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Del Stubbs

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Everything posted by Del Stubbs

  1. I concur with Jerrod, mine sure seem to be hygroscopic. I am careful about keeping the lid on as soon as I am done with HT. I hadn't thought about starting with low temp as he suggests, I presume to prevent steam pops. Perhaps setting the control for 200F for a day uncovered would dry it out? I am getting ready to do another batch of 400 small blades this week, but my concern has always been the chemical change from the addition of the high temp salt that covers every blade (I use the same low temp for marquenching as Ido for tempering.) But haven't changed the low temp salts in 4 years, just
  2. In 1982 a skilled woodworker friend traveled to Japan to acquire the best handmade chisels he could find. In 2018 he lost his timber framed shop, and all his tools, to the now famous Camp Fire of northern California. I asked for the honor of saving these precious tools for him. My shop puts out about 2,000 precision woodcarving knives a year out of O1. The HT schedule I currently use is : Austenize in salt bath @1485F with a 10 minute soak at target temp. Each ring of 75 tools then goes into a salt marquench at 420F for 10 minutes At about 80F they go into low temp salt
  3. A streak of comet tails, taken through a hand lens. A streak like this is quite unusual in my work as I normally only see an occasional single one, but this more extreme example makes for better study. This pic is from an iPhone mounted on a tripod looking through a mounted 40x hand lens, with side light provided by a small led spot. The tiniest changes in lighting dramatically change the image seen, and made me appreciate metallurgical microscopes that have the light coming through the upper lens, not just externally upper lit. Here’s the same setup with a slightly different light
  4. The low power photos with the 'comet tails' are significant to me. I see a few of these in every batch as I am polishing out and always wondered if they were voids or inclusions. I would sure like to get a good close look at them to help determine when in my processes they are occurring. And how to improve my abrasive stages to avoid seeing them at final polish. I can see the streaks fairly clearly with my 20x or 40x hand lenses, but not clear enough to tell what the void or inclusion is. I have tried to figure a way to macro-photograph these but the lighting is seemingly quite a trick, esp
  5. Though I'm a full time knife maker the only forum I follow is this metallurgy one - most interesting and sometimes quite useful. I thankyou all. So perhaps the page I am attaching will be old hat to most of you, but this was a new chapter to me in the history of heat treating. Years back I looked seriously into using austempering, but because I stubbornly stick to only 01 (where bainite is a bit of an uphill road) I have not practiced it myself. https://clarksonhistory.wordpress.com/2013/05/06/secrets-of-the-dead-the-richtig-knife/
  6. I marquench O1 into low temp salt from high temp salt doing batches of 400 small blades every 2 months. I put a PID controller on an old Hamilton Beach roaster, works like a charm. I'd be curious of the thermal conductivity comparison of salt @ 220C, I did the 50C oil quench for years, but it's sure nice to be away from the smell and the residue on blades - and to have such predictable control of the HT process.
  7. My 2 cents.....I've been wet grinding knives for 15 years with a 2x72. At first I tried all kinds of misting settups, even put machinist's surfactants in the water. I got tired of the mess pretty quick. My solution amounted to a tank above that drips water, via a copper tube, onto an arm mounted sponge that rotates down onto the belt. The sponge is key to using much less water. In front of the sponge I have a drop down hard plastic sheet that nearly touches the belt, this catches most of what spray does make it off the belt. Originaly I just used water-cool only to take any chance out of cha
  8. I was a bit surprised when a search in this forum didn't bring up 'salt bath foam'... Since I do quantities of small tools I now run 2 martempering - tempering baths to recieve the rings of knives from the high temp bath. The older one foamed to beat the band this time. Since the stuff is so darned hygroscopic I presume it is excess water - it's been a wet summer here and the lid isn't always tight. I presume that to dry it out one would leave the lid off - while keeping it hot for a day. Has anyone else had this happen? It made for some excitement when I put in a ring of 75 1500F blades - an
  9. I've worked thousands of blades of O-1 over the years but only had one batch do the micro-crack disaster. Never did solve exactly what happened. I currently have a batch of several hundred almost ready for the salt bath in a couple days, I will hold out a handful to for a delay-to-tempering-test. It will probably be something like 6 hours, 24 hours, 48 hours. Maybe I'll learn something! if so I'll pass it on. I concur that 1084 is a more predictable steel for non-technical settups. I think it was Kevin Cashen who had on the net a thorough & extensive document on fine tuning the compl
