Hss Tool Threading O2 Drill Rod

[mikey]

I am using O2 drill rod because I have it on hand. It is not a requirement at all!

Is there an easier steel to work with that would hold a thread at these tiny dimensions? Obviously the amount of strength required in the finished piece is miniscule and the weakest of materials would probably work. And I would like to harden the screw after construction anyway (and heat blue it as well).

What steel would you recommend for screws of this size?

There are a number of medium and high carbon steels that will harden but not all of them will cut easily. Personally, I like O-1 for most things but something that cuts easier and still hardens nicely is 1144 Stressproof. Cuts easily, finishes really nice (that live center I showed is made from 1144 for the arbor and body and hardened/tempered O-1 for the tips) and it may just be my favorite steel. 4140 also cuts nicely but can be tricky to make nice threads unless your tools are sharp. I don't use W-1 or the other tool steels much. I'm sure others will chime in with other options.

My favorite easy as pie steel to turn is salvaged printer rod. It is some kind of stainless steel, soft as butter and threads like a dream. It doesn't seem to work harden but I've never tried to harden it with a torch so I don't know if it will take it. I've never seen a steel to match this stuff with regard to ease of working - way easier than even 12L14 or 1215. If you want something that does not need to be hardened then go assault an old printer - you'll like it.

 

[RJSakowski]

I have used steel salvaged from old printer as well and also found some of it very machinable. However, some of it is quite hard. Is spark tests like a medium to high carbon steel. If you do salvage some, a spark test is a fairly easy way to determine carbon content, at least roughly. Low carbon steels have long spears with little branching. The higher the carbon content, the more branching. If possible, build up a library of known steels for comparison.

Stainless steel will not have much branching but tend to have more reddish sparks. Same for high speed tool steels. There is lots of info on the internet regarding spark testing including spark patterns and color.

Unless you really need to have a hardened screw, I would stay away from the high carbon steels. You can still heat blue a low carbon steel if you want.

When you get to cutting features as small as you are, tool geometry can be very critical. In polishing a tool surface, it is very easy to curve the surface towards the cutting edge resulting in an interference when cutting which can cause the part to ride over the tool causing damage to either or both. It doesn't take a lot of cutting pressure to deflect a 1mm rod.

 

[mikey]

I have used steel salvaged from old printer as well and also found some of it very machinable. However, some of it is quite hard. Is spark tests like a medium to high carbon steel. If you do salvage some, a spark test is a fairly easy way to determine carbon content, at least roughly. Low carbon steels have long spears with little branching. The higher the carbon content, the more branching. If possible, build up a library of known steels for comparison.

Stainless steel will not have much branching but tend to have more reddish sparks. Same for high speed tool steels. There is lots of info on the internet regarding spark testing including spark patterns and color.

Unless you really need to have a hardened screw, I would stay away from the high carbon steels. You can still heat blue a low carbon steel if you want.

When you get to cutting features as small as you are, tool geometry can be very critical. In polishing a tool surface, it is very easy to curve the surface towards the cutting edge resulting in an interference when cutting which can cause the part to ride over the tool causing damage to either or both. It doesn't take a lot of cutting pressure to deflect a 1mm rod.

RJS, do you know what that soft printer rod is made from? I would like to buy some raw stock if I can reliably identify it. I have some other projects that I would love to use it on but in bigger sizes. I thought it might be 416SS but it isn't - 416 stuff hardens if you look at it funny and while it machines okay it is not a nice material to work with.

I've been very lucky - haven't run across a hard printer rod yet but I'm sure they are out there.

 

[RJSakowski]

RJS, do you know what that soft printer rod is made from? I would like to buy some raw stock if I can reliably identify it. I have some other projects that I would love to use it on but in bigger sizes. I thought it might be 416SS but it isn't - 416 stuff hardens if you look at it funny and while it machines okay it is not a nice material to work with.

Mikey, printer rod covers a lot of ground. I have salvaged rods from dot matrix, ink jet, and laser printers as well as an ancient Zerox type copier. These come from a variety of manufactures like Zerox, Epson, HP, and several Japanese manufacturers so the hope of finding a consistent practice for steel selection is fairly well non-existent. Unfortunately, I hadn't made any effort to catalog the salvaged steel so I could tie it to a particular manufacturer.

The two pieces that were hardened are 5/8" dia. by 17.5 long with eccentric axles. I don't believe they are stainless because of some minor corrosion on the surface. They are not file hard but do not machine easily and they have a fairly high branching in the spark stream.

I haven't done this yet, but I understand that major recyclers have x-ray spectroscopes that can identify steel composition. It might be worth a small fee to identify a salvage piece that you particularly like.

 

[mikey]

Okay, thanks. I don't know if I would bother with spectroscopy but it would be nice to know the ID of this steel. I've not seen a definite ID on the net anywhere else, either.

 

[Bill C.]

You might try annealing your O2 steel before threading it. It might have been hardened. Suspend it from a magnet, over a some dry sand or better yet, wood ashes. Heat it with a torch (probably will need acetylene and Oxygen) until it falls from the magnet. Wait until its cold. Then try threading it.

That is a great tip, never knew about using a magnet.

 

[chips&more]

HSS should be able to cut annealed O2 without any problem. BUT, single point threading the stuff can be challenging. Instead of a nice cut finish, it can look more like the metal was torn off instead of cut off. For this problem I have found that a proper cutting fluid was the only fix. And I realize that white lead is a no no now, but it’s one of the best cutting fluids made. Maybe one of the made today substitutes are as good, I don’t know. Also when working with small diameters, tool height position is very important. Make sure the tool is on center. Running your lathe under hand power should not be a controlling factor. But would be for carbide as you found out. You would need a faster cutting speed for carbide. Stick with the HSS and try a different cutting fluid, or a different billet steel. There are many free machining steels that can be heat treated…Good Luck, Dave.

 

[RJSakowski]

That is a great tip, never knew about using a magnet.

Magnets lose their magnetism when heated. For that reason, I momentarily touch the magnet instead of using it to suspend the heated piece over the quench bath.