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Doug Ayen

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How do you measure the brightness of a polished metal surface? [Jan. 24th, 2015|04:29 pm]
Doug Ayen
How do you measure the brightness of a polished metal surface?

During a recent knifemaker symposium, the topic of stainless damascus came up with the stated problem that nobody really knows which high carbon stainless steels (HCSS) have the greatest contrast. In fact, the expert said in his opinion it was just easier to mix in either non-stainless (D2, L6) or non-high-carbon stainless (305, 315, 420, etc) and accept the inconsistency in the final product. What I would like to do is take a sample of each common HCSS (ats34, bg42, 440c, sv30v, etc), say 20mmx20mm, heat treat, polish to a standard grit, probably .5 micron(A5, 1500 grit ANSI) and then measure the brightness, or reflectivity of the surface, then etch with some standard etchants and see what that shows.  The problem is, I'm not sure what to use to do the measurement. Back when I did typesetting, we used a reflectance densitometer to do something similar, but I'm not finding the right tool. Any suggestions?

Ideally, what I'd want is a calibrated light source aimed to reflect off the surface at a specific angle and hit a photoreceiver that can measure how much of that light is being received. The comparative numbers should give a better idea of what existing HCSS would have the highest contrasts, and given the metalurgical analysis of the respective steels, might suggest alloy formulations to try for an even higher contrast. Just don't know what the tool would be to do that measurement.
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Got the press home and in the shop [Oct. 31st, 2014|06:49 pm]
Doug Ayen

My birthday present to myself this year is a hydraulic forging press, something I've wanted for a couple of decades but could never really justify the expense for.

Today, I picked up the press, got it off the truck (about 700 lbs), moved it in the shop, though it still needs to be moved to its final location. Moving the press off the truck was the hardest part -- I ended up using a 2500lb rated chain wrapped around a couple of overhead beams, attached a couple of 1000lb rated ratchet straps to the base, and used a 2-ton come-along between them to lift and lower the press. Then I just levered it into the shop in case of rain. Took about an hour from arriving home to getting it in the shop, not bad for one out-of-shape guy.

Pics behind the cutCollapse )

All this, of course, ignores the really important question: What color should I paint the press? Right now it's just primer black.
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Nanog Baltimore [Oct. 4th, 2014|12:39 am]
Doug Ayen
I'll be at NANOG Baltimore on Monday, if you'd like to catch me I'll be manning the Carpathia booth until 11:30, then panels and the social afterwards. Anyone else going?
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Research trip to the Met pics [Aug. 20th, 2014|12:07 pm]
Doug Ayen
[Tags|, , , , ]

I was up in NYC last weekend, I went to the Met's arms and armor gallery, took a good look at some swords and got some good pics as research for some projects.

Pics and commentary belowCollapse )
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New knife, slicer with hamon [Jun. 4th, 2014|01:35 am]
Doug Ayen
Steel is W2, there's a nice hamon there, hard to see in the photos but quite evident in real life. Handle is macassar ebony. This is the first knife heat treated with the new molten salt pot heat treat setup I built.

Slicer final - side B
Slicer final-side A
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Powered makita sharpener troubleshooting. [May. 31st, 2014|06:01 pm]
Doug Ayen

Anyone know motors? My Makita sharpener has a custom 560rpm 1.1 amp motor, which usually has plenty of torque, but suddenly the speed and torque dropped to the point where it can't do the job anymore, and the motor housing gets very hot. Pic attached of the insides. I'd like to fix it if possible, but replacement motors aren't available, assuming it's not that great honking capacitor, which is available, but I don't know where to even start troubleshooting. I suppose I could buy a replacement unit, I've had this one since 1998, and it's seen many hours of use, but I'd like to avoid the expense if possible. Any advice before I blow the tool budget again?

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latest knife: W2 small chef [Dec. 22nd, 2013|10:30 pm]
Doug Ayen
After a few failed attempts at getting a hamon with W2, I think I have it. It's a small chef's knife, about 6" of blade, cord-wrapped handle (stage tie-line), ground to x16 then hand polished to bring out the hamon. I made this one on the winter solstice, after a similar design failed during heat treatment (ping of death during the quench.)

solstice a

solstice b

Any questions? What do you think of my hamon?
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Outdoor pizza oven ala blacksmith [Oct. 19th, 2013|11:57 am]
Doug Ayen

As a blacksmith, I’ve built several forges -- 4 at last count, and rebuilt a couple of others. I know something about heating and getting high temperatures in an open space.

I also like making pizza and baking bread. Combining these two hobbies leads to the inevitable idea of building a wood-fired oven, but one that goes a bit beyond what I’ve been finding online.

Most wood fired pizza/baking ovens are little more than a heavy construction of brick and stone to hold the heat, a hearth to burn some fuel, and the same hearth to bake the goods on. This means you build a fire, let it burn down, scrape and push it back so you have a hot surface to cook on, then try to make a pizza that doesn’t have a layer of cinders on the bottom. This is why pre-modern-oven bakin would use a thin layer of dough -- called cake, as in the infamous “let them eat cake” proclamation -- as a base for their baking.

Even so, as a fellow pizza enthusiast noted, they don’t really get hot enough (700F or better) to make a good pizza. I know wood, or at least charcoal, can get above 2000F, so that seems a solvable problem.

