# Really hard (stuff) question



## graham-xrf (Nov 21, 2019)

I have a YL10.2 tungsten carbide bar, 16mm (about 0.63 inch). It seems extremely precision ground, and straight.
What would it take to give it centers on the faces, so it can be mounted between centers?



Grinding a MT3 taper on one end is another option, but I believe I already know what is needed to do that.

My regards all
Graham


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## pontiac428 (Nov 21, 2019)

Tungsten carbide is second only to diamond in hardness.  You'd probably have to grind centers into it.  Personally, I'd use it to make tool bits with.  Looks like you could get some drills, countersinks, boring bars, d-bits, even lathe bits out of that length of material... if you can cut it.  I'm interested in what others have to say, since I only know annealed tool steel, and drill banks, and tool bit blanks.  Tungsten carbide is a level up from that stuff.


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## NortonDommi (Nov 21, 2019)

Stefan Gotteswinter    made a video about machining Carbide   



as usual one can only be awestruck.


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## RobertB (Nov 21, 2019)

graham-xrf said:


> Grinding a MT3 taper on one end is another option, but I believe I already know what is needed to do that.


 That's not big enough diameter for an MT3 taper, you could't even get the full length of an MT2 out of it.


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## cathead (Nov 21, 2019)

You could silver solder some short mild steel pieces to the ends of your carbide rod and then center drill.  Another way would be to press fit
some softer ends onto the carbide if you don't want to use any heat on it.


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## graham-xrf (Nov 21, 2019)

NortonDommi said:


> Stefan Gotteswinter    made a video about machining Carbide
> 
> 
> 
> as usual one can only be awestruck.


Oh my. That is amazing! Looking at the "cloud" of chips flying into the chuck made me think it cries out for a vacuum cleaner hose held right there. If any of those chips get stuck between the slide-ways and the carriage, they would roll about under there scoring things up real bad!

At least I know now that a boron nitride centre drill can cut some centres into the rod. Usually one makes the centers, then turns the rod. This time I would want the centers in spot-on first time. Carbide is not the right material for this, even if it is already superbly accurate as a rod.


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## graham-xrf (Nov 21, 2019)

cathead said:


> You could silver solder some short mild steel pieces to the ends of your carbide rod and then center drill.  Another way would be to press fit
> some softer ends onto the carbide if you don't want to use any heat on it.


Yes - I had already been dreaming on a scheme like that. Heat would not bother the tungsten carbide at all. The scraping enthusiasts are always brazing carbide onto steel. Press fit would also be OK. Arguably certain types of bearing locker superglue could work. I think giving the rod some more workable ends is the more sensible thing to do.

Regardless - One has to be impressed by the video! Wow!


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## graham-xrf (Nov 21, 2019)

RobertB said:


> That's not big enough diameter for an MT3 taper, you could't even get the full length of an MT2 out of it.


Robert - You are quite right of course. I have two tailstock quills, from two lathes, both needing some TLC on the MT2 up them. One has been cruelly abused, apparently partly drilled out, not even concentric, and for what purpose I cannot imagine! Amazingly, the remaining part of the MT2 back there still grabs on to a MT2 chuck taper. It makes me sad!



The motivation around the carbide rod was, noting it's ground accuracy, to deploy as a test rod. eBay has MT2 and MT3 test rods, and sometimes MT2 on one end, and MT3 on the other, (from India I think). For the price, it seems to be the more sensible route. It's a pity. When I hold the rod, it is so heavy, and uncompromising, I was trying to find a good use for it.


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## Latinrascalrg1 (Nov 21, 2019)

Lol I was gonna suggest turning a couple press fit end caps made from a softer material but thats been suggested more then once already.


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## pontiac428 (Nov 21, 2019)

I got one of those India test bars, and it's good for what its for.  The difference being the test bar cost $15 and is what it is, while that big chunk of carbide probably cost a whole lot more and can be made into several useful tools.

(edit) ... if you can cut it.


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## mmcmdl (Nov 21, 2019)

graham-xrf said:


> I have a YL10.2 tungsten carbide bar, 16mm (about 0.63 inch). It seems extremely precision ground, and straight.
> What would it take to give it centers on the faces, so it can be mounted between centers?



What are your intensions with it ? You could mount it in your chuck and grind the ends for female centers with a relatively cheap die grinder . ( if it suits your needs )


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## graham-xrf (Nov 21, 2019)

pontiac428 said:


> I got one of those India test bars, and it's good for what its for.  The difference being the test bar cost $15 and is what it is, while that big chunk of carbide probably cost a whole lot more and can be made into several useful tools.
> 
> (edit) ... if you can cut it.


Amazingly Mo, I got it for only £13 UKP. That's about $16.79 U.S. Dollars. A bargain I thought! Cutting it is tedious, but goes OK with a thin wheel in an angle grinder, and it makes an abrasive mess! I am pretty sure one does not want any of that stuff up the lungs either, for which my choice is the 3M 7502, but I am sure the are many other masks that will do.


