How to fix it, before I mess it up REAL GOOD?!

Kalindras

Kalindras

Joined
Aug 24, 1999
Messages
933
Wow...nothin' fer years...now two in a week! And of course, it's problems, problems, problems! Okay, so I'm building a steel-framed workbench so that I can bolt my vise to it and have plenty of space to set up the various grinders and stuff that I use to work on my knives. I want it to be solid, I want it to be flat, basically, I want it done right. However (you KNEW there was going to be one of those, now, didn't you?), this is also extra practice for me to work on my welding.

Problem is, I've got the top put together, and it's trying to warp on me. Right now, it's just a touch (maybe 1/4" over the 8' length), but I need this thing flat, so that I can also use it as a surface to lay out my next welding project(s). Is there any way to straighten this thing out, without an oxy torch rig? I'm arc-welding, and I have access to the little propane hand torches, but nothing huge, without doing some digging. I suppose it couldn't be as simple as just putting a few blocks under the opposite corners and throwing some weight on there, could it? :confused: Also, what's the best way to test it for flatness? I'm really just eyeballing it, right now, since my driveway's somewhat...less...than optimally flat.

I think the warp happened during the welding, since it looks a little bit like the warp is set at one of the points where a crossmember attaches. I don't really have any place to work that's "flat and level", like all of the websites I've checked suggest. That's one of the reasons I'm trying to get this thing right, so I'll HAVE someplace to work from! I've done a little searching on the 'net, but most of what I'm finding is with regard to straightening warped wood or sheet metal. The frame I've made is built out of 1-1/2" Box tubing, 96"x30". For that matter, once I have it in place, will the weight of the bench, itself, cause the opposing corners to settle? I've made sure that the legs I've cut are all identical in length (to the extent that my tools will measure, at least--I didn't drag out the callipers or micrometer...okay, I don't actually HAVE a micrometer, but you know what I mean), so if I do my part and weld them properly flush to the frame, that should ensure that if all the legs touch the floor (and IT'S level, at least in that area), everything's good, right? Riiiiiiight... :o

Anyway, I know a bunch of you folks know a ton more about welding than me, so I'm hoping that some of that hard-earned knowledge will come to my rescue, before I get this thing all twisted to Hell. Thanks for any advice!
 
Any welding is going to cause warpage to some degree. I take it the table top is sheet metal? You can minimize warpage by welding small sections at a time and allowing to cool and welding other areas to spread the stress around. Kinda like torquing an engine head, you tighten cross wise, well, weld a small area on one side and switch to the other side, and back and forth. And it's probably best to have the top tacked down all four corners and middle. The thing about welding is that where you've welded the metal is hot and is expanded, when it cools it shrinks. Also if your top is thin it's going to flex around your cross members, no much but enough to notice.

That said I like a wood top on all my benches unless building a welding/hotwork table. Most of my benches are made from 2"x4" lumber screwed together with torx head deck screws with 3/4" hardwood plywood tops. They are very sturdy and solid and flat. My grinder table is wood as well, but the top is make from 2x4 sections as it was made from salvaged lumber. For any work requiring real flatness, I use the granite surface plate.

If your worrying about using a vise on a plywood top, plate the bottom with 2x4's to help secure the bolts through the vise.
 
Thanks for the speedy reply, Will52100. Actually, all I've got right now is the skeletal frame of box tubing. I plan to put a 1-1/2" to 2" top on it out of either ply or mdf. I'm toying with the notion of throwing a sheet of 16-gauge steel over that, just to keep the top from getting torn up too quickly, but that's down the road a ways from now, at least. I wonder if the top will do anything to correct the minor warpage, or if it will just conform, over time, until it, too, takes a bit of a warp?
 
If your main problem is the frame, then tack everything together and weld a little at a time, skipping around works there too. Main thing is to not throw too much heat in one area at one time, and to brace everything as well as you can. And a hammer can be your friend.

I wouldn't put a metal top, good quality plywood will hold up very nicely, 16 gauge will get just about as beat up as the wood and you'll have the added issues of rust. Not saying it won't work, just that I wouldn't prefer it.
 
Kalindras said:
Wow...nothin' fer years...now two in a week! And of course, it's problems, problems, problems! Okay, so I'm building a steel-framed workbench so that I can bolt my vise to it and have plenty of space to set up the various grinders and stuff that I use to work on my knives. I want it to be solid, I want it to be flat, basically, I want it done right. However (you KNEW there was going to be one of those, now, didn't you?), this is also extra practice for me to work on my welding.

