Greg Sigworth

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  1. As Carl Stross mentioned leaded steels have good machine ability and the cutting tool does not weld to the steel. The lead is insoluble in steel. When the melt solidifies the lead stays separate and precipitates out as microscopic round lead inclusions. These act as holes in the steel filled with lead so a chip hitting one of these breaks off instead of becoming long, chip breaker. The lead also may act as a lubricant in the cutting process and prevent welding on the cutting tool. I worked in the auto industry and their material standards did not allow lead to be present in the steel, so we never saw nor dealt with leaded steels. If one turned up it was a big problem. Other than the inclusions mentioned their should be no noticable effect on the steel because of the insouluability factor. If an alloy has soluability in steel the alloy atoms will take the location of an iron atom in the solid. It becomes part of the steel. Lead does not do this; insoluable. The chrome is the alloy which makes stainless steel a non-rusting steel; stainless. I was surprised to see that leaded steels are still in use.
  2. Another thought about lead. They used to put lead in iron as a lubricant. I don't know if this had any value as a lubricant.The lead is insoluble in iron so it shows up as round balls, very small, in the steel which rub off and act like a sort of lubricant. Under a microscope they are small gray round inclusions. This is all outlawed now and there are strict regulations against this. It could be that the lead is just there because of corruption from junk yard steels with who knows what goes into the melt. If your steel has lead in it it will leave the marks you see. Like a pencil. This is the reason pencil graphite is called pencil lead. They probably used to use lead to leave a mark on paper.
  3. Reminds me of my first violin and the aluminium arching forms I made. When I moved the forms over the wooden plates where there was contact it left a dark mark. It acted like a marker. I removed wood where there was marking until it marked everywhere. Somehow the aluminium was wearing off on the wood leaving a dark line. Kind of like a pencil. Your planes are doing the same thing. You got some planes that are made, I am afraid, out of some real junk material. Who knows what is in it. Sealing the surface or putting something thin on the surface might fix the problem. You stated that it originally left marks with the plating on it. Maybe some of the plating is still in the surface of the metal causing the marking. It the plane is flat on the bottom try sanding the bottom on a flat surface to try to get a bit deeper into the plane and maybe leave behind the the substance causing the marking. You have to give the Chinese credit for being creative.
  4. I have found some growing in the woods near me in a sandy area next to a stream. Can I dig some up and transplant it to my property? What is the best way to do this? I pulled one up from the sandy soil and it had a lot of root structure attached. My second question may not be on target for this subject; how to use the plant for sanding/burnishing plates. I took some that was dried up and put it in a coffee grinder to make powder. I don't think the dust was healthy to breath. I have tried holding a bunch in my hand and using it like that to sand plates. I also tried slitting a section open and attaching it to the back of a felt pad which had adhesive on it. It made a kind of sanding block. Any ideas will help.
  5. Thanks for the post. The print is fine so I will have to print it out. There are a lot of stresses in cast metals from the solidification process. I guess the study the Navy did looked at this for cast gray iron which the body of planes would be made of. The study was done in 1955 and many of the references go back to the early 20th cent. That does not mean it is not correct. If there is some kind of thermal cycling going on, like a car engine heating up and cooling off that will provide the necessary added strain/stress to caused internal relaxing of stress from casting. A high temp anneal will solve the problem. If planes are flattened when new to a reasonable value where does all the distortion come from In older plane bottoms? Does the added stress during use cause the yield stress to be reached locally within the plane. Seems like every plane I see is not close to being flat. I wii read the report, thanks. I have to print it out.
