultra sharp and their edges hold up very very well... Most of the modern alloy steels don't behave this nicely for me... Feather edges and wire edges tend to be much more persistent... And the strop may remove it after carefully honing the bevel and back - but it won't without taking a light pass or two on the stone...

After some test cuts - I finished cleaning up the backs so they would register right on the work..

[David Ragan]

Back flattening may be a modern phenomenon due to our ability of more accurate measurement.

It is highly doubtful 18th and 19th century workers took a caliper to their shavings.

Many of my planes came to me set up how they were last used. Mostly they were capable of shaving wood from a board. Tuning them up made them able to be regulated to take a chosen thickness of shaving through their full range.

If a chisel could be made to do its work, that was probably good enough.

Now we have multitudes of people who are mostly doing woodworking in their spare time. Two centuries ago, people likely didn't have any concept of "spare time."

jtk

So true

It is baffling to see the woodworking of yesteryear, w no modern alloys, sharpening 'systems' and so forth. Very humbling indeed.

[Charles Guest]

A lot of the old timers ended up using chisels that one would sharpen the same as a straight carving gouge, with a bevel on both sides though not as neatly done as a carver might. There's certainly nothing wrong with this and by definition they work fine for paring as just about any carver would tell you.

But, if you want a flat back they are relatively easy to make thanks to the abrasive choices we have now.

[Warren Mickley]

Some of the responses in this thread are kind of far fetched. If one is going to use a chisel for daily work for a lifetime, the amount of time he spends getting the back to a fine state is trivial. If on the other hand one plans to fool with a chisel in spare time and then buy a whole other set next year, the time spent bringing it into service seems like a burden. I am having trouble imagining using chisels with double bevels as suggested by some. Put yourself in the position of a craftsman- nobody wants to screw around like that.

Some guys seem to think that when they find a chisel or plane at a flea market, it has remained untouched since a fine craftsman last used it in 1790 or whatever. It is many times more likely that it was used by some farmer or handyman in the meantime. That some one ran it into the ground without much care or skill.