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After looking at several wood fired oven designs, I decided that the “build a fire on the cooking surface” was a losing proposition, and remembered my historical alchemical furnace designs. The reverberatory furnace, specifically, isolates the heated area from the burning fuel, while allowing the combustion gasses and both direct and indirect heat to interact with the cooking area. Since I generally like smoke flavoring, this seems ideal.

In a reverberatory furnace, the firebox is either behind or below the heating area, with the flow of heat passing over and around the heated object, or in the case of the lower firebox, also heating from beneath. Normally they have a natural-draft airflow; adding a blower and a tuyere (air pipe) to the firebox should increase air flow and raise heat generation to the desired levels. This is how charcoal and coal forges operate, and they both can get to the point of melting steel without much time or effort.

Also, at least for the test bed, I didn’t see the need for a large, permanent structure. A 2’ x 2’ baking surface should do fine.

So, for the first attempt, my design is to take a sturdy stainless steel table, such as used for food service, and build the oven on that. The base layer, the bottom of the firebox, is a layer of firebrick, with 8-10” of vertical space to build the fire in. Sides are also of firebrick. A steel structure holds a double layer of quarry tile or other heat resistant material that forms the roof of the firebox and the floor of the oven proper, or maybe do what the pros use and get a 24” x 30” piece of ½” steel and rest that on the brick sides. While ideally any supports would be of titanium, high-temerperature steel, or other heat-resistant (and therefore expensive) material, cheaper steel protected by a layer of inswool or a protective coating like itc-213 should also do the trick.

On the bottom of the firebox, a perforated pipe accessible from the outside acts as a tuyere, supplying air from a blower to increase the burn rate and heat generation. While in a forge precautions would need to be taken to keep the pipe from melting, in this case the desired temps are well below the melting point of iron, so standard black iron pipe should be fine. If not, a thick-walled copper pipe should do the trick, it’s what is generally used as a tuyere in short-stack smelting operations, with temperatures around 1800F or so.

At the back of the oven, a gap is open between the roof/floor and the upper baking chamber allows the combustion gases and heated air to enter the upper chamber. The upper chamber has either a cast refractory or brick-and-mortar construction, in a classic forward-sloping  or half-barrel dome. Construction would involve building a form out of styrofoam, then either applying a thick layer of castable refractory mixed with grog or sand, or building a brick-and-mortar structure around it. Coating the foam with a release agent should allow removal, or it can just be burnt out.

At the front of the dome there will be a chimney with an adjustable damper, both to induce a draft when not using a blower and to control airflow during baking. Both the firebox and oven fronts will have steel doors to help control heat as well.

During operation, a fire is lit in the firebox, and once it is going the doors are closed and the blower turned on. A thermocouple monitors the temperature inside the oven, and when the desired temperature is achieved, the blower is turned off, and any ash that migrated from the firebox to the oven proper is brushed away.  The ceramic or steel floor of the oven should hold a high temperature for quite a while, though just having the coals and embers in the firebox should be enough to keep it suitably hot. Wood chips can be added to the firebox for a smoked effect, and an adjustable vent in the firebox door can help modulate temperature and burn rate.

I’ve sketched out a few diagrams, and am looking for the right table. I have firebricks aplenty, and castable refractory and steel are available locally.

I think I have my winter project.

Bill of materials:

stainless steel table    $150

Castable Refractory    $120

½” x 24” x 30” steel     $60  (assumes local pickup, shipping is in excess of $100)

Firebrick x 30        $225 (replacement cost)

Steel, hardware, etc    $50


total            $605

I can go cheaper by making up my own castable refractory or even by using the local clay, but since most outdoor pizza oven kits go for $3000 or more, I figure this is a win.


Chimney is at the front, firebox (with tuyere) on the bottom, there's a hard-to-see gap at the back allowing airflow from the firebox to the baking chamber.
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shop time [Jun. 21st, 2013|12:54 am]
Doug Ayen
I wasn't sure I'd get any shop time in tonight, was feeling kinda tired after work, but after a light dinner I decided to give it a shot. On the pizza wheel front, I tried using the heat-treat oven again, but quenching in water. Result: the test piece hardened all the way through, even under a quarter inch of refractory on each side. When I did the bend test, it just broke into two large and a couple of small pieces. Since it's clear this will be a hands-on heat treat method for at least the near future, I did the other two test pieces by hand in the gas forge. They're etching now in hot vinegar.

While waiting for the furnace to come up, inspiration struck, and I made a knife. Details and pics later, but I got the grinding and polishing done, and even made the handle, which is getting it's first coat of finish now. I'll mate the two pieces tomorrow, then do the final finishing and see if I can get this done by Saturday.
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When all else fails, destruct test [Jun. 19th, 2013|11:01 pm]
Doug Ayen
When all else fails, destruct test.

I took the smallest, thinnest wheel, one I'd not bother to much with anyway, put it in a vice, and bent it. It bent, no cracks. Thinking it might have been tempered too soft somehow, I tried to re-harden with the heat treat furnace, slapping on a thick layer of furnace cement, heating, quenching -- and again it bent without cracks. I pounded it out on the anvil, clayed it up again, fired up the forge, and heated until it was at the temperature I'm used to seeing. I heard it crack in the water, forgoing the uber-expensive quenching oil, and when I pulled it, I saw it had warped under the stresses. Back to the vice, on a bend it cracked about a quarter inch in from the edge, but the middle was still soft. I ground off the refractory, gave it a quick polish in a few spots, and etched in hot vinegar.

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