# Cobalt Lathe Tool Bits Good Or Bad ?



## steamtoys (Aug 5, 2011)

I have just made 2 Tangential Diamond Tool Holders & looking at purchasing some tool bits. Am considering 5-8-10% Cobalt, what would be best. Considering 10% Cobalt. Any disavantage or avantage to Cobalt? Ron


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## Mainer (Aug 5, 2011)

I use Cleveland Mo-Max cobalt toolbits and like their performance. I don't know offhand what percentage of cobalt they contain, or the relative merits of different percentages.


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## Omnimill (Aug 5, 2011)

I have both home made and commercial Tangential tool holders and the commercial supplier (http://www.eccentricengineering.com.au) say this on their website:

"_The Diamond Tool Holder can only be as good as the piece of HSS it is holding. Each tool is supplied with one piece of M42 grade,8% cobalt HSS, from a reputable manufacturer. Don't be suprised if you don't get the same performance from a piece of cheap HSS that you bought at the Sunday market._"

Most of the stuff available from model engineering suppliers seems to be around 4-5% Cobalt and It doesn't seem to cut too badly.

Now, lets see some pictures of your tool holder!

Vic.


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## Ken I (Aug 5, 2011)

steamtoys  said:
			
		

> Any disavantage or avantage to Cobalt? Ron



Apart from the price none that I'm aware of - when I previously ran an automatic lathe shop I used Bohler 1200 (12% Co) for all tough form tool applications.

Ken


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## Anko (Aug 5, 2011)

I read somewhere that the adition of cobalt in HSS increase the heat resistance of the tool bit, allowing to turn faster, for lathes the common are 8% to 10% Co I think :

hope this helps

Saludos


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## Omnimill (Aug 5, 2011)

5% cobalt here: http://www.chronos.ltd.uk/acatalog/...ets___Loose_HSS_Toolsteel__5__Cobalt__66.html


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## t_ottoboni (Aug 5, 2011)

10% Co for long lasting tooling
12% will be even better.

The tooling won`t be different in sharpness, but cutting edge will last longer with increase in Co.
There are some parting-off blades with 50% cobalt, but I had never tried one.


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## tattoomike68 (Aug 5, 2011)

Cobalt can make the tool brittle so plan accordingly . believe me i know how to destroy a tool. ;D


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## dvbydt (Aug 5, 2011)

WKE 45 (11% cobalt) stands a fair amount of abuse, but takes longer to grind. I got lucky with 25 100mm lengths of ASP 2030 (8.5 %) a few years ago. This is powder metal technology, is fairly easy to grind and holds an edge for a long, long time.

Ian


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## Tin Falcon (Aug 6, 2011)

I have just made 2 Tangential Diamond Tool Holders & looking at purchasing some tool bits. Am considering 5-8-10% Cobalt, what would be best. Considering 10% Cobalt. Any disavantage or avantage to Cobalt? Ron

First of all entire books small ones or chapters of large books have been written about tool selection. 
they give multiple choices for a reason I will look it up when I get a chance. 
IIRC the main advantage to cobalt is it increases red hardness, in other words when a too gets too hot from friction the tip or edge will start to break down or wear quickly. cobalt increases the temperature when this happens. 
The disadvantage is it takes longer to grind your tool bits. 
Another consideration is source. An Asian import tool bit may or may not perform as well an American or uk name brand.
Asian stuff just does not have the metallurgy and QC that the good stuff does. 
I have and use asian stuff as well as name brand with a couple exceptions it does what I want it to and what it was made for. 

Name brand stuff trust to wok consistently as advertised. Import tools could have hard spots or soft spots anywhere any time. 
Tin


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## Omnimill (Aug 6, 2011)

It's academic for many folks as all thats _easily_ available is the imported 5% stuff. Luckily I have a small supply of some older English stuff that I assume is likely to be a good grade ...

Vic.


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## steamtoys (Aug 7, 2011)

Thank You to everyone replying to my question. With the info I received I have ordered the following. Square Size (Inch): 1/4 Material: Cobalt Material Grade: 10% Tool Bits Overall Length 6 inches Price $5.05 each Enco Master Catalog Page 186 (useenco.com) They have 5-8 or 10% Cobalt listed at what I considered a fair price. You can use Code FSCAUG to get free shipping on orders $25.00 or more. Again Thank You Ron


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