Harbor Freight Instructions


Harbor Freight Tumbler Instructions

Harbor Freight tumblers made by Chicago Electric directions will help you operate your single or dual barrel machines. These models both use 3 pound rotary barrels and the directions for abrasive measurements and steps are the same.

Success Key is Observation and Adaptation

In similarity to other rotary models you will generally be following  the most common instructions for general rock tumbling in Rotary Tumblers. Many variations can be found in regard to tumbling instructions that make adjustments for different tumbling equipment and different types of rocks. The most important tips are standard. Your tumbler manufacturer may have specific instructions for your tumbler. Presented here are general guidelines and the most common consensus on tumbling methods. You might find the rock hardness information helpful on the Mohs Scale reference.

We Offer a Pre-measured Grit Solution

Be sure to see our grit kit designed specifically for Harbor Freight tumblers.
If your tumbler says "Chicago Electric" on it, all of these instructions and specifications will apply the same.

If You are Tumbling Rocks Start with Good Rock Selection

The tumbling process starts with good rock selection. Pick rocks that are of the same hardness and similar size ratio (the biggest should be no more than twice the smallest) to coordinate their development in the tumbling process. Gather enough rocks to fill your barrel between 2/3 and 3/4 full. Avoid using unusually odd and non-rounded shaped rocks with the more common rounded shapes as these will be more difficult to sculpt.

Single Barrel VS Dual Barrel

The instructions here apply to each bar that you are using. You can have totally different stages of tumbling in each of the barrels. Meaning you could be on step one in barrel A, and step three in barrel by. Just keep a track of which barrel is which, left or right.

Four Step Process for Rocks

Rotary tumblers use a four step goal oriented tumbling process:

  1. Coarse Grind
  2. Medium Grind
  3. Pre-polish
  4. Polish

Between each of the four steps remove, thoroughly rinse your rocks, clean out the barrel and remove any grit or rock debris. This is really important as the coarser grits from one step will act adversely in proceeding steps,scratching rocks as you are refining them with finer media. As always, it is advised not to throw used grit down a drain as plumbing will be damaged. Use a bucket and a screen to collect used grit and slurry.

Step One (Coarse Grind)

The goal of this step is for all surfaces of your rocks to be well-rounded.Place rocks in the tumbler and add the 60/90 silicon carbide grit. You are looking to round your rocks in this step over 7 to 10 days. The Grit to rock ratio here is 2 tablespoons of grit per pound per pound of rock. Add water until it is just below your top layer of rocks. Seal the barrel and invert it to check for leaks. Once the tumbling starts watch for a few minutes to be sure there are no leaks. Proceed with tumbling, and at the early days if this step, check daily on the progress by opening and inspecting the barrel. If the barrel appears to physically swell, open it to vent the buildup of gas which may naturally occur, be prepared with safety glasses and precautions for that. You can also add a teaspoon of baking soda to prevent gases.  Examine  your rocks and slurry (the grit and water now mixed with some rock trailings). If it seems thick enough to impede the smooth tumbling of your rocks, thin it with a small amount of water.  Some of the rocks may be now too small or too odd to continue working with them, so you will remove these rocks. As for the rest, once you see rounding has occurred for most or all of your rocks this move on to step 2.

Step Two (Final Grind)

In this step your purpose is to conclude the shaping process to your satisfaction. You will be removing and declensions and pitting that may have been present after step one.This step usually takes 7 to 10 days also. You have already removed rocks that are not responding sufficiently or have evolved to an unattractive shape. Put your cleaned rocks in the barrel again, add a 120/220 silicon carbide grit in the same proportions as in Step One – 2 tablespoons per pound of load. Add water up to the bottom of the top layer of rocks and, if you had any problem with gas buildup last time, add a pinch of baking soda. Seal and tumble as before. Your slurry should be a little thinner than in the last step varying with the softness or fragility of  materials your are processing. Your goal again in this step is to see that all the scratches from the first step are ground away,  and the rocks have a smooth, matte finish. Using a magnifying glass may help check for smoothness.

Step Three (Pre-polish)


In this step the goal is to make the rocks extremely smooth. As always start as with Steps One and Two, put cleaned rocks in the cleaned and fresh barrel to make a full load. Use a pre-polish of either silicon carbide 500 or aluminum oxide 500 for this step, about  1 tablespoon per pound of load, and then add water up to the bottom of the top layer of rock. Tumble time here is up to 7 days, with more checking slurry consistency and general progress every day or two. You may be pulling some of the rocks out earlier than others as they will become smooth sooner and even show some luster.  For softer rocks, you may need to do a second pre-polish step or just keep them in a little longer. At the end of this step it is most crucial to really clean the rocks and barrel which will be more difficult as you are using a finer grit. This is so important because any grit can ruin the progress of your rocks in the final polish step.

Step Four (Polish)

By this time your rocks are looking pretty good and ready for that lasting final shine. You have been extra diligent on cleaning the rocks and barrel. Place your rocks in the tumbler and add Aluminum Oxide Polish, about 1 tablespoon per pound of rock.  Step four takes up to seven days but be sure to check the rocks as you are proceeding because some will be finished earlier. The best check for completed rocks is that they look as now as they would if wet. Once that is the case you are done with this step. One final detail, its best to clean up now by cleaning your equipment thoroughly before everything dries and encrusts. So you'll be ready for your next project with rock tumbling.

Tumbler Tasks

If you are using your tumbler to burnish metal or polish brass, or any type of metal cleaning, we have instructions for that process. If you are interested in any other functionality and usage for your tumbler we have some other ideas

In addition to the instructions above, it may be beneficial and interesting to see our section on the Science of Rock Tumbling. This is a behind the scenes look at the technical and scientific foundations of the rock tumbling process.