Hand Tools

Subject:
Numbers are just one part of the equation

Derek Cohen (in Perth, Australia)
Hi David

Since you have linked to one of my articles, and Warren has commented on this as well, it seems relevant that I add my bit here.

Just in case others are not aware of the location of the original thread, and wish to read it (warning - it is long!):

http://www.woodworkforums.com/f279/chisel-hardness-study-step-216507

The thread was begun by Rob Streeper, who hails from San Antonio. His interest in woodworking to date has been building backsaws. The research on chisels was to guide his proposed venture into making chisels. That was 2 years ago. As far as I know, all has remained theoretical. Rob is a nice guy. I believe that his background is a PhD in medical technology (so he would be familiar with research methodology), but my memory may be faulty.

Early on (post #9), I asked:

Why is hardness relevant? Can you explain this?

Have you taken into account steel composition, and the manufacturers recommendation in this regard? Blue Spruce is A2, and some of the others variations of O1. I am not sure what Pfiel are?

Rob replied:

Hi Derek,

Why? Because it's there of course.

The purpose of this effort is to determine the hardness of the chisels that have gone before is relevant in that the results of my analyses will hopefully guide how I will make my chisels. My perception is that hardness is important, but how hard is best is unclear to me. Other processes will also be considered in due time.

Steel composition influences hardenability, toughness, and wear resistance, subjects I hope to address in the future insofar as they are relevant to woodworking tools. The openly available literature in this area is scant. I'm sure that the companies that make industrial tooling have done a lot of work to understand these factors but none of it is available to me.

Regards,
Rob

I did not consider this to be an adequate response (as the thread did not appear to be aiming to include these aspects), but by then any further response would have been seen as argumentative, so I left alone. My view remains that there is much more to steel in chisel (and plane) blades than hardness - which is the point that must be made for our own discussion. Chisels are struck (impact resistance) and used for paring (abrasion resistance). This is why I did separate test for each ...

http://www.inthewoodshop.com/ToolReviews/ChiselBladeTesting-5Steels.html

http://www.inthewoodshop.com/ToolReviews/ChiselParing.html

The results of the two tests were interesting in that they demonstrated that the wear in chopping and paring is so different with the same tool steels. Abrasion resistance and impact resistance place quite different demands on steel.

The thread in question has remained about hardness, and all the other ways of wearing steel have not been addressed. The same is happening in this thread, which presents hardness as a major player in steel wear.

Regards from Perth

Derek

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