Eureka! Carbide tooling for my lathe

[lathesmith]

I have been doing a lot of research recently on "updating" my little shop with some carbide tooling. I have always been a High Speed Steel guy, since that is what I learned with. Since browsing several forums, I have come to the shocking realization that grinding HSS is becoming a lost art, it seems. So, I had to find out about using carbide to cut metal. I mean sure, in the woodshop these days, of course you use carbide; the advantages are overwhelming with very little downside. Metal cutting is a different story, though. For the beginner, it can be quite intimidating; fast speeds, TiN coated or not, C6, C5, C2; ccmt, tcmt, 3252, 2151; positive rake or negative; and on and on and on...you get the idea. The mind boggles! Anyway, without getting too carried away with all the teeny weeny details and minutae , I finally decided to pay the local Grizzly a visit and dip my toe in the water with an inexpensive 1/2" set that uses TCMT 3251 inserts. These tools came with some uncoated C5 inserts, and after centering one of these I was ready to do some cutting. To start with, I tackled a job that had given me fits with my HSS cutters; I was making some backing plates and things for my lathe, and needed to face some 4 3/4 inch steel. I am not sure what this stuff is, but it seemed to have hard spots that would dull my HSS cutters, and was very slow to work. I chucked up a chunk of this, ran it at a faster than normal RPM--I've read that carbide "likes" faster RPM, and I have confirmed this to my satisfaction--and started cutting. Imagine my delight when this piece cut very easily with the carbide, and was as smooth as a spanked baby's bottom! Eureka! I was in machine shop heaven! This stuff is great, I am a convert for sure now.
The key for the small shop seems to be to stick with Positive rake tooling; that negative rake stuff needs lots of RPM, horsepower, and rigidity, all of which are in short supply in the average small home shop. You will find lots of "less filling, tastes great" arguements out there, but the bottom line is this stuff WORKS if you find the right combination. I have not dumped my HSS entirely though; sometimes, you need a special cutter shape, and other things, and you still need to know how grind it. If you have been thinking of giving carbide tooling a try, but have been a little intimidated like I was, I encourage you to go ahead and give it a shot, it's worth the effort. I am sure glad I did!
lathesmith

[Jon K]

lathesmith,

Welcome to the modern age of tooling technology........wait til you find need for ceramic and diamond inserts............$$$$$$

Jon

[Morgan Astorbilt]

Yes, but the best finish cuts are still made with a good, sharp, M2 or cobalt tool.
Morgan

[Buckshot]

...............I have a set of those from J.B. Roush taking the TPMM-TT inserts. Most of my boring bars are carbide insert types, and I have a couple holders for standup and laydown threading inserts. However as Morgan said, I have 4 bits for finishing. They are NOT used for general turning! :-). These are the 'killer' bits that only come out at the bitter end, or if less then a thousandth needs to come off. Lots of rake and sharp as a razor.

I do agree that there are some guys who think if you still use HSS you must be working in a lineshaft shop. One the other hand look what was done with simple forged high carbon tools and HSS was only a dream. Of course they weren't spinning any of the exotic alloys we have now, but still.................

...............Buckshot

[dubber123]

My brother and I just set up an old Excello vertical mill in his shop, and are just getting into the tooling aspect of it. I have scrounged quite a few carbides, but ordered some plain HSS bits which we tried last night. The HSS bits seem to cut well to me, and are MUCH less expensive for "hobby" type guys like us.

[Bret4207]

I found my little Atlas doesn't much care for carbide. Just not rigid enough. Too bad too. Some of the rusty garbage I turn would cut better with carbide, I'm sure.

[lathesmith]

Jon, always something "better" to spend the money on, eh? I know the feeling....

Morgan, point well-taken. Like any general rule, though, there are exceptions, epecially with this positive rake stuff. Another thing, with special shapes and certain "softer" steels HSS still is easier to use and gives a very nice finish, in my opinion.

Buckshot, I haven't yet tried carbide for threading, I am still quite happy with my HSS threader bit for this. It is so cheap and effective for the stuff I work on, and some of those threader-only carbide set-ups can be quite pricey. If it ain't broke... I am now looking at a decent boring bar setup, and reviewed those threads you guys started on carbide boring bars with carbide inserts. That looks great! I need something small enough to work on sizer dies; this eliminates the triangular inserts. Drat! Oh well, I think I will concentrate on the CCMT stuff, you only get two edges instead of three, but that is a compromise that must be made in the interest of getting the smaller sizes.

Dubber, mill tooling is a whole different world, at least to me. So far, I have been well-served with HSS two- and four- flute cutters, with a little TiN coating thrown in. I only have a very small mill, but I have been looking at some of those smaller carbide-insert facers and inserted boring-head bars. Stay tuned....

Bret, that old Atlas is probably a better machine than I have. Unless it has tons of wear, I'll bet with the right positive-rake carbide tooling it would cut drill rod and other tough stuff like butter.

As is the general consensus here, I ain't ready to turn my HSS out to pasture. Not now, probably not ever. But it is nice to have options!

lathesmith

[JIMinPHX]

Carbide certainly has it’s advantages, but it is not the answer to every machining issue. As you’ve already figured out, HSS still has it’s place in the modern world.

Those little hole-in-the-center indexable bits that you have are good for repeatability on lite duty cuts, but they lack the strength needed for heavier cuts. The top clamp designs & CNMG inserts are better for that. Brazed-on carbide bits are a good cheap roughing tool if the high price of CNMG bars is out of your reach.

The big problem with carbide in general is that it chips easily. That’s the thing that you really need to watch out for. As you already figured out, the negative geometry stuff is for the big heavy machines. If you’re not pulling a cut 1/4" deep in steel, then negative is usually not the way to go. Some materials like aluminum & stainless like very positive geometry. Coated stuff is good for general-purpose use, but I find that uncoated carbide seems to work better in stainless for some reason.

[JIMinPHX]

I found my little Atlas doesn't much care for carbide. Just not rigid enough. Too bad too. Some of the rusty garbage I turn would cut better with carbide, I'm sure.

What tool tip radius were you trying?