What Are the Pros and Cons of Coolant vs. Mechanically Driven Heads?
Every product has advantages and disadvantages in terms of its suitability for a given application.
Mechanical heads and fluid driven heads are really so different that they probably shouldn't be compared.
Mechanical heads have been around a long time and fair or not have earned a reputation more as a necessary evil than as a desirable tool to have in your shop. No one buys a mechanical head because they are great to machine with. They have historically been a tool of last resort. Because of the obvious similarities it is easy to paint a fluid driven head with the same brush.
We believe fluid driven heads are most often a better choice or we would also be making mechanical heads. There are however applications where mechanical heads are an appropriate choice.
Mechanically driven angle heads, because they are driven by the machining centers spindle, have the ability to develop more torque and horsepower than do coolant driven heads. They also do not require that the machine be equipped with a high pressure coolant system. Mechanical heads tend to be larger, bulkier, require installation of a stop block and may or may not go though your tool changer. They cannot be indexed where multi-position machining is required.
Coolant driven heads tend to be more compact, fast, and rigid as compared to bearing mounted mechanical heads. They are also indexable for multi-position machining. Because they are cooled by the fluid even at very high speeds they can be operated continuously. Mechanical heads are most often limited to 6 minutes per hour especially at high speeds.
The below chart is a quick reference to compare the features we will discuss here in more detail.
Mechanical vs Titespot Comparision
|Requires high pressure coolant.||No||Yes|
|Requires stop block||Yes||No|
|Duty Cycle||6 min / hr.||Continuous|
|Indexable for multiple radial positions||No||Yes|
|Max Spindle Speed||6,000||36,000|
|Go-through tool changer||Maybe||Yes|
Mechanical heads in general have an advantage when brute force needs to be applied. A quick look at the Angle Heads Performance page will tell you the maximum power you can expect from your fluid driven head based on your coolant systems pressure and flow. Our tools are rated up to 2000 PSI138 Bar and 14,500 RPM. Theoretically they could develop over 8 horsepower6 Kilowatts, in practice, however, they are almost always limited to applications requiring 2 horsepower1.86 Kilowatts or less.
If your application requires more than 2.5 horsepower1.86 Kilowatts you are likely going to be happier with the more powerful mechanical head where possible.
If other issues such as indexability or compactness require a fluid driven head be employed often a different approach is required. For example, circular interpolation of a large hole instead of a large drill. This is not to suggest that a fluid driven head is a toy. We have successfully drilled 1/2"13 MM diameter holes through 2"50 MM of heat treated 4140. You can see other typical applications in our case histories.
Mechanical heads are usually limited to about 4500 RPM. Fluid heads are rated to 14,500 RPM. In our testing we actually ran a head at 20,000 RPM for 24 hours. We decided to rate the head at 14,500 because at that speed the life curve was much more favorable. After 100 continuous hours the motor still passed the specifcations for a new motor. For small drills, high finish requirements and machining aluminum, getting sufficient surface speed can be very important.
So which to choose? At each end of the spectrum: if access to the cut is not a consideration, the application is "heavy duty", say a 1/2"12.7 MM hole in inconel and the machining center or lathe is not equipped with a high pressure coolant system, a mechanically driven head is probably the best choice.
If, on the other hand, access is limited, torque and power requirements, say 2.5 horsepower1.85 Kw or less, are reasonable and multi-position machining is to be performed on a machine equipped with a high pressure coolant system, a coolant driven head would certainly appear to be the best choice.
Anything in between? Give us a call with the details, and we will always give you our honest opinion.
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