A jig grinder is designed for grinding difficult holes and shapes that need the highest levels of accuracy and finish. It is similar to the jig borer, wherein the spindles and table positioning are very accurate (more accurate than a manual milling machine).
A jig grinder is often used by tool and die makers in making jigs and pegs on dies. There are a lot of peripheral elements to a big jig grinder, such as separate hydraulic motors, various cooling and air compressors. It works by means of a fast air spindle revolving a grinding bit.
The air spindles are interchangeable and removable to attain variable surface speeds. Some spindles are adjustable speed (30,000 up to 50,000 rpm), others are fixed speed (60,000 rpm). You can also find spindles with very high speed (175,000 rpm).
A standard X-Y table is found in most machines but some have knee travel. The indices of the axes is .0001″ through a vernier scale, with better accuracy available by means of measuring bars.
The head of the machine has 2 vertical travels, one precise spindle adjustment and the other a rough head adjustment.
The spindle where the removable air spindle is fitted also revolves at a variable speed and can normally outfeed .100″ while operating, with an accuracy of .0001″ or greater on the handwheel.
A jig grinder that is well maintained will dependably position work to a higher level of accuracy than if you only had the handwheels. These features are very important in positioning a peg and hole system at a specific distance from a reference edge.
The most crucial consideration for a jig grinder is the dual-spindle structure. The main spindle is approximately located between 1″ to 2″ of travel while the .100″ of outfeed is utilized during use of the machine outfeed into the work.
You may make use of a spacer bar between the main spindle and grinder, allowing large work (9 inch radius or more) to be accomplished. The main spindle has a lot of speed options to ensure that the appropriate rates for grinder feed are achieved.
Grinding tools and machines function with the help of abrasive wheels, running at high speeds. The sparks, flying debris and other hazards trigger concern for the user’s safety. So in line with this, it’s helpful to know some basic safety guidelines:
Know what you’re doing. Do not use the machine when tired, sleepy or under the influence of drugs, meds and alcohol.
Never use the machine wearing loose clothes or jewelry as they could get stuck in the machine causing not only damage to the machine but also injury to the operator.
Check if the machine is switched off before plugging it to a power outlet.
Maintain proper footing and balance when working so you can have good control of the machine.
Wear safety gear including goggles, protective gloves and even a face shield if possible. Other people going near the machine should wear protective gear too.
Make sure you have a proper guard to protect you when broken fragments and spark come flying to your direction.
It’s vital that you let the machine run first before working, so as to warm it up.
Do not exceed the manufacturer’s recommended speed. Wheels running past the recommended speed can fly apart, triggering damage and injury.
What are The Functions of Grinders?
There are three basic types of grinders:
Pedestal or bench grinders are grinding tools utilizing 2 wheels instead of just a single one. Used for forming or sharpening tools, smoothing surfaces that are rough, they are important in any type of roughing or finishing process.
Belt grinders are usually needed in processes that work with metals that have coated abrasives. This machine operates just like a belt sander except that it is used for metal instead of wood.
Hand grinders are transportable tools that are fitted with a moving grinding wheel. These machines are used for smoothing, cutting, and shaping objects. Examples of portable grinding tools are jig, surface, and cylindrical grinders.
Bench Grinder Safety
It is necessary to inspect grinders and safety guards prior to operating the machines. Chips and cracks can trigger the grinder wheel to fall apart during use. You should also have a machine guard.
Do not adjust a workpiece while operating the machine. Moreover, you should never walk away if your grinder is running. You will need a tool rest to steady the workpiece.
Other safety precautions include following specifications in the proper placement of the workpiece. Check signs of gaps between the tool rest and wheel as well as ensuring that the grinder is safely held together.
Hand Grinder Safety
Regulations for grinders, are listed in the OSHA Standards 1926.303 for hand and power tool safety. Since the hand grinder is not fastened to a pedestal or bench, it is considered a power tool.
If you are using a hand grinder, be warned that you should use the correct tool and only use tools that are in good condition.
Flying particles of metal and similar fragments are just some of the hazards of using this tool, along with burns and electric shock.
For the most part, dangers can be avoided by ensuring you follow the instruction manual and keeping your machine in good condition.
You should also inspect your portable grinder before use, so you can check for signs of damage and if each component is securely in place.
Personal Protective Equipment
When using a grinder, you need to wear the proper PPE. A clear face shield or safety goggles are needed to protect the face and eyes. Leather welding gloves also come in handy to protect your hands. You can wear ear muffs and other hearing protection device as well.
It’s vital that you know the safety rules before using a jig grinder. Doing so ensures you and others around you are safe, and that your machine won’t get damaged from mis-use.