How to tell if steel is High Speed

[Dean Center]

We have recently helped a club member disperse his shop tools and the new owner of a couple of Sorby scrapers asked me how to determine if they're high speed steel. He doesn't want to sharpen them on his CBN wheels if they're carbon steel. My metallurgy knowledge is limited to "if you can file it, it's annealed".

The tools are a little darker than current HSS, and say "Sheffield Steel" on them, rather than the "HSS" that is typically found today. The prior owner had been turning for 10 years or so, but I suppose he could have acquired these used from someone and they could be older than that.

Thanks in advance for your expertise.

 

[Michael Anderson]

I believe if you grind them, the sparks are different colors. HSS will give orange sparks, and carbon steel will be whiter and more dramatic. Here is a thread on the subject (just found):

Sorby Tool - HSS or Carbon Steel?

I bought this Sorby scraper 30 years ago. I’d like to re-shape it into a negative rake scraper, but I’m not sure if it is a high speed steel or carbon steel tool. If it’s not HSS, I don’t want to use my CBN wheel and will use my regular grinding wheel to do the job. Any suggestions on how to tell?

www.aawforum.org

 

[Donna Banfield]

I recall from my very early days one of my mentors described the sparks coming off carbon steel when using an Aluminum Oxide Wheel (CBN wheels were not in our world for quite a while yet). The sparks will look like the lit Sparklers that we played with as kids on the 4th of July/Independence Day celebrations.

 

[Dean Center]

Thank you! I should have searched first, but couldn't recall seeing this discussed.

 

[john lucas]

Spark test works fine.. however if you treat your cbn wheel with the slick stick sold by woodturnerswonders you can safely sharpen carbon steel tooks.

 

[robo hippy]

We had a round table demo once about sharpening your tools. One turner came with a 'high speed steel' scraper. It was not high speed because it loaded up my CBN wheels. As for cleaning them, I just use a scraper. Once, with an old almost worn out set of wheels, I loaded it up with copper, brass, aluminum, and soft steel. It took about a month before I could not see any metal coloring on the wheel. As for the slick stick, maybe I need to experiment with it some more. It didn't spread evenly on the wheel. It might work better if applied to the bevel. I do use some of the Trend lapping fluid, and apply that to the bevel of the tool rather than putting it on the wheel. I did get one racing stripe on my smock before I figured I needed another method...

robo hippy

 

[Lennart Delin]

I sharpen all my tools on a 180 gr CBN, carbon steel and CBN. I have never had any problems with clogging. Here is what it looks like after many years.

Pictures of sparks, cannot insert video. From ceramic wheel, practically no sparks from CBN.

 

[Donna Banfield]

I sharpen all my tools on a 180 gr CBN, carbon steel and CBN. I have never had any problems with clogging. Here is what it looks like after many years.View attachment 60057

Pictures of sparks, cannot insert video. From ceramic wheel, practically no sparks from CBN.View attachment 60058 View attachment 60059

Image on left, a memory from my youth of sparklers on Independence Day in the USA.

 

[Doug Rasmussen]

Spark testing testing, in my reading, has been widely discounted of late. At best, it's always been only a guess and requires significant experience to make accurate judgments. Part of the current distrust of spark testing comes from the variety of special alloys that exist today as opposed to the 1930's when spark testing was commonly accepted. Apparently spark testing can't distinguish between HSS and S7 steels.

Lots of factors are at play. Hardness of the steel, type of grinding wheel, pressure applied to the grinding wheel and so on.

For years Sears Craftsman cutting tools were advertised as HSS, and they may well have been. But they were noticeably softer than more expensive competitor's tools. Possibly softer because they purposely weren't heat treated to the hardness that might make them too brittle and more likely to break in amateur's usage.

So, what does it matter if a tool is HSS? I bet an experienced turner could do a better job with a carbon steel tool than an amateur could with a tool of the most exotic tool steel.

In alloying a steel to meet a certain spec like M2 the mills have a fair bit of leeway in the elements which might allow a 20% difference in required composition. If a mill was producing M2 on price rather than quality they might skew the more expensive elements that give the alloy its good characteristics to low end of the spec's required percentage thereby producing a lower performing product. About any hobby machinist learns quickly how difficult an alloy like 304 stainless can be to machine. There are mills that produce 304 that machines like butter by playing the percentage game. They skew the elements that make the material easier to machine to the high end of the percentage. Likewise, the elements making 304 difficult to machine are skewed to the low end of their required percentage. In this case you pay a premium for the material, but worth it for the ease of machining.

 

[Donna Banfield]

Spark testing testing, in my reading, has been widely discounted of late. At best, it's always been only a guess and requires significant experience to make accurate judgments. Part of the current distrust of spark testing comes from the variety of special alloys that exist today as opposed to the 1930's when spark testing was commonly accepted. Apparently spark testing can't distinguish between HSS and S7 steels.

Lots of factors are at play. Hardness of the steel, type of grinding wheel, pressure applied to the grinding wheel and so on.

For years Sears Craftsman cutting tools were advertised as HSS, and they may well have been. But they were noticeably softer than more expensive competitor's tools. Possibly softer because they purposely weren't heat treated to the hardness that might make them too brittle and more likely to break in amateur's usage.

So, what does it matter if a tool is HSS? I bet an experienced turner could do a better job with a carbon steel tool than an amateur could with a tool of the most exotic tool steel.

In alloying a steel to meet a certain spec like M2 the mills have a fair bit of leeway in the elements which might allow a 20% difference in required composition. If a mill was producing M2 on price rather than quality they might skew the more expensive elements that give the alloy its good characteristics to low end of the spec's required percentage thereby producing a lower performing product. About any hobby machinist learns quickly how difficult an alloy like 304 stainless can be to machine. There are mills that produce 304 that machines like butter by playing the percentage game. They skew the elements that make the material easier to machine to the high end of the percentage. Likewise, the elements making 304 difficult to machine are skewed to the low end of their required percentage. In this case you pay a premium for the material, but worth it for the ease of machining.

Interesting information, Doug. My take on this, is the 'cheaper' tools may be worth exactly what you're paying. Not much. If you stick with the better quality, or premium steel/tool makers, you will get what you pay for.

Generally, my philosophy with respect to tools and machinery, is to get the best quality you can, even if you have to pay more than you can afford. Because you only cry once, when you pay for it, and not every time you have to use junk.

The only exception to that rule is if you are a brand new woodturner, and you need to learn how to sharpen. Go ahead and buy the cheaper tools. They won't hold an edge for very long, making you (I hope) return to the grinder often. Sharpening has a learning curve, and you will make mistakes. Make them on the cheaper tools, and when you eventually need to replace them, you're ready to step up to a better-quality tool. You won't be wasting $$ because you know how to just refresh the edge to get the sharpness back.