OK, I'm STILL working on this metal-frame/ceramic top end-table project...<g>. I'm using 1/8" thick 1" angle stock (forged steel) and a Chicago Electric (Harbor Freight's brand) Flux-cored arc welder (115V, 90amp setting, wire feed speed set at about 2.5 out of 10 clicks). So far, I've cut and welded the horizontal pieces. I cut each piece with a 45 degree angle, so when the 4 horizontal pieces are put together and butt-welded I actually got a pretty strong joint. I couldn't break it apart by hand, so I'm satisfied with it. I grinded it down to a pretty decent looking joint. The butt weld seems to have come out pretty strong.
Just FYI, it's a very simple design with the horizontal part of the frame having angle stock such that there's a lip on the inside for the piece of plywood and ceramic tile to sit on. The legs will be angle stock as well, essentially welded to the outside of the corners.
Which is where I'm now having the problem. I welded the legs on (a lap weld) by just doing the weld on the underside, so that I'm welding two spots in the corner (like in the corner of a "T"). I have tried it twice, and I didn't get enough penetration for the weld to be strong enough that I couldn't pull it apart by hand. From reading in the "Welder's Handbook" I have, I believe that I simply didn't get enough heat into the metal at the joint. (The book says that a lap weld requires more heat than a butt weld because there's simply more metal mass to heat.) I only did the weld underneath, because the FCAW is really messy in terms of splatter, and it looked really good when you couldn't see the weld from the top.
The welder is set at it's highest amp setting (90 amps). The areas where I'm welding have been grinded down to a shiny finish with no mill scale or oxidation. So, questions:
1) I've got the heat setting as high as it will go. Should I turn down the wire feed speed to deposit the filler more slowly? Will this help me heat the parts to be joined better and get the necessary penetration?
OR
2) From reading in the "Welder's Handbook", I'm wondering if a small spot welder (resistance welder) would do the trick. This way, I could make the joint where the pieces overlap (middle of the lap) rather than along the corner. I looked at an inexpensive (about $200) 115V 1.5KVA model on Harbor Freight's web-site, and it says that it can join material that is up to 1/8" thick. Do you think this would work better than trying to weld only underneath the joint between the horizontal frame and the legs?
OR
3) Should I just weld all around the joint between the horizontal part and the legs (top, sides, and bottom rather than just the bottom), and then just grind for a few hours to make it look decent?
OR
4) Would a 115V stick welder give me much better results than the FCAW, even though it's harder to use? (I'm thinking the answer is "NO".)
I'm a newbie at this, so any advice appreciated. Please keep in mind that I'm on a limited budget for this, and that I'm building end-tables (not an automobile frame), so it needs to look nice and be reasonably strong (the whole table surface needs to support maybe 30-40 pounds). I'm currently leaning toward the spot welder, as I think it might give me the neatest looking joint that is strong enough to do the trick...
Best regards and thanks in advance!
Dave
Oh, btw, there's two horizontal sections for each table. The end product will end up looking kind of like a cube with two horizontal surfaces. I designed it this way so there'd be some reinforcement for the legs as well as two horizontal surfaces. Even with two welds for each leg, I was still able to pull it apart by hand...
Regards,
Dave
Dave,
I had some similar problems in the beginning with a rather much larger 250 amp (small) single phase welder. Technique, material selection & parameters are the keys to solve your problem.
If the selection of equipment were up to me I would look toward oxy-acetelene and braze the joints, presuming the table will take paint or other finish. The torch will also allow you to soften and bend the steel into shapes otherwise unattainable. There is no spatter. Bronze is softer, and easier to grind than steel, but has somewhat different characteristics (being capillary) than a true weld. Because it is performed at a lower temperature there are less problems associated with the heat-affected zone of the weldment, like cracking you will probably encounter while learning if you get your hands on an "adequately" (depending on who you are speaknig with) powered welder. Once you are good at it you will not even need to dress the joint, which will make up for the slightly more attention required for preparation.
If you look into plumbing service equipment you'll find inexpensive (Prestolite and similar brands) air/acetylene torches that will get the steel hot enough to silver-braze. A properly designed and executed joint even silver brazed (sometimes called silver-soldered) will have more than adequate strength for an end or coffee table. Joint construction might take a little extra time, though, and jigs may need to be a bit more creative on complex joints where multiple parts come together.
Used equipment is readily available around central NewJersey (flea markets etc) and a small "B" tank will get you pretty far at about 10 bucks per fill depending on where you go. Best prices around here are at HVAC and Plumbing wholesale suppliers rather than weld shops, but they won't service O2 needs.
Use cadmium-free alloys for safety, though.
Regards,
D
I am struggling a bit to understand exactly what your joint looks like. If my understanding is correct, and you are only welding two very small "spots" to keep the legs on, then I believe that the problem may lie in your design. You need to have welds of adequate length to give you the strength. This is especially so where you have a large lever such as a long leg for the table with only a very small corresponding area for applying the weld.
If however, your problem is one of penetration, then decreasing the wire feed speed will decrease the current and correspondingly result in less penetration.
Can't really give you advice on the spot welder option.
Regards
Niekie
I have a little Lincoln wire feed welder at home, and I had a hard time learning how to use it, similar to your problem from the sounds of it. At first I wasn't able to get descent penetration/fusion on anything thicker than sheet metal. Then I read the recommended settings on the inside of the machine, and found out that these little machines are very counter intuitive. When you are using a big machine, as Nieke says, to increase the penetration, you want to turn the wire feed up to increase the amperage. On my little machine, as per the recommended settings, when I am welding thicker material, I turn the voltage up, and turn the wire feed down. I usually have the volts on the highest setting, and wire feed on the second lowest setting. The lowest one seems to be so slow, all the weld metal ends up as fumes, and not much on the base metal. I am guessing that with such a little machine, when you turn the wire feed speed up, the machine just can't keep up with what kind of amperage you should be using, so it turns out to be a cold, ropey looking weld. When you turn the wire feed speed down, the amerage is more proportional to the wire diameter, and the weld turns out beautiful most of the time. Also, if you are using .035 flux core, try the .030. It seem to help out a little, as the current density is higher. Keep playing with your settings until you get what you want. Assuming there is nothing wrong with your machine, these little guys can put out some nice welds, albiet at a slow pace.
G Roberts
I have built these tables before...they are cool and cheap to do...if it were me i would hold off on the spot welder unless you were going to spot weld a lot of sheet metal or other thin metals in the future... for another 100 bucks you can get a lincoln AC/DC arc welder...its the bottom end arc welders you see in the home improvement centers...i think you can get about 225 amps out of them...very small duty cycle...but they will work great for what you are doing? can you stick weld? i know your thinking of having an appealing look on the tables..you will have nice bead contours with 7018 or 6013...use a 3/32 inch electrode on DC+ (DC reverse) @ about 70-90 amps...practice if you have the material to waste.. and both are low spatter...i would personally put welds on all four joints on each leg....having each weld being about an inch long should do the trick.
good luck
David
By -
Date 07-04-2002 18:44
i have welded angle iron from bed frames for tables to a garden cart.i use a schumacher mity mite 70 amp arc welder at max amp with campbell hausefeld 6013 5/64 rods. with great results. althought i have welded my vicegrips to many things.they give me a tight fit.i dont have good luck with welding magnets.
