Newbie- Machinable steels and tool types?

[cnczoner]

Hi all,

I need to make a few jigs and other light-use tools, and want to do this out of steel rather than aluminum for durability. I've never machined steel before....

For the target material, I see cold-rolled and hot-rolled available readily, but not sure if these are machinable. Where does tool steel fit in compared to these? I know from working on cars that I usually use "mild steel' there, but those are bolted or welded usually. Not sure if this is hot or cold rolled or something else.

For endmills, I use 2-flute HSS (mostly uncoated) for aluminum, but I have some TiN coated 4-flutes. Are these okay to use on steel? Or do I need something else. For what I will be making, finish will be unimportant, btw.

Thanks,
-Neil.

[cam1]

Hi:
Hot rolled steel is a low carbon steel .1-.2% carbon.Typically has a scaled outside surface with large radii (bar stock).
Cold rolled steel is hot rolled steel that has been resized to closer tolerances, the rolling process also enhances the mechanical properties (slightly higher yield point).Cold rolled is weldable, and is on size with sharp edges.
The sheetmetal that cars are made from is typically HSLA high strength low alloy, designed to be thin, light, strong,formable and cheap.

Cold rolled can be machined with HSS (80-100SFM to start), but caution must be exercised, as it will warp and distort if you only take cuts off 1 face (machining relieves the stesses from rolling). Not desirable for jigs if you are going to remove material from 1 face. You could stress relieve with a heat treatment to reduce the stresses, and then machine.

Tool steels is a broad term used to describe a large variety of steels that can be used to make punches, molds, dies etc. You would need to look up some applications in the machinery handbook, to match your requirements.
Hot rolled steel is very soft, but it's reasonably stable compared to hot rolled. It's very easy to machine with coated or uncoated HSS, but you need to make sure the first cut bites through the hard scale.

Based on your description, I'd go with hot rolled if the design required alot of machining. If you are just drilling holes and bolting together, I'd go with cold rolled.

regards

[cnczoner]

Cool. Thanks.
One thing I'm wondering now is if there is a way to determine what type of steel Home Depot or Lowe's carries (not sure if those are up in Canada) as I cannot remember seeing a designation for it.
And also, is there a way to determine what type of steel those mystery pieces laying around in my garage are?

Thanks,
-Neil.

[DSL PWR]

There is no good way to tell what the mystery pieces are. If you can cut it with a file, or hacksaw, you should be able to machine it. The utility stuff at the home centers is probably low grade and may have some high carbon spots (very hard) that will be a bugger to machine.

[cam1]

Hi: Places like Home Depot would only stock mild steel (low carbon), but you would be paying through the nose....try your local steel distributor, we also have Metal Supermarkets in Canada, yes the price is slightly higher, but there are no minimum charges. A trip to the local machine shop (with coffee and doughnuts) around breaktime, might give you some access to their off cuts......you would be amazed what gets scrapped sometimes.

regards

[cnczoner]

I've not found any good sources or machine shops locally (West Palm Beach, FL) that sell scrap, though there are suppliers of full sheets/lengths. I need small pieces to make things such as this... (it's 4" long, btw)...



I usually get metal (aluminum) from online metals or speedy metals, but I'm looking through their steel selection and I see these under Cold Rolled...


* 1018 - FLAT BAR COLD FINISH
* 1018 - ROUND BAR COLD FINISH
* 1018 - SQUARE BAR COLD FINISH
* 1144 - CD STRESSPROOF ROD
* 12L14 - CD ROUND
* 4130 - ALLOY ROUND BAR
* 4130 - ALLOY STEEL SHEET
* 4130 - ALLOY TUBE ROUND
* 4340 - ALLOY ROUND BAR AIR MELT
* 8620 - ALLOY STEEL CF ROD
* A-366/1008 COLD ROLL SHEET
* A513 - TYPE 5 STEEL TUBE DOM
* COLD ROLL SHEET SAMPLE PACK
* MARAGING STEEL (18Ni)

and these under Hot Rolled...

* 8620 - HOT ROLL ALLOY STEEL ROD
* A36 - HOT ROLL ANGLE
* A36 - HOT ROLL FLAT BAR
* A36 - HOT ROLL ROUND BAR
* A36 - HOT ROLL SQUARE BAR
* A36 - HOT ROLL TUBE - RECTANGLE
* A36 - HOT ROLL TUBE - SQUARE
* A36 - STEEL PERFORATED SHEET
* A569 - HOT ROLL SHEET / PLATE
* A653 - HOT DIP GALV. STEEL SHEET
* HOT ROLL SHEET SAMPLE PACK


For 0.375" x 0.75" x 1 ft long flat bar, my options are 1018 cold ($1.92) or A36 hot ($1.75). So cost is not the issue here, and I'll just tack this onto my next aluminum order. I'm guessing I should just stick with hot rolled for this app, right?

Cheers,
-Neil.

[Geof]

For a small clamp like the picture cold rolled will give a cleaner job. Just machining the two slots into it will not cause warpage that will interfere with its function.

If you want to machine the top and/or bottom surfaces then use hot rolled.

[cam1]

Hi Neil:
The Shops may not be in the business of actually selling their scrap, as opposed to enjoying a nice cup of coffee...., and a chat with someone who is making something interesting (most machinists are "motor-heads").
I'd recommend speaking to the shop foreman. I've had many a person pop in looking for a little bit of this or that, and it never bothered me to let them take away what I was going to recycle. It's nice to help out.

regards