Re: [hobbicast] Re: Trying to build my first furnace.
- Hello Pete,
If your looking for personal opinions, my answer would be build a small
furnace first to break the ice (so to speak). The operation and safety
practices are the same for a small furnace as a larger furnace.
I built a Gingery gas fired furnace for my first furnace and have used
it a lot. A couple of years ago I was given a small burner that needed
to be used so I built a small furnace using a 2lb coffee can for a form.
I lined the can with 1" of refractory. That gave me enough room to use a
#1 graphite crucible inside. I must say that little furnace gets more
use now that my larger furnace melting aluminum, ZA alloys and even
brass and bronze. In other words, I find the little furnace very handy
for casting small items. Another plus is everything is much lighter to
On 9/17/2012 9:01 PM, pete lamberty wrote:
> So, do you guys think it would be a good idea for me to make my first furnace out of half of a 55 gallon drum? I am now thinking that I will do it this way. All in favor email ayes, against nays. Any advice is greatly appreciated. Thanks, Pete
Camrose, Alberta, Canada.
- Those making small fanl-blown burners should find this flux of interest:
Markal Aluminum Flux Paste (active ingredients stannous chloride, zinc chloride, fluorides) this flux is also rated for stainless steel, chrome, brass, and copper; works well with tin/silver solders. Available through various online dealers and through Wal-Mart.
----- Original Message -----
From: michael a porter <michael.a.porter@...>
Sent: Sun, 14 Oct 2012 15:49:18 -0000 (UTC)
Subject: Re: [hobbicast] Re: Fan-blown 3/8" funnel burner update
3/8” Funnel burner with 3” Squirrel Cage Fan
This is a naturally aspirated funnel burner, with a 12V DC squirrel cage blower fan used as a booster, whenever more volume of flame is desired (it can be run with or without the fan).
The main part is a 6-1/2” long stainless steel mixing tube, with an outside diameter of 0.625”, and an inside diameter of 0.495”, which can be ordered cut to length from Onlinemetals.com: http://web.mail.comcast.net/zimbra/h/%3Cspan%20class=" yui-spellcheck?>http://www.onlinemetals.com/merchant.cfm?pid=12950&step=4&showunits=inches&id=902&top_cat=0">http://www.onlinemetals.com/merchant.cfm?pid=12950&step=4&showunits=inches&id=902&top_cat=0 Scroll to the bottom of the page, and you’ll find an interactive feature that allows you to order the material cut to length, and even adjusts its price.
This tube is nearly twice the length needed to properly mix gaseous fuel and air. However the extra length is needed to ensure that its plastic fan won’t get overheated by heat gain traveling back down the mixing tube from the nozzle area.
At the front of this burner is a 1” O.D., by 0.834" I.D., by 1-1/2” long stainless steel tube; this forms the nozzle: http://www.onlinemetals.com/merchant.cfm?pid=14865&step=4&showunits=inches&id=902&top_cat=0
The burner’s flame nozzle slides over the mixing tube, and is kept centered on it with a 0.875" O.D., by 0.635" I.D., by 1/2” long spacer sleeve made from an S.S. tube, which is split in one area with the help of a rotary tool and cutoff wheel. Neither the outside or inside of this tube fits properly on its own; thus the slit, which is gradually widened until the three parts fit well together: http://www.onlinemetals.com/merchant.cfm?pid=12958&step=4&showunits=inches&id=902&top_cat=0
Three equally spaced Allen screws are threaded through both nozzle and spacer, at about 1/4” in from its back face; these are used to lock the nozzle into position, once the proper amount of overhang is determined (about 7/8” beyond the mixing tube’s forward end).
The back end of the mixing tube is silver soldered or silver brazed to a hip flask funnel. Flask funnels come in different sizes and shapes. You are looking for a stainless steel funnel of about 1.38" outside diameter (at the rim) by about 1.18" tall; the diameter of the funnel's smaller mouth is about 0.315''.
