I want to make 1/64 scale models of construction equipment. I have looked at using brass and soldering it together, but it doesn't stick together well. I can break it apart at the solder joint. Is this normal or is it my soldering skills? I also want to lay a bead of solder along a 2" joint and then grind it smooth. Is this possible? Should I braze it instead of soldering it?
I have thought about using sheet metal and a mig welder instead. Will this work with very small parts and thin metal?
If you have a good solder joint with enough overlap (4 to 8 times the metal thickness) then on a new joint you should break the metal as often as you break the solder.
The solder joint needs to be ever so clean before you start -- scrubbing it to a shine with steel wool is not a bad idea. Fingerprints will tarnish badly, so for an intricate part you should probably start with clean metal and always wear rubber gloves during handling.
Use good acid flux (_not_ just acid-core solder) and solder sized to match the sheet. I like to use electronics solder as it is very fine and the rosin doesn't seem to mess up the acid flux. Pretinning the parts is a _very_ good idea.
Make sure your parts are hot enough -- you should be able to melt the solder on the part, not just the iron.
Get some Harris Staybrite silver-bearing solder. It works just a little above usual soldering temperatures, and it sticks very well to brass, also to steel and stainless. You can use a small torch, a soldering gun or a soldering iron. Strength is about 24,000 PSI IIRC. It's not as strong as a braze or weld, but it's considerably stronger than ordinary lead-tin solder -- and it is very easy to use. For flux, use Harris Staykleen, or ordinary tinner's fluid.
You don't "lay a bead" with this material. It wets and flows like water when it melts. It will "follow the heat". If you want a bead, lay brass wire or narrow strip where you want the bead and solder it in place.
I'd braze the joint, or possibly use silver solder.
Ordinary soft solder is simply not suitable for what you are trying to accomplish.
I have an Oxy/Acet torch available, but I normally just use an inexpensive MAP gas torch on jewelry and small items. Silver soldering is arguably a bit easier than brazing, but either technique should work for your application. Both require specialized fluxes to do a good job. The flux should be available from the same place that you purchase your silver solder or brazing rods.
I think the metal will expand a lot and cause problem during the heating. I tried making a small windmill by silver soldering brass rods together. I could not keep thing straight do to the expansion during soldering and the cooling afterwards.
FWIW - silver-bearing solder is available at Radio Shack. You might want to try there rather than purchase a larger quantity as it is normally sold through welding supply sources. It comes as a "cored" solder similar to soft solder with contained flux. IMO, the flux core is not good unless you use some other agent for cleaning prior to soldering. AFAK, the shack doesn't handle recommended special flux such as Harris StayClean. It is available in 4 ounce quantities through welding supply places. Incidentally, silver-bearing solder appears to be about the same stuff jewelers use. I recently "sized" an old ring by cutting it open and soldering in a small piece of similar material (14k gold) from a junk piece of jewelry.
OTOH, silver-bearing solder is fairly strong. For a test, I sawed open a brass tube and then silver-soldered it back together in a butt joint configuration, preserving the internal contour of the tube. Then many passes were made in the lathe, taking the tube down well below original diameter. The silver-soldered joint held up with no problems taking fairly light cuts. The joint appeared to be nearly as strong as the native brass.
Consider a resistance soldering unit ... they're hard to beat for 90% of light structural soldering like you propose. almost all the real quality constuction models are made of soldered and cast brass. How much strength do you need? Something the size of this (1/64) can always be easily bent or broken, even if solid sheet or cast metal.
Use the correct solder, use the correct flux, and, as others have stated, **CLEAN** the metal before soldering! Also, lear the various types of joints, and how to reinforce them for added strength.
For examples of the miniature structural soldering art look at any of the fine quality brass model railroad models available ... and the COST! even in HO scale, $2000 plus for a model is now common.
Also, it's your model, but why 1/64? 1/64 is common for farm tractor models, but not construction models. Cnstruction models are usually in
1/87, 1/48-50 (most common of all), 1/24, or 1/16. A vast number are commercially available, including some parts, like working metal link tracks, winches, lights, etc. Most are diecast metal, but the better ones are either resin/diecast combination, or all brass construction. Again, a nice 1/24 scale D8 Cat is about $1700!
Not the same stuff, Bob. The RadioShack stuff is 62 Pb36Sn2Ag. Staybrite is about 96Sn4Ag. It's considerably stronger than lead-based solder like the Radio Shack stuff. I did misremember, though; it's more like 14,000 PSI, not 24,000 PSI. Still considerably better than 64Pb36Sn which is about 5000 PSI. I used it last week to repair a decorator light fixture made of very thin sheet steel, this for my daughter-in-law who was delighted to have that old pieca-- uh, piece restored.
The silver-bearing lead-free plumbing solder sold at Home Depot is probably much closer to Staybrite, probably being mostly tin. I don't think it wets as well as Staybrite.
There is a Staybrite 8 with higher silver content that has a plastic range so it can "build" a little in loose fitups. I haven't used it.
