I worked on a piece of steel stock today and after milling off the black surface layer, I saw a crack-like line running across the surface. I needed to mill off the surface by as much as 0.2 mm before the crack disappeared. The seller of the stock told me that it was cold-rolled steel but the surface finish is kind of rough and exactly the same as hot-rolled steel stocks that I have used in the past. Is this a piece of crap ? I am not sure if I should continue to work on it.
-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
Cracks on surface of rectangular steel stocks
- Thread starter compact8
- Start date
- Joined
- Jun 7, 2013
- Messages
- 10,089
Sure looks like hot rolled to me --- probably the best that China had to offer, as depending on what you intend to make out of it, it may be OK to use or not.
That doesn’t look like cold rolled to me, it should be a smoother surface on cold rolled.
The lines look like it could be indentations from the rolls used to size the material. Over time, the rolls need to be machined to put a good surface on it again and this could be from an old roll that needs maintenance done. If it was a crack, I would not expect it to be so straight, so once you get deep enough, the rest of the material is probably fine.
The lines look like it could be indentations from the rolls used to size the material. Over time, the rolls need to be machined to put a good surface on it again and this could be from an old roll that needs maintenance done. If it was a crack, I would not expect it to be so straight, so once you get deep enough, the rest of the material is probably fine.
Yes, the stock was bought from on line vendors in China. I have bought steel stocks from China before and the quality has been good. The dimension error is very small ( well within a thou ) , machining properties are all expected. Only this one is a disappointment, the dimensions are smaller then the spec by as much as 6 thou, cracks on the surface reduces the usable amount of meat further and the vendor giving false basic info is a surprise.
Last edited:
- Joined
- Nov 23, 2020
- Messages
- 787
Looks like hot rolled to this rookie eye.
The crack line appears on both pieces ( see picture 2 ). My plan is to make two clamps out of it. Other than the clamp being thinner than desired, everythings are OK so I will just use them. Will never buy from the same vendor though. I have the feeling that the crack lines are caused by the metal at the surface being folded together in the rolling process. May be the metal was not hot enough when it was being formed ?
Attachments
Last edited:
- Joined
- Apr 23, 2018
- Messages
- 6,532
That's my guess. Otherwise known as a failure in quality management. Better off to start with a seasoned axle shaft or similar known salvage if material availability is an issue. That's a fine looking hold down, though!