# Hss Tool Threading O2 Drill Rod



## ProfessorGuy (Jul 5, 2015)

I have been trying for weeks to make a steel screw.  I'm trying for one about 6mm long and with about a 1mm shaft.  I am using O2 drill rod for the screws, and I can easily cut the profile and even the thread relief.   But when it comes to the threading, no luck so far.  I've been filling a little box with my ruined attempts.

My lathe uses handwheels for threading (no motor), and I use a 4x jeweler's loupe as I thread, so I have excellent control over the process.  I just don't know what the heck I'm doing.

I started with a 60 deg. carbide tool, but the tip of that tool shattered within the first 5 mm of cutting.  But I don't want to use carbide, I'd rather use steel.

The tools I've ground so far are from 1/4" HSS blanks.  On the first one, the tip became rounded off on the first pass (about 3mm) after taking a 0.04mm cut.  I ground a new one, then tried to harden it by bringing it to cherry red, then quenching it in black oil.  Then I tried taking only 0.02mm cuts (just dusting).  The tip of the tool crushed down, with the very tip (just the last 0.01mm) slipping down off the edge--ruined!

Made yet another tool.  The screw simply bent out of the way of the tool, which cut nothing.  Each subsequent pass just pushed the screw further out of the way until it bent and was ruined.

What's the secret of cutting a tiny steel screw with steel?  I know the old timers were able to cut steel--they weren't using carbide in the 1880's.  How did they do it?


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## gi_984 (Jul 5, 2015)

I've never tried threading such a small diameter shaft on the lathe under power.  Perhaps you should try turning down your drill rod to the major diameter and then use a threading die in a handheld wrench to cut the threads while still chucked up in the lathe.  I use the tailstock to get the die aligned at the start of the thread.  After you get the thread started one to two turns you can back the tailstock off.  After hand threading use a cut off tool as usual. I've threaded the ends of several larger shafts like this.
Drill rod is pretty hard stuff.   Perhaps a different type of material would be easier.  I've used O-1 and 1045 for bolts before.


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## RJSakowski (Jul 5, 2015)

ProfessorGuy said:


> The tools I've ground so far are from 1/4" HSS blanks. On the first one, the tip became rounded off on the first pass (about 3mm) after taking a 0.04mm cut. I ground a new one, then tried to harden it by bringing it to cherry red, then quenching it in black oil.


HSS steel is so called because you can heat it to a fairly high temperature before you soften it making it ideal for high speed work.  The annealing temperature is actually around a cherry red incandescence,  about 1600F.  To harden HHS, you have to heat it to a much higher temperature, 2200F.  The tempering temperature is around 1000F.  What you actually did in your heat treating was to soften the steel.


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## mikey (Jul 5, 2015)

I have some suggestions:
1. You need tailstock support - period.
2. Use a 1/8 cobalt blank and grind the tool with 15 degrees of side relief, then use a diamond stone to put a very tiny flat on the tip. What I bet is happening now is you are fracturing the tip of your tool and increasing the cutting forces so the tool won't cut. Hone the tool to a fine finish before using. Optionally, you can try a P1N parting tool and grind the tip of that as a threading tool, same angles as above.
3. Stainless will work harden and push away from the tool. I suggest taking 0.002" cuts for the first 2-3 passes and then lighten up a bit.
4. Use sulphur based cutting fluid.

Edit: for some reason I had it in my mind this was stainless - my mistake. Ignore #3.


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## T Bredehoft (Jul 5, 2015)

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.


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## brino (Jul 6, 2015)

Hey Professer,

I am sorry I don't have anything new to offer, any suggestions I had were already said above.

But I did want to add that I am already watching this thread. I have never tried something so small, but I am keenly interested in how it can be done.
Please keep posting your findings (what helps _and_ what doesn't).
I'd like to learn about this.

Thanks!
-brino


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## mikey (Jul 6, 2015)

I've been thinking about this and you might have better luck asking this one on one of the horology forums or the Yahoo Sherline group. There is a guy named Jerry Keiffer who hangs out on the Sherline group that does a lot of fine model work and he makes screws an order of magnitude smaller than you're doing here. If anyone can help you, he would be the one.


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## ProfessorGuy (Jul 6, 2015)

Thanks for the suggestions.  I have a couple of comments and questions:

No magnets are allowed in my shop--watches don't like them.  This limits the tooling and storage systems I can use, but I like using less modern methods.  Can I use the "sharpie" method of annealing O2: that is, can I heat it until a sharpie mark on the surface disappears (as you would on silver or copper)?

I polish the tip of my tool to a mirror finish (or as close as I can come) because I need the last 0.01mm of it to do the very shallow thread cutting.  I thread under magnification and could easily tell if the tip were damaged.  At one point I had a beautifully-shaped, undamaged tool that wouldn't cut, but rather pushed the work out of the way.  Huh?

How can I use my tailstock?  Once a chuck is within a few mm's of the headstock, there's no room for the 1/4" tool, much less for the toolholder or the cross slide which carries the tool.  And how do you start the threads if the tip of the screw is chucked?

I just applied to join the Yahoo Sherline group.  Thanks for the heads up.


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## mikey (Jul 6, 2015)

Prof, I was under the impression that the O-class of tool steels was sold in the annealed state. I don't know how to make it softer still. I've heard of the Sharpie thing but only as it applies to silver. If I recall correctly, and it has been a few years, the Sharpie disappears at the temperature silver anneals at. I don't know that this is the same annealing temp as O2 but I suspect it is not. Could you not just have one magnet that you could leave outside the shop where you do your torch work? If not, send it to a heat treat facility and have them do it for you. Another option is to use another kind of steel - is O2 necessary?

Okay, if the tip of the tool is okay then could the tool not be on the exact spindle centerline? A slender work piece like you have would require this.

You can use the tailstock if you have an extended tip live center. Of course, they don't sell one so you'll have to make it or maybe make an* extended dead center* that will accurately fit the tailstock. At hand-turning speeds a dead center would work fine, I think.

Anyway, here's my solution:





I used this to make a screw for an archery arrow rest that used 4-40 threads. Granted, not as small as yours but it worked fine and it was in 303 stainless, not O1 or O2. I ground a P1N blade (o.038" wide) to screw cut it and it walked right through that thread. The good thing about using a parting tool is that it is very stiff vertically and can be extended without adversely deflecting under the forces of a hand-turned piece when taking very tiny cuts. You might consider it. It is a good idea to have a very solid parting tool holder when doing this, though. If you don't have one, make one.

As for threading a screw when the tip is chucked, I have no idea unless you cut it in reverse, which the Sherline can do. 

Regarding polishing, I use a Translucent Arkansas to polish when working with this scale of thread. Sharp takes on a different meaning when working with small diameters. The same applies to tool geometry - cutting forces on very small work pieces become big deals. I assume you already know this but others may not.

I've pretty much shot my wad with regard to tiny stuff. Ask on the Sherline Yahoo group - many skilled guys who know how to work on a Sherline lathe there.


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## ProfessorGuy (Jul 6, 2015)

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?


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## mikey (Jul 6, 2015)

ProfessorGuy said:


> 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.


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## RJSakowski (Jul 6, 2015)

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.


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## mikey (Jul 7, 2015)

RJSakowski said:


> 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.
> 
> ...



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.


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## RJSakowski (Jul 7, 2015)

mikey said:


> 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.


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## mikey (Jul 7, 2015)

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.


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## Bill C. (Jul 7, 2015)

T Bredehoft said:


> 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.


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## chips&more (Jul 7, 2015)

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.


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## RJSakowski (Jul 8, 2015)

Bill C. said:


> 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.


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