Insert Convert, maybe...

[RussZHC]

Rather interesting late afternoon/early evening.
Got lathe going for first time since last fall...just randomly making swarf to see how much I forgot, anyway, the usual mystery steel good in places, tons of chatter (to point of knocking sounds) in others, so figure hey, why not try inserts?

Well colour me impressed...and I have to conclude it was actually the metal since with the inserts there was still some chatter, way, way less but in certain sections (solid round, about 12" long, started out a bit over an inch in diameter) the chip definitely changed. Getting away from the area previous cut with HSS there was no chatter.

Got 4 variations on the chip by adjusting SFM and feed rate, a tight spiral maybe a 16th in diameter and nearly a foot long, a looser spiral about 3/8ths diameter and 3" long, one in-between those two in terms of diameter but much more tightly wound and around 6" in length (those were all, more or less, like springs) and small balls of a spiral wrapping around itself until a ball maybe a 1/4" in diameter was formed.
The longest pieces did not form more than one or two bird's nests and even near the chuck did not seem to want to wrap around either the work or the chuck jaws.
HSS on the same material certainly cut but definitely chip as opposed to spirals.
The bonus was I could feed at a greater rate as well as pick up the SFM...pretty much along the lines one could expect making comparisons across the various feed/speed charts.

Micro 100 (M100 Dex), generally SCLCR series, CCMT 21.5x (060202), Tungaloy/Toshiba if anyone cares, dry

The other noticeable thing was, and this could be wishful thinking, I could swear it sounded as if the motor and whole machine did not have to work as hard.

The finish was a bit rougher than with HSS but by varying the depth of cut a sort of happy medium could be found where less metal was removed but finish was about what HSS was AND if a shallow cut it was equal to about 120 grit shop roll after cutting with HSS. A close to "mirror" finish was possible but I am assuming it was more or less just rubbing (this was, after all, listed as general/roughing insert). The depth of cut was never as deep as with HSS but it maybe possible, I just did not want to push my luck tonight.

[rohart]

One nice thing about carbide inserts is that when you find an insert that gives you a really nice finish - and I say find, as I don't grind carbide, and I don't know how I'd persuade an insert with chipbreaking to produce a nice finish - once you do, it will stay a nice insert for much much longer than HSS would.

I was boring CI with HSS in a rotating bar today, and I had to sharpen my HSS bit once per pass ! That just doesn't happen, at the same workloads, with carbide.

And yes, I know what you mean. If your machine is up to it, with carbide it's like the engine is revving more freely, as if there's less exhaust throttling.

But have you tried really cranking it up ?

[Black_Moons]

12 diameters long is going to be very chatter prone unless supported by the tail stock and even then will still be prone to chatter in the middle on deeper cuts.

For a true metal removal test, try working on something thats only 3 diameters long, like a 2x6" chunk of steel, with 2" of it into the chuck jaws.

Just keep pushing it until you hear the motor start so slow down

What size is your lathe? We can suggest some DOC/Feed rates to try depending on its size and weight.

[RussZHC]

No, I don't think I was really pushing it, was looking more at "finish" using a roughing insert at various speeds and feeds...I know, I know "roughing" but as it is early days these were the only inserts I know were meant specifically for steel (not 100% certain what the use of the inserts that came with the tooling...have not bothered to look it up on the Micro 100 site yet)

3/4 Hp, 10" Sheldon, older model (well used, rigidity and improving methods are issues)...at most 6" sticking out, it was the largest handy stock I had that fit through the spindle bore...tried both the .0031 and .0062" feed rates at both 254 and 485 rpm, finish very reasonable for me at 254 but for metal removal and finish compromise the .0031 and 485 seemed about the best (sorry, no DOC numbers, I did figure it out last year but did not write it down at home...something to try and remember tomorrow...know its 125 increments but did a few "accuracy" checks last fall and IIRC it was not 100% truthful)

[Jaakko Fagerlund]

If I understood correctly, you have a workpiece diameter of about 1". For carbide, the RPM would be good to be above 1000 (1600 I'd use for plain structural/mystery steel), if the material is steel and the tool is carbide. And even that is a bit low

[michigan doug]

I use carbide inserts 80 or 90% of the time. Much of it is with the cheap crappy common TPG inserts. Both on the lathe, and on the mill. I have pretty good luck with them, and they are cheap and common. I also resharpen them with a cheap ($35) diamond cup wheel adapted to an old motor I had laying around. I can put a new edge on 3 or 4 times before it gets too short for the holder.

Hey, I'm frugal. And Hey, it works.

Please carry on.

doug

[Clevelander]

And some times you don't. I was having a hard time making up my mind as to whether I was going to go with HSS or Inserts with my new lathe as I expect to do a lot of work (in relation to what I'm doing) in 6061 T6. I finally just broke down and bought both a set of insert cutters and a set of professionally cut HSS so I have a base of comparison without the clunker of my lack of experice in tool sharping.

The thing that I found interesting was that in some of the research I did I saw a rating for Carbide inserts that they will only provide roughly 2 hrs of cutting time at 0.030" passes in CRS. That can add up pretty quickly.

This is also one of the reasons that I'm going to be using lubricant for my cutting, to extend tool life as well as improve finish quality and size control.
I have to admit that the heat generated from turning and it's affect on diameter is not something that I had ever considered in the past.

[Black_Moons]

And some times you don't. I was having a hard time making up my mind as to whether I was going to go with HSS or Inserts with my new lathe as I expect to do a lot of work (in relation to what I'm doing) in 6061 T6. I finally just broke down and bought both a set of insert cutters and a set of professionally cut HSS so I have a base of comparison without the clunker of my lack of experice in tool sharping.

The thing that I found interesting was that in some of the research I did I saw a rating for Carbide inserts that they will only provide roughly 2 hrs of cutting time at 0.030" passes in CRS. That can add up pretty quickly.

This is also one of the reasons that I'm going to be using lubricant for my cutting, to extend tool life as well as improve finish quality and size control.
I have to admit that the heat generated from turning and it's affect on diameter is not something that I had ever considered in the past.

Yea, I really don't see it as "Do I use HSS or do I use carbide in my shop" its more of "Do I use carbide or do I use HSS *for this cut*"

HSS can still save you a lot of money, perticularly when you need a tool to get somewhere tight, or need a special groove or feature.

And yea, lube is great. I find myself checking how warm the work is and taking a short break from the job to do something else if it is really warm before I do the finishing passes on a critical diameter.