The mixing tube and funnel can be joined with any tin/silver solder, but 95% tin & 5% silver alloys work best. You can silver brazewith an alloy that has 52% or more silver in its content. Whether you choose solder or braze filler alloy, the flux used must be ratedfor cleaning stainless steel. The flux should also match up with the filler’s flow range; not that you can’t use higher rated flux, and let the part cool a few seconds before applying filler to the heated joint, but it becomes an inconvenience; a flux with a lower activation range than the filler’s flow range simply isn’t going to work.
Handy Flux B-1 (contains boric acid, boron, potassium fluoride, potassium tetraborate tetrahydrate); for high chromium stainless steels, tungsten, chromium carbides, and molybdenum alloys. Particularly in applications where a larger amount of refractory oxides may form, use Handy Flux Type B-1 (boron modified). Its temperature range is 1100 to 1700 °F (600-925 °C: riogrande.com/Product/Handy-Flux-Type-B-1-for-Stainless-Steel-and-Nickel-Silver/504088?pos=14\">http://www.riogrande.com/Product/Handy-Flux-Type-B-1-for-Stainless-Steel-and-Nickel-Silver/504088?pos=14\
Harris Stay-Clean #40002 liquid flux (zinc chloride, ammonium chloride, muriatic acid); active range 0 to 700 °F; can always be ordered through Sears or Amazon.com; it is good for all metals but aluminum, magnesium, and titanium; clean up with hot water: http://www.amazon.com/Harris-Stay-Clean-40002-4oz-Flux/product-reviews/B001L66PNI
Kester #817 (ammonium chloride, hydrochloric acid, zinc chloride) inorganic acid flux is formulated for soldering to stainless steel, but it can also be used on all common metals, except aluminum and magnesium; can be ordered from a few sources on line.
Superior #71 is a very high activity inorganic acid flux, containing ammonium bifluoride, ammonium chloride, hydrochloric acid, and zinc chloride; it is formulated especially for soldering stainless steel and high-chromium content alloys, but is also recommended for use on, nickel, cast iron, steel, monel, inconel, copper, and brass; it is not recommended for aluminum, or magnesium; its active heat range is between 200 and 600 °F (93 to 315 °C). Clean up with heated distilled water: ccis.com/home/hn/page21.html">http://www.ccis.com/home/hn/page21.html
Also available from: http://www.ccis.com/home/hn/page27.html
Superior #78 high activity non-fuming gel flux (active ingredients include zinc chloride, ammonium chloride, and hydrochloric acid) for soldering of stainless steel and high-chromium content alloys, nickel, cast iron, steel, monel, inconel, copper, and brass; it is not recommended for aluminum, or magnesium; its active heat range is between 400 and 800 °F (204 to 425 °C). Clean up with hot water: http://www.ccis.com/home/hn/page18.html
Also available from: http://www.ccis.com/home/hn/page27.html
Lenox liquid inorganic acid flux for stainless steel and high chromium alloys. Useful for close fit joints: drillspot.com/products/438856/Lenox_WS78208_Stainless_Steel_Flux?s=1&gclid=CLyhhL3w_rICFYl7QgodHX0Ayg">http://www.drillspot.com/products/438856/Lenox_WS78208_Stainless_Steel_Flux?s=1&gclid=CLyhhL3w_rICFYl7QgodHX0Ayg
Carr's Brown Flux for nichrome, piano wire, stainless steel syringe needles, etc., is a very aggressive acid flux; avoid fumes; clean up with warm water; do not heat joint to 752 °F (400°C): dccconcepts.com/index_files/DCCsolderfluxes.htm">http://www.dccconcepts.com/index_files/DCCsolderfluxes.htm
Note: If you braze, you must leave a generous “bead” of filler alloy on the outside of the joint because the cross-section of your two parts is so thin; otherwise the joint will have no strength. Solder isn’t very strong in the first place, so in addition to leaving a bead of filler on the joint’s outer surface, adding an outer brace is wise.
Caution: Don’t attempt to use lead based solder on stainless steel. Even after surface abrasion, stainless steel joining requires employment of acid based fluxes, which deposit zinc chloride in the joint during soldering; it can’t be removed, and reacts with any lead content in your solder to form (weak brittle) lead carbonate; it continues to do so until the join fails.
