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View Full Version : Have a go with Tungsten Carbide (if you're not already)



Magic9r
08-01-2007, 08:41 AM
If you're considering giving Tungsten Carbide tools a go I suggest that this is a very good idea.

My reasoning behind this is that nearly everything I've done with carbide, both indexable and solid tools has been covered on the Internet as difficult, impossible or inadvisable for the HSM, there's a lot of complete rubbish coming from aparently experienced machinists

http://s135.photobucket.com/albums/q158/magicniner/?action=view&current=05fd3c54.flv

is a link to a quick movie I shot as I was taking a 30 thou cut from the case hardened surface of a J&S Clamp Knurling Tool which I am repairing & modifying to fit my Myford Super 7 lathe.

So it's an interrupted cut (3 insert face mill) on a narrow workpiece that has a hardened surface and the cut is being made with a gear head benchtop mill with a 0.12HP 3phase motor running from a single phase fed VFD.

I completed the job & returned the tool to the drawer with three intact, sharp inserts,

I'm getting good results in the mill & on the lathe with 316 SS, Aluminium, Titanium, Tool Steel, Mild Steel and Cast Iron.
For anyone who has not tried one I recommend the ripper style endmills, I've been using my 10 mm ripper for all of the above metals and it's still going strong.

Go on, have a go, there's some bargains in carbide tooling now it's so common in industry,
Regards,
Nick

Evan
08-01-2007, 09:17 AM
I use carbide tooling on my SB9 from time to time with difficult materials even though my SB isn't considered as having the power or speed to make good use of it. Recently I was turning a piece of hardened shafting to use as a bearing shaft for the power unit on my picket twister. HSS wouldn't cut it so I switched to carbide. I don't buy carbide tooling or inserts but use various grades of solid carbide that I grind to shape on a slow speed 10" diamond wheel.

In this case I turned the shaft dry at high rpm to the point that the material was sparking. The resulting finish was mirror smooth. I use zero or slightly negative rake.

Carbide has a place in the home shop but in most cases HSS tooling will do the job at at considerably less expense, especially if you must buy preforms. If given the choice between the two when either will do then HSS tools are my choice. It's much cheaper, easier to shape and sharpen and takes a finer edge.

J Tiers
08-01-2007, 09:23 AM
The people who say "you can't use it" are assuming you want to use it, or any other cutting tool to the maximum possible economic limit of speed, feed etc.

That's like saying you cannot whittle with a steak knife, you HAVE to use a jack-knife.

In either case, the "other" tool may make some things easy, others more difficult. It may be best suited to certain things.

But, anyone who wants to can go ahead and turn their 4140 pre-hardened with their "perfectly suited to that low power lathe" carbon steel tools.......

Thanks, I'll use carbide for that, even HSS dulls too fast.

Evan
08-01-2007, 10:05 AM
But, anyone who wants to can go ahead and turn their 4140 pre-hardened with their "perfectly suited to that low power lathe" carbon steel tools.......

Even carbon steel tools have a place. Nothing takes as sharp an edge as plain old carbon steel tooling. I use it sometimes on aluminum as it gives an excellent finish without much danger of overheating and drawing the temper.

aboard_epsilon
08-01-2007, 10:09 AM
http://s135.photobucket.com/albums/q...t=05fd3c54.flv

I wouldn't be doing it like that ..I would have the cutter so that it only just comes over the other side of the work ..

That way you're not knocking the cutting edges twice......AND KNOCKING THE HELL OUT OF THE BEARINGS ON YOUR MILL.. I would be sending the cutter in and arc across the piece .

that's how I've found works best for me anyway ....

In-fact i would not even use a face mill until the work was at least 3/4 of the diameter of it .

you want the cutting front to be as long as possible

yep carbide face mills are OK ...

but found with the carbide endmills ...

you make one little mistake and chip the tooth ...the chip revolves around and smashes all the rest of the teeth, making the cutter scrap.

just my own preferences .....anyone want to say I'm wrong are quite welcome to tell me why and point me in the right direction.


