Spindle Identification

The spindle experts at PDS want to keep your production running at peak efficiency. This information is designed to educate and enhance your process. The spindle nameplate identifies your spindle by serial number, model number, rated speed, motor and operating specifications. If you need service or have questions about your spindle, call PDS at +49 (0) 5221 / 69 44 00. Please have the serial and model number available to identify your spindle.

Spindle Repair Application Data
Spindle RPM and Feed Rate Calculations/Chip Load Formula

To optimize chip removal, the rotating speed to the cutting tool and the linear axis speed that the tool moves must be balanced to maximize metal removal, machine performance, and cutting-tool performance. Following is background information to help maximize machining performance.

Spindle Speed

Incorrect spindle speed is a common error in CNC machining. Each material type and type of cut has an ideal tool profile and cutting speed. Larger diameter tools require slower cutting speeds. The spindle speed and feed rate for a given cut must be balanced for best work quality, tool life and spindle life. A frequency inverter controls the speed of the spindle. All spindles are 3-phase asynchronous motors with infinitely variable speed from 0 rpm to the maximum rated rpm. The speed can be achieved by correctly programming your frequency inverter drive to match the spindle.

Feed Speed

The feed rate of the cutting tool must be proportional to the spindle speed is set. A change in any of these parameters causes a change in the other. To reduce low feed speeds, the tool life as a result Overheating. This can also to cause burn marks on the workpiece. A slow moving tool builds heat, because there is not enough Material is removed to cool the interface. The best Feed rate is based on experience and systematic Try to Obtain the best results. The table listed with feed speeds for possible areas of Start values. In the case of Initial start-up you should start in the middle area. Your Tool Supplier can you Cutting data for Your specific Application recommend.

Chip Load

Chip Load is a term used to describe the thickness of a chip removed by one cutting edge of the tool. Chip load is sometimes referred to as “feed per tooth”. The chip load — radial depth of cut of the cutting tool in one revolution — is calculated as follows:

Chip Load = Feed Rate ( Ipm ) ÷ ( Cutting Rpm X Number Of Cutting Edges )

The head and the chip thickness is a factor, with the starting value for Cutting speed (rpm) and feed rate can be determined during the initial setup. In the case of wood is a low-head chip thickness leads to Overheatingthe generated shavings and dust are "similar" and can leave burn marks on the workpiece. In case of high head, the chip thickness and the cutting pushed to the tool through the Material. As a result, high radial loads acting on the spindle bearings, which in the course of time to a failure of the Spindle, excessive tool wear and tool failure can result. There are two Methods: constant velocity and counter-run milling. Woodworking the obtained Machining better results with less Tear-out. Some are also of the opinion that as a result, the tool life is increased.

Chip load is one of many factors used to size the spindle and determine machine requirements such as:

  • Speed range and required power of the spindle
  • Tool load for the determination of the type and quality of the cutting tools
  • The strength of the torque generated for the implementation of the section

We strongly encourage you to consult PDS on new spindle applications to assist in establishing your baseline cutting values. Our staff is here to discuss your technical questions by phone or email. The chart below provides chip-load values for common router tools. These are “not to exceed” starting point values for first-time setups. Actual values will vary as a result of many machine factors such as: rigidity, horsepower, collet condition, spindle integrity, part clamping, hold down, and others.

Spindle Repair Application Data Chip Load

Spindle Repair Application Data Feed Rate

Cutter Entry Angle (Plunge Angle)

Cutter Entry Angle (Plunge Angle)

The approach angle that the cutting tool feeds to depth is referred to as Cutter Entry Angle. This angle creates radial and axial stress on the machine spindle and the cutting tool during the material removal process. The following information provides background to help determine base-line starting values for your setup.

