What are Cup Saws and how do they work?

In a previous article we presented the cup saws in general terms and we describe its components, as well as the advantages and disadvantages of these tools.

Now we are going to deepen the topic by focusing on the applications of the cup saws and in some advice practical when choosing and working with them.

Parameters that define cup saws

First of all, we must point out that in trade we will find different types of cup saws that are distinguished by a code of each manufacturer. That code can be made up of numbers and / or letters, and encompasses a particular tool intended for a particular use.

Let’s look at some of the parameters that determine that particular use.

1) Material with which they are made

As we mentioned in the previous article, the cup saws most common are bimetallic with body of alloy steel Y high speed steel teeth, but we can also find saws whose teeth contain tungsten carbide grains or diamond, either in the cutting edges or all over the tooth.

2) Speed

Not all cup saws they operate at the same speed, measured in revolutions per minute (rpm). This depends fundamentally on the diameter of the tool, which can be offered in metric or imperial measurements, and the material to cut. The smaller the diameter, the faster they should rotate. On the other hand, to cut, for example, wood and plastic requires a number of revolutions approximately 10 times higher than to cut steel, while saws that cut aluminum rotate about three times faster than those that cut stainless steel. That is why it is advisable to use cup saws on drills with variable speed.

The table below shows the recommended speeds (in rpm) for some materials depending on the type and of the diameters (the less and the higher) of the cup saws:

3) Material and thickness of workpiece

The cup saws they are designed according to the material to be cut. Thus, for example, we have, on the one hand, saws for carbon steel and alloys, stainless steel, non-ferrous materials and wood; on the other hand, saw blades, cellular metals, interrupted cuts and electrical panels; we also have saws for ABS, wood, fiberglass and other non-metallic materials; and finally, saws for ceramics, marble, granite, glass, resins and formica.

4) Drill to use in cutting

Hand drills, and especially hand drills wireless, no They are usually fast enough to reach that recommended by the saw manufacturer. Therefore, there are some cup saws specially designed for cordless drills. It is important to also take into account the diameter of the chuck of the drill to select the correct size saw.

5) Step type

The He passed of saw teeth is measured in number of teeth per centimeter or inch. When the distance between teeth is constant around the entire perimeter of the saw, we say that it is a regular pitch saw or constant. This step is ideal for cutting solid materials on cutting machines with efficient clamping and is very effective on high-alloy steels, brass, aluminum, copper, and wood.

When the sierra presents groups of different tooth pitch, which are repeated at regular intervals along the length of the saw, we say that it is a variable pitch saw or dimmable. This concept is intended to reduce vibration and resonance during cutting, speeding up the cutting process and extending the life of the saw. Typical applications for variable teeth are cutting thin-walled and materials in groups or bundles with little clamping, especially steels, stainless steels and bronze.

Taking into account these parameters that we have just seen, we can prepare an indicative table like the one that follows, where the main applications that respond to them are detailed.

How to use cup saws

Once we have chosen the saw according to the work we want to do and the manufacturer’s instructions, a series of steps should be followed to ensure excellent drilling. Although these steps may vary depending on the work piece (for example, drilling a door to install a lock is not the same as drilling a ceiling to install, for example, a light fixture) in general they comprise the following procedure:

1. With a pencil we draw a circle in the place where we want to make the perforation and we mark the center of the circle.
2. We insert the pilot bit in the drill and we tighten it firmly so that it does not come loose during the rotary movement.
3. We assemble the cup saw on the shaft that passes through the end of the shank through the opening in the bottom of the saw. The pilot drill should protrude 0.63-0.95 cm from the teeth of the cup saw.
4. We install in the drill the cup saw already assembled. The end of the shank is placed in the chuck of the drill and we tighten well.
5. We plug in the drill and align the pilot bit with the center of the circle marked at point 1.
6. We operate the drill, keeping the hand steady and perpendicular to the work surface. The piercing should not be done in one go. It is advisable to apply light pressure, drill part of the hole and then remove the saw. We repeat this procedure as many times as necessary until the hole is completely drilled. In this way we reduce the friction of the saw and extend its useful life, in addition to preventing a chipped hole from forming in the material.

Some tips for using cup saws

It is also useful to take into account some recommendations that will help us to get the best out of our tool. Among them we can highlight the following:

• Above all, it is essential to follow the usual safety rules, such as wearing protective glasses, suitable clothing and collecting long hair.
• The manufacturer’s instructions are essential, therefore we must respect them and follow them carefully.
• We should not rush to make the cut, but let the saw do its job. If we perceive the presence of smoke, it is because we are working too fast or with a worn saw.
• Whenever we remove the saw from the material to continue drilling again, we must remove the chips or debris. This will prevent the holes in the saw from becoming clogged with these residues. In general, multipurpose cup saws They incorporate grooves in their body to facilitate the exit of the waste.
• If the button of perforated material remains attached to the saw, we extract it with a screwdriver or chisel.
• When cutting most metals (except cast iron) and ceramics it is recommended to use oil or coolant.
• If we must cut tempered steels, vitrified ceramics or aggregate materials that contain concrete, it is better to use a saw with diamond grains (or diamond), which will offer a longer service life.
• Do not use cordless drills with cup saws, since not having enough power, your engine can burn out. To do this, we must take into account that some manufacturers offer cup saws for exclusive use in cordless drills, so it is advisable to purchase this type of saw if we cannot use another drill.

The video that follows shows some types of cup saws offered by the Starrett firm and its main applications.