Monday, December 11, 2023

How to use a crown saw or crown saw?

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We recently published this technical article in reference to the Copa Saws also called, crown glasses or crown saws, depending on the country. There we gave detailed information related to manufacturing, components, parts, among other aspects. As a result, we have received several inquiries regarding utilization. There are many myths about how, when and for what should the glass saws be used. We will now try to answer the main queries, leaving open the possibility of supplementing with new technical articles dedicated to specific topics on the cup saws.

Bimetallic Cup Saw

How, when and for what should the glass saws be used??

This broad question encompasses a whole series of aspects that we will deal with below. 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 which are distinguished by an identification 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 see some of the parameters that determine the use or application:

1) Material with which they are made

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

2) Recommended speed of use for cup saws

Not all crown saws they operate at the same speed, measured in revolutions per minute (rpm). This depends fundamentally on the diameter of the saw, that can offer in metric or imperial measures, and of the material to cut. As a general rule, although not a fixed rule, the smaller the diameter of the saw cup, 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 in drills with variable speed, depending on the application, in bench drills.

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:

Recommended speeds RPM for cutting with cup saws

3) Which saw cup to choose based on the material and thickness of the workpiece?

Bimetallic Cup Saw for Wood

Bimetallic Cup Saw for Wood

The crown 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. In a future technical article we will delve into each of these models.

4) What drill to use depending on the saw cup?

The first thing to check with manual drills, and especially cordless ones, is whether they have enough speed to reach the speed recommended by the hole saw manufacturer. Therefore, there are some cup saws specially designed for cordless drills that run even at lower rpm. For more complex, more challenging cuts, for production and especially when using cup saws with carbide teeth, the use of the bench drill is recommended.

5) What is the “tooth pitch” in cup saws?

The He passed of the teeth of the crown or crown saws, 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 glass saw or steady pace. 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 steps, which are repeated at regular intervals along the length of the crown 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.

Types and Applications of Cup Saws

How to use cup saws?

Once we have chosen the goblet saw according to the job we want to do and the manufacturer’s instructions, a series of steps should be followed to ensure optimal 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 (also known as tree or bracket) 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, shaft or bracket 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 (usually has a thread) in the bracket of the cup saw already assembled. The end of the shank is placed in the chuck of the drill and adjusted just like a conventional bit.
  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 (to cool it). 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.
Bimetallic Cup Saw - metal cutting

Bimetallic Cup Saw – metal cutting

Some tips for the safe use of 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 follow the usual safety rulessuch as wearing protective goggles, appropriate clothing, and tying up 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 glass do its work. If we perceive the presence of smoke, it is because we are working too fast or with a worn saw.
    • Whenever we extract the crown 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, taking care not to hit the teeth of the saw cup.
    • 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 low speed cordless drills with cup saws, since not having enough power, your engine can be damaged. 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.

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