steel plate thickness for welding table?

[John Stuckey]

I have a 2' by 4' study wooden table with an 18" X 22" X 1 1/4" piece of steel plate on it that I use for support for projects that I TIG weld. The 1 1/4" plate has been thick enough and has not warped thru several years of use (I don't weld to the plate). What is a good guideline for minimum thickness of a plate say 30' X 36" that will remain flat (resting on a solid base)? I can't manuever a 1 1/4" plate this size out of my truck and onto the table so I can either go with something thinner/smaller or just be happy with what I have.
Thanks for your help,
John

[airweld]

I use a table that is 3'x5'x 1/2" T-1 steel with no support other than 4, 3"x3"x 3/8" angle iron legs and it has been in service for 5 years without any distortion. I don't usually weld directly to the table, tho. It has become magnetised over time and that is annoying. Anyone know of an easy way to de-magnetise a table?

Scott.

[Pin Head]

Originally posted by airweld
Anyone know of an easy way to de-magnetise a table?

1) Make a 100 ft coil from your ground and stinger leads and pass 200-300 amps of AC current through them while passing the coil over the surface for a couple of minutes.

2) Heat the surface above the austenitic phase transition temperature.

[Nelson Hendrix]

Tables

My tables in my shop are 5/8" and 3/4". I do weld to them occasionally without any permanent damage. I would not hit them with a sledge hammer though. without abusing the top with a hammer, 3/8" would be thick enough to work off of with a little framework under for support.
Have fun, let us know what you choose.

Nelson