All the best.mark

J Tiers
08-01-2007, 11:07 AM
Even carbon steel tools have a place. Nothing takes as sharp an edge as plain old carbon steel tooling. I use it sometimes on aluminum as it gives an excellent finish without much danger of overheating and drawing the temper.

yurp........ Good so long as temps are low

But not so good for straw-blue chips on 4140.........

Mark Hockett
08-01-2007, 11:22 AM
yep carbide face mills are OK ...

but found with the carbide endmills ...

you make one little mistake and chip the tooth ...the chip revolves around and smashes all the rest of the teeth, making the cutter scrap.

just my own preferences .....anyone want to say I'm wrong are quite welcome to tell me why and point me in the right direction.


All the best.mark

Mark,
That is absolutely correct about carbide end mills. Carbide EM's will work on a manual mill but will not last very long due to chipping. Carbide EM's don't work as well when cutting in the conventional direction, they work best when climb cutting where the chips are pushed behind the cut and not in front of it. Heavy climb cuts can be difficult on a manual mill due to the backlash.

Idexable carbide tooling is a different animal. It has a much more robust cutting edge and can handle a fair amount of abuse. I have many indexable carbide cutting tools I use on my manual mill.

Magic9r
08-01-2007, 11:36 AM
With carbide endmills if you climb-mill there's less tendency for chips to carry around to the cutting edge again, and if you clear the chips with air, vacuum, coolant or even a paint brush it just doesn't happen at all.

I do find that a tip with a larger radius is better for aluminium.

What are you guys paying for inserts? I'm using predominantly triangular, about 10mm on a side and pay under $2 a piece even taking into account the prevailing exchange rate.

I tried the cut with more of a sweep but since cutter 1 leaves the work before cutter 2 hits it it made no difference to tone or loading on the mill, I'd have done the job with an endmill but I was unsure what the depth & hardness of the surface treatment was so I went for this in case it ate a few inserts, better that than a nice endmill. Perhaps I could apply a small friction load to the spindle to keep the geartrain loaded but I don't make a habit of cuts like this one, Honest:)

I still use some HSS for certain operations like cutting multi-vee pulleys with a hand ground, single point tool, but for straight cuts in the time it would take to sharpen a HSS bit I've rotated the insert and completed the operation. I don't mind sharpening tool tips but it's not why I'm in my workshop.

It may be that my Super 7 is a bit wierd in that the plane nose bearing allows high speed running and this is why I can get the lathe up there where carbide really does it's thing (the 1HP 3PH motor with VFD allows speeds from zero to double the motor's rated rpm) allowing me to go up to around 4000 rpm provided the chuck is rated for that (my 4-jaw isn't).
Regards,
Nick

BigBoy1
08-02-2007, 07:59 AM
Every tool has its place and knowing when to use them and not to use them is one of the things experience will provide. I have both HSS and Carbide tools and each has a job it can do. Sometimes they overlap and both can do the job and other times, only one type will work. The big thing is knowing the difference and when to use one over the other.

Bill

pcarpenter
08-02-2007, 12:48 PM
I am curious about the notion of a plain (plane?) nose bearing allowing high-speed running. Typically, plain bearings can limit safe high speed running, although 4000 RPM is not that high as spindle speeds go. It's quite high for a lathe spindle, but milling spindles running on very low tolerance ball or roller races are turning ten times that in some special machines. Is the implication that if you had a ball or roller bearing headstock you could not turn that fast?

I use both and prefer carbide for harder stuff as others have said. While carbide does offer the ability to do high-speed machining, that is rarely important to folks using machines in the Super 7 class (home shop types). Usually we are looking for better surface finish and that often comes from the use of HSS. The other big advantage to HSS is that its easy to tweak cutter geometry to improve finish....something that is more limited with insert cutters that require the purchase of a package of fairly standard inserts.

People often labor over grinding a HSS tool. While care in desiging the angles and grinding them is a good idea, resharpening does not need to require regrinding. Often a few strokes of a good stone will bring an edge back up to sharpness. "Sharp" carbide inserts for insert holders are often pretty rare and that can make for more load on a machine as well as for the need for deeper depths of cut. As a home shop type, I often sneak up on a dimension and my last cut may be a few thousandths...which is often less than the ideal depth or chip load for a carbide insert with its chip breaker back a good ways from its leading edge (by design).

