Intro: Third, Fourth, and Possibly Fifth, Hand
An adjustable jig for work holding while welding, gluing, or other assembly. It's a light industrial ring-stand from your last chemistry lab. Most likely anyone who wants to build one of these will already have the tools and knowledge necessary (see the caveat section below...), but there are two (maybe three) non-apparent little details that make it all work:
1) A plumbing union makes a great lockable swivel joint (thank you Crucible classes).
2) (usually) 1" pipe makes a nice telescoping slide fit over 3/4" pipe.
3) (maybe) Having a swivel vise on a different center from the stand makes it possible to align different sized parts in (all?) orientations.
The sky's the limit on dinguses that can be added for various uses. What you see in the product photo is,
from top to bottom, a hand rest for welding, a rotatable C-clamp for holding stuff, another smaller rotatable C-clamp which matches up to, an old swivel vise I had laying around. In the second photo, the smaller C-clamp is set up to hold a pair of vise-grips that can then rotate in three dimensions to get at those hard to reach places.
The third photo shows the stand in use holding a piece of tube at an angle to another larger cylinder, ready for tack welding. If you can do that some other way, you don't need to read any further...
The last photo in this section is a full scale version of the product shot so you can see as much of the detail of my bad welding and assembly as possible, should there be any question.
Caveats: I have a fairly complete machine/welding/electronics shop and have been wanging on things with various kinds of hammers since my grandfather gave me one when I was about 5 yrs old. This is my first post to this site so instructions may be rougher than necessary, but I never follow receipies and so I'm writing for those of my kind....
Step 1: Tools
Pretty much anything you got...
I pre-suppose that you can:
a) cut up to 1" diameter water or gas pipe;
b) drill and deburr holes in round and flat steel things;
c) tap holes for 1/4" or 5/16" bolts;
d) grind stuff to make it fit together;
e) weld steel -- we can get around this, but it involves larger drills and more tapping...
(I mean, heck, this IS a welding jig...)
Step 2: Materials
Again, basically whatever you have lying around...except that a couple things need to fit together on their own.
My example stand is made using:
-- 1/2" steel base plate, about 8"x10";
-- 3/4" black pipe, for the vertical stand, mine's about 18" but whatever length you like;
-- a 3/4" coupling (or could use a floor stand) to attach vertical to the base plate;
-- 1" black pipe in 2"-4" sections for sliding "ring-stand" clamps;
-- 5/16" bolts with extra nuts, to lock sliders onto the vertical;
-- 1/2" black pipe union, to swivel gripping things onto the ring-stand sliders;
-- a 12d nail, as a tightening handle for the union;
-- 1/2" black pipe 4" nipple to extend C-clamp to position over vise;
-- a small C-clamp, preferably stamped rather than cast (see below);
-- a 4" swivel mount bench vise;
-- some 1" square tubing for spacers under the vise.
On the key subject of the pipe union: A union is used to join (unionize?) two pieces of pipe that cannot be threaded into a fitting together, say because they will un-screw from some previous fitting while being screwed into the new one. If you haven't run across one before they comprise three pieces. Two of the pieces thread onto standard pipe threads and mate together with a slightly spherical surface. These two pieces are then clamped together using an enclosing nut, which one hopes makes a water/gas tight seal. The upshot is that when you loosen the enclosing nut you can rotate the two ends independently... Ipso-de-facto...a lockable swivel joint! See the photo below, or just go play with one at your local Art Supply Store.
As mentioned in the introduction, 1" pipe -- usually -- slides nicely on 3/4" pipe. I just tested this at my favorite Art Supply Store (Big Jo's Hardware in Santa Fe, NM) with randomly selected galvanized pipe nipples. (OK I can't resist...haven't you always wanted to walk into a hardware store and ask, "Do you have galvanized nipples?"). (Sorry). However I have recently had trouble with some black pipe I got at my fiendish local Home Despot, so it seems that the actual dimensions can vary somewhat. In general, plumbing pipes run about 1/8" larger inside than their "sized" diameter and the walls are somewhat smaller than 1/8", which makes the 3/4"->1" fit thing almost perfect. Some pipe has internal seams that ruin all this nice calculation, so caviet emptor during the materials procurement phase of this project, unless you have a boring lathe...in whch case you have probably already stopped reading these pointillist instructions.
A couple welding notes:
On the galvanized versus black pipe issue. Galvanized and other plated stuff is very bad for the welder, and a littly messy to weld as well. The fumes from the plating materials are poisonous, and those materials should ONLY be welded where there is a LOT of VENTILATION . Therefore I recommend using "black" pipe and fittings (generally used for gas plumbing) where ever possible.
In my construction I welded pipe fittings, which are cast steel, to pipe which is not, this usually leads to weak, cracked welds. I used nickel filler rod to alleviate this but it's danged hard to find. I also tig welded it...So, for the benefit of the less well endowed I have written these instructions to mostly avoid making those welds.
Step 3: Make the Stand
There are a number of ways to go with this part.
1) You can just weld your 3/4" vertical pipe to the base plate. This is the easiest way, assuming you can set up something that is nicely perpendicular and weld it before it warps into some other dimension. The downside is that you then have a pipe permanently attached to a plate and can't take it apart to transport or change the length.
