Complete 2014 Catalog

USINGTUMBLINGABRASIVES

TUMBLING INFORMATION

The main principle in polishing stone is to start with a

coarse abrasive for grinding, and work through a series

of increasingly finer abrasives to the final polish. The

process is basically simple, but there are variations in

gemstone properties, types of abrasives, many recom-

mended grit (abrasive) sequences, and results produced

by the different types of tumblers. All these variations

and choices can be confusing, especially to a beginner,

so it should be remembered that tumbling is basically

simple, not an “exact science”, and can be great fun

once the basics are mastered.

The first choice to be made is the type of tumbler to

be used, Rotary or Vibratory. A brief description of

the two types is given on page 59. Further descriptions

can be found on the pages in this catalog listing the

tumblers themselves.

Both rotary and vibratory tumblers use the standard

silicon carbide grits with water in the mix as well as

a filler of some type. However, Vibra-Dry mixes can

be used in vibratory tumblers for the polishing steps,

and produce higher polishes on almost all stones and

metals. (See page 71.) Vibra-Dry mixes do not use

water, and can be re-used multiple times.

The beginner should be aware that some stones will

not polish in either type of tumbler nor with any grit

sequence. In order not to waste your time and money,

be selective. See section on “Selecting Stones”.

Over the years, individuals have developed procedures

and grit sequences that give them good results. As a

result, you will find that advice, books and manufac-

turer’s instructions vary in their recommendations. All

follow the basic principle of tumbling, but reading “Use

80 grit to start” in one source and “Use 60/90 to start”

in another is confusing. Both work, and there is actu-

ally little difference between those grit sizes. In fact,

most grit sizes that are used actually cover a range in

particle size. Finer grits and polishes are more closely

graded so that particle size is more uniform and so are

the results. Finer grits and polishes are more expensive.

Fillers are recommended for use in both types of

tumblers and in each step in almost all grit sequences.

Fillers soften the action, fill space between stones, and

carry the grit to the stone’s surface more efficiently.

Fillers generally can be reused if thoroughly cleaned

between grit sequences. We recommend the ceramic

bits for both stones and metals as they seem to do the

best job and will last longer.

It is important that you select stones that will polish

in order to be successful at tumble polishing. The

looks of rocks can be deceiving, but in general,

those with a hard surface and sometimes shiny

look to them, are likely to polish.

Stones with hardness of around 5 to 7

⁄

on the

Moh Scale of Hardness are best. This includes

the agates and jaspers which are the easiest to

polish. Softer and harder stones, and certain stones

such as Apache Tears and jade are special chal-

lenges, and require special procedures.

SELECTING STONES

MOH SCALE OF HARDNESS

1. Talc

6. Orthoclase

2. Gypsum

7. Quartz

3. Calcite

8. Topaz

4. Fluorite

9. Corundum

5. Apatite

10. Diamond

CRATCH TEST FOR HARDNESS

Use the simple field test below to identify the

relative hardness of a stone. Stones in the range

of 6.5 to 7.5 will usually polish well.

Fingernails scratch

2 to 2.5

Pennies scratch

Knife blades scratch

5.5

Window glass scratches

5.5

Steel files scratch

6.5

Garnet scratches

7 to 7.5

Carborundum scratches

9.5

ROCK FOR TUMBLING

Package contains assorted gemstonematerials of suit-

able size and hardness for tumbling. Mixed varieties,

sorry no choice. Stone size varies, but averages 1" in

diameter. Can be broken into smaller pieces if desired.

Approximately 2 lbs. per package.

403-TR-10............Shp. Wt. 2

⁄

lbs.................12.75