What makes internal cleaning work?
Two things at once: the filament tips reach every part of the wall, and the brush gets through the whole passage without jamming. The bore diameter alone does not tell you enough. Length, bends, steps, ports, the shape of the bottom, the residue and the side you reach from all change the brush.
How does the shape of the passage change the brush?
- Straight through-hole: single or double stem, pushed and pulled or turned under power.
- Blind hole: a radial or fan tip that reaches the bottom without a cut stem end.
- Cross hole: side contact or abrasive nylon that reaches the edge where the holes meet.
- Curved tube: flexible stem, cable, pull-through brush, or a system that uses fluid flow.
- Stepped bore: a tapered or multi-diameter brush section.
- Threaded port: diameter and fill chosen to reach the thread root without damaging the crest.
Which fill for which residue and surface?
| Residue | Surface | Fill |
|---|---|---|
| Dust and chips | Metal, plastic, glass | Fine nylon, PBT, horsehair, or a brush used with air |
| Oil film | Metal or plastic | PA612, PBT or polypropylene, with detergent flowing |
| Carbon and baked residue | Hard-wearing metal | Stainless, carbon steel, brass or abrasive nylon |
| Rust and scale | Steel | Carbon steel, stainless or coarse abrasive nylon |
| Light burrs | Machined bore or cross hole | Abrasive nylon, grit chosen for the edge radius you want |
| Delicate polished channel | Glass, coated metal, medical or plastic device | Fine polymer fill and a protected tip |
Which stem, tip and connector?
A single stem suits small diameters and hand cleaning. A double stem adds torsional strength for denser powered brushes. A loop end is for pulling the brush through by hand; a cut stem goes into a drill or collet; a thread joins rods, flexible shafts and tube-cleaning machines. The tip, whether fan, radial, tied or protected, decides how the brush enters and how it meets the bottom.
What are the limits?
Never force a brush through a sharp bend or a narrowed port. Too small a brush leaves bands untouched; too large a brush folds over, jams or breaks its stem. Long unsupported stems whip at speed, so use guides or a flexible shaft, or slow down, once the stem is longer than it can run steadily.
How do you check the result?
Look at the whole circumference, the bottom, the ports and the thread roots. Record the number of passes, fluid, speed, brush wear, trapped debris, surface finish and any broken filament. In production, give operators a go/no-go gauge or a brush marked with its size, so nobody swaps in a smaller one.
