[Review] Thumlers Model B Heavy Duty Rotary Rock Tumbler 2024

Thumlers Tumbler Model B Heavy Duty Rotary Rock Tumbler Review

The Thumlers Model B rock tumbler is an all time favorite of ours – affectionately known as Big Red by those in a popular rock tumbling forum!

This is perhaps the top level rock tumbler which people in the hobby aspire to owning, due to its huge barrel and overall rock tumbling capacity.

The thumlers tumbler model b is used by enthusiasts all over the world once they are well and truly hooked on producing stunning gemstones and need that extra bulk to boost their hobby to the next level – which is often creating jewelry with their stones and selling it on either their own online store, or another platform.

With its robust barrels, this machine is often used to polish brass as well as being popular for lapidary. The winged nuts on the barrel lids ensure an adjustable tight and even fit all the way round, ensuring that there is no leakage of slurry during the tumbling process.

A rubber lining inside the standard barrels helps to keep the noise down – but as you can imagine, with a load this large – there is a lot more banging around inside and naturally more noise is produced.
One owner said that a wedge beneath the motor adds additional support and helps to align the drive belt, however this has not been established as a requirement by other users.


  • Bulk Bulk and More Bulk – at a whopping and versatile 15lb initial rough rock capacity, the thumlers model b is ideal for people moving up the trading ladder.
  • Smooth operation and easy to fit the lid – the screws really do offer peace of mind over the traditional screw on lids, or even the water stretched rubber ones which use boiling water to expand the lid allowing it to fit over the barrel – this then shrinks as the lid cools. No such hassle with a model b.
  • Spare thumlers model b parts are easily attainable due to the huge popularity of the brand.
  • There is always someone to ask online should you need any model b specific hints or advice.
  • When rock tumbling with a lower spec product, you will notice that many of the barrels are perfectly round in shape. With the thumlers tumbler b – they have shaped the barrels. What this means is that the rocks (or other contents) cannot simply slide back and forth on the bottom of a rotating barrel, which results in flat sections of the polished rocks forming – imagine an apple cut in half. One side is flat and this can be a major problem with rock tumbling as load volume diminishes as the media (grit) grinds away at the rough. The shaped barrels constantly “trip” the stones over each other creating an ideal wave action which in turn causes an even surface grind and polish.
  • Some people with the round barrels do overcome this though by sticking very hard wareing rubber strips on the inside, to flip the stones over as the barrel rotates.
  • For extra safety, there is a thermal switch which will cut out should the motor overheat.
  • Operating at 1550rpm (this is quite fast), 115 Volts, 1/30hp motor, it comes with a 1 year warranty on the motor and an impressive 5 year barrel and liner guarantee.
  • The size of the inner volume enables hobbyists to attempt larger samples than they would be able to do – one trick is to place one or two oversized pieces in surrounded by the usual (or smaller) sized chunks which act as slaves to work against the large specimens. We have seen some fantastic final works using this method in the model b.


  • From our perspective the only thing wrong with the model b is the fact that it gets dirty and doesn’t look as good as it did when first purchased! Take care when choosing as there are two versions with different speeds – the high speed is recommended for brass.

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