  6. The flatness of planes and their ability to stay flat over time is an issue. Cast iron like wood has a lot of stress in it which will over time relax and with this there will be shape change. I went to a private Volvo shop many years age and this was before Volvo was brought by Ford. The owner was from Sweden and had been to the Volvo factory that made the cast engine blocks. He said they simply piled up the new blocks and let them sit for a year and after becoming more dimensionally stable machined the bearing areas. Those engines could have 200,000 miles and be as true as when new. This is true for cast iron planes. When I look at an old plane often the center of the bottom is concave where the outside edges reinforced by the sides has resisted this movement. A new plane could be flat and in 5 years be warped. It costs money to either anneal the blank or just let is set to get the strain out. I see old planes warped and it seems to always indicate this kind of dimensional change.
  7. The plates of violin #6 rready to assemble. The inside is sealed with Vernice Bianca and a thin coat of propolis in acetone. I put some money into the wood from met music stow Vermont. The plates had a nice clear ring tone especially in # 5 mode. I did the edge work on the front sides after Roger Hargreaves analysis of Guarnari’s work. Very rewarding and felt like I was actually becoming a violin maker and actually learning how to do it. Will post more later after I make the neck/scroll. Model is Plowden from Strad poster. Outline and f holes from poster. Corners need to be finished yet and they are a bit narrow. Comments please. Anything I know I learned from those who have shared their knowledge.
  8. Not so much now, but a few years ago you could buy cutting tools and bits made of high grades of steel from china. They were terrible; they didn't heat treat half the stuff or did a very poor job doing so. The heat treatment which includes a proper temper probably has a greater influence on the finished product than the material it is made from. Melvin, that possibly might explain why your knife is poor.
  9. I just went to the website, it is correct. You need to look at their instruments. They are works of art!! I wouldn't be surprised to find out that I was way low in the estimate of their high end instruments.
  10. I made one for my wife from a kit sold by stew mac. It went well and I used my finishing skills from violin making. A good way to start. Also, there is a real neat Ukulele Store in Waikiki, Hawaii at 226 Lewers St. Suite 218, Honolulu, Hawaii 96815. There phone # is 808-888-5469 and web page at www.Ukulelestorehawaii.com; e mail is ukulelestorehawaii@gmail.com. They sell high end instruments made on the islands. The top end sell for about $5-7000.0. Over the last six years they have been there. I picked their brains on the finishes of the best ones. True Oil is on many of them. They may be able to give you some information or contacts with makers there on Oahu. Every time we go by the store I want to go in and look around. They have low end instruments starting around $3-400.00. They specialize in selling hand made instruments from Oahu.
  11. We used to use the stainless foil mentioned. It works quite good. Add some brown paper towel material inside the foil wrap. This burns when temperature is reached and exhausts the oxygen inside the foil. Be very careful when working with the foil. It is very thin and sharp.
  12. Crucible Steel has a good website and they have specifications for heat treating their PM steels and other tool steels. I used to have their data in a nice book form which I gave to a budding blacksmith. Its all available on the web site for those needing heat treat recipes. Most PM steels that would be good for cutting take a temperature over 2000 Deg F. to austenize the steel. This takes some expensive treatmen and should be done only by a professional HT facility, and many will not be able to go to the required temperatures, and it has to be held at that temperature for at least one hour. The quench is dangerous; putting yellow hot steel into oil. I am sure that they Crucible have a sales dept and would suggest steel PM grades to use for knives and possibly sell useful blank sizes. They would sell pre-heat treated steel which could be shaped and then finished grinding/sharpening after heat treat. They might even be the supplier for Veritas. Carpenter Co. is another big PM supplier. You would then have to find a local HT facility to do it for you. They might be able to put it in a bigger load they are processing at the same time to keep the cost down. Calling Veritas and asking them for finished knife blankes of their steel might be a better way to go. The value of PM steel is the uniformity of structure throughout the steel. PM steel is not formed by solidification of molten steel and does not have the segregation of materials resulting from the solidification process. Steel is reduced in size by the repeated forging process which helps to eliminate segregation of elements and structure. The blades made of steel folded over and over again eliminate this. Well , PM does it from the get go; resulting in an excellent steel. Power metal from the different elements to be in the final steel are mixed and in a large can are pressed together under incredible pressure. This is called sintering. Then the sintered block, mechanically welded together, is placed in high temperature well above 2000 deg F and the metal fully welds together and the elements go into solution and move (diffuse) around in the solid metal. The result is a very fine grained steel with great uniformity and structure throughout. Crucible may make their PM materials and sell to the knife market. I may try to call them and see what I can find out. Normaltool steels come in various grades: O1, A2, S7 and H the W series. A series are quenched in air, the slowest of quenches, air cool; O series are quenched in oil, W series need a fast quench and are put in water, the S series are shock resistant steels and the H series are high temperature steel such as used in die casting. The number after the letter refers to different grades in the series, Metallurgy 101.