Note: Above a flux’s given activation range, stainless steel will often oxidize faster than the flux can chemically reduce it, making soldering very difficult.
To prep the funnel, use a rotary tool and cutoff wheel to remove its small tube, then pass the funnel’s small end back and forth over #120 grit sand paper, quickly enlarging the opening to match the mixing tube’s inside diameter.
Employ a sintered diamond burr (cheap through eBay, and from Harbor Freight Tools) on a rotary tool, to grind an interior bevel on one end of the mixing tube, which somewhat matches the funnel angle.
Use sand paper, or a flap disk to abrade those surfaces in the area to be joined that haven’t already been roughened by grinding; this physically removes nearly all oxides, and leaves a roughened surface to help with “wetting.” Either solder immediately, or else “tin” (pre-coat) the parts with solder to prevent reformation of oxides. Hold the funnel and tube together with a long bolt or threaded stock, two nuts, and two flat washers, for joining. Flux both parts before fitting them together (even if they have been “tinned” earlier).
Phosphoric acid-based fluxes (ex. Naval Jelly), unlike more aggressive fluxes, leave innocuous residues, and are suitable for pre-tinned stainless steel parts: lowes.com/pd_117792-133-01-80277-01_?PL=1&productId=3009567">http://www.lowes.com/pd_117792-133-01-80277-01_?PL=1&productId=3009567
Also available through Amazon.com: dp/B0007TQW5G">http://www.amazon.com/Permatex-81756-Rust-Dissolver-Gel/dp/B0007TQW5G
Drill three or four holes through the funnel at its large end, fit it over the end of a 3” blower from Sparkfun, and pin the parts together with screws: https://www.sparkfun.com/products/11270">https://www.sparkfun.com/products/11270
Fuel gas is delivered to the point where the funnel is connected to the mixing tube through a gas jet made from heavy wall capillary tube (between 0.018” and 0.022” I.D. orifice, by 1” long).
The gas jet tube is soldered or brazed into an annealed copper 1/8” O.D. refrigeration tube. The refrigeration tube can be bent 90 degrees, and pushed through a hole drilled for it in the side of the funnel, then soldered or brazed in place, so that the gas jet orifice is centered over the joint between mixing tube and flask end. The copper refrigeration tube is heavy wall and annealed (easily bent without danger of collapse).
But, the surest way to affix copper tubing exactly where you wish, is to pass it through a brass compression fitting (ex. 1/8” to 1/8” connector), which has been drilled out with a 1/8” (this drill bit may leave the hole a little close if the refrigeration tube isn’t in perfect shape) or 9/64” bit (this bit may leave the hole a little larger than you’d like, but the ferrule will still work well enough to catch the tube, and gas tight isn’t a concern for this particular use), and cut down into a sort of through the (funnel) wall nut, with a cutoff wheel on a rotary tool; this allows you to move the finished gas jet into exact position, and then tighten the nut, causing its brass ferrule to collapse against the tubing, so that it is trapped in position.
You can solder the refrigeration tube’s other end into a suitable NPT pipe fitting (1/8” size recommended), and thread the fitting into a needle valve, or cut the barbed end from a fitting, solder it onto the copper tube’s end, and run rubber tubing from a valve to it. 1/8” refrigeration tube can be purchased in most hardware stores.
Heavy wall capillary tubing can be purchased in stainless steel, brass, and copper versions. Brass or copper is easiest to solder. After cutting the tube, you need to pass the cut end over #250 or finer grit wet/dry sandpaper, in order to successfully remove internal burrs, which would otherwise interfere with smooth flow of the fuel gas.
EDM tubes are a typical way to acquire acceptable tubing for the gas jet.
10 Copper Tubes 0.0525” OD x 0.020” ID x 12 L EDM Electrode: ebay.com/itm/10-Copper-Tubes-0525-OD-x-020-ID-x-12-L-EDM-Electrode-/380227923832?pt=LH_DefaultDomain_0&hash=item588759af78">http://www.ebay.com/itm/10-Copper-Tubes-0525-OD-x-020-ID-x-12-L-EDM-Electrode-/380227923832?pt=LH_DefaultDomain_0&hash=item588759af78
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