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Sawing of rocks:

(Copyright 2005 Allen’s Treasure House)

 

Rocks are ordinarily sawn with a circular diamond-edged blade in a machine which typically holds a coolant. Common rock sawing falls in 2 main types: Slabbing and trimming. Slabbing refers to the reduction of a large rough rock into slices which are practical for subsequent work. (In this category we can also include the cutting of faces on large rocks in preparation to use them as bookends or bases). Trimming refers to the rough=cutting around a design drawn onto a slab of rock, in preparation for grinding it to a desired shape. We distinguish between these two types of sawing because the machines for them are somewhat different. The slabbing saw typically uses a large (10 inch diameter or more) blade and a vise having a screw crossfeed and a self-propelled carriage into which the rock is mounted. The trim saw typically uses a smaller blade and usually has no vise, or if it does have a vise, the vise is manually operated and may lack a screw crossfeed.

 

 Small lapidary saw.

 

In either kind of saw, most blades require that a coolant be used also. The type of coolant needed is determined by the type of blade and also the machine specifications. Common blades and machines should be run with a light cutting oil (see blade instructions) only, or may be run in water solution if a suitable concentrate is added. Other types of blades can be run in plain water, and still others can be run dry.  (Not surprisingly, the water or dry blades tend to be more expensive. Nevertheless, there are reasons for using them: some gem materials are degraded when impregnated with oil; and others might be damaged by water also. Water (or no coolant at all) cleans up much more readily, and presents much less of a disposal/pollution issue.

 

If using water as a coolant, it is important that both the blade and machine be compatible with water. Many machines will rust badly if water is used in them. These problems can in many cases be mitigated or eliminated by combining the water with a rust-inhibiting concentrate designed for cutting, but even so you should check the instructions of both the blade and machine before proceeding. In many cases you will be instructed to drain the machine after using it this way, keeping it dry when not in use.

 

The coolant in most saws is simply the tank in which the blade spins partially submerged. The coolant remains in the machine at all times (unless intentionally removed).

 

Before beginning to use a new diamond blade, please read the instructions as to such matters as the preliminary dressing many blades require, or they will not cut!

 

There exist high-speed machines and high-feedrate machines, which require the use of special blades designed for such use. These are of interest mainly to commercial users.

 

Cabochon cutting:

(Copyright 2005 Allen’s Treasure House)

 

A cabochon is a dome-topped gemstone. This is a very versatile form, for it admits of not only ovals and round profiles, but also hearts, crosses, and other unusual shapes. Cabochons lend themselves to being hung on chains via any of several fittings, or being set in custom made silverwork, or being glued to a fitting such as a bola slide, or onto a surface such as a carved wood box.

 

Cabochons are made by sawing off a slice of rock (such slices can often be purchased ready-cut), drawing the desired profile onto it, perhaps with the aid of a pattern or standard template, roughly sawing out the section of rock to be used, then grinding the rock to the indicated profile. This is followed by rough-doming on the coarse wheel, then refining and smoothing the shape on a sanding wheel, then bringing it to a dull gloss on the prepolish wheel, and finally to a brilliant shine on the final polish wheel. (Some stonecutters prefer using additional steps, but this is largely a matter of personal preference or for specialized work; for most work it is not needed.)



The LU-6X cabochon machine.
The LU-6X cabochon machine.


Grinding and sanding operations using conventional abrasives are normally done wet for cooling purposes and also to control dust. The cooling water for grinding and sanding, unlike for sawing, is not retained in the machine, but is brought in by hose or other device, and sprayed on the wheels from an external system. The machines feature hook-up ports or fittings for such plumbing, but the user may choose the water system most satisfactory. The most common water systems are these: Direct hose from house plumbing, hose from portable overhead tank, recirculating pump in tank under table, under-wheel air-driven fountain, and hand-held spray bottle.  Drainage is by hose to any suitable receptacle, location, or recirculating system (sewer not recommended; rock slurry tends to plug sewer pipes).

 

Grinding and polishing can be accomplished also using diamond dust. Diamond-dust setups, like their conventional counterparts, grind, sand, and polish all in one unit; however the number of wheels is greater (typically having 6 wheels), and these setups cost more than conventional setups. However, the performance and durability is much better, and these machines are preferred for serious workloads and commercial production.

 

In earlier times, sawing, grinding, sanding and polishing were accomplished on separate machines. Today, a single machine can do all steps.  Or, some lapidarists prefer a separate saw, with all subsequent grinding and polishing in a single machine; or do not do their own sawing, and need only grinding, sanding, and polishing.

 

 

We normally stock the following sawing and grinding equipment:

 

Name

Wheel size               

Functions

Remarks

Rock Rascal J

6 inches

Trim saw

Optional vise; probably the least expensive such unit on the market.

Rock Rascal T

6 inches

Trim saw, grind, sand, polish.

Probably the least expensive such unit on the market. Optional vise; Compact; Comes with blade, 1 conventional grindstone, and a half-face endplate for sanding and polishing disks. Adequate for all ordinary-size gemstones. Requires external motor (except complete model) and cooling setup of user’s choice.

Lortone LU-6X complete lapidary machine.

6 inches

Trim-saw, grind, sand, and polish.

In one unit, includes saw, grindstone, sanding drum, full-face sanding-polishing endplate. Complete unit comes with motor, blade, wheels, vise, saw hood, and an assortment of accessories. (Requires separate coolant arrangement of user’s choice.) Can accept other standard 6  inch wheels.

Lortone TS8 saw

8 inch

Trim saw

Optional vise; optional clear plastic hood.


Other sizes and machines, including slabbing saws up to 18 inch blades, and 6-wheel arbor machines, are available by special order.

Grindstones 6 and 8 inch diameter; and Standard diamond blades 6, 8, and 10 inch diameter; are regularly stocked. Others can be had by special order.

We also stock cooling water equipment of various types.


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