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July 15, 2014 at 4:05 pm #49130
I’m sure there are lots of publications that give long and detailed (yawn) descriptions of the types of material used in making staffs, but I can never find what I’m looking for 100%
So I”d like to tap the resources here for opinions and techniques..
1. What type of material should be used to make a new staff. Please give as comprehensive list as possible of all materials that could be used, common and uncommon.
2. Should the material be hardened steel, if so, should the temper be reduced prior to machining then re-tempered (blued) upon completion, then burnished and polished.
For example, drill bits can be used to make a staff, they are already hardened, but are a bugger to turn, so the temper has to be reduced, then re-introduced?
3. The cooling/quenching stages and what mediums are used for what carbon content types… oil, air, sand, jello 😆
I gotta admit that my brain gets into porridge like state when I start thinking about this, the apple cinnamon kind, or a mucking fuddle, but we all have something right 😆July 15, 2014 at 5:08 pm #58624
There were several blogs on this topic I think starting in 2010/2011 but I’m not sure exactly when. Keep in mind that when the standards were laid down for watch staffs hundreds of years ago, the machinery, cutting tools and steel selection was crude and very limited. Several things have to be considered when selecting a steel the most obvious being availability. The most common recommended staff material that I know of is water hardening tool steel. Oil hardening and air hardening tool steels are fine but cost a little more than the water hardening steels.
One major reason for prehardening and tempering the steel before machining is to make it possible to machine with the equipment that was available hundreds of years ago. The problem is hard metal is harder to machine and requires more cutter force. This is one of the reasons it is stressed to use sharp gravers or cutting tools. When you start turning a 3/16 inch piece of unhardened drill rod, once you get the diameter turned down to about .010 inches, it breaks off because the material is too weak to stand up to the cutter load. Prehardening the steel to a spring steel hardness and toughness prior to machining increases the tinsile and yield strength and allows the part to spring back rather than break off when you get to a small diameter. This increases your odds of getting the diameter down to the proper pivot size. Getting the pivot from .010 inches down to .004 inches (.01 mm) is a real challange. This is also the reason for the strange looking watchmaker lathe accessories with slots and holes in them, turns, Jacot tools, polishing stones, burnishing tools and so on. If it was easy to do this stuff would not have been invented.
Bob has done a lot of experimentation with different steels for pivots and certainly has some great insight on this matter.
davidJuly 15, 2014 at 6:40 pm #58625
Thanks David my brother, how did I know that my question would be the proverbial baited hook for you 😆
I’m having a problem, getting my hardened head around which damn steel to use and how 👿 There are so many types and I’m like ARGHHH 😆
I think I’ve found one but the designation is a Spanish one I think… F521 which is a tool steel.
I managed to find the SAE equivalent of the F521 which is D2, and it is air hardening… Problem is, the only size they have is 2.5cm round, too large to fit in my mini lathe 😥
So this steel is pre hardened and I should be able to work it as is ? Or do I have to temper it first before working on it 😆July 15, 2014 at 8:00 pm #58626randyParticipant
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Type “blue tempered pocket watch pivot steel” into Ebay Chris
I think that there’s a bloke selling an assortment for around $17.00
Sure that I’ve also found it in other parts houses…or similar.July 16, 2014 at 1:17 am #58627
The 2.5 cm (@1 inch) rod is far too large will not do; especially if it is pre hardened. If I were you I would order the material that Randy suggested. It looks like it is the standard staff material and it is available. If you can find an industrial supplier that sells drill rod and will ship to you the material will cost far less. Water hardening drill rod is the least expensive product and should only cost @ $2.00 for a three foot length. Oil hardening rod cost a little more and air hardening cost the most. The material you want to start with should be close to the finish diameter to reduce machining time.
davidJuly 16, 2014 at 7:17 am #58628
Randy and David have hit on the most important points of what to choose and whether to machine the staff in a tempered or non-tempered state. My preference for a readily available steel is W1. D2 is an excellent wear resistant steel and is used in tool and die applications probably more than any other air hardening steel but being air hardening makes it a bit difficult for us to work with since we’re (meaning I am) after something that is quick and easy to heat treat and pull back to a tempered level suitable for the job at hand. W1 fits the bill perfectly…AND you’re in luck cuz I have a bunch of it here with me in Calif. right now. I’m gonna cut a few short lengths of it for you to experiment with and put it in a normal white envelope for you. I’ll drop it in the mail this morning so you should see it before too long. Should be enough to cut a few hundred staffs. I have your address on file here but will email it over to you for confirmation just in case I have a number, street name or something else wrong.
