Regular A500 square tubing is not uniform enough to get a good fit plus
there is usually a miserable weld seam. Also, A500 is likely to be a
much rougher surface finish, ask for A513 mechanical grade.

Choice one is to get the material that is made to telescope toghether.
Telespar is the usual brand name to specify.

The other choice is to weld shims on the inside lip of the larger tube,
outside of the smaller tube. They only need to be 1/2" or 1" wide,
thickness can be ground down to get any fit you want. You will likely
have one side of the inner tube shim cut away to clear the weld seam on
the outer tube. Example: 2" sq x.120" wall outer tube with 1-1/2" inner
tube would use .125" shims and give you about .010" clearance.

DeepDiver wrote:
I'm in need of a small amount of telescopic square or rectangular steel
tubing (24" long outer piece and 24" long inner piece). The dimensional size
of the outer tubing is not critical, but I'm looking for something roughly
2" x 2" square. The inner piece must be able to fit entirely within the
outer piece, must slide freely, yet must not be a sloppy fit.

If I were to buy A500 series structural square steel tube:

- 2" x 2" x 11 GA (0.120" wall) x 24" long (for the outer piece)
- 1.75" x 1.75" x 24" long (for the inner piece)

would that work? Or will I have problems with interference from the welding
seam and surface finish inside the outer tubing?

I know there are manufacturers of hitch receiver tubing and other industrial
telescopic tubing, but I don't know of any supplier of small (and reasonably
priced) quantities of the stuff.

Thanks,
Michael