Just like the title says, I have several questions about flatness, more specifically, during the course of making a DIY fixture table, is it possible that the plate can develop a deformity as the drilling progresses? Obviously, if significant heat or other forces are applied to the plate, it can deform, but as a result of just drilling holes?
It’s a fact that a 1” thick plate measuring 8’ wide by 20’ long will sag downward in the middle when the supports are placed at the ends (19’ apart), I’ve seen this with my own eyes, and it’s simple physics as well. That’s not what’s happening in my case; I have a 1/2” thick 3’ by 5’ plate, on 2 sawhorses placed 3’ apart. When I started, the plate was visibly straight; I meant by eye, I put a 6’ straightedge along the length, and it was within a 1/16” of an inch. The more holes I drill, the more deflection I get, and what’s making me ask the question in the first place is the plate is bowing UPWARDS, against the force of gravity. For reference, initially it was within 1/16” over 5’; now it’s just about 1/2”, or slightly more.
I know there are many types of steel, and many grades of strength involved; tempered, annealed, hardened, stress relieved, etc., I used a piece of A36 hot rolled, torch cut from a much larger piece. I can only guess that perhaps there was some kind of residual stress already in the plate when I got it, but would simply drilling a bunch of holes cause the issue I’m having? I’m not naive enough to think I can achieve the flatness of a dragon wagon, but I can’t really fabricate anything remotely accurate when my plate looks like a half pipe and I have skateboarders knocking on my door.
Any thoughts?
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An interesting puzzle. I can visualize that drilling the holes will 1) alter the mass, 2) reduce strength, and 3) potentially release stresses, but of those my guess is that the stresses might be able to cause the upward bow you’re observing. Assuming you start on a 3’ edge, how far have you drilled? Hopefully you have some ideas about a stout frame for the plate so that you can push/pull it back to a flatter state.
–Larry
That’s the only thing that makes any kind of sense; at least in my mind. Pre existing stresses somehow got released as the drilling progressed, it just seems weird that the plate bowed up, instead of down. I noticed it at about 2’ in, but it wasn’t as pronounced as it is at 4’. I’m hoping that 540 holes will allow the plate to flex enough that I can proceed according to Jason’s plan when he came out with the pro series tables; using plate straps and 1” x 2” tube longitudinally. If not stiff enough to straighten out the plate, I think that I can substitute some cold rolled bar in the same size.
Yes Larry is correct, the material has internal stresses that your relieving as you drilled the holes.
Welcome to the battle of search for perfection. This is why pro tables cost what they do. This is a battle all manufacturers have.
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Well, at least my initial thought wasn’t too far away from reality. But using either the rectangular tube like you did during the pro series table build, or switching to solid steel bar stock, I have no doubt that I can get the warping under control, even if I have to abandon the using the plate strap kit and use 1”x 3”, or even 1” x 4” bar stock, and align all the adjustment holes parallel to the frame members, I can get damn close, as in “can’t detect any variations using a 6’ level as a straightedge”. That’s plenty good enough in regards to flatness for my personal preference.
Trying to achieve the flatness of a precision ground surface, like a dragon wagon table? That’s nothing short of insanity, especially in a small shop, or cave with electricity, in my case. I never questioned the price of a dragon wagon table, and while I personally don’t like the fact that they are made at Chuck E. Chinese’s and then shipped to the USA for final dimensioning, if they were 100% USA made, they would probably be at least twice as expensive, if not more.
Even “stressproof” steel has some stresses in it. If you want to see your table become a potato chip, try drilling that many holes in some cold rolled. It has a ton of internal stress. Hot rolled is much better, but far from perfect. A cast plate would probably fair the best, or annealed and cryo treated plate.
You can straighten the plate after drilling and it should stay flat. With all the holes it would not be hard to use bolts and strongbacks with spacers to pull it flat, or a small hydraulic cylinder. You can also flame straighten it, but that is something of a black art.
FIRE! Yeah, not gonna lie, that was my first thought, but I did remember…….something…..like it’s some kind of voodoo magic type art, so I asked the brain trust on this site first.
Good news-
Got the flatness problem under control, and more than likely, when I actually get the entire table built, I’m thinking I can completely solve it. Still have 169 holes left to go, but I no longer need to worry about the plate running away or giving me any more problems as I’m trying to get done. All I had to do was drill, tap, and install the plate straps and the long frame tubes, crank em tight, and whammo!
Flat plate, well flat enough; with a 6’ straight edge, it still has +/- 1/16” crown in the center, but I only have 5 out of 26 plate straps installed. Another 21 installed, and I’m 100% confident that I will be able to fully “fine tune” the top. The DIY table kit definitely delivers as promised! (DIY template accuracy is a completely different matter). And if the DIY version works this good with what ended up turning into a bowed piece of plain A36 hot rolled plate, then anyone who buys at least the pre drilled plate will have ABSOLUTELY no problems making a great quality table! Great job Jason, the entire concept is well thought out and works perfectly!
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