The Radio Shack stuff is handy in that it's small -- .022 dia. Staybrite can be made into thin ribbon with a hammer. Welding stores do sell small quantities of it in blister packs that include a little bottle of flux.
I ordered a 1 lb roll of Harris Staybright from a local welding supply. I don't remember if it was 20 or 40 bucks. I compared the price to MMC catalog and the price per pound was about the same.
I also ordered 1 oz of true silver solder 56% silver (melt at 1200) for about 20 bucks. A good mapp gas torch will work on small parts. I was also surprised to fine that 1 oz of thin silver solder is pretty long, over
20 ft.
Did you use a hard silver solder or staybright? Staybrite is about 95% tin and 5% silver. It would surprise me to hear that stay bright is that strong.
Staybrite is available in several different sizes diameters from very thin to fat and in several package sizes as well. I found it on their web site and then ordered it via a local welding supply company via the phone.
PM research will sell you 1 oz and a bottle of flux for 8 bucks. One oz is considered enough to solder one of their boilers!
When you say that you can pull the solder joint apart, do you mean just tap it and the joint falls apart or that you can do a joint and then rip the joint apart, bending the brass as the joint comes apart. Soldering of small pieces like you are discussing in 1/64th scale (basically S scale in model railroading) shouldn't be any problem. The first thing is to clean the brass so that the solder sticks to the brass and forms a nice thin "tin coating" type surface. If you have places where the solder doesn't flow then you don't have a good coat of the solder. Then clamping the two pieces together and heating the joint with the addition of a little bit more solder will make a very strong joint. The edges of the joint should be nice fillets rather than a convex bulging looking interface. Another thing is that you don't want to overtemp the solder as this just doesn't help with the metals involved. 400F is hot enough to melt solder and that is a good enough temp to work with for the actual joint. The use of flux in doing large area joints is also a positive thing as the flux will allow for the solder to flow properly over the metal before it oxidizes. The soldering iron is a very important part of the heating equation. I prefer Weller temperature controlled irons for my work as you can control the temp of the iron and keep the iron from getting red hot which just makes messes of things. There are other brands out there that offer temperature control. Hot irons heat the metal so hot that it usually oxidizes the brass before the solder can flow over the brass. It also burns the flux off of the metal which is a bad thing to have happen as the flux then becomes contaminants in the solder. I usually pass my file over any joint surface just before soldering to insure that there is no oxidation on the surface. For solder, eutetic (63/37 solder) is probably the weakest but works very easily. Then there are, on the other end, silver bearing solders with a few percent of silver in them that are more than strong enough for your work. With the silver bearing solder, I will do butt joints in low to medium stress joints without any problems.
-- Why isn't there an Ozone Hole at the NORTH Pole?
Don sez: "> Not the same stuff, Bob. The RadioShack stuff is 62 Pb36Sn2Ag.
If this is true, then RatShack is lying on the product descriptions on their packaging.
The latest silver-bearing solder I purchased from RS says on the package:
64-026 E, Silver-Bearing Solder, Lead Free, 96/4. The sales type said that the 96/4 referred to the percentage of tin and silver. It comes in a 0.5 ounce tube.
I have a much older package of Silver-Bearing Solder from RS, maybe about 10 years old, packaged in a blister pac with a small roll of material inside,
0.46 ounce. It says on the front: Kester Solder, Silver Solder, Alloy 4% Silver 96% Tin, High Strength For jewelry, Antique Silver, Melting Temperature 440 F, Special Flux Core Included.
I used what Radio Shack described as 96 tin, 4% silver, with Stay-Clean flux. I was a little surprised at its strength - but the metal soldered wasds brass; not known for high strength.
That sounds like the right stuff, all right. The melting temp also jibes pretty well; staybrite goes at 430.
My roll of RS is part number 64-013E, sez 62/36/2. It's only a couple of years old. It's better for elex work, particularly surfacemount, because of the lower temperature.
This effect is largely a result of uneven heating.
If you carefully clamp the work properly and heat it evenly, you will not have a warping problem. If you simply lay it on a flat surface and only heat the area that you are soldering, then of course it will warp like Hell becaue the area that you are soldering is hot and the rest of the object is cold.
A Silver-Bearing solder PASTE called Solder-It melts at 430F, and amazed me with its strength. I tossed all my AG4 and AG2% stuff from Rat Shack, which may or may not be only slightly better than "ordinary" Pb/Sn stuff.
The paste also has excellent flux. Hypodermic type container, about 7 bux Canadian at Canuck Tire, likely at most hardware stores although I haven't seen it at Home Depot. / mark
As when welding castings, sheet metal parts can sometimes be heated in an oven to just below soldering temperature, then taken out and quickly soldered. This will reduce warpage, as the entire part is at nearly the same temperature. When working with preciously solder-assembled parts, avoiding a too-high temperature is critical. It's one place where a variety of solders with different melting points can be useful.
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