Just buy tubing with correct id for bolts and make your own sleeves.
I just buy pipe nipples at the hardware store and cut them to length. You can really geek out on your weld detail for these "bolt stretch" tubes but a simple filet around each end works very well in most cases.Do these things exist? What are they called? I don't even know how to start searching for that.
I'm building a transmission crossmember from some 2x3 square tube. I would like to fully enclose the tube to minimize moisture and rust on the inside. I would like to drill the bolt holes clean through both sides, and I have in my head the idea that I could buy a steel tube that would run the 2 inches, and weld into the crossmember on both sides, that would be the right size for my bolt to slide through. This would help me seal the opening, and add a little strength to that spot. Hopefully I explained that well enough. Do these things exist? What are they called? I don't even know how to start searching for that.
Check out the Swag off road finger brake- really handy and not too much $ , combined with on sale harbor freight press. I'm really happy with it. My lathe is an old delta wood lathe with a cross slide attachment for metal turning. Not very capable, but cheap and gets the job done on little simple turning like bosses. My vote is get the welder first though! Opens up so many possibilities!I need a lathe and a tig welder and a heavy brake to bend metal and plasma cutter. Lol.
I'm not a great welder, but for what it's worth- I love the TIG. It's so nice to have more control. I started with a small 110V MIG, and then sold it to get a basic Lincoln TIG150. It's been really great. I use it for everything. The only time I wish I still had a mig is when doing welds in close quarters where it's hard to get both hands and filler rod into position and also reach the pedal. MIG is pretty nice when laying on your back doing overhead stuff in tight spots, so I wish I had both- but I'm space constrained so staying with just using TIG.Thanks for the tips. Will take a look at Swag. Been welding with mig for years. Time for a tig welder.