Rock tumbler noise: how loud it is and how to make it quieter

What the noise tells you: rattle, hum or squeak

Stand next to the tumbler and match the sound to a row. A new sound on a machine that used to run quietly points to the load or the drive, not the barrel material, so start with the rows on bangs, squeaks and belts.

Are rock tumblers loud? Decibel levels by type

RockTumbler.com measured ten tumblers with a digital sound meter at three feet. Rubber-barrel rotary machines came in lowest, at 55 to 64 dB. The two toy tumblers were the loudest rotary machines at 70 to 75 dB, which the site puts down to a plastic barrel and an inexpensive motor. Normal conversation is around 60 dB. So a rubber-barrel tumbler behind a closed door is background sound, and a toy tumbler on a kitchen counter is not.

Vibratory tumblers are not automatically quieter. The two in the same test span 61 to 74 dB. See rotary vs vibratory tumblers for the other differences.

Why is my rock tumbler so loud? Rattles and bangs

Rock-on-wall noise depends on the barrel and the load. Rubber absorbs the impact and hard plastic rings with it, which is why rubber barrels are quieter. You cannot change the barrel material, but the load is in your hands. Below half full, the stones are lifted and dropped instead of rolling, and each drop is a bang. Those drops also chip the stones.

Fill to about 2/3, mix small stones in with the large ones, and bring a short load up to level with ceramic media. On a tumbler with a speed dial, drop one setting: the right speed gives a steady rolling grind with no banging. The speed chart shows the rpm range for each barrel diameter.

Hum and vibration: the surface matters

A hum that carries through the house is the surface under the tumbler acting as a soundboard. Hollow shelves, cabinets, wooden tables and upstairs floors are the worst places. A concrete floor in a garage or basement is the best. Put a dense rubber or foam mat under the machine to break the contact, and check that all the feet sit flat so the frame does not buzz.

Note.Keep the mat clear of the motor vents, and make sure the tumbler cannot creep off the edge of a bench as it runs.

Why is my rock tumbler squeaking? How to oil it

A squeak or chirp in time with the rollers is a dry shaft bearing. The two roller shafts pass through a bearing or bushing at each end, four in all on most machines. The Lortone, Highland Park and Harbor Freight manuals all call for oiling them about once a month.

1. 1

   Unplug the tumbler and lift the barrel off so you can see where each roller shaft enters the frame. Most machines have 4 of these points.

2. 2

   Put 1 drop of lightweight machine oil on each bearing. Tilt the machine so the drop runs along the shaft into the bushing.

3. 3

   Turn the rollers by hand 4 or 5 times, then wipe away any oil left on the shafts or frame so it cannot reach the rollers.

4. 4

   Repeat every 30 days of running. Check the manual before oiling the motor: Lortone motors need no oil, while the Thumler's A-R1 motor has 2 oil ports that take 1 drop each per month.

Note.More oil is not better. Excess oil collects grit, and oil on the rollers makes the barrel slip.

How to make a rock tumbler quieter: fixes ranked by effect

Work down this list in order. The first two change the noise the most and the last two trim what is left. None of them means modifying the machine.

• First, location: a garage, basement or utility room with the door shut. A concrete floor carries the least hum.
• Second, a rubber barrel: rubber-barrel machines measure 6 to 20 dB below toy tumblers in the RockTumbler.com figures.
• Third, the load: about 2/3 full with mixed sizes or ceramic media, so the stones roll and do not drop.
• Fourth, a rubber or foam mat under the machine, so vibration does not reach the furniture.
• Fifth, a lined box around the tumbler, built with open ventilation for the motor.

Compare rubber-barrel hobby tumblers →

Rock tumbler quiet box: keep the motor ventilated

A box lined with foam or carpet cuts the clatter, but tumbler motors are air cooled. RockTumbler.com advises against simply putting a cardboard box over a tumbler, because the air under it heats up and the motor overheats. Never fully enclose the motor.

If you build a box, leave the motor side open or cut large openings low and high so air can pass through, and keep the lining away from the belt and rollers. After the first hour, feel the motor housing and the air inside. If the tumbler starts stopping and restarting, the thermal cutoff is tripping, so open the box up. See rock tumbler not turning for the other causes.

Quick answers

Short answers on tumbler noise. The decibel figures are the RockTumbler.com measurements at three feet quoted earlier on this page.

• Are rock tumblers loud? Rubber-barrel rotary tumblers run at about 55 to 64 dB at three feet, close to normal conversation. Toy tumblers with plastic barrels reach 70 to 75 dB.
• Why is my rock tumbler so loud? Usually a hard plastic barrel, a barrel under half full, or a speed setting that is too high. A new noise points to the belt or bearings.
• Why is my rock tumbler squeaking? A shaft bearing is dry. Put one drop of light oil on each bearing and repeat every 30 days of running.
• How do I make a rock tumbler quieter? Move it to a garage or basement, fill it to 2/3, put a mat under it, and add a ventilated box only as the last step.
• Is there a quiet rock tumbler? Rubber-barrel hobby machines are the quietest rotary type. No tumbler is silent, since rocks grind inside it for weeks.