How much life does an old head have left?

[Ziggy99]

Excuse a dumb question from an axe newbie: given that only the bits were likely to have been hardened and in use of course these get filed back, you might buy an old head that just has soft steel for an edge. Are there manuals for the big makers' products that specified how much was hardened - so that you could assess an ebay wonder by its poll to edge length?

I gather that these days the US standard specifies at least half an inch. Doesn't seem a lot to me. Old makers did better?

 

[Curt Hal]

If you soak an old head in vinegar for 24-48 hours, when you take it out, the section of the bit that has been hardened will show up black. That's how much much tempered steel you have to work with. In my experience, depending on the maker and the age, you will usually find 3/4" to 1 1/4." It is good to know the general dimensions of a head of a particular weight, just in case the head is shown next to a ruler. Another thing to watch out for is any discolouration and/or grind marks on the edge. Using an electric grinder on an edge can take the temper out of the steel. Also (and I have been burned on this a couple of times) watch the shape of the eye on the photos, especially if there is a lot of mushrooming on the poll. Extensive hammering on the poll (why do people do that???) can lead to a misshaped eye, which causes a lot of grief when rehafting. Welcome to the hobby! Just a warning, it's highly addictive.

 

[Ziggy99]

Thanks Curt, appreciate it.

Yes, for a simple tool there's a lot to nut out and I'm finding that interesting.

When I cleaned up one of my own axes the hardening line was clear. It's hard to ask an eBay seller though to set up a vinegar bath.

I've rehabbed a lot of other woodwork tools - planes, bench chisels etc - and found that time-consuming but satisfying. In those cases, there's usually agreement on the shape and presentation of the cutting edge. With impact tools, well, there's a lot of opinions! But that's another topic.

 

[300Six]

Today's recreational users will be hard pressed to ever wear out an axe. If the one you are looking at is domestic made (and stamped is even better) compare the profile with that of pristine others. If there's a considerable amount of blade ground or filed away then start scouting around for another head. Luckily old axes are neither rare nor expensive. Temper lines seem to vary considerably, enough that only vinegar soak or a file will provide firm answers.

 

[Steve Tall]

Plumb used to advertise that its axes had "twice the life" with the bits being heat treated for "two full inches". This could imply that the other axe makers generally heat treated about one inch. These days, ANSI standards call for hardening at least a half inch back from the cutting edge, and Council Tool has said that it aims for 1-1/4 inch from the edge.

On vintage axe heads, watch out for excessively worn toes (and/or heels).

...Plumb advertised its axes as having "twice the life". Below is an ad from the December 3, 1921 Saturday Evening Post which said that the bits were "double tempered for two full inches above the cutting edge". These days, ANSI standards call for hardening at least a half inch back from the cutting edge, and Council Tool aims for 1-1/4 inch from the edge.

...

 

[Agent_H]

That's a good question. I think the responses you got are right on. There are other signs of use/abuse that 300six and Curt Hal shared that have to be taken into consideration of course but your question made me think of a different aspect of the "how much life does an old axe head have?".

My brother was sending me auction listings to ask what I thought. I know that he is hinting at wanting another axe but he seems interested in the Jersey pattern. Many had very worn toes. I told him if he wanted one I would find him one but the ones he was forwarding me were priced lower due to needing reprofiling or some major file work to even out the existing wear.

Along the lines of your question, are there particular patterns that seem to still perform well after the loss of steel due to use then "cleaning up?". I know it depends one whether the bit is inserted, over-laid, or homogenous steel that is tempered.

For example, I have a Jersey that still has about an inch of tempering left that I took a lot off of to reprofile. It splits rounds really well. I am thinking the lugs might retain some weight in the body and a Jersey's pattern shape kind of allows for a longer edge presentation, even worn back but evened up. Not prime of course but usable. Maybe the Connecticut pattern will be similar as it also inherently stays wider quite a ways back from the original edge?


In comparison, a Michigan pattern I have taken back that far for a reprofile seems to have quite bit less area to present to what's being cut.


Suppose it depends on the maker's interpretation of patterns but a really worn Dayton (with tempered but still there to work with) might fall in the same category as a very worn Michigan.

Of course, none of that makes any difference if you run out of tempered steel to work with.

Didn't mean to stray from your original question but it made think of tempered bit to overall shape ratio I guess. I'm just up early and not at home so this might just be my rambling but your question did get me thinking.

 

[300Six]

It is probably not uncommon to stumble across a perfectly good-looking axe head.....but one that has survived a house or garage fire. No matter how much blade steel there is the intense heat will have ruined the temper.

 

[Ziggy99]

I'm a bit puzzled by the heat treatment terms used here.

My understanding is that the process is to heat the bit and then quench it (hardening), and the result while hard is too brittle so then it's heated again and allowed to cool slowly (tempering). Reference works indicate that the tempering temperature of axes is about 270º C. So tempering is actually 'unhardening' somewhat in order to get a more ductile bit. But I'm no metallurgist so may have this all wrong.

As for old axes, here in Australia double-bitters are as rare as hen's teeth so I've bought a couple from US eBay. Good sellers show the length but without knowing the original size you can't judge the bit loss.

 

[Steve Tall]

I'm a bit puzzled by the heat treatment terms used here.

