Do free machining steels come rectangular stock?

[thackman]

I have a small mill and sometimes I need something stronger than aluminum that is easy to machine, 80% machinability or better. It seems that there are a several good choices for lathe work but if you check speedymetals, onlinemetals, and my local steel supplier your only choices in rectangles are A36 (generic hot rolled) and 1018. There are a lot of choices for screw machine steel (12L14, 1117, 1144 stressproof, 1144 annealed) and they are all reasonably priced but flat and squares for a mill only come in a36 hot rolled (fairly low strength and scale to eat your cutters) and 1018 cold rolled ( higher strength but has lots of built up stresses to warp your part). Other than those two you jump to the outrageously expensive tool steels. McMaster carries 12L14 in square bar but I'm looking for 1/2" x 2" rectangle. Are there any online suppliers that have reasonable prices on annealed rectangles?

[Geof]

I think you are probably out of luck; the free machining steels are nearly all oriented toward lathe machining (screw machines) so they are symmetric shape. I have asked about other shapes in C12L14 and received blank stares.

You should be able to get C1018 in hot rolled as well as cold rolled and it is the best compromise for stability, strength, cost and ease of machining. The scale can be a real problem if you are using HSS tooling and if your machine has the capacity the best approach is to clean up the surface with a face mill using carbide inserts. When doing this for maximum tool life, not maximum material removal rate, keep the speed down around 300 FPM with a feed of 0.003" to 0.005" per tooth and a depth of cut no less than 0.030"; your little machine may be groaning a bit.

Tapping can be a pain when you are not working with a big machine and peck tapping capability. Try going slightly larger on the tap drill size; some charts give you an option for 65% threads as well as 75%, the loss of strength is not great but the tapping is much easier and you can often use longer bolt engagement to regaing strength. If you can find it use good old fashioned high sulfur tapping lubricant.

[RICHARD ZASTROW]

You could try hot rolled A36 Descaled or Descaled & oiled. (was pickled & oiled for us old farts). There is cold rolled 11L17 available in flats from 5/16" thick X 1" wide to 3" thick X 4" wide. This is from a Central Steel catalog.

Dick Z

[thackman]

My local supplier only stocks structural shapes for construction and doesn't have anything in P&O. I've tried doing it myself w/ vinegar and it's slow, it's a pain to grind off, and when your done it still has a yield strength of 36kpsi.

Thanks for the tip on Central Steel. I think I'll give them a call it looks like they have a facility 25 miles from me.

[DSL PWR]

Originally Posted by thackman My local supplier only stocks structural shapes for construction and doesn't have anything in P&O. I've tried doing it myself w/ vinegar and it's slow, it's a pain to grind off, and when your done it still has a yield strength of 36kpsi. Thanks for the tip on Central Steel. I think I'll give them a call it looks like they have a facility 25 miles from me.

Muriatic acid (hot tub acid) works quite well for the descaling. You do need to paint or oil it soon after you get it out of the acid, as the steel will flash rust.