  13. There a number of reasons why the immediate surface area of a post blade sharpened heat treat could produce a cutting edge which crumbles or has other undesirable qualities. Even in the best protected atmosphere there will be some high temperature oxidation going on which will degrade the immediate surface and make grain boundaries weak and subject to breaking. This could extend to .0015" deep. Also the very edge of the blade will quench much faster than the interior of the blade making is more hard/brittle surface edge. This is very material sensitive. And there are a lot of other surface problems related to heat treat. All of this would advise that in a post grinding heat treat to regrind the edge to get below this surface affected area. Another metallurgical idea, the temper is very important to the quality of the steel and it also is material sensitive. One temper program will not work on all steels. All of these processes involve big expensive furnaces and hours of time to do; costs money. A double temper is required for many steels and is often desirable to make a more stable blade which will hold a good edge longer. Some will even cryogenically cool the part after normal quench to -150 deg f. Then temper a second time. The reason for a second temper is that in the heat treat process at high pre-quench temperatures the steel is FCC structure Austenite , and when quenched does not have enough time to form BCC Ferite and forms very hard martensite; the product of high carbon quenched, rapidly cooled, steels. This martinsite has to be tempered as it is very hard and brittle. Tempering takes a little hardness away but greatly reduces the brittleness. After the first quench some of the austenite remains, retained austenite, and later when the tool is in use may change to hard brittle un-tempered martensite; then be a site for fracture under stress. The second temper reduces the amount of retained martensite and gives a more uniform structure of tempered martensite. If you have a blade which is too hard or brittle you could put it in your wife's oven, danger danger!! get her permission first, at around 375 to 400 deg F. for at least one hour. Then resharpen the blade. Of course this temperature may be too low for some of the more exotic steels. We tempered all our heat treated steels carburized steel once at 400 Deg.F. Once in a while we would repeat to increase the toughness and durability of the steel parts. Maybe this will help some of you in your tools and sharpening/use of them.
  14. Sorry about that. I meant 130mm. Also I will not know the final stop length till it is assembled. I placed the f holes where they are on the original top in relation to the whole top. I am guessing the stop will be a little over 192mm. Thanks for pointing out my error. My mind hates to memorize things. It wants to understand why something is instead of memorizing facts; that's no excuse. I need to be more careful.
  15. I am making two violins now #6 and #7 from the Strad poster of the Plowden. I have been told by a fellow luthier that the original has the nut moved into the peg box a little to obtain the 120mm needed length for the nut to upper body length. I will make the neck/scroll of proper length so as to have the nut in the proper location and still have the 120mm length.The stop on the instrument is short at 191mm so some compromise has to be made on the string length. My stop probably will be around 192.5mm as my overhang is a bit more than the original and my mold may be a bit larger. I copied the f hole from the bass side of the poster and used it for both f holes. One last thing. I made an inside mold from the strad poster but used the base side of the top for both sides of the mold. I ended up making two molds. There was wear in the upper bout on the treble side of the plate from left hand wear so I used the bass side outline for both sides. I used the arch heights for both plated but made my own arching contours. When I finish the violin I will try to give pictures. I need to make the neck/scroll, assemble and finish and then find out how it sounds. Both plates are done and the rib garland also finished.