Nos vemos mi amigo!
BobJuly 16, 2014 at 8:16 am #58629
Hey guys, thanks much for the info AND support… I feel kinda thick headed because I should know this stuff 😆 Not sure why, but I’ve always had a tough time understanding the metallurgy end, it’s like having a key that does NOT fit the lock 🙄
Bob, that’s great buddy, very much appreciated. With all the gas mileage going from small remote shop to big supposed “industrial” supply houses here, it would have been cheaper for me to fly back home, rent a container, and ship a bunch of gear over this end 😆July 16, 2014 at 8:25 am #58630
Hey Chris happy to do it!
I’m not in Calif. that often so I try to get all my post office stuff done when I’m over here. Perfect timing!
Have the lengths cut already and now hunting around for an envelope! lol
Also putting a small piece of 01 flat stock for you to make a few parts with. I don’t want to put too much in the envelope so that it will pass as ‘samples’ in case it draws any attention on your end.
I sent you an email with the address that I have for you. Can you check it and make sure it’s correct?
Ok…back to the search.
Take care Chris,
BobJuly 16, 2014 at 12:04 pm #58631
Take a look here Chris – https://www.cousinsuk.com/catalog/consumables/pivot-steel/pivot-steel-blue#select
I have bought a couple of lots of this stuff, it is quite hard but you can still cut it with HSS gravers.
Some of the stuff on e-bay I would be a little wary of, I bought some a couple of years back and it seemed a little soft?
Hope that helps
Paul.July 16, 2014 at 4:29 pm #58632
This would be a perfect application for a Knoop Hardness Tester. Once a hardness number (Knoop or Rockwell) is assigned to the material that works best for your application, you then know exactly what you are dealing with. Knoop would be my preferred test due to the small size of the staff material.
davidJuly 17, 2014 at 10:33 am #58633
this is a new one on me, I have not heard of the “Knoop” test. How is it carried out and is the equipment expensive?
Paul.July 17, 2014 at 4:21 pm #58634
Both the Rockwell tester and the Knoop tester use diamond tips that leave an impression in the metal. The Rockwell test measures the depth of penetration and the Knoop test uses the area of the impression. As far as the practicality of the test goes the Rockwell tester leaves a visible punchmark in the metal while the Knoop test leaves a virtually invisible extremely tiny mark that has to be measured with a high powered microscope. The microscope and micrometer stage are part of the machine and come with it. I bought a used one a couple of months ago for less than $1000.00 dollars. Metrology labs are selling off the old machines as the new testers are faster and more efficient. New testers are computerized, automated and extremely expensive (around $8000.00 to $12,000.00). Mine is still in a crate in my woodshop but I don’t need it at the moment as I have not gotten my heat treat oven yet. The Rockwell testers are a lot less money and a new one starts at about $900.00 up to $2000.00. These machines are very heavy and It costs around $200.00 for the shipping cost.
davidJuly 21, 2014 at 8:14 am #58635
Thanks for the explanation David, let me know when you have it set up and I can send you some steel to test for me
PaulJuly 21, 2014 at 8:48 am #58636
It is going to be awhile before I get my oven; probably 2015. I am currently paying of a lot of bills from buying watch tools and other stuff to set up my shop. I won’t need to use the hardness tester until then. One nice feature about using an oven of this type is there should not be any discocoration in the metal after it is hardened and tempered. The Rockwell tester can also be used but not on the actual part. A sample of scrap would have to be put into the oven along with the actual parts and tested.
davidJuly 27, 2014 at 7:12 am #58637
Did those pieces get there yet? Went first class in white envelope. Went out eleven days ago and post office said it should be about a week .
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