Custom Spring Brushes

It is a bore brush with a spring in it. In one form, the fill is wound in a spiral around a helical spring core, so the whole head flexes. In another, a length of coiled spring joins an ordinary brush head to a handle, rod or drill, and the spring does the bending. A third form uses a compressible radial section that squeezes down through a narrow point and opens again behind it.

In each case the spring does two jobs. It carries push, pull or rotation down to the head, and it lets the brush body follow a bend instead of jamming in it. A plain twisted-wire stem can do the first job but kinks if it is forced round a tight bend too often.

The rule of thumb: if you have already bent or broken stems in a passage, a spring section is the fix.

One product is listed, made to order: the spring brush, spiral-wound for bores, tubes, threads and shafts, in diameters from about 3.2 to 50.8 mm, from 100 pieces per design. For curved pipes and flues there is also the flexible rod brush, a twisted-wire brush on a flexible rod, which is listed with the tube brushes. Other sizes and lengths are built to the passage.

• Spring: stainless steel, usually 304, so it does not rust in wet passages and keeps its spring after bending.
• Fill: stainless wire for scale and hard deposits; nylon or PBT for wet and dry cleaning; flagged polyester for fine dust and lint; abrasive nylon for internal finishing.
• Ends: a threaded end for rods and extensions, a loop or handle for hand use, or a shank for a drill. A rounded or tufted tip leads the brush into bends.
• Sizes: brush diameter, head length and spring length are set by the passage. A typical head is around 40 mm across and 300 mm long, but small bores take far smaller heads.

Start from the tightest part of the path, not the widest. The head diameter is set near the bore to wipe, a little over it to scrub, with less oversize for wire fill. The spring length has to cover the bend, so the head is always pulled or pushed by spring, not by a rigid stem. Measure the minimum bend radius: a tight bend needs a shorter head and a softer spring. Where the bore narrows, the compressible section has to squeeze through the narrow point without folding the fill over.

Feed it in steadily and let the spring find the bend; forcing it bunches the coils. Push and pull is the normal motion. On a drill, run it slowly so the spring does not whip against the pipe, and keep it moving so it does not wear one spot. Pull it back and check the size if it starts to stick. Rinse or blow it out after use, so deposits do not set in the coils.

• The full path: bore diameters, length, bends and the tightest bend radius.
• Where you can reach it from, and any narrow point or obstruction.
• The pipe material and the deposit.
• Hand, rod or drill drive, and the end connection.
• Fill preference and the quantity per design.