[mjarus]

I have a 7x12 and am messing around with some 3/4" 1018 (to balance my adapter plate... see other post). Anywho, the turning cuts seem rather rough even when taking VERY light cuts. There is no noticeible chatter and it goes smothly under the power feed, but the cuts are coming out pretty darn rough.

I have tried 2 different M2 HSS bits that I ground, one very rounded and one not so much (only very slightly rounded). I have also tried the cheapo carbide bit that came with the lathe, but I think it was dull.

So is 1018 hard to get a good finish on, or am I doing something wrong? Is there another type of bit to try?

My facing cuts come out very nicely. I did notice that at first they were slightly convex, but I turned my QTCP in towards the piece very slightly (7 degrees or so) and the convex problem seemed to clear up. Is that normal too, or should I keep everything at 90 degrees? The angle seems to neither hinder or help when turning.

Thanks for any help,

mjarus.

[lakeside]

ceck your tool center hight or slow feed down also see if back of tool is draging on peice

[Trapper14]

gibs tight? turning steel can be tough on these little lathes and if everything isn't tight you will see it in your finish.

[mjarus]

Thanks for the fast replies.

I checked to see if the back was dragging and it is clear.

I will re-tighten the gibs and try again. I wish you could lock the gibs down like on the mini-mill. I was just thinking about that the other day...

mjarus.

[pastera]

If this is hardware store 1018 - then you'll learn to deal with the finish, the stuff is garbage. Let me guess, it looks like it is tearing the metal away?

I grind my tools with a lot of rake (think Aluminum) and use dark threading fluid as lubricant to deal with this stuff.

Aaron

[mjarus]

Its not hardware store stuff. I got it from the local metal dealer. I am getting some nice looking bands coming off of it, but the surface looks like a very fine pitched screw when examining closely. 6061 never has done this. I will try some cutting oil and see if that helps.

Thanks for all your help Aaron... I am actually machining the inserts for the adapter plate like you mentioned in my other post! They obviously don't have to look pretty, but I would like to figure this out for future reference!

mjarus.

[Ken_Shea]

If the finish is looking like a fine thread then your feed is to fast and/or your cutting tool is too pointed, a small radius on the tip will do wonders for finish.

The next time you need steel and your part does not require hardness or great strength try some 12L-14, wonderful stuff. for machining.

Ken

[widgitmaster]

Try increasing the RPM and feedrates, put a slight radius on the point of the tool, and use a high grade of carbide, C5 is good! Use brown thread cutting oil, the sulpher it the oil will stick to the chips and keep them from sticking to the cutting edge. 1018 does have a tendency to smear instead of cutting, so increasing the RPM raises the temperature of the cutting surface, and helps the oil do its chemical bonding to the chips! The feedrate needs to be proportionate to the radius on the tool nose, the bigger the radius, the slower the feedrate necessary to eliminate the high to high points left by the cutter, and you get a smooth or shinny finish!

Eric

[Runner4404spd]

i had a similar problem on my 9x20. what i ended up finding out was that the toolpost was rocking back and forth from the force of the material. i'm not familiar with the 7x10s and if they use a 4 bolt or 2 bolt tool post hold down but once i built my 4 bolt hold down my problem just about went away.

[Mcgyver]

The only time I ever see a good finish on 1018 is in industry where they attack it with carbide on a $100k machine AT the feeds & speeds carbide is meant for. On a light machine, you can get everything perfect, mirror finish on the tool edge, flood coolant, the right speed and feed, everything at centre etc, and you'll still get a crap finish = 1018 is miserable to work with. Get some free cutting steel like a 12L14, leaded free machining steel

PS, I should add that unless you quantify it, a 'good finish' is subjective. I'm talking in a general sense of no tear out, and being left with a smooth shiny surface.

on the facing cut, you should be getting a (very) slight concave, shape - what is the QTCP and what's it got to do with with it? the facing cut is down by the cross feed with should be almost but not exactly spot on 90 degrees to the lathe axis. Other than changing the angle the tool is presented to the work at, changing the compound or tool post should be irrelevant to whether the face is concave/convex/flat - more info?

[HuFlungDung]

I dunno, Mcgyver, my cnc lathe only cost $65k and it does a good job on C1018

I'll echo what the guys are saying about C1018 being difficult to get a good finish on. I long ago swore off of it, and use C1045 instead for routine usage. I reserve the C1018 for production jobs on a fast machine, or for low strength applications that may require welding where preheat is not available.

