Weld thru primer and stitch welding questions ...

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I need some advice.I am building a "rolling stand" for my drill press to allow me to move it around my very small shop. It will be a rectangle about 20 by 27 inches made from 4 by 4 by 3/8ths angle. If you think about what this will look like when I get done it will be a "rectangular box with a 4 inch vertical side and a 4 inch lip around the inside of it forming a large rectangular hole in the bottom of the box".Into this box I will be placing a 3/4ths inch plate that will be cut to snugly fit inside the box and rest on the 4 inch lip. As such the plate will overlap the lip by 4 inches all the way around the box.I will then stitch weld the plate to the sides of the box, flip it over, and again stitch weld the plate to the edges of the "hole made by the lip" in the bottom of the box.So one of the questions is - What should I do to protect the surfaces where plate and the lip overlap? Obviously it will be 'blind' after it is completed so there is no way to paint it after assembly.Option (a) is weld thru primer. If that is the recommendation, then which primer? U-POL seems to be the favorite based on my unscientific google survey.Option (b) is cold zinc galvanizing paint. Cheaper and more readily available that weld thru primer.Option (c) is regular primer and paint before assembly, then remove the paint where the stitching will take place, stitch, re-prime and repaint the stitched areas.Option (d) is do nothing because the stand and the drill press will always be in the shop and never exposed to the elements and what happens in the overlap will not be an issue. The "out of sight, out of mind" methodology.And as long as I have your attention, the other question is - How long and how frequent should the stitches be on the plate-to-side-of-the-box welds and the plate-to-the-bottom-lip? The goal is to make the platform as solid as possible without warping anything.Note that all of the welding will be done with a Lincoln PowerMIG 300, .045 solid wire, Stargon gas - 90% argon, 8% CO2, 2% oxygen, spray transfer.Thanks for the advice,Arvid
Reply:Personally I wouldn't even paint it.Well, maybe I would.  I painted my drill press stand, and milling machine stand.  AND THEY LOOKED NICE FOR ABOUT ONE DAY  Coolant plays hell with anything but special paint.You say the plate sits inside the lips of the angle iron.  I would probably do 2" welds every 4-6".  It's enough to lock it in place and won't weird out your angle iron.  Welds on the top, and underside will balance the heat and keep the angle from wanting to pull in at the top or do other weird things"Any day above ground is a good day"http://www.farmersamm.com/
Reply:4 x 3/8 angle and 3/4 plate..a man after my own heart.. id hit it with some rustoleum..
Reply:why not weld the whole plate all the way around, then prime and paint
Reply:Thanks for the feedback. Originally Posted by farmersamm ... You say the plate sits inside the lips of the angle iron. ...
Reply:Full length welds can be the kiss of death in certain situations.  Mega distortion.Welds not only shrink in their cross section, but they also shrink lengthwise.  If uncalled for, unless there's a  special reason, they're best avoided.I guess another analogy would be bolting something together every inch.  If it isn't necessary for strength, why do it?I'm being simplistic, and will probably get slammed for it, but it's my theory, and you do see it in engineered builds quite a bit."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by arvidjI need some advice.Into this box I will be placing a 3/4ths inch plate that will be cut to snugly fit inside the box and rest on the 4 inch lip. As such the plate will overlap the lip by 4 inches all the way around the box.I will then stitch weld the plate to the sides of the box, flip it over, and again stitch weld the plate to the edges of the "hole made by the lip" in the bottom of the box.So one of the questions is - What should I do to protect the surfaces where plate and the lip overlap? Obviously it will be 'blind' after it is completed so there is no way to paint it after assembly.Thanks for the advice,Arvid
Reply:Is it this, or this??   I still can't, without a drawing or picture, figure out what's goin' onEither way both edges of the angle, where it meets the plate, should be welded to balance the heat and pulling Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by gclampI Would think if I understand you, A. the lip will only be 3 5/8". 4" angle is just that, 4" on the outside of the leg, inside is 4" minus the thickness of the leg plus the radius on inside of angle ...
Reply:I'm ignorant without picsI still would like to put some metal on the topside of the plate, but you'll probably be ok.I usually figure 3/8" clearance for welds.  I do it a lot with square tubing.  I cut 3/4" long so that I can have a fillet on either end of a tee joint.I don't do decorative work, so I can get away with the extra on the end.  I feel more comfortable with a full fillet on both sides of the joint. Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:The other thing to think about.is if you are building the outside of the box to fit exactly on the base of the d/p, that means your castors are going to be closer to your center of gravity. Easier to tip. You might want to re-design your rolling base before you build it.Lincoln Ranger 8                        Lincoln 175                          Drill pressLincoln 225 mig                            Plasma                              8 ft brake        52" jump shear
Reply:Maybe redesign the base so that the castors are on outriggers for a little more stability?
Reply:Originally Posted by SpyGuyMaybe redesign the base so that the castors are on outriggers for a little more stability?