Chisel Question

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steve355

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Hi

My chisel set has built up over the last couple of years by buying vintage from eBay/ car boots etc. They are mostly Marples/Sorby etc and generally seem very good. I can get them very sharp and generally it takes a small amount of regular honing to keep them that way. Except one…..

I have a half inch chisel I’m having trouble with. It looks good quality, nice boxwood handle, nice bevel etc. I followed my usual process for it but the edge quickly deteriorates. Not just blunts, but dents / burrs over. I presumed that perhaps this chisel was only hardened at the tip when new, so I went through my usual hardening routine of heating until no longer magnetic and quenching in oil. But it hasn’t solved it - maybe Improved it.

I imagine this is what is called “not holding an edge.”. Is this chisel for the bin, or can anything be done?

thanks
Steve

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sell it on ebay.....only joking. seriously that's quite a recent chisel. many older chisels are not quite right either tbh. they are cheap enough to no waste to much effort on. it may be a alloyed steel that demands a certain treatment or just the beginning or end of a pour?



historically chisels could be cheaper dearer the difference being the steel and the time/ effort spent
 
I'd say it was a heat treatment issue, either from the factory not quite done right or through previous sharpenings on powered grindstone/ linishing.
I only say this as I've messed up a few cutting tools this way and seen some brand new ones that don't hold an edge

does a file skate over it?
 
It does look like the steel is rather soft. Have you tried a steeper sharpening angle (perhaps just at the tip)? The steel should hold up better.

In more detail: I've read about people getting good results with soft chisels--up to a point--using what's referred to as David Weaver's "unicorn" profile. It's all about modifying the geometry of the bevel and not a method per se. Keep a shallow primary bevel and make the very tip much steeper (can be in the neighborhood of 45 degrees!) by any of a number of methods, including hitting the tip with a buffer, "rolling" the chisel on a fine stone or strop, and so on.

This might help, or the chisel might still be too soft.
 
If you are not able to harden it through heating and quenching, then there is something amiss with the steel. Probably time to move on and replace it.
I remember using Casenit at school in the metalwork class. This you could use to harden the outside of blades, but it only hardened the very outside. It is no longer available as I believe it contained Cyanide.:unsure:
 
Hi

My chisel set has built up over the last couple of years by buying vintage from eBay/ car boots etc. They are mostly Marples/Sorby etc and generally seem very good. I can get them very sharp and generally it takes a small amount of regular honing to keep them that way. Except one…..

I have a half inch chisel I’m having trouble with. It looks good quality, nice boxwood handle, nice bevel etc. I followed my usual process for it but the edge quickly deteriorates. Not just blunts, but dents / burrs over. I presumed that perhaps this chisel was only hardened at the tip when new, so I went through my usual hardening routine of heating until no longer magnetic and quenching in oil. But it hasn’t solved it - maybe Improved it.

I imagine this is what is called “not holding an edge.”. Is this chisel for the bin, or can anything be done?

thanks
Steve

View attachment 151481
View attachment 151483
Might improve after a few more sharpenings? Sometimes had the feeling with new ones that they are soft at first, perhaps over-heated with the 25º grind which goes right to the edge.
Power grindstone has to be used with caution. A lot of beginners immediately spoil chisels!
 
Last edited:
What was your rehardening process?

If you’ve just blowtorched the end and dunked in oil and it’s still soft then I’d suggest redoing but dunk in brine (salt and water). Will either harden or break or you could just keep it as a beater chisel.

If it holds a lot of meaning to you, knocking the handle of and reheatreating could be done - cost of post back and for is probably the same as getting another from a boot sale though.
 
It does look like the steel is rather soft. Have you tried a steeper sharpening angle (perhaps just at the tip)? The steel should hold up better.

In more detail: I've read about people getting good results with soft chisels--up to a point--using what's referred to as David Weaver's "unicorn" profile. It's all about modifying the geometry of the bevel and not a method per se. Keep a shallow primary bevel and make the very tip much steeper (can be in the neighborhood of 45 degrees!) by any of a number of methods, including hitting the tip with a buffer, "rolling" the chisel on a fine stone or strop, and so on.