For Milling Operations designed high-speed electric spindles are equipped with Bearings, the high speeds to allow numbers and radial loads are resistant (editing page). To optimize performance and service life of the spindle bearings, should loads, the axial Cutting at a low level remain. One way to do this to select low tool insertion angle from 0º to 20º from table (in the case of vertical spindles). A low angle allows for higher feed speeds – for most applications, up to 100 % of the calculated values. The workpiece requires a steep angle of entry, must be the speed of the feed be reduced in order to reduce the axial load, thus, the Spindle bearings take no damage. Various insertion angles can be read from the in-feed/plunge angle table. When using a low angle of dip of the axial forces are minimized, thus reducing the bearings have a longer service life. In all cases, a "collision" of the spindle with the table, other crops and avoid the workpiece. PDS special spindles for applications where steep angle with high axial loads are necessary. You can contact the PDS application group for details and recommendations.

Spindle Repair Application Data Plunge Angle

Spindle Cooling Methods

Spindle Cooling Methods

Electric spindles are cooled by three primary methods: fan, compressed air and chilled liquid. The more efficient methods allow for higher power ratings, longer duty cycles, smaller packages, and more severe applications. The type of spindle cooling is selected as an option and is specific to the spindle model.

Fan cooling

In spindles with electric fan this is electrical Blower at the rear of the spindle. The fan provides a constant air flow and heat dissipation, regardless of the spindle speed and whether it runs or stands (not rotated). The electric blower is quiet, affordable, and the most common cooling method.

Compressed Air Cooled

Compressed air cooled spindles are machined from a solid aluminum billet or tube. This housing style provides increased stiffness and vibration dampening. The high degree of cooling is achieved by directing compressed air to dissipate heat from the rotor and stator. Compressed air cooled spindles are designed for applications involving high duty cycles and harsh environments. The amount of air consumption varies by spindle size and design.

Chilled Liquid Cooled

Chilled liquid cooled spindles are designed for use with an auxiliary closed loop chiller system. Liquid cooled spindles are machined from a solid aluminum billet or tube. This housing style provides increased stiffness and vibration dampening. The high degree of cooling is achieved by the flow of chilled liquid to dissipate heat. Liquid cooled spindles, which deliver higher performance, are used in high-power applications, high-duty cycles and harsh environments.

Tool Clamping Types

Tool Clamping Types

Basically, there are two types of spindles: Manual Tool Change Spindles and automatic tool change spindles. The spindle type is selected depending on the application and size of the tools for the application.

Manual Tool Change

Electric spindles with manual tool change clamp the tool/cutter using a spring collet in the taper of the spindle shaft. This method offers excellent rigidity at a low cost. The disadvantage is that tool setup is done online, with the machine usually out of cycle for about two or three minutes each change.

Automatic Tool Change

Electric spindles equipped with automatic tool change (ATC) can be integrated with a CNC for quick tool changes without manual intervention. Typical tool change times are less than 5 seconds. On applications requiring multiple cutters, an ATC spindle offers higher productivity. With an ATC spindle tools/cutters are pre-set in tool holders. Tool holders are typically clamped in the electric spindle by a spring loaded clamping system. Tool holders are released by compressing retention springs and opening the clamping system (typically with a pneumatic actuator). Pre-setting tools occurs off-line using jigs for accuracy and without interrupting production.

ISO and HSK are the two most common tool holders used on CNC routers, robots and milling machines. ISO 30 is more popular than the smaller taper sizes ISO 25, 20 and 15. HSK 40, HSK 50 and HSK 63 tool holders provide better cutting accuracy and reliability. Their popularity is growing rapidly due to performance.

Spindle Repair Application Data Tool Clamping

Spindle Repair Application Data Tool Clamping

Spindle Maintenance and Service

Electric Spindle Service and Maintenance

A schedule of preventive maintenance will help keep your spindle operating at peak performance.


Spindle housing, blower and piping must be clean to ensure a free flow of cooling air. Cone of tools, cavities of the collets, waves and clamping pliers denatured alcohol to clean. The tools never lubricants or Oils to use. Dirty tools can to misalignment of the tools Unbalance, Slip of the tools and bad editingresults.

Warm Up

Electro-need spindles a warm-up phase, in order to provide optimal performance. Never a cold electric spindle under