My understanding is that the process is to heat the bit and then quench it (hardening), and the result while hard is too brittle so then it's heated again and allowed to cool slowly (tempering). Reference works indicate that the tempering temperature of axes is about 270º C. So tempering is actually 'unhardening' somewhat in order to get a more ductile bit. But I'm no metallurgist so may have this all wrong...

Your understanding seems correct to me. I think the problem is that the word "temper" or "tempered" is sometimes used as a shorthand for "quench and tempered" or "hardened and tempered", especially in advertisements.

 

[Square_peg]

My understanding is that the process is to heat the bit and then quench it (hardening), and the result while hard is too brittle so then it's heated again and allowed to cool slowly (tempering). Reference works indicate that the tempering temperature of axes is about 270º C. So tempering is actually 'unhardening' somewhat in order to get a more ductile bit. But I'm no metallurgist so may have this all wrong.

Essentially correct.

If you've ever heated up a piece of shiny clean steel and seen the colors run then you've seen the tempering process. I'm not talking about the red/orange/yellow (1500° F and up) glow you get at forging temperatures but just the much lower temperature used in tempering - typically between 400° and 700° F. It varies by the type of steel and the desired hardness of the tool. These charts give you a pretty good idea of the temperatures involved.

 

[Ziggy99]

Interesting. Thanks.

 

[Bo T]

As long as the eye and poll were in shape, the ax would have a new bit welded in or on. If the head broke, then the wrought would be used where useful and the welded bit could be used to make a cutting tool. This has been pretty standard over the last couple of millennia, 'cept for the last century or so.

 

[Ziggy99]

Yes.
I see some Japanese axes are still made with forge-welded steel bits on an iron body.

 

[Bo T]

There are also a number of custom makers who do this.

 

[Ziggy99]

Yes.
I gather in Japan it originated because steel was expensive and it continued, particularly with knives, since lamination allows a combination of a hard but brittle edge supported by a softer more ductile iron.

 

[jake pogg]

Yes.
I gather in Japan it originated because steel was expensive and it continued, particularly with knives, since lamination allows a combination of a hard but brittle edge supported by a softer more ductile iron.

It "originated" in every culture once the Iron age(a relative archaeological term specific to each separate culture,i.e. the time that they started playing around with Fe)had advanced for them.
And it normally remained,in the whatever form,ranging from the differentiated heat treatment,to soldering carbides or other hard/wear-resistant tips on the working edges of tooling.

There wasn't anything particularly new in it,as during the Neolithic and possibly earlier eras people commonly used obsidian,or other hard materials,in a similar way,to tip a softer/more viscous,=tougher matrix,like wood...

 

[jake pogg]

The Hardness of edge is relative to (at least)two factors:Your specific use of the tool(wether you'd be chopping pine or eucaliptis);and the blade geometry that you may choose for that particular application.

That's speaking very broadly,of course,as then the things get kinda complex,and get further broken down into how likely you may be to hit something nasty,say,like an embedded rock(i chop a lot of driftwood,meself...),and how willing you are to loose a chip out of your edge,vs bending the edge over(how replaceable that tool is for you,vs how much time you'd be willing to spend resharpening).

 

[Ziggy99]

Sure. Maybe we should call that edge retention? I think of edge hardness as having to do with the steel composition and heat treatment.

As for J-tools, my understanding is that the Japanese had shortages of steel compared with western countries and that drove common lamination in edge tools. They have of course since made an art form of it and arguably do superior knives because of it.

 

[jake pogg]

Edge retention sounds good(it's probably the correct term).

And so,back to the issue of how much of the original HT may be retained(given that the steel bit itself still remains):One aspect i've noticed to be missing from previous replies is the so-called Through-hardening qualities of a given steel alloy.Older Carbon alloys had rather poor ability to harden throughout.(HT specs are normally given "per...N thickness"(normally 1/2",i think).
Later,more modern alloys have changed that by means of other than C alloying elements(especially Mg is instrumental in allowing the alloy to harden through to a greater depth).
So,just because the "temper-line" extends certain way up the blade,it's not a guarantee that Inside that thickness the blade has formed the necessary structure,i.e. has aquired the desired edge retention qualities.
It can still be a crap-shoot.So it goes.

The hardness can be judged exactly using the hardness tester.Or it can be eye-balled by trial and error.Or any combination of those(tip of a file of a known hardness,et c).

I (personally)have doubts as to the exact relationship of economics and laminating dissimilar steel alloys by the Japanese,as every steel-working culture has practiced that very technique:The Scandinavians(especially Swedes,who have no dearth of ores OR charcoal to this day)used it almost always,on most tools(almost unto the present day the commonest knives in the world,Morakniv,were laminated...).So did the Yakut of central Siberia,or the Frankish tribes of the Rhine valley(who supplied the entire Euro-centric world with metal products till...well,the present,really,Solingen and such-like...),so did the ancient kingdom of Zimbabwe,who forged away all their forests and left an arid desert(without ever running short of iron ores,i think....So,it'd be a tough call!

 

[Bo T]

And, even the hardness testers are prone to error. Until recently (the last century or so) mono steel tended to be of low enough overall quality that the laminated blades offered a superior product. Also, the higher quality steel bits were/are relatively thin so I'd guess, in most cases, a small variance in hardness through the depth.