Grinding Welds - Strength Lost?

[Hunt6246]

I recently built a small two wheeled cart to move a small generator around the garage and when camping. It has a 1" x1" x 3/16" steel angle frame with expanded metal on the inside for a platform. When building it, I mitered each of the four sides to a 45 deg. angle on each end and then welded the outside of where each of the two sides joined to form a 90 deg. corner. Welding on the outside was also necessary to correct some minor cutting errors that resulted in minor gaps between a couple of the frame pieces. Welds were strong and I couldn't flex them at all. I had a slight twist to the frame that took two of us to straighten using 2x4's as levers. But, you couldn't see a lot of penetration through the joint or discoloration on the off side of the frame. After the expanded metal was welded in position inside the frame, I welded the inside four corners of the frame. I then ground the weld on the outside corners smooth so it would look good after painting.

Question is - If welds seem to have penetrated the material and the joint between two surfaces seems strong, how much if any do you sacrifice by grinding welds smooth to match the exterior surface? Or, said another way, what is gained by having a bunch of weld piled up on the surface of the metal you are trying to weld? I'm a retired engineer and know this could get into a whole bunch of engineering talk and probably some high brow calculations but am more interested in generalities.

Thanks.

[usmcpop]

Check this thread, especially post # 17.

http://www.hobartwelders.com/weldtal...rinding-welds&

[Northweldor]

I recently built a small two wheeled cart to move a small generator around the garage and when camping. It has a 1" x1" x 3/16" steel angle frame with expanded metal on the inside for a platform. When building it, I mitered each of the four sides to a 45 deg. angle on each end and then welded the outside of where each of the two sides joined to form a 90 deg. corner. Welding on the outside was also necessary to correct some minor cutting errors that resulted in minor gaps between a couple of the frame pieces. Welds were strong and I couldn't flex them at all. I had a slight twist to the frame that took two of us to straighten using 2x4's as levers. But, you couldn't see a lot of penetration through the joint or discoloration on the off side of the frame. After the expanded metal was welded in position inside the frame, I welded the inside four corners of the frame. I then ground the weld on the outside corners smooth so it would look good after painting.

Question is - If welds seem to have penetrated the material and the joint between two surfaces seems strong, how much if any do you sacrifice by grinding welds smooth to match the exterior surface? Or, said another way, what is gained by having a bunch of weld piled up on the surface of the metal you are trying to weld? I'm a retired engineer and know this could get into a whole bunch of engineering talk and probably some high brow calculations but am more interested in generalities.

Thanks.

The post umcpop recommended covers it all pretty well, but I would add that full penetration welding on 3/16" really shouldn't require welding on both sides, and, that you should be able to see full penetration, either while the weld is being done, or though later examination of the reverse side. Another point is, that except where a smooth finish is desired or necessary, many of us like to leave our welds in as welded condition for the admiration and emulation of future generations!!!!

[Hunt6246]

Thanks all - the post, especially #17 was very helpful. Yes, I agree that welding on two sides of the 3/16" stock should not be required. Probably half as much weld as I used would be more than sufficient. More weld gives me a chance to practice my technique and probably helps make up for any deficiencies. Part of my problem is that I work up a design on CAD and only buy the materials I need for a job and don't have a lot of scrap stock to practice on. It seems that the welds at the beginning of a project leave something to be desired but improve steadily as the project progresses and get looking pretty good at the end. Grinding helps remove some of the early results that I'm otherwise not too proud of!

[k45]

and only buy the materials I need for a job and don't have a lot of scrap stock to practice on.

Oftentimes it is less costly to buy larger pieces. The extra is future opportunity Don't buy at your local box store. I can get 12' or more of angle iron for the price they want for a 4' piece.

Ken

[Hunt6246]

K45 - Yes, I've found the same thing. I have a fellow nearby that runs a metal supply/ fab. shop. He'll sell steel for a fraction of the cost of Lowes, Home Depot, Tractor Supply and others. He doesn't charge for cutting or bending. For this project, I was $27 for the steel and $26 for the pneumatic wheels/ tires. I saw a cart like I built for sale for $99. Mine has a folding handle and a couple other features that the store bought version doesn't have.

[k45]

Hunt6246,

Well get a little extra, or ask him for some scraps or "drops" to practice with. The small pieces that aren't worth their keeping may be just the ticket for you to practice with

Ken

[usmcpop]

Maybe you can borrow some scrap for practice. Take it back to him so he can recycle the scrap.

[k45]

Maybe you can borrow some scrap for practice. Take it back to him so he can recycle the scrap.

"Borrow scrap for practice" sounds very funny but your idea does make good sense. Run enough beads on a piece and it will increase the scrap value

Ken

[usmcpop]

When you are a "bottom feeder", you have to develop symbiotic relationships.

[billbong]

Hey, if you're welding 3/16" thick stuff you won't do much damage if you grind back to look pretty......but if you have doubts on the weld strength then you've only plastered metal on top of the tube....that's a recipe for more practice needed on scrap.

It definately pays to keep an eye open when you go to your local scrap metal merchants, especially for all those "handy" pieces of square tubing you always need to do a simple project.

The big problem is with plate stock, and unless you have a cutter, either plasma or Oxy, cutting the stuff to a size you want becomes virtually an impossibility......even a bandsaw struggles on a 1/2" thick bit of plate.

I once heard a guy describe a job that had been scrapped as "value added scrap"....LOL.
Ian.