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## pontiac428 (Nov 21, 2019)

Yeah, at the current exchange rate anything bought in pounds is a bargain!

Glad you're wearing a respirator.  Tungsten carbide will not give you cancer, but will cause mechanical damage.


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## graham-xrf (Nov 21, 2019)

mmcmdl said:


> What are your intensions with it ? You could mount it in your chuck and grind the ends for female centers with a relatively cheap die grinder . ( if it suits your needs )


Looking at the hard accurate finish, I had thought it might have a role as a test alignment rod, if I could persuade accurate centers into it. This is not really so sensible a notion, given that a ready-made test rod is not so costly, and the carbide rod can be useful in all sorts of ways into the future, doing what it does best. It will probably get steadily shorter over time.


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## GrayTech (Nov 21, 2019)

Braze an insert on the end and you have a solid carbide boring bar.


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## MontanaLon (Nov 22, 2019)

You'll probably laugh but you really don't need a 60* center for it to work as a test bar. You just need a hole in the deep enough that the point of your center's won't bottom out. I'd use a diamond burr in the drill chuck on the tailstock of lathe.  

The accuracy of it will be all up to how close you can get it to true in the 4 jaw. It's not easy but once you get into under  .001 put a DTI to it and decide how close you want to get. Use water for coolant and be patient and use almost no pressure feeding it. When hole is 2.5 times deeper than wide flip it end for end and repeat.


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## whitmore (Nov 22, 2019)

graham-xrf said:


> I have a YL10.2 tungsten carbide bar, 16mm (about 0.63 inch). It seems extremely precision ground, and straight.
> What would it take to give it centers on the faces, so it can be mounted between centers?



We press carbide cylinders (short ones; RNG inserts which are just carbide disks) into accurate bored steel sockets,
heating the steel and pressing/dropping the carbide in.   Then you can machine the steel endcap as you wish.
If you want to hammer something flat, a flat carbide surface encased in a steel block makes a good anvil.
And a pointy one in a steel block makes a reliable dent.


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## graham-xrf (Nov 22, 2019)

GrayTech said:


> Braze an insert on the end and you have a solid carbide boring bar.


Is that because the carbide bar is perhaps stiffer, more solid, uncompromising, less prone to shudder than a steel bar with a carbide cutter on it? I had been thinking of a chunk of carbide as the cutting tool material, rather than as a boring bar body.


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## graham-xrf (Nov 22, 2019)

MontanaLon said:


> You'll probably laugh but you really don't need a 60* center for it to work as a test bar. You just need a hole in the deep enough that the point of your center's won't bottom out. I'd use a diamond burr in the drill chuck on the tailstock of lathe.
> 
> The accuracy of it will be all up to how close you can get it to true in the 4 jaw. It's not easy but once you get into under  .001 put a DTI to it and decide how close you want to get. Use water for coolant and be patient and use almost no pressure feeding it. When hole is 2.5 times deeper than wide flip it end for end and repeat.


Now _this_ is the answer that revives the notion of using it as a precision test bar, (unless the attractions of using it as a very solid boring bar wins out)! The lathe (a South Bend 9A) is at present in pieces, with various bits in paint stripper, but as it goes back together, I will be measuring the heck out of it. A carbide fundamental test bar seemed to be a nice start. The resolve may be a bit like new year resolutions - we shall see!

My measurement skills need some improving if I am going to be putting a dial indicator up to a test rod. That, and using a micrometer capable of reading tenths, is still prone to inability to repeat any measurement, and get an answer close enough to inspire confidence.  I cannot follow my Dad's advice that the way to feel confident about a measurement is to never measure anything more than once!


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## graham-xrf (Nov 22, 2019)

whitmore said:


> ...
> If you want to hammer something flat, a flat carbide surface encased in a steel block makes a good anvil.
> And a pointy one in a steel block makes a reliable dent.


 Hammer? I thought tungsten carbide was kind of "brittle".


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## bhigdog (Nov 22, 2019)

Plunge EDM..............Bob


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## macardoso (Nov 22, 2019)

pontiac428 said:


> Tungsten carbide will not give you cancer, but will cause mechanical damage.



Actually, I fear that is not entirely true. Tungsten carbide is a matrix of very very fine tungsten carbide powder bound together by a binder material, usually cobalt. Cobalt dust is rather toxic when inhaled. For this reason, grinding carbide does have some health risks.



			http://www.icctool.com/msds.htm
		


View the "Effects of Overexposure: Inhalation" section


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## pontiac428 (Nov 22, 2019)

You're right about the matrix.  The risk basis for cobalt is respiratory sensitization and pulmonary function change, which are exposure factors that are considered for a chronic occupational exposure scenario.  In a hobby setting, the dose makes the poison.  FWIW, the ACGIH lowered the TLV for cobalt to 20 micrograms per cubic meter, 5x lower than OSHA, but the TLV is weighted for sensitization rather than disease outcome.  I was commenting on pure tungsten/tungsten carbide as equivalent to abrasive dust in toxicity without regard to cobalt or chromium (not chrome VI) in the matrix.  Good to read the SDS, that's more than a lot of professionals who grind daily might do.