  10. Well well, that's good news!, and a relief, thanks Willman. I'd given up on them long ago. The salt baths have revolutionized my knife production, I can't imagine having to go back. I'd still be interested in folk's knowledge on mixing salts that aren't exactly the same from batch to batch. It's a situation I think any salt heat treater could be faced with any day. When a salt mix is no longer available for any reason - do you then need to 'dump and scour', or can you just add a different mix. I have no chemistry background, thus I lack the terms to use, perhaps it boils down to being able t
  11. The last time I bought both high and low temp salts was when Ellis was still in biz. It's high time I restocked my pots. Does anyone know the mixes he sold, or perhaps more importantly, if to change to another salt means dumping and scouring both pots and starting over - just to be safe? In other words, can salts generally be mixed safely that are within a certain temperature range? Thanks, and a grand 2013 to you all. Del Here's a shot of two different types of my specialty carvers knives going into HT, the straight one is ready for austenizing, the hook knives are just coming out, heading
  12. Here's the certs on the latest batch of O1 I've purchased (Austria = country of melt / Precision Marshall supplier ) C - 0.9400 MN - 1.0300 P - 0.0180 S - 0.0050 V - 0.0900 CR - 0.5900 W - 0.5100 SI - 0.1900 CU - 0.1200 In TTT charts for O1 I see ranges for Ms of about 400F to 450F, but to continue working out bainite & bainite mix it would sure be nice to nail down the Ms / TTT accurately. I have tried this site http://calculations.ewi.org/vjp/secure/TTTCCTPlots.asp But no matter how I tweaked it the result wasn't even in the ballpark I am used to. (I plugged in 1088K for
  13. I'd say you've made as good a decision as possible. Three years ago I worked with Tim and Evenheat to build a custom salt pot kiln for my rather unusual needs. Exquisite workmanship, the controls are straight forward and intelligent. Six months after getting it one set point wasn't working quite right - the engineer took it personally, and things we're put in order pronto - nice to be dealing with a fellow proud craftsman. I too will be most interested in your journey with this. Del (noticed your quote by Eugene Debs, I live a couple miles from Debs MN, named after the fellow)
  14. Soon I'll have my new elec. high temp bath functioning, (just finished my new shop bldg.- infloor heat is wonderful!) The pot I had made up is 1/4" 304 stainless 9" dia x 10" deep. ( the fabricating shop didn't have 316, I'm hoping it will hold up with elec. heat) My intention is to do both martempering and austempering with batches of 25 to 50 blades at a time. I'll use a rack made of stainless rod, which will of necessity go back and forth between the two salts. In the recent topic 'up in smoke' it was mentioned that contaminating the high temp with low temp is not a good idea at all. Does
  15. My latest test run was even goofier - Austenized 10 test blanks @ 1525F for 5 minutes, austempered @ 505F for 9 hours (finally had to go to bed! I didn't start til noon cause AM it was -20F in the unheated forging shop) , left O1 blanks in low temp salt to cool down over night, reheated bath next day to 465F for 2 hour temper. Blanks were easy to file deeply - but snapped with a light hammer blow! Good grief. I was delighted that with a bit of tin and insulation I was able to get my modified $25 deep fryer to maintain over 500F, +- 5F So...I called up Omega and ordered their best hand
  16. Thanks for the inputs, I make about 1500 knives a year, about 1,000 of which are O1. So I am well acquainted and quite happy with her. I am ready to consider anything at this point with my confusing austempering tests. I get my steel in 6" x 36" sheets, I usually buy from Starrett or Uddeholm, last 10 sheets I got from TSS in Chicago, but everything about it seemed identical. If it's not O1, what could it be that sparks, grinds, & hardens like O1, yet forms no bainite in 8 hours @ 450F? Propane forge temp. is determined by an Omega thermocouple and digital reader. Salt bath is a dee
  17. I produce woodcarving knives for a living, and have a call for a quantity of very thin blades. My preferred steel is O1. So austempered lower bainite, or a hybrid martensite / bainite seems to me a good answer for avoiding breakage by an aggressive carver. I am hoping for at least RC 59. (Most of my tools are RC 60-62) I have tried a number of times to achieve this with O1 but so far it's been a 100% failure. TTT charts vary, but the way I read them, it looks like a hold of around 425F for 4 to 5 hours should have gotten me in the ball park. Here's my latest batch of trials: O1, 1/8" x 3
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