Round or Flat Tube End Closing? Plastic Plugs vs Welded Caps vs Spin Closing
There are three common ways to close the end of a metal tube: a plastic plug, a welded end cap, or closing the tube end itself on a tube end closing (spinning) machine. If you choose spin closing, you also decide whether the closed end is round (domed) or flat, and whether it keeps a hole. This article compares the options and how to choose.
Three ways to close a tube end
| Method | Pros | Cons |
|---|---|---|
| Plastic plug | Cheap, no equipment needed | Can fall out, yellows with age, traps dirt, looks cheaper |
| Welded end cap | Strong | Welding and grinding, weld seam and heat effect, extra labour and consumables |
| Spin closing (tube closing machine) | The tube end itself is formed closed in one piece – no seam, no weld, no plug; ready for plating or painting | Needs a closing machine and tooling; the tube must be ductile enough |
Round end or flat end
| End shape | Features | Typical uses | TONG DA model |
|---|---|---|---|
| Round (domed) | Smooth, safe to touch, optional center hole | Gas spring and shock absorber cylinders, chair legs, strollers, heat exchanger tubes | TD-31040 three-station tube closing machine |
| Flat | Flat end face, optional hole | Tubes whose end face must sit against another part, e.g. small heat pipes, furniture and baby chair tubes | TD-21025 flat-end tube closing machine |
Fully closed or with a hole
The end can be fully closed or keep a center hole of the size you need – useful for fittings, cables, venting or drainage. If the tube will hold pressure, the closing method needs separate evaluation; see Closing pressurized tubes: 4 ways to make a tube end gas-tight.
Which tubes can be spin closed
- Steel, stainless, aluminium and copper – provided the material is ductile enough.
- Diameter and wall must suit each other; for sizes outside the usual range, send samples for a trial.
- On welded (seamed) steel and stainless tubes the weld seam must be sound, or the end may crack during closing.
By industry
- Furniture, strollers, outdoor chairs: replace plastic plugs with a clean end that cannot fall out – see TD-31040 for furniture and stroller tubes.
- Heat pipes and heat exchangers: a one-piece closed end with no weld or plug gap – see TD-31040 for heat pipes and heat exchangers.
- Gas springs and shock absorbers: the cylinder is closed first, then grooved, assembled and charged.
Why TONG DA
- TONG DA has built tube closing machines since 1989 and also offers tube end closing as a contract service.
- Tooling is designed to your tube and drawing; sample trials available.
- CE certified; machines sold to the USA, Germany, Turkey, the UK, India, China and more.
FAQ
Can one machine close different tube sizes?
Yes, by changing the chuck jaws and forming tools.
My volume is small – can you process the tubes for me?
Yes, TONG DA offers tube end closing as a contract service; you can buy a machine once volume grows.
How do I arrange a trial or a quotation?
Send the tube OD, wall, material, length and closed-end drawing to sales@tdco.com.tw and we will reply promptly.