1018? 4130?

[bdarin]

I have some 1018 steel that's supposed to be very user friendly, but I can't turn it that it isn't rough and bumpy. Is it possible to get a glass smooth surface on 1018 or 4130? Tried some 12L14 once, and that was very nice. Using carbide (C6) and HSS tools. Any help appreciated.

[C. Tate]

The numbers 1018, 4140, 12L14, etc represent the chemical composition of the materials you are using. The "L" means leaded. Leaded stock comes in several grades 12L14, and 12L15 are probably the most common. The lead makes the material more machinable and friendly. You can get very good finishes on all of these steels if you get the speed and feed combos right. Many people run carbide to slow resulting in poor finish. You should try running 1018 in the 500-600 sfm range and feed .007-.010 ipr. 4140 should be 300-500 sfm with the same feed. HSS should be 70-150 sfm for both and feed approx .007-.010. The surface finish is directly related to the nose radius of the tool and the ipr feed rate, the larger the radius the faster you can feed and maintain a given finish; likewise, the smaller the radius the slower the feed. The above suggestions are for a tool with a nose radius of .015-.030. I am assuming your tool is properly ground considering you have had good results with 12L14 but is worth looking at you cutting edge and clearance angles.

These are suggestions, nothing is for sure and it is nescessary too adjust to your situation and machine. Read your handbook and keep on trying, nothing can replace expirenece.

sfm= surface feet per minute
ipr= inches per revolution
rpm = sfm/dia * 3.82

Good Luck

[halfnut]

I second C. Tate, but also you might try adding in some cutting oil to the situation.

A ragged finish in coldroll becomes nice sometimes with a dab of oil. Same with 4130. Depends on the condition of the 4130, plain annealed is a bit gummy like cold roll.

What oil, this is where debates start, I say whatever you have. Maybe the best is Bacon Greese, or so says Forrest Addy, smells good also he says. I have never used lard oil or bacon drippings, although I have heard the old timers refering to it. I use sulferized cutting oil, Black Oil, new stuff isn't as black, doesn't have as much sulfer. In a pinch motor oil, hydralic oil, tranny fluid, etc. will work better than none.

Watch how your chips come off, usually poor finish is caused by chip welding on tip of tool, thence the oil.

Good luck

[SGW]

The first thing to do is make sure you have a SHARP tool. For a home shop, HSS is probably better than carbide for most situations. Typical home shop equipment isn't rigid enough to get the full benefits of carbide. Grind the proper angles on a HSS toolbit, finish it off on an oilstone, look at the edge under a 10X glass, and be depressed at how bad it looks. The better you can get the cutting edge, the more likely you are to get a good finish.

Halfnut is right about the cutting oil. You can get "thread cutting oil" at plumbing supply places that will work pretty well.

Some steels just cut more cleanly than others. 1018 isn't all that great, as far as getting a good finish goes, although in my experience it's not as bad as drill rod. About the worst I've encountered is that cold-rolled rod from the hardware store.

I've had excellent results as far as finish goes with Stressproof and Fatigueproof steel. One has to go somewhat more slowly, but the resulting finish I get is really good.

The leaded steels are amazing.

And C.Tate is right -- keep experimenting. Nothing replaces experience.

[Thrud]

The best book I have found on using carbide tooling (as well as a history of steel tooling) is the Sandvik Coromant book titled: Modern Metal Cutting (ISBN 91-972299-0-3)

This book has excellent sections on turning, boring, threading, and milling. It goes into the coolant/no coolant factors and their effect on tooling and finish.

I use positive geometry inserts with a small nose radius (when possible) and get superb results dry machining. The only "bad" result I get with the positive inserts is when facing shafts - the last 1/16" in the center is "not as nice as the rest". (lathe maxes out at 2800rpm)

I found that the brazed carbide tools were useless for the fine work. I have some Kennametal Negative rake toolholders to cut really nasty stuff.

[halfnut]

I tried lard oil, works just fine. Since my folks don't butcher anymore I can't raid my mothers lard stand.

Saved grease from a pork roast, smelled just like the pork roast when using.

I have an idea, save bacon grease for morning, sausage for mid day, and roast for evening.

I'm getting a bit silly I know, the bacon grease would probably be best, it will have just a trace of salt and nitrates in it that would keep it from becoming rancid.

The old timers would combine lard oil with other ingredients for different jobs. I remember lard oil and kerosene for aluminum.

Local machine shop instructor mixes it with tapmagic, says it works the best.