Thread: Steels is/ain't steels

Hi gngh,
Unfortunately there is no easy way to put this....i wouldn't consider either of those to be good finishes. They are about the best i can easy get from black bar though. I'll attach a few pics of what i consider to be good finishes, one done on my new lathe and one on the mars. The other is a pic of some black bar machined at the same feed rates, surface speed and DOC as the bright bar.

Cheers,
Ew

Are you using carbide ueee?

Well you know I've read my post over and over and I just can't see where I said either was a good finish. But I did say I wasn't making medical instruments or sending rockets to the moon, so I guess that sort of says 'not a good finish', what do you think? What I was aiming at was cutting both the same with the same feed rate, same depth of cut, etc, to show both the black and bright I have, cut the same. I don't profess to be a good turner, I'm just a rough old backyarder doing the best he can. Sorry if my lack of expertise has offended you.

I am simply following on from the other post which was about good finishes, which i thought was were this post came from, that you could get a good finish on either black bar or bright bar. Seems i got it wrong.
I too can chuck a plain HSS tool in the lathe and get a finish like that on either type of steel. We were talking about a good finish in the other thread.
I'm not sure where you get the idea that i am offended from....

Yes Andre, all 3 of those cuts are with carbide. The difference in finish is remarkable if you ask me. With the right HSS tool i can get a similar finish on the bright bar but it takes far more time than the carbide.

Ew

Well I suppose if this was a continuation of the other thread, it would be in the other thread, what do you think? As for good finishes, it's all in the eye of the beholder; and, the job it's intended for. Isn't comparing cuts with HSS and inserts a bit like comparing apples with oranges. Seems to me I've heard that somewhere else recently, it'll come to me. Offended, you gotta be kidding, have you ever heard of 'tongue in cheek'?

Originally Posted by gngh

Offended, you gotta be kidding, have you ever heard of 'tongue in cheek'?

Thats what we have smileys for.....bit hard to pick up the tone of what you are saying in text.....

I'm not one for arguing, clearly i totally misunderstood the whole meaning of this thread.

I am comparing apples with apples, read again!

Ew

hi gngh. have you tried getting under the scale with your first cut if the scale is
giving you trouble.
I think the your cutting tool was to sharp and may need a little radius .
aaron

Tungsten (and having a machine rigid and fast enough to use it effectively) makes a massive difference. I have managed to get HSS to the shape required to get as nice a finish, but speed has often helped the finish at the cost of tool life. Im bo no means an expert though, ive managed to have some great luck with metals that should be difficult and ive had days where I cant take a trick. The best surface finnish ive achieved was on S7 tool steel, which left a finish like glass, even under a 10x loupe. The only problem with that stuff was I could not get the chip to break, it would just make rediculously long strings of swarf that came off blue. 1020 leaves a nice enough finish, but it appears a little matte and under the loupe it has very small amounts of tearing. 1045 (hot rolled) leaves tears that would make you think im making something out of papier mache. Ill have to take a pic or two on the weekend.

Hi all,

The difference between BMS and black is both interesting and confusing to me. Some say that BMS is slightly harder than black yet the people at my local steel supply say thay are made up of the same composition. They say that the only difference is the dimensional tolerances are tighter of BMS.

I really can't be sure who is correct but I achieve similar finishes on black as on do on BMS (once you get through the scale of the black) I'm yet to achieve what I would call an excellent finish on either. So far, If I have needed a good finish I just finish with some emery! The best finishes I achieve are with carbide and a moderate (<0.5mm) DOC. I'm sure I could get a better finish if I fluffed around with a HSS finishing tool but you would want to save that for the last few passes and certainly not use it to remove the scale on the black stuff.

The way I figure, all finishes are crap! it's just a matter of how much magnification you need to see it!

Simon

What is the difference between "Bright Mild Steel" and "Black Mild Steel"? - Yahoo! Answers

I use 1214 (12L14) wherever possible, with HSS it gives a very good finish.

Originally Posted by Big Shed

What is the difference between "Bright Mild Steel" and "Black Mild Steel"? - Yahoo! Answers

I use 1214 (12L14) wherever possible, with HSS it gives a very good finish.

Good point, the high machinability steels are always a pleasure to turn even more so with anything with a little lead thrown in. BMS and MS rate only pretty average, better than 304 or 1095, but nothing like 12L14.
-J

Originally Posted by Brobdingnagian

Good point, the high machinability steels are always a pleasure to turn even more so with anything with a little lead thrown in. BMS and MS rate only pretty average, better than 304 or 1095, but nothing like 12L14.
-J

I machine a lot of 303 and 304 and I can get a far better finish on that than on BMS and MS, using HSS.

Careful Simon L. you'll raise the ire of the non believers, suggesting black turns the same as bright is apparently a big no no. Funny you mentioned the distance at what the pictures were taken though - apples, oranges? For me comparing HSS cuts with insert cuts is the same, but as has been pointed out I'm wrong there too. Oh woe is me!!!

But anyway just to extend this argument a little (it's a hobby), I turned up the same pieces of steel again this morning and achieved what I call 'a good finish'. Now, I'm sure you will all disagree with what I call a 'good' finish; however, It's the best I can do and more than good enough for what I use my lathe for.

Again I used the same depth of cut for both (1 click on the compound set at 45 degrees), roughly the same feed rate (manual not auto) and I sharpened and radiused the bit before turning each piece as before. The pics were taken at around 40-50mm distance, if you think the cut too rough, let me know and I'll take the the pictures from further away and re-post.
For those that can't see the point because I don't know the grade of steel: that is exactly the point, all I know is one is black and one is bright. All of my stock is of unknown grade, I don't worry about material data sheets simply because I'm not making medical or dental components or rockets to send to the moon. I use whatever I can get. I guess that would make me an orphan here, what do you think? For those that need them, pick one to suit:
Anyway the pics of my terrible work. Now I know I'm not supposed to say this, but again I simply can't see any difference.

Originally Posted by Big Shed

What is the difference between "Bright Mild Steel" and "Black Mild Steel"? - Yahoo! Answers

I always thought Black Mild Steel is hot rolled, whereas Bright Mild Steel is cold rolled.

In my personal and limited experience, hot rolled steel is dimensionally less accurate than cold rolled steel. But once the skin is removed, it is of very uniform quality and does not show deep reaching cracks under the skin, and also warps less when milled.

Whereas cold rolled steel, especially if from dubious provenience, may have been passed more often through the cold rolls than allowed without beeing annealed in between passes. Especially from low cost 3d world mills, it is apparently not unheard of if stocks of a certain size run low, to simply roll existing bright mild steel stock again a few time to get to the next smaller sizes, without the cost of first annealing. This practice can result in bright mild steel that looks perfect from the outside and holds dimension, but as you machine it you may fiind surface cracks that reach 5 or 10mm deep under the skin. Making it garbage for any structural purposes. That stuff also often turns to the dreaded "cat's tongue" surface finish.

I guess if one pays the price for good quality cold rolled stuff, it is certainly preferable over hot rolled. But if one is on a budget or shopping cutoffs, hot rolled is the safer option. Please correct me if I got this wrong. Chris