Making screws, what metal, heat treat?

[FatJackDurham]

Hi fellows, I've been gone a while working on my house. I have taken a break from that to play with my lathe to practice making screws for some obsolete guns. Right now, I am using mild steel from the hardware store to practice, but I wanted to know what is the correct steel to use for the final part, and if you should do any hardening or tempering for the screw?

I see a lot of people use drill rod, but that comes in the same wide variety of steels. What is your opinions and experience in this area?

Thanks,
Steve

[Chuck 100 yd]

I use O1 oil hardening tool steel to make most small parts. It makes fine screws in my experience.
I coat them in Brownells scale preventing powder and heat to non magnettic and quench in oil. Placing the piece in boiling water will cook off the scale preventing compound leaving the part in the white and with a slightly frosty look. I then temper in an oven at about 400-425 degrees for 30 minutes. Polish the head and blue. This is the same method I use to heat treat a carbon steel knife blade.
O1 is very inexpensive and can be bought in all sizes cheep from Amazon or any of the machine tool dealers. It is called drill rod.

[FatJackDurham]

Thanks, chuck, that is a great, concise little guide. I didn't know about the anti scale powder, that is a good tip.

How to you hold the work to heat it and test for magnetism? Last time I made a spring, I made a little oven with some bricks to reflect the heat back at the piece and used a propane torch, but it would be hard to reach in with a magnet and detach it from the magnet without dropping it. Do you suspend the work with a wire or just lay it on a brick and heat it in the open?

I always thought Tempering required higher temps than a regular oven could do. Another webpage suggested carburizing the piece and submerging it in molten lead.

[Chuck 100 yd]

Tiny parts are dificult to handle. I usually just do them by color. After you have heat treated a few pieces you learn to recognise the proper color to get it to harden. I do lay tiny parts on a fire brick and heat to Cherry red and brush it off into the quench. The draw(temper ) heat only needs to be around 400 deg. For a knife blade. I usualy draw a little more for screws and such. You can go to violet or even blue for springs. A little testing with a piece of scrap would be a good way to make sure it is what you want for hardness/ toughness. Screws dont need to be all that hard IMHO.

[hondo1892]

Chuck gave good advise with O1. But most of the time I case harden my mild steel screws if I want a hard one. I still have some Kasinit which isn't made any longer but someone else is making case hardening compound now. Don't remember the new stuff's name though. The easiest way I have found to draw back springs is just cover the spring with used motor oil and light the oil and let it burn completely out. The spring now has the right temper.

[stretch]

What Chuck said.

O1 drill rod is the way to go. Cheap, easy to work, and easy to heat-treat.

One point worth thinking about is how hard you really want the screw.
Maybe not much harder than what you're fastening to? Or maybe a little
bit softer? Put another way, of something is going to strip, do you want it
to be the screw or the irreplaceable antique receiver you're fastening
something to? Maybe tempered to blue or even purple is the best bet - as
has been mentioned.

-Stretch

[Chuck 100 yd]

[quote="stretch"]What Chuck said.

"O1 drill rod is the way to go. Cheap, easy to work, and easy to heat-treat.

One point worth thinking about is how hard you really want the screw.
Maybe not much harder than what you're fastening to? Or maybe a little
bit softer? Put another way, of something is going to strip, do you want it
to be the screw or the irreplaceable antique receiver you're fastening
something to? Maybe tempered to blue or even purple is the best bet - as
has been mentioned."

I agree, most screws have no need to be real hard.