A top roller is a steel core wrapped in glued leather 3-5 mm thick, pressed down on the fluted bottom roller by a weight so that the yielding surface grips fiber without crushing it. Its faults are uneven cover thickness, which makes the nip pressure differ from one spindle to the next, and leather that sets flat or hardens, so check every nip by pulling a paper strip through it at the same load and reading a spring balance.
Part of Spinning Frame
Making, loading and maintaining the leather-covered pressure rollers that hold the fiber against the grooved bottom roller.
The Leather Must Give A Little, And Give The Same Everywhere
The overview describes top rollers as pressure rollers: steel cores covered with glued and wrapped leather, cover 3-5 mm thick, providing grip and a slightly yielding surface. The bottom roller sets the speed (Fluted Bottom Rollers); the top roller only follows it and holds the fiber in the nip. If the top roller slips, the strand is dragged at the wrong speed and the draft changes.
The overview does not say whether the top rollers are one long shaft or separate bosses. The design assumed here is one boss per spindle or pair, each with its own load (see Roller Weighting), so it follows small variations in the bottom roller. The roller diameter is the core plus two thicknesses of cover: for the overview’s 3-5 mm cover that is 6-10 mm more than the core.
Why Leather
Bare steel on grooved steel would crush the fiber and cut it. Leather conforms to the flutes, spreads the load and grips by friction. Leatherwork covers tanning; for rollers the quality that matters is even, firm leather of uniform thickness. The overview does not name a tannage, so test a sample for hardness and for how it takes glue before committing.
What You Need
- Steel cores turned true, with journals (Metal Turning).
- Leather of even thickness, an adhesive, and a way to hold the wrap under pressure while it sets.
- A lathe to turn and grind the cover true on its own journals.
- A spring balance and paper strips.
Method: Covering And Checking A Roller
Step 1: Cut the leather to wrap exactly once around the core with a butt or scarfed joint, not an overlap.
Step 2: Glue and wrap it tight, keep it under uniform pressure until set, and let it dry fully.
Step 3: Turn or grind the cover to a uniform diameter on the roller’s own journals. Cut shallow; leather tears if the tool is blunt.
Step 4: Test every nip. Close the weighted roller on a paper strip laid in the nip and pull the strip out with a spring balance at a steady rate. Record the force for every roller in the frame. The spread between rollers is the unevenness you will see in the yarn; this test is workshop practice, recalled, and the acceptable spread is not sourced, so set it from the evenness of your yarn.
Step 5: Re-test monthly and after any change in weather, since the leather takes up moisture.
Worked Example
The overview’s nip load is 5-15 N per cm of roller face. A boss 3 cm wide (an assumed width) carries 15-45 N, about 1.5-4.6 kg-force. If a strip pull reads 4 N at one spindle and 7 N at its neighbour, the grips differ by 7 ÷ 4 = 1.75 times, which is enough to give that neighbour a different draft and a different yarn.
Common Mistakes
- Leaving the weights on a stopped frame. The leather sets under the load and develops flats. Lift the weights when the frame stands idle for long (recalled practice).
- Oiling the cover, which makes it slip.
- A joint that rises above the surface, hammering once per turn.
- Replacing one cover and not re-gauging the nip.
Safety
Adhesives, hot glue and the nip
Hot animal glue scalds; keep it away from children and use a thermometer or double boiler. The finished roller is a nip that pulls in fingers, so keep hands clear while the frame runs and follow the stop procedure in Drive System. Leather dust from grinding is irritating; ventilate.
What’s Next
- Learn next: Roller Weighting — how the pressure is applied and adjusted
- Combine with: Roller Spacing and Gauging — the gauge between pairs