I have an old smallish English lathe that I use for hobby stuff. (11" throw.. 51/2" cntr height) The lathe regularly handles 3/8" cuts in free turning steel (silver steel). I use ccmt insert tooling, and I have some tpmg tooling as well, all in 3/4" tool holders.
I started a little project this afternoon, turning down a 2 1/4" chunk of 1045 steel. I want to make a tailstock mounted (mt2) die holder out of it. I can only take very light cuts with the tooling that I have, and I guess it will take the best part of a day to make up the die holder, which I was hoping could be reduced, as I don't have that much free time to scape away at a job like this at the moment.
Does anyone have any tips for machining this hard stuff, that they would be willing to share?
If it's annealed, it's not all that hard, and machines similar to C1018----although the tendency to tear is reduced, and the tearing is more shallow. It tends to be somewhat abrasive, so tool life is shortened. It will cut with a bright, shiny finish if surface speed and depth of cut are adequate, otherwise it doesn't cut cleanly. That's normal------so don't go crazy trying to get a shiny finish by other means. That's very hard to do. Be advised that it, very typical of carbon steel, doesn't like shallow cuts-----unlike many other materials. It's nearly impossible to skim off a thou, although it can be done. If you tool is the least bit dull, it's likely to skip, then tear. Finish is lousy, and size goes to hell.
It roughs real well with negative rake carbide, but you must have the machine to run it that way. Deep cuts and coarse feeds, so the chip comes off in little C's or 9's, and blue from heat. From the description of your lathe, I dare say you don't have the machine for it. Could be wrong. HP tells the tale. If you have a couple horse motor, could be it would work, assuming it's rigid enough.
Assuming negative rake carbide is out, if you're good at grinding chip breakers in HSS, you can grind a tool that will take the metal off nicely by grinding a left hand turning tool with a parallel chip breaker, somewhat broad, and deep enough to form the chip either into a coil, or to break it. The chip breaker would need positive rake at the cutting edge, say 8 degrees or so, and must allow for smooth flowing of the chip. It would look like a rounded recess that parallels the cutting edge. A combination of width and depth, along with the proper feed rate will yield a very nice way to remove the metal. It would work best if run with coolant, but you can also use a brush and apply oil to keep the chip lubed. If you haven't ground such things, it could be very trying for you to achieve the necessary configuration. Experience really helps.
If I was in your position and wanted to end up with a nice job, I'd probably use Stressproof.
Isn't "silver steel" British for "tool steel", as in O-1 or something? That' not the same as the "free turning steel" (one type of which is
12L14). If you are comparing mild steel or leaded low carbon steel to
1045, I would certainly expect a difference. I have a 10 inch swing Atlas lathe and it isn't as rgid as I'd like for taking well controlled cuts with carbide tooling. I do use it though. But, since carbide cutters have to have good support underneath the cutting edge, I keep HSS tools around and use them when I need to. Some times I go for months at a time promising myself that I'll never use carbide again------. The one exception is that I have some TPMM 431 (note the "1") holders and they work real well for me. BTW, I do use stressproof (1141 or 1144, I forget) when I need nice shiny cuts in medium carbon tool steel. That stuff is amazing to me.
While Harold's advice never needs reinforcement, the above is excellent advice. HSS can actually take a very aggressive DOC if you're conservative with your speeds and feeds. On interrupted cuts it can blow carbide out of the water when there's no money for special inserts to handle the shock.
Thank you very much for the replies. To clarify, when I mentioned making easy 3/8" cuts, I was referring to
12L14 free machining leaded mild steel. I now realise that there are different terms for the same materials, depending on geographical location. I am in Australia, and looking up on the web, I believe the above description refers to U.S terminology.
Thank you very much Harold. Your reply pretty much answers my question. I have am low on power at the moment, until I can get a VFD to run a
3hp motor that I have. I know a fellow that has the identical machine, and uses a 3hp VFD combination with good results. Here is a link to his pages which have a photo of the machine.
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I will drag out an HSS blank and grind as per your description and give it a go over the weekend, but will have to wait for more HP and use higher feed rate if this doesn't work.
============== Lots of good advise in the other responses.
One thing that you can try if you are grinding your own HSS tools is a high shear tool like a round nose shaper tool. You can not take heavy cuts and these tend too wear quickly so are mainly useful for a finishing tool.
Basically these have a very high [45 degree] side rake and the nose is ground with a large [c. 2-4] inch radius. In setting up the center of the tool nose should be on center, and the chips should be very curly. Relief angles of about 7 degrees along the nose radius is a good starting point.
Take a look at
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also see
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Monday, February 12, 2001 9:49 AM 36006 shaper00.jpg Tuesday, February 13, 2001 10:53 PM 3878 shaper00.txt Monday, February 12, 2001 9:49 AM 37036 shaper01.jpg Monday, February 12, 2001 9:49 AM 35836 shaper02.jpg Monday, February 12, 2001 9:49 AM 41892 shaper03.jpg Monday, February 12, 2001 9:49 AM 37167 shaper04.jpg Monday, February 12, 2001 9:49 AM 36032 shaper05.jpg Monday, February 12, 2001 9:49 AM 27155 shaper06.jpg Monday, February 12, 2001 9:49 AM 32590 shaper07.jpg Monday, February 12, 2001 9:49 AM 47167 shaper08.jpg Monday, February 12, 2001 9:49 AM 47179 shaper09.jpg Monday, February 12, 2001 9:49 AM 42615 shaper10.jpg
Let us know how you make out.
Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.
John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).
That combination is likely to encourage hogging and chatter. Not saying it won't work, but I'd shy away from it, particularly on a light duty machines. Such lathes tend to resist the use of tools with broad contact. A respectable depth of cut, along with a reasonably heavy feed rate, with the right amount of rake will usually work far better. The heavy feed tends to cancel chatter and break the chip, and the modest rake angle, accomplished by grinding the radius I suggested, makes the cut occur at lower pressure, without adversely affecting tool edge life, with the added benefit of reducing hogging. It's sort of a balancing act, and usually has a "sweet spot", where it works best, a combination of diameter of the part, depth of cut, feed rate, and spindle speed. Change any of those and the tool will usually work differently.
Do remember, given enough power and rigidity, even a poor tool will cut with some degree of success. It's important to learn what works, and how to arrive there, so one can make informed decisions when faced with moving stock, or improving surface finish for those critical applications that demand such.
==================== Actually there is very little contact.
The large radius nose contacts the round part and until you go in a few thousandths depth of cut there is essentially *point* contact. This is one reason I suggested a shallow depth of cut.
If you look at the pictures, you will see that the chips are both narrow indicating a narrow contact between the nose radius and a flat, and very curly indicating high shear. The chips will be even narrower for a cylindrical workpiece.
No good for production [shallow depth of cut and tends to wear quickly], but will generate a very good surface finish on most materials, which was the question.
Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.
John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).
That defeats the OP's purpose. He said: "can only take very light cuts with the tooling that I have, and I guess it will take the best part of a day to make up the die holder, "
By grinding the tool with a small tip radius and chip breaker as I suggested, depth of cut (and likely feed rate) can be increased considerably. I agree with your configuration for a fine finish, but that's not his primary purpose in this instance.
We're both headed in the same direction, for sure. Both methods will yield success, it's just a matter of degree. I'm known to use all combinations of grinds----and use a lot of HSS for machining. After all, when I broke into the trade, carbide left a great deal to be desired, and often performed poorly. HSS and Stellite tended to perform far better, depending on circumstances at hand.
As mentioned above, not exactly. He was talking about the long time it would take to remove material. I'm real keen on roughing parts, having worked production on manual machines for years. You get a feel for what works, and what doesn't.
1045 tends to be hard on tool life, mostly due to abrasion, so the shorter the interval of contact, tool to material, the better. You need to get the material off as quickly as possible to avoid endless tool sharpening. Shallow cuts defeat the purpose and tend to yield a hopeless, "I'll never see the end of this" feeling in the operator. Learning to properly rough all materials is key to success in machining. Needless to say, one's machine plays a huge role in the outcome. Small, light duty machines have little hope aside from scratching away. Proper tool configuration gets you as close as is possible.
I ground up a 3/8" HSS blank this morning and gave Harolds' suggestions a try. I didn't get the chip breaker correct with my first attempt and was getting long coils. I ground the chip breaker a touch deeper on my second attempt, and got quite good results. 1/8" cuts at low speed and the piece finished quite well at higher speed. The chips were not all "c's" depending on rate of feed. some were coming off in longer spirals, but I got the job done without any grinding and shaking of the machine. I intend to experiment a bit more more with the tool to get closer to perfection.
I just need to finish off the taper on my friends machine, as he has a nice grinder setup.
Thank you very much everyone.... I have learn't something valuable out of this post. :-)
Congratulations, Steve. Your results are exactly as they should be. Keep the general geometry in mind, for it will serve you very well for most materials. It's especially effective machining aluminum, where it provides superior chip control. Avoid such a configuration for free machining brass, which will tend to hog.
You have made a major step forward in your ability by absorbing this very useful information, or at least you should have. It was true in my case. We stand on the shoulders of those that went before us.
First off, Season's Greetings to All, and Families, here on RCM.
We are headed out from here before supper tomorrow, to visit with our son over Xmas. We fly into Burbank on Tuesday afternoon. No real itinerary planned, except hoping to drive up to Taft for a quick visit at Gunner's home place.
I realize it is a busy time for everyone, and short notice to boot, but anyone in the SoCal area open to a cup of coffee in the days from Dec 20 to 28? Drop me a phone contact number to
snipped-for-privacy@ciaccess.com AND a copy to snipped-for-privacy@yahoo.com
No guarantees, but I'll try. And not important, but it's always nice to put a face to the writers here.
And dont forget to contact Leigh at MarMachine down in Costa Mesa. His shop is worth a visit..and Id be happy as a bug to take you over to Reliable Tool in Irwindale later this week.
And Ill have the coffee on when you come up.
Bring a pickup and a cat carrier....
Gunner
Political Correctness
A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
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