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What Type of Machine Should You Choose?
Machines and Equipment
There are many different kinds of machines and equipment available to the stone restoration contractor. The type of machine needed will be determined by whether you will be dealing with a floor, a wall or a countertop. Let’s start with the machines available to grind, hone and polish stone floors.
Machines and Equipment for Floors
To grind, hone and polish a stone floor there are several makes of machines available, but they can be classified into three main groups:
- Traditional Italian floor grinding machines that could have one or more rotating heads.
- Mono-rotary floor machines a.k.a swing floor machines.
- Planetary machines.
- Another machine that’s been rather successfully adapted to do stone and concrete floors is the so called “walk-behind scrubber” or automatic scrubbing machine.
No matter which type of machine one chooses; the general design requirements for the best results must be:
- Grinding: the machine in its whole must be totally rigid. No floating heads, no rubber padding. To level (grind) a stone floor, there must not be one single element of the machine that will give. This requirement must be met to avoid “rounding” of the lips and/or rippling of the stone surface that could occur with class C and D marbles and travertine or in the case of floors mixed with stones of different degrees of hardness.
- Honing: once again a rigid machine would always be better, but in the case of the honing of non-ground marble or travertine floors with lippage within industry standards (1/32”), some rubber padding could be acceptable. Floating heads could be acceptable also, without rubber padding. Floating heads without rubber padding could create visible imperfections on the floor surface even with resin-bond synthetic diamond pads.
- Polishing: there is no issue. With the planetary machines, polishing with powders is virtually impossible because of both the inherent deign of the machine itself and, the typical high-speed of the planetary heads (600-800 RPM or more). With the mono-rotary machines, the polishing is usually done with either a nylon polishing pad or a natural fiber polishing pad typically ¾” thick. With the traditional floor grinding machines, the polishing can only be performed on perfectly flat (ground) floors by using polishing “stones” (manmade hard blocks of polishing compounds, like 5X and such).
Traditional Italian Floor Grinding Machines
By today’s standards, a traditional Italian floor-grinding machine may be considered obsolete, but it’s still the favorite piece of equipment in many countries with an old stone culture where marble and granite floors are still installed with unsurpassed method dubbed “grind-in-place”. They still perform quite well and, in the hands of trained craftsmen, deliver results that are hard to match. These machines come in different sizes which span form one-head, to several heads, and even ride on “monsters”.
The only advantage of a traditional floor-grinding machine is an excellent final product which, as said before, is hard to match.The disadvantages are many, especially in relation to residential work. The machine is designed to grind a floor (three-step procedure), not to just hone and polish it (two-step procedure). In fact, it can’t tolerate even the slightest lip. The grinding elements (man-made “stones” in different grits made of silicon carbide and aluminum oxide) grab the stock quite strongly and therefore, require an amount of water for lubrication purposes that’s many times the requirement of planetary and mono-rotary machines operating on the synthetic diamond technology. The adoption of late of grinding and honing elements based upon the synthetic diamonds technology somehow mitigated the water requirements.
Mono-Rotary Floor Machines
They are an all-around, ubiquitous piece of equipment that can do just about every grinding/refinishing job on marble, granite and any other stone floor.
To process stone efficiently however, a mono-rotary machine must meet certain requirements:
- Motor: at least 1.5 HP
- RPM: no more than 175. 140 to 150 RPM is better
- Weight: at least 110 lbs. or a machine that starts out at less than that but is designed to bear additional weight as applied to it without burning the motor or drawing excessive amps (no more than 14).
The ideal mono-rotary floor machine should have 3-4 HP (which will require 220 volt) and weigh in at 130 lbs. with the possibility of bearing additional weights. The diameter can vary according with the size of the job at hand however, the most popular size is 17”-18”.The advantage of a mono-rotary machine over a planetary one is that with it one can do everything: grinding, honing, and polishing.The disadvantage is that the grinding and honing are done at a pace that is far slower than a planetary machine. In particular, the first grinding cut does not have the accuracy typical of a planetary machine either (but this only applies if the comparison is made between a mono-rotary floor machine and a rigid planetary machine).
A planetary machine is a machine with an electric motor driving a main plate to which typically there are attached three counter-rotating heads, driven by belts or other suitable devices. The counter-rotating heads are those that hold the grinding and honing elements, typically synthetic diamond pads.
They come in different sizes that can range from 17” diameter overall with 4” diameter counter-rotating heads, to 21”-24” with 7”-8” counter-rotating heads, all the way to 500 lbs. plus behemoths with a working path on or around 30”.
The average planetary machine (21”-24” with 7”-8” counter-rotating heads) usually holds three 3” diameter synthetic diamond pads on each head.
As a group, these machines perform best at grinding and honing, but they just can’t polish with the commonly available polishing powders. The design of the machine itself is not suitable to the task, plus the speed of the counter-rotating heads- typically on around 600-800 RPM- is way too high. Once again, the rating as best grinding performers is given exclusively to rigid planetary machine; planetary machines with floating heads, and rubber padding would not make the rating.
Which types of machines to choose?
It depends on the size of the company one has, its financial resources, and the typical kind of work (size) the company’s involved in.However, the beginner should consider starting out with a good-quality 110 V. 17”-18; mono-rotary floor machine engineered to do stone work. The more powerful the motor is, the better. No matter in which direction the company will go and the size that it will reach, such a basic piece of equipment will never be obsolete and it will always represent an ubiquitous daily work-horse. There are certain mono-rotary floor machines that offer the possibility to attach a separated planetary accessory, which is connected to the machine without the need of any tools, as if it were a pad holder or a brush. Such an accessory absorbs a lot of amps; however, it may damage the motor in the long run, and/or trigger the electric breakers with such a frequency that it just can’t handle such an accessory.