How do you turn steel on a watchmakers lathe? It took me forever to reduce the diameter of a piece of steel.

[GregG]

I finally got my lathe up and running, and I tried turning a few pieces by hand.  I needed to create an M0.6 dial shoulder screw, so first I practiced on a piece of aluminum.  And since aluminum is so soft, I was able to turn down the diameter using a Vallorbe diamond-shaped graver pretty quickly.  I acquired a bit of confidence in using the graver, so I decided to try on steel.

I would normally try on O1 tool steel since it's comparatively soft, inexpensive, and hardens well, but I didn't have any.  I do have some pivot blue steel, so I tried on that first.  I also have some A2 steel, which I tried as well.  In both cases, it took me so long to turn down 3 mm into 0.6 mm (and then on top of that, I overpowered the piece and ended up breaking off what was supposed to be the threaded portion ).

So I'm wondering if my technique is incorrect, or if I'm using the incorrect type of graver, or if something else.  Thanks!

[Dell]

The diamond graver is the correct one did you use the graver diamond up or diamond down because how you present the graver to the work is different as is how you present it to different materials .

Brass & bronze needs natural or positive rake whereas steel needs negative rake & the graver needs to be very sharp but a blunt graver will cut soft aluminium quite easily.

Have a look at one of my videos, I don’t profess to be an expert but I do get the job done, also a lot of people say you need speed when using a graver but I don’t agree because to much speed can lead to work hardening making it difficult to cut what is needed is good torque, you will see from my video I run the lathe quite slow but it still cuts very well the steel is EN1.

try altering the angle that you present the graver to the work & make sure the graver is sharp also practice practice practice.

Dell

[oldhippy]

Just to backup Dell, a slower speed is better, people think fast speed will get the job done sorry to say it doesn't work that way. You might be better with a different graver, many prefer to make and sharpen their own to suit them in the way they hold the graver.  

[Dell]

As OH said it makes sense to make your own as I make my own gravers but apart from the round & parting gravers they are all diamond just different sizes & different angles.

Dell

[Neverenoughwatches]

As above,  the graver needs to be very sharp. I cut mostly diamond up and slow to medium speed. Too fast and the graver will start to burnish rather than cut. Maintain the cutting edge, any thoughts you have that it's losing its edge will be after it's already gone. A carbide edge will outlast a hss one . I look for curly shavings to know that it's sharp. 

[Dell]

Although I have carbide gravers I very rarely use them because I find them to brittle because the tips break off but it may be me being to aggressive, I find HSS gravers a lot more forgiving & easily sharpened & don’t forget to get a good finish it needs to honed as well.

It’s always nice to have conversations like this. because it’s always possible to learn things from other people .

Dell

[nevenbekriev]

Something else to add. OP, You are trying to make screw out of blue steel. This is wrong. You will learn sooner or later to work it with gravers and there will be no problem to shape it to 0.6mm rod. But then it will be not possible to cut thread on it. Unless You have carbide or very  special fancy die.  You have to start wit soft steel, and after making the screw and the thread and cutting the slot on the head, only then harden and temper the screw.

[caseback]

I'm no expert, but I found that the carbide gravers mentioned in this post by @nevenbekriev work great and are dirt cheap. Cutting blued steel was absolutely no problem for them. For a lot of applications you can use them "out of the box" without the need to reshape them. I only rounded one off for making the radius on balance staffs.
 
https://www.watchrepairtalk.com/topic/29977-balance-staff-just-can’t-get-to-02/?do=findComment&comment=254624

Edited Sunday at 01:35 PM by caseback

[GregG]

Thanks everyone for the responses. @Dell, I tried both positive and negative rake, both performed about the same.  I was running my lathe pretty fast (over 2,000 RPM at the motor), faster than in your video.  You mentioned at about 5 mins in that you're running 700 RPM.  Is that 700 RPM at the motor or 700 RPM at the lathe?  If your pulleys are different diameters then the speed of the motor doesn't translate exactly to the speed of the lathe.

I also definitely have to resharpen the graver.  My practice time probably wore the edge, and attempting to turn potentially work hardened steel wouldn't help.  A few weeks ago I created a jig that holds screwdrivers at the precise angle to resharpen them, so I'll probably try something similar with the graver.

4 minutes ago, nevenbekriev said:

Something else to add. OP, You are trying to make screw out of blue steel. This is wrong. You will learn sooner or later to work it with gravers and there will be no problem to shape it to 0.6mm rod. But then it will be not possible to cut thread on it. Unless You have carbide or very  special fancy die.  You have to start wit soft steel, and after making the screw and the thread and cutting the slot on the head, only then harden and temper the screw.

What steel do you typically use?  Like I mentioned, O1 is widely used for making steel components since it is cheap, available, and hardens easily.  But if there is a different preference for watchmaking I'd like to know.

[caseback]

When using steel that hardens easy, like O1, you have to be careful not to heat it when turning. This will "work harden" it and you might damage your die anyway when cutting threads. When using sharp gravers, you'll find that you don't need high rpm's.

Low rpm's and sharp cutting edges will keep the temp low.

Edited Sunday at 01:49 PM by caseback

[Neverenoughwatches]

The important rpm would be the headstock turning  speed, motor rpm doesn't matter.

It's how fast the workpiece is spinning.

Once you get to know what a sharp graver is and how it cuts ,then you will know when to sharpen it.

12 minutes ago, caseback said:

When using steel that hardens easy, like O1, you have to be careful not to heat it when turning. This will "work harden" it and you might damage your die anyway when cutting threads. When using sharp gravers, you'll find that you don't need high rpm's.

Low rpm's and sharp cutting edges will keep the temp low.

Absolutely Cees , my best brass shavings are produced at ridiculously low speeds, steel higher but still quite low. A keen edge makes all the difference. 

[nevenbekriev]

41 minutes ago, GregG said:

What steel do you typically use?  Like I mentioned, O1 is widely used for making steel components since it is cheap, available, and hardens easily.  But if there is a different preference for watchmaking I'd like to know.

When I need to make screw, I use soft У10А, which is russian steel, very similar to O1. I would use O1, but for me it is harder to source because of the place I live.

When I need blue steel, I usually temper to blue rollers from roller bearings.

When turning blue steel with HSS gravers, You will not only have to resharpen the graver, but to sharpen it often (several times while turning). This is not only sharpening, but polishing too. I find for myself carbide gravers are much better, but this is personal and one will find for himself what serves better for His needs. High speed (revolutions) is not needed as the friction will cause heat and heat can make the work to harden and the HSS graver to get dull. If You notice the graver is not cutting well, then sharpen it immediately. Blue steel is easy to work harden with dull graver and it is hard to get rid of the hardened portion, especially with HSS graver. Work hardening has nothing to do with heat/quench hardening, it is rather due plastic deforming on the surface by dull graver or drill bit.

Edited Sunday at 02:17 PM by nevenbekriev

[Dell]

GregG

Both my pulleys are the same diameter on purpose so I can rely on the display, when removing metal fast I have it a bit faster than when I am getting close to the finished size.

Dell