Spark Test?

[Arbalist]

I’ve seen pictures in books of spark tests to try to broadly identify a type of steel.  I admit to finding it difficult.  Would any of you hazard a guess as to this type of steel. Is it more likely to be O1, HSS or something else? It will eventually be a traditional Japanese wood turning tool.

 

[Frosty]

NO. People who say a spark test can help identify a steel don't know what they're talking about. A spark test is only useful for estimating CARBON content PERIOD.

From how it appears on my computer monitor I wouldn't expect the steel you're sparking to hold an edge. The sparks appear orange red without any branching. It looks to be low carbon, below the dividing line to medium carbon. With one caveat, there are some alloying elements that can cause similar sparking in high alloy cutting steels. You would however know it because those alloys will cut groves in your grinding wheel pretty darned quickly.

The best way to learn to spark test is to compare to known steels in your possession. 

Unfortunately no matter how good a person is at reading sparks it can NOT tell you what steel you have with any reliability, only ESTIMATES of the carbon content.

Frosty The Lucky.

 

[Arbalist]

1 hour ago, Frosty said:

 

From how it appears on my computer monitor I wouldn't expect the steel you're sparking to hold an edge.

Frosty The Lucky.

 

It’s not my steel. It’s a picture from a Japanese wood turning site. In traditional Japanese wood turning each turner forges his/her own tools. I just wondered what type of steel this was likely to be as there’s no indication given. I suspected it might be some kind of spring steel as this often seems to be pressed into service as cutting tools in traditional crafts.

It seems that Machine Learning can improve the accuracy of spark testing according to this article.

https://www.sciencedirect.com/science/article/abs/pii/S0263224121012550

 

[Frosty]

You can download spark test color comparison charts online as well as color temperature charts. 

If you're making wood chisels, hand, hammer or lathe spark testing will tell you what you need to know. It's a good thing to learn and can save you lots of time experimenting.

Frosty The Lucky.

[swedefiddle]

Good Morning Arbalist,

It is impossible to see the spark trail, if it is going into the guard. Hold your test piece nearer the top of the stone, yes it will spark at you. Don't be shy with the face protection!!   If you take the rest off the grinder, you may be able to see the sparks, better.

The Spark Test only gives you a guess, on the Carbon Content. Nothing More than a guess.

Neil

[patrick]

Hey Guys- I know I'm a bit late to this conversation but I thought I'd add a little bit. The spark test actually was used for differentiation of more than just carbon until fairly recent times. I have a copy of the spark testing training manual that was used at Inland steel and it very clearly shows and discusses how to distinguish the spark characteristics of elements like molybdenum and chromium. The training required to get that good was extensive. The manual was given to me by a former salesman who represented the successor to Inland Steel. I asked why that technique was still in use since laboratory methods that are much better have been in place for a long time. He said the method was used with a hand grinder by inspectors checking bundles of bars as the left the mill. The goal was to quickly hit the ends of the bars in the bundle and confirm different steel grades had not been mixed in the bundle. Up until fairly recent times there was no other method fast enough to keep up with production in a steel mill setting. Within the last 10 years or so portable X-ray analysis tools have replaced the spark testing method for this application. Interestingly, the most common laboratory method, optical emission spectroscopy, is really just an advanced version of the spark test. In this method an electric arc is struck between a steel sample and a tungsten electrode in an environment flooded with argon. Special optics and software analysis the colors in the light and determine the percentages of each of the elements present in the steel. The use of the traditional spark testing technique to sort steel by carbon content is one of the earliest tests. By 1916 this was a well established test and is discussed, with illustrations, in the book Heat Treatment of Tool Steel by Harry Brearly.

The image shared by the original poster does not have a lot of spark features shown. I agree that pictures zoomed out with more of the spark showing, especially the burst if there is one, would be helpful. Assuming there actually are no bursts then I'd guess this to be something like a high speed steel rather than 01, but I don't think there is enough info to say for sure.

[evfreek]

I would agree with HSS, but the shape of the tool is not consistent with what I would expect for a piece of HSS.  I have ground HSS drill bits mixed in with simple carbon steel drill bits, and anybody would be able to tell the difference if you had a pile to sort out.  Usually I identify the simple carbon steel drill bits as ones which blow out their edges rapidly at 100 sfpm, and these almost always give the bushy spark pattern.  They consequently head straight to the trash.