2) You can weld a 3/4" pipe coupling to the plate. Then you can thread the vertical pipe in and out all day long. In my version I cut a black coupling in half, just to reduce the length (and save the other threaded half to make another stand). The issues here are welding cast to rolled metal, and, again, getting the thing perpendicular. Grinding the end of the fitting square helps a lot, as does setting it up with the vertical pipe attached so you can check it with a square as you go along.
3) You can use a 3/4" floor flange instead of the coupling. This makes it easier to get things perpendicular and, if you are not a welder, the stand can be bolted to the base plate. If you are a welder, you may just goop a lot of rod between the cast and rolled materials and look the other way. Also the base doesn't have to be steel, any old piece of 2x10 might suffice. The downside here is that the flange takes up some space on the base plate that you might wish was flat during some future endeavor
Step 4: Make a Clamp
Here you get to be creative and design your own gripping systems. For the purpose of the instructions I will describe a hybrid of the two clamps shown in the photos. Hybridized because I don't really like my construction of either...Anyway....Using the photo of the big clamp as a guide, here's what to do.
You'll want a 2"-4" section of 1" pipe to use as the slider on the vertical stand pipe. You can just buy nipples of the right size, but pipe-on-the-hoof is a lot cheaper (assuming you have a chop saw or some easy way to cut it to length). Make sure the ends are deburred, both inside -- so it will fit over the 3/4" pipe -- and outside-- so you don't cut yourself. The before photo below shows two possible deburring tools. You can also use a grinding wheel to smooth the outside and get a headstart on the inside.
Note: This part involves welding. If you do not have access to someone who welds, you could use a 1" tee fitting in place of the 1" pipe as a slider (if you are lucky you should be able to find one that has 1" through and 1/2" on the tee). However you will have to drill the threads out of the straight-through part of the tee in order for it to fit over the 3./4" vertical. This is probably a 1-1/8" drill, or a quick boring job on a lathe. Both of these options require some heavy machinery. If you don't mind a sloppy fit you might use a 1-1/4" tee fitting and a bunch of bushings to adapt to the 1/2" pipe I use below. If you use a tee fitting, then all you need to do is thread a short pipe nipple into the T-leg and skip the next paragraph.
OK, the rest of us are welding then...In the photo I show the union welded directly to the slider, however this requires welding cast material so I'm changing the design a bit. Instead we will weld a short pipe nipple to the slider and thread the union onto the nipple. To do this, start with a double ended pipe nipple and cut it in half so you have two threaded-on-one-end pieces. The length of the pieces is up to you and your creative clamping designs. In any case, grind a notch in the un-threaded end of the nipple so that it fits around the slider pipe more snugly than just the flat end, and then weld it in place to make your own tee fitting.
To attach the clamping bolt I drilled and tapped a hole in the slider opposite the newly attached tee. Then, to strengthen the threads I put a nut onto the clamp bolt, threaded the bolt into the slider, and _lightly_ tightened the nut to the slider surface. Then I tack welded the nut to the slider. Hopefully you will still be able to un-screw the bolt when you are done...You might have to chase-tap the whole ensemble to get it to thread nicely again. To make it easier to tighten the clamp I bent the bolt by wanging on it with a sledge hammer while holding the threaded end in a big vise. Your technique may vary.
Before threading the pipe union onto your new tee, drill a hole in one face of the enclosing nut and weld a 12d nail into the hole to make a convenient tightening handle for the swivel. In accordance with the bad-first-design principle I put the union nut on the outside, but I think it makes a bit more sense to put it on the inside. That way you can easily swap clamp types on the end of the swivel without having a bunch of the nuts clanking around. But either way works...
On the other end of the pipe union we can attach any of the gripping opitons we have dreamed up. Here I would make another modification to the design in the photo and thread the second half-nipple into the union. This way we can weld the clamp to non-cast metal more successfully. See the photo of the vise grip clamp for one example of attaching the clamp to the pipe. In that case I cut a notch in the end of the pipe with my chopsaw, filed it wider so it fit around the clamp, and welded it all together. Again note that many C-clamps are cast steel, so the welding may be tricky. If you are not welding you could notch one side of the pipe and drill through pipe and clamp to bolt them together. Another attchment option would be to use some industrial epoxy, such as Ten-Set or PC-7, but you should make a good mechanical fit first.
And there you have your first third hand.
Step 5: Some Design Issues
As shown in the product shot I mounted a small swivel vise onto the base-plate and made one of the clamps just the right length to sit above the immobile jaw of the vise when it is perpendicular to the clamp mount. See the middle photo in the ariial views below. If you draw some concentric circles around the centers of the stand and the vise swivel you can see that this allows one to position the clamp and vise jaws in a multitude of ways. In practice I find it pretty easy to get two pieces centered to each other, as seen on the introduction page. The only other trick with the vise was to mount it up high enough (on the square pipe spacers) that its handle clears the bench top when in use. That way iit doesn't clang annoyingly on the metal welding bench on every turn.
I risk putting the vise-grip clamp combo photo up once more in order to draw attention to the two washers welded on either side of the pliers. The washer's were drilled out to fit over the round faces of the C-clamp and thus ensure that the pliers stay captured in the clamp. This also provides a center of rotation for the pliers as one positions objects. I found a mostly flat, parallel spot on the pliers to put the washers. In this case they "fall half off the edge" so there is also a spacer between them for the C-clamp to grip.
Once you make a couple of the slider and union components you can start thinking of all kinds of gripping devices to mount on their business ends. I'd like to see some of them.