Crobalt Tool Alloy

Hi Just made a Tangential tool holder along the lines of Michael Cox's design, just modified the bit clamp, don't know if it will perform any better. It's to go into a tool turret I made for an ORAC lathe. I don't have a forced lube except what comes out of a can of WD40. Does any know if this Crobalt alloy will perform better than M42 tool steel? It's £18 for 2.5"

TIA

Michael

Michael, I got a piece of crobalt with the one I bought from Eccentric Engineering. It was ok but I had to keep sharpening it to keep the edge. Ive now got a piece of 4" HSS which I cut in two.It seems the same to me. I've seen,on ebay I think 5 pieces of 4" for £12 ish. thats 10 pieces. Doubt whether Crobalt is 10 timesbetter ? John

Edited By john kennedy 1 on 14/07/2013 18:28:05

I thought that M42 was an alloy including cobalt.

Russell

Hi Russell

It is, about 5% I think. The Crobalt is 50%.

Just wondering if there is any real advantage in the Crobalt, if it held its edge for longer there might be. John is saying he didn't find that to be the case, I have enough M42 to keep me going for a few years at my current useage.

Michael.

Helpful details about Crobalt cutting tools are given on the Eccentric Engineering Website.

It sound to me that Crobalt tooling is only worth the extra price over normal HSS if you have to turn particularly difficult or tough materials or if you have to work at production rates that are above those normal for model engineering.

I guess they have advantages for industry but I doubt they are worth the extra cost for "normal" materials and model engineering applications.

Eric

Hi Guys

As Michael says, Crobalt is a cast alloy containing 50% cobalt, the other half is made up of tungsten and chromium, it has no iron or steel in it.
Crobalt comes into its own when used on tougher materials such as cast iron and stainless steel, it will work fine on any other materials that you would normally use HSS for but will withstand much higher working temperatures. Coolant is not usually needed unless to improve surface finish.

If you are just doing light turning of mild steel or brass, Crobalt will give the same sort of results as M42 HSS, although the cutting edge will normally last longer on the Crobalt, that's why it was used on repetition lathes in preference to HSS until carbide took over.

There is a video on the Eccentric Engineering website showing a test between Crobalt and a premium brand M42 HSS. The test was done on 304 stainless, and cast iron, the results were pretty emphatic.
The video is on the Crobalt information page, just click the orange Eccentric Engineering ad on the right hand side of this page if you want to have a look.

Crobalt also have an information page here www.crobaltusa.com/index.htm

Cheers

Gary
Eccentric Engineering

I hear what Gary is saying concerning Crobalt tooling when used in E E's (or home made) tangential tool holder. I am sure it has a place in this application and that it will perform very well.

I understand however that Crobalt is not suitable if the tool has to be ground into the various time honoured shapes used for "normal" tool holders i.e for making knife tools, form tools , threading tools etc. as it is not recommended to grind the Crobalt in such a way as to produce a cutting edge away from the as-cast outer skin. The performance of the Crobalt relies on cutting with the outer edges only. Thinking about it I cannot see that it has any application in my workshop other than in a tangential tool holder.

Eric

Hi Eric

Yes you are correct about the outside edge having the best cutting properties, and that works well with tangential tool holders.
However, the cast alloy doesn't lose hardness as soon as you grind through the surface, although its cutting ability does lessen as you get closer to the centre of the tool bit. The stock has already been ground down to size from a casting at the manufacturers anyway.

For a normal knife tool it would be fine as you are not removing much material, but for say a thin grooving tool where you are grinding off a lot of the stock on either side it would be better to use HSS instead.

A tip for users of the Diamond Tool Holder that want to grind a tip for thread cutting, use HSS for this operation instead of Crobalt as I've found it's a bit more brittle and tends to chip easily with the small point on heavy cuts.

Crobalt, like carbide and HSS, has its pros and cons. Some operations such as turning stainless it excels at, and some such as thread cutting it is not so suitable for.

Gary

Anyone remember Stellite?

Still have some Stellite welding rods somewhere I used to use for Hard Facing.

Ah! Stellite. Wonderful stuff, I still use it often. Very expensive though.

Stellite hard facing really comes into it's own nowadays since we have affordable TiG welding in the home shop.

Very easy to overlay a blob of Stellite onto a rough ground form tool such as an internal screwcutting tool and finish ff on a conventional grinder.

I used to grind up stellite "D" bits for drilling holes in hardened dies where the drawing office had forgotten to include for say - a punch. If I rember correctly it cut more efficiently without coolant. And talking of esoteric materials, we used to manufacture prototype car body dies in a scuff resistant material called "kirksite". Awful stuff to grind when the inevitable re-working was needed - bits would fly of all over. ----- Rik

You can use a reel of hard facing wire on a Mig welder as well. Spent many a happy hour hardfacing Cat Bulldozer scarifier ploughs with one. You could do make your knives and forks last longer as well

The theory behind cutting hard materials is to create enough heat to get the shear zone at the tool tip to red heat. At which point the workpiece is much easier to cut as the metal is locally soft. So using coolant would be a considerable disadvantage. Of course the cutting tool needs to be able to withstand red heat. When I've machined HSS and hardened silver steel I've always cut dry.

Regards,

Andrew

I have a relatively new milling machine (HBM series 25) and some time ago I used several 8%-Cobalt mill bits to machine the hard steel block I used to make a new cross-slide for an old lathe. I provided minimum coolant and the tool cut very well indeed, no 'forcing' nor biting and the bits performed better than any others I have in the workshop.

Most of the advertisements I see in M.E.W. and the like seem to refer to 5% versions, but I bought mine here in the Netherlands and I don't know if these are widely available in the U.K. Nevertheless worth the extra few quid for a set.

> Cat Bulldozer scarifier ploughs with one

Now I know why teh teeth have bright wiggly welds on them!

Ressurects thread: stupid question, but has anyone tried grinding cutting bits out of stellite faced exhaust valves?

Neil

Rik Shaw:

Your mention of Kirksite rang a bell as it is mentioned in a book I have here by the late Richard Buckminster Fuller. He used it in the production of his "Dymaxion Dwelling Machine". Apparently it consists chiefly of tin and at the time of writing (1973) the American aircraft industry's stocks of Kirksite dies were reckoned to exceed the known quantity of tin remaining in the ground world-wide. The dies were dressed to size from cast "simply by sandpapering", possibly the same process you mention.

Hi

I regard R Buckminster Fuller as one of the great innovative minds of the 20Th century. I have a number of his books. For those that may not know much about him the following link will pave the way to an exciting journey.

**LINK**

Regards
John

Edited By John McNamara on 11/10/2015 02:59:19