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## whitmore (Nov 22, 2019)

graham-xrf said:


> Hammer? I thought tungsten carbide was kind of "brittle".


Well, yes, it is; but, under compression (like, shrinked into a steel pocket) with compressive force
applied... it'll flatten a hammer face before it'll crack.

We were doing high pressure research, the carbides (and a few diamonds) were expendable.   It took
good machining to seat the carbides in steel, and we seated the diamonds on carbides.


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## graham-xrf (Nov 23, 2019)

pontiac428 said:


> Tungsten carbide is second only to diamond in hardness.


I get it that to work up anything out of tungsten carbide, you need basically metal wheels with diamond powder pounded into it, or one of those resin diamond loaded  cup wheels. The "green wheel" that came with my DIY store budget Hilka bench grinder does work on carbide, after a fashion, but that whole thing is counter-intuitive. A steel nail offered at the green wheel just chews it up! Carbide is clearly too hard for the grey wheel. I was told the soft nail pulls chunks out of the green wheel.
I guess it has to be diamonds then - if we go for the modern ways.


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## mikey (Nov 24, 2019)

Graham, would not a test bar made from silver steel make more sense? Save that carbide bar for an appropriate tool, maybe?


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## graham-xrf (Nov 24, 2019)

Mike, absolutely I agree. That makes sense!
A simple eBay search for "test bar MT2 MT3" brings up all kinds , short and long, and even some with MT2 on one end, and MT3 on the other.  You can get them in combination sets even, and for what they do, the price seems reasonable. They all seem to come from India. So far, I see no signs of adverse reputation.

The eBay.com page (in U.S. Dollars) of the eBay.co.uk site finds these:
They were free postage in UK.
Single bar --> LINK#1
Double-ended bar -> LINK#2

It is just that when you have hold of more than a foot of solid, precision ground sintered tungsten carbide, and the upcoming need for a test bar, the mental leap seemed obvious! I thought to start using it for one thing, before putting it to use later for another.

The great properties of the stuff make it a not-so-sensible choice as a test bar if it did not come with centers, although one particular posting from MontanaLon showed how to make them (the centers). The first suggestion was to use it as a very rigid boring bar. I know this site will be full of stuff about other good ways to use carbide.

*Getting the lathe right*
All the good possibilities about using a nice chunk of carbide comes as a side-issue to fixing up my South Bend, a story which is surely for another thread.
I start with the ways, which do not seem very worn. No sign of a "wear ridge". Just some dings where chucks got dropped, etc.
All the stuff about cleanup, replacing wicks, checking bearing shims, clearances, etc. have to at least be checked out.
The tailstock quill is sad! I have not yet decided what to do about it. Given it still "sticks to" a chuck taper, it should also take a test bar.

As soon as the headstock goes on, we start needing a test bar. I agree that this stuff is better done using a purpose-made tool steel version.


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## mikey (Nov 24, 2019)

I am of the opinion that the most accurate "test bar" is *cut* on the lathe, regardless of if you are checking headstock alignment, tailstock alignment or if the lathe is level. The reason for cutting the bar is because the bar will proof itself, especially as you make changes based on the results of your tests. Relying on something that is made or ground by some guy in India and then using it with a whole bunch of stacking tolerances by sticking it in a Morse Taper would not give me confidence in the results. Similarly, a test bar that requires accurate centers requires truly accurate centers. Trying to do that in solid carbide with a grinder or some cobbed up method will just not do. You are far better off researching test bars or start a thread to discuss it with the guys. 

There are better ways to do this.


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## graham-xrf (Nov 24, 2019)

I know it sounds a bit belt-n-braces, but you can bet that I will be exploring how well an "Indian" test bar compares to all varieties of cut-on-the lathe methods. All of them are described in great detail and demonstrated in videos on YouTube. There is the awkward truth that in my hands, the South Bend has not cut anything yet, and needs to go together with at least the beginnings of knowing what it does. 

In all it's forms, getting  centers into a test bar _after_ it has been ground is just hopeless! Entirely the wrong way round. It _can_ be done, but the effort is not worthwhile.

Also, I have already lost faith in the ability of my admittedly budget dial indicator to faithfully return to where it was where I zeroed it. Even the flea market 2nd hand Mercer seems to do rather better!


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## mikey (Nov 24, 2019)

I recommend Compac, Tesa or B&S indicators, in that order.


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