Paul

Evan
08-02-2007, 03:42 PM
While bearings without rolling elements may be plain they are plane bearings. It means "planar bearing" which doesn't mean only a flat plane but also any bearing made up of two congruent surfaces.

If you have any doubt just click this link:

http://www.google.ca/search?hl=en&safe=off&q=plane+bearings&btnG=Search&meta=

pcarpenter
08-02-2007, 03:48 PM
Ya learn something every day. I would have assumed that the term "plane bearing" would have been used for something whose bearing surface existed in a single plane.....like a way surface for example.

thanks!

paul

lane
08-02-2007, 07:37 PM
A plain bearing Don`t got no balls. Thats all.

Evan
08-02-2007, 08:35 PM
Planar is generally taken to mean a flat plane but the essential definition is that something which is planar has extent in two dimensions but not a third. This describes the surface of a cylinder as well as the surface of a sphere. The study of this is a branch of mathematics known as topology. If you really want to know more here is a good web site with animations describing planar machines.

http://www.math.toronto.edu/~drorbn/People/Eldar/thesis/index.html

BadDog
08-02-2007, 10:08 PM
As for the original topic, I've got a whole selection of inserted and brazed tooling for the lathe. I got a bag of 50 new TGP 322(?) us made inserts for $20(?) along with (3) 1" shank Kennametal holder ($5 each) in left, right, and facing configs to hold them. I milled a 1/2" x 1/2" notch out of the lower back of each so that they fit my Royal turret tool post. These were shimmed to center, and I use it like a quick change by just sliding the QC out of the t-slot, and sliding the Royal in with everything already on center. Index to the one I need, and I'm ready to go. Only problem is I scrapped one (and a 1/2 solid carbide rougher) of the holders when cutting it down due to taking too big a cut (MAN that steel is TOUGH!) and sucking it out of the vice. And unfortunately it was probably the single most useful cutter as it would allow orientation parallel to the work piece axis and turning toward the headstock up to a shoulder without getting in the way. <sigh> Still, I find that lately I prefer HSS for lathe work unless the material is abrasive or hard/tough.

For the mill I have both solid and inserted cutters along with the typical fly cutters, and planning to add a small inserted face/shell mill or two when I stumble onto a good deal. In general I like carbide on the mill more than on the lathe. That's in part because I have a local inexpensive source for good quality (not import) solid carbide end mills. These hold up very (or so it seems to me) in my use, which includes fairly frequent cuts through mill scale and scrap metal (black pipe or whatever) that tend to eat HSS when I use them. So I reserve HSS for aluminum and fine finish cuts.

NickH
08-03-2007, 10:01 AM
Lane,
you'd have to argue with Myford about that one, their centerless grinders used a plane bearing and wer renowned for quality, precision & bearing life, perhaps you are not taking into account that this is a hydrodynamic plane bearing?
I get excellent results and the lathe can hapily take cuts which use all the power available, it would potentially not be ideal for heavy side loads at low speed but the only op I do regularly that requires this is knurling & I just finished modifying my J&S clamp knurling tool,
Regards,
Nick

loose nut
08-04-2007, 10:32 AM
Evan, wouldn't a cylindrical planar surface act the same as a flat surface at any given point, if the cylinder gets larger in dia. the more it becomes like a flat surface.

"The shortest distance between two points is a circle of infinite diameter."

rbregn
08-04-2007, 10:51 AM
Carbide is always my first choice. I have HSS but prefer to use inserts. Just a carry over from one of my old jobs. I have all my tooling set up to use the same insert for 99% of my machining.TPU32X, my milling inserts are TPG32X, Because of consistency in size. My end mills are colbalt. I am used to running things at high speeds and my equipment can use it. The last time I bought inserts they were 99 cents apiece for the unground ones and 1.29 for the ground ones. They where coated also, which seem to last longer for me.I use TPG320 coated for the majority of my threading also and absolutely love them for threading. Yes you can run them slow if you want. I have used them for over 15 years. The secret to being cost effective is using the right tooling so you can use just one style of insert. Not those high dollar inserts either! TPG is perfect for the home machinist in my opinion.