Problem is, I've got the top put together, and it's trying to warp on me. Right now, it's just a touch (maybe 1/4" over the 8' length), but I need this thing flat, so that I can also use it as a surface to lay out my next welding project(s). Is there any way to straighten this thing out, without an oxy torch rig? I'm arc-welding, and I have access to the little propane hand torches, but nothing huge, without doing some digging. I suppose it couldn't be as simple as just putting a few blocks under the opposite corners and throwing some weight on there, could it? :confused: Also, what's the best way to test it for flatness? I'm really just eyeballing it, right now, since my driveway's somewhat...less...than optimally flat.

I think the warp happened during the welding, since it looks a little bit like the warp is set at one of the points where a crossmember attaches. I don't really have any place to work that's "flat and level", like all of the websites I've checked suggest. That's one of the reasons I'm trying to get this thing right, so I'll HAVE someplace to work from! I've done a little searching on the 'net, but most of what I'm finding is with regard to straightening warped wood or sheet metal. The frame I've made is built out of 1-1/2" Box tubing, 96"x30". For that matter, once I have it in place, will the weight of the bench, itself, cause the opposing corners to settle? I've made sure that the legs I've cut are all identical in length (to the extent that my tools will measure, at least--I didn't drag out the callipers or micrometer...okay, I don't actually HAVE a micrometer, but you know what I mean), so if I do my part and weld them properly flush to the frame, that should ensure that if all the legs touch the floor (and IT'S level, at least in that area), everything's good, right? Riiiiiiight... :o

Anyway, I know a bunch of you folks know a ton more about welding than me, so I'm hoping that some of that hard-earned knowledge will come to my rescue, before I get this thing all twisted to Hell. Thanks for any advice!
Click to expand...

If you want flat, you get a granite surface plate, or maybe some thick glass to work on.

Even if your table is perfect, the floor will not be.

http://stronghandtools.com/buildpro/

They have adjustable threaded levelling on every leg
Say a nut welded on the leg bottom and threaded rod to the floor.


Don't attach your top by welding, it will warp.
 
First, make sure your floor is flat :)

To straighten the warped frame before the top is assembled, put a 2X4 under a low leg. Have a friend help you, and on the count of three both of you shove down the two adjacent high legs. A few good pushes usually will straighten things out. After that, place heavy weights, like cinderblocks or barbell weights on the corners when welding to keep everything flat. Let all welds cool before taking off the weights. If all else fails, put a piece of 1" steel plate on as a countertop ( that should make it straight).

The old shop teacher ( that's not what they call it anymore) at a local high school called me a few months back and wanted to know if I would like the old welding tables ( they can't teach it there anymore). They are 3'X6' with 4" steel legs and frame with a 1.5" thick steel top. They weigh about 3/4 ton each according to him....I passed on them.
 
another thing you can do is use weld to help out. If a piece is bowed you can run a bead on the inside of the belly of the bow. Hit it with a wet rag. Not enough run another bead. But, if I was going to stick on a 2" thick top I would just shim between the top and the frame till it was within your tolerances. I wouldn't worry about the floor being flat because every metal table I ever built I welded a big nut (for like a 1" bolt) on the bottom of each leg. Yhen weld a round piece of plate to the bolt head and you can adjust all you want. I also agree with the granite plate thing too.


Tracy, I wish I could have snagged one of those tables. A good solid welding table is a great thing.
 
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Okay, so from what I'm hearing, I can go one of a couple of directions: 1) use some lumber under the low corners and then apply pressure to the high ones to try and straighten it, 2) See if I can find the specific points where the warpage occurs and apply extra weld on the INSIDE curve of the warp, in the hopes that the heat/metal will equalise the warp out, or 3) Stop worrying, learn to love the bomb and just live with it, it's not so critical to have a perfectly flat workbench, anyway.

I'm probably going to have try one of the first two options because a) I'm a control freak, and b) I just can't shake the feeling that anything I build on a warped workbench will, by necessity, be doomed to be inherently flawed from the get-go. Of course, due to my lack of any sort of real ability or idea of how to do any of this stuff, I'll almost certainly wind up going with option 3 at some point in the next month, after much cussing and personal injury. Heh, maybe if y'all're lucky, I'll video some of it, and at least get a chuckle out of my antics. :P
 
Try and see how it works on some scrap,

Where you add heat, or weld it will shrink. how much and exactly where, that's experience.



Stacy I'd have bee there to pick up those tables in a heartbeat.
 
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