With milling cutters there is quite a lot to know for proper machining. You need to know the types of cutters for specific cuts, do you need a Woodruff key-cutter or a T-slot? Maybe you need a two lip end mill to do the job. While we don’t have the space in this article to go into a comprehensive list, today we are going to go into some basic information such as types of milling cutters, how to select them, proper care, and safety. Let’s discuss some basics about milling and milling equipment!
What is milling?
So, what exactly is milling? Well, milling is a process where a cutter is employed in order to remove material from the surface of an piece which you are working on. The cutters which are involved are typically made of high grade steel and come in a variety of shapes and sizes depending on the results which you are try to achieve with them.
Types of milling cutters
The cutters in question are many and varied and most often used in milling machine but there are other types of equipment which may employ them as well. Some examples of the types of cutters used in milling machines are as follows:
- Ball mill cutter - Also known as ‘ball nosed cutters’, these are hemispherical in their shape and they are used for cutting 3-dimensional shapes.
- Dovetail cutter – Dovetail cutters are used to create angled grooves with which to fit parts together.
- Fly cutter – A fly cutter is a single-point cutter that looks rather like a T-shape, with one end pointed, and is used for creating involutes in gear teeth.
- Hobbing cutter – This type of cutter is used in a machine called a ‘hobber’ and is designed for cutting gears, sprockets, and splines in a flat cylinder of metal.
- Hollow mill - A hollow milling cutter looks like a pipe which is smooth on the outside but has the cutting teeth on the inside.
- Involute gear cutter – Like the hobbing cutter, this is used for cutting gears in their involute form.
Selection of milling cutters
When it comes to selecting a milling cutter, there are some rules to keep in mind that can help to make things a little easier. Some important factors to keep in mind are as follows:
- Size – When you are selecting your cutter you should try to find one which can do the job in one pass. If you cannot, keep in mind that a smaller diameter cutter can traverse the surface plane more quickly and may be better suited for the job.
- Heat resistance – If the material that is being worked is higher on the hardness scale you will generate more heat during the cut. Be sure that your cutter is heat resistant enough for what you are doing.
- Production speed – Cemented, steel, and satellite high-speed rated cutters can get the job done faster in the proper milling machine.
- Is it a specialized cut? – Not all cuts will required a specialized milling machine and cutter, make sure you don’t already have a cutter that will do the job.
- Fine vs. Coarse – A Coarse-tooth cutter is designed for the roughing portions while the fine-tooth variety should be used for detail and finishing.
Proper care of milling cutters
When it comes to taking care of your milling cutters there are some good rules which you can follow that can help to extend the life of your tools as well as to help to keep them safer for use. A few good rules are as follows:
- Oiling – Before you store away or use your cutter you will want to make sure that the machine has been properly cleaned and oiled. Failure to do this will greatly reduce the life and efficacy of your machine.
- Watch the vise – Always be careful to ensure that the cutter never contacts the vise. This may seem like common sense but can happen quite easily if you are not being proactive.
- Store carefully – If you have to store cutters close together then you will want to make sure that the cutting edges are not touching. It is much better if you can adopt a system with hanging pegs or other mediums with which to ensure separation to avoid accidentally damaging your cutters.
- Faster is not better – High speed means more friction and a resulting higher heat. Use at the recommended speeds to avoid wearing your cutter down prematurely.
- Do not use it backwards – This will cause too much friction due to the clearance angle and can break your cutter. Don’t do it.
- Keep it sharp – Separate your dull cutters for future grinding, you only want to use the sharp ones. Using a dull cutter requires more energy, generates more friction, and is a bad idea in general. Keep your cutters sharp.
Don’t forget safety
These machines are powerful and dangerous, so be sure to follow the proper safety procedures when using them. For instance, don’t forget splashguards when adding cutting oil, as this can make it
“Hold milling cutters with rags when you are changing them”
dangerous for you or for the next person operating the machinery. Hold milling cutters with rags when you are changing them out to keep things safe. Always use a rake or a brush when you are removing chips from a cutter. You know the drill, never be too relaxed with these machines, keep things productive and safe!
In this article we’ve described some of the cutters that you might encounter in milling, what kind of cuts they make, how to select a proper cutter, caring for them, and more. While there is quite a lot to cover we hope that this has given you a taste of the information that you will soon be digesting as you explore and practice milling for yourself. Machining is a vital art and the expertise required is great but with a bit of time and practice you will be milling like a pro!