This might help, or the chisel might still be too soft.
I do this with mine, create a microbevel. more material behind the microbevel does stabalise the edge more and gives it more stiffness and strength
But like you say if the HRC of the steel is too low it'll still deform or lose the edge pretty quickly
 
I do this with mine, create a microbevel. more material behind the microbevel does stabalise the edge more and gives it more stiffness and strength
But like you say if the HRC of the steel is too low it'll still deform or lose the edge pretty quickly
Doesn't everybody do a "micro bevel" to start with, i.e. if it's ground at about 25º then hone a "micro bevel" at about 30º ?
I always do, though the micro bevel eventually becomes macro of course
 
If the edge folds, then the hardness of the steel is too low. The reason could be over tempering or a bad steel batch. If you quenched and did not temper, the metal would be extremely hard and brittle. However, if it's still folding, the steel is junk.
 
What was your rehardening process?

If you’ve just blowtorched the end and dunked in oil and it’s still soft then I’d suggest redoing but dunk in brine (salt and water). Will either harden or break or you could just keep it as a beater chisel.

If it holds a lot of meaning to you, knocking the handle of and reheatreating could be done - cost of post back and for is probably the same as getting another from a boot sale though.
I don't think many people heat them enough when trying to harden, or hold them long enough at the correct temperature, you have to get past the Curie point or it wont work. And the you must re-temper (which can often be done in the oven at home (220 for 20 minutes ish ??)

And all that depends on what it is made of, there is a lot of complex alloys now in tool steel, I believe there are now some non tempering nickel alloys.
 
Just to add to some of the points in the thread

The OP has already tried to re heat treat so the factory condition is gone.

It’s pretty old so will be a fairly simple steel, so shouldn’t need much soak time at temp ( soak at temp is needed for alloyed stuff).

Curie point (where metals lose magnetism) is a handy coincidence for low alloyed stuff in hitting target temp (curie is 770c,most carbon steels need 780 to 820c range).

The failed HT suggests quenchant will need to be pretty quick so brine, or if using veg oil preheat to 70c first to thin it down which increases quench speed.

I’d only temper at about 170-180c and then check for chippiness- 220c will drop most stuff down to mid 50s HRC which is a bit low, especially as unlikely to hit full hardness with a makeshift HT on an unknown steel.
 
as % carbon goes up austenite threshold comes down, so for something like an old chisel (1¼%) getting beyood the curie point should be OK. Otherwise how can temp be measured, expensive equipment? The Colour which many claim to know but in fact needs lots of experience (that I don't have) they reckon some of the old hands in the steel foundries could be within a degree. but someone on a one off?

for tempering I have never come across such a low figure for chisels, but may be your right if the first bit has not been done well.

As for quenching, how you move it as it cools in the liquid is possibly just as important as the type of liquid.?
 
as % carbon goes up austenite threshold comes down, so for something like an old chisel (1¼%) getting beyood the curie point should be OK. Otherwise how can temp be measured, expensive equipment? The Colour which many claim to know but in fact needs lots of experience (that I don't have) they reckon some of the old hands in the steel foundries could be within a degree. but someone on a one off?

for tempering I have never come across such a low figure for chisels, but may be your right if the first bit has not been done well.

As for quenching, how you move it as it cools in the liquid is possibly just as important as the type of liquid.?
Interesting stuff, but as a woodworker I'd say, what about just binning it and buying another? They are very cheap.
 
as % carbon goes up austenite threshold comes down, so for something like an old chisel (1¼%) getting beyood the curie point should be OK. Otherwise how can temp be measured, expensive equipment? The Colour which many claim to know but in fact needs lots of experience (that I don't have) they reckon some of the old hands in the steel foundries could be within a degree. but someone on a one off?

for tempering I have never come across such a low figure for chisels, but may be your right if the first bit has not been done well.

As for quenching, how you move it as it cools in the liquid is possibly just as important as the type of liquid.?
Yeah curie is helpful in the case of simple steels, and a magnet is cheaper than a thermocouple or an IR thermometer.
Household salt melts at 800c so can be another useful guide for temp without needing any kit.

With tempering part of why I’m suggesting lower is as in a home oven you can see some big swings compared to the temp on the thermometer- and easy to correct under tempering with a re temper at a slightly higher temp- vs over temper where you need to re harden
 
Yeah curie is helpful in the case of simple steels, and a magnet is cheaper than a thermocouple or an IR thermometer.
Household salt melts at 800c so can be another useful guide for temp without needing any kit.

With tempering part of why I’m suggesting lower is as in a home oven you can see some big swings compared to the temp on the thermometer- and easy to correct under tempering with a re temper at a slightly higher temp- vs over temper where you need to re harden

I actually have an IR thermometer which measures up to 1200 deg which I use for my home made foundry. But I guess this isn’t about temp as much as the Curie point, so the loss of magnetism is the key.

I like the idea of hotter oil for quenching.

thanks
 

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