Stressproof is also nice to machine, not noticeably tougher on tools, but you gotta watch those chips that fly everywhere. It may not finish up real shiny, either, but at least built up edge does not present such a problem. Always use cutting oil for finish cuts when doing manual turning.

[Geof]

I dunno, Mcgyver, my cnc lathe only cost $65k and it does a good job on C1018

$CDN38,500 but I will admit it was second hand.
I will reiterate the advice on going to leaded steel; it is almost identical in strength and more than adequate for most applications.

[HuFlungDung]

$CDN38,500 but I will admit it was second hand.
I will reiterate the advice on going to leaded steel; it is almost identical in strength and more than adequate for most applications.

OMG, how low $$ can it be done for?

[mjarus]

I really appreciate all the info. Looks like just going back to 6061 is the solution and using the 12L14 when needed. The only reason that I am even messing with 1018 now is because I needed the weight of the material, I guess any form of steel would have worked...

the facing cut is down by the cross feed with should be almost but not exactly spot on 90 degrees

This is what (I think) I have managed. When I had the post and cross slide at exactly 90 degrees the shank of the bit would rub into the workpiece on the facing cut as I advanced the cross-slide. I wonder if it was actually at 90 degrees? Oh well, it works now.

on the facing cut, you should be getting a (very) slight concave, shape

I guess my question there was really... what would cause a more concave shape. I think that, after reflection, it was that I had not locked down the carriage and it was being pushed back from the work piece by the cutting force. Is there anything else that could cause it?

Anyway, thanks for all the GREAT replies, they really help.

mjarus.

[mjarus]

I finally got through my issues. I can sum up 1018 in 2 words: it sucks. Well, for machining on a small asian mill anyways.

Thanks for all of the replies. I have learned about, cutting off, grinding bits, tool height, speed and feed, all just having to mess with this 1018. Call it a right of passage I guess.

Now if you excuse me, I will go back to my aluminum.

mjarus.

[cncuser1]

I use 10L18 instead of 1018.
The L stands for Lead. It makes the alloy much more machinable, a charm in fact.

If you are really considering giving up on steel, then try the 10L18!

[mjarus]

The other guys were saying 12L14 was good too. If only I had knew about these alloys before I bought the regular stuff... Oh well, like I said working past the issues forced me to learn alot, and I am sure that I have a lot more to go.

One noob question about these alloys though... is the lead content high enough to have to worry about? I mean, I don't plan on eating the stuff, but will day to day contact with it be something to worry about? Whenever I solder I wash my hands about 10 times before I eat anything... call me paranoid...

mjarus.

[Geof]

I have worked with leaded steel for over forty years and have never come across any information that the lead poses any hazard. The lead content is very small and it is tied up in the steel and cannot easily leach out.

Refraining from eating it is probably a good idea.

[Trapper14]

Yes in college they went over the micro structure in steel and such, and the lead percentage is very small but it is spread out sorta of in little pockets, very very small pockets thruout the entire piece of material (we are talking a little bigger than molecules here) and when the cutter (mill or lathe) his the pocket it lubricates the tool. All this happens extremely fast of course, but leaded steel is much better for our type of machining than any other type of steel IMO

The carbon content plays a pretty big role in the machinablilty of the steel

these are AISI-SAE codes
for example 1018

code 10 means Plain carbon steel (no alloys in it) the first two numbers btw are the primary elements in the steel
the last two numbers are the carbon and low alloy designations



now if you has say 11L17 that would be resulphurized with lead, and as I recall .17% carbon content. Its not 1.7

moral of the story is from 1016-1030 your surface finish isn't going to be that wonderful and are that good for threading as I recall, or at least looks like crap. At least on our lathes. And steels in that range have a high enough carbon content to be hardened.

Stainless is a whole different ballgame


most of my info is correct as I recall, its been a few years since college call me out on something if you think its wrong guys.

Sean

[dertsap]

I finally got through my issues. I can sum up 1018 in 2 words: it sucks. Well, for machining on a small asian mill anyways.


mjarus.

it just sucks no matter what kind if machine you put it on , even if you do accomplish a decent finish it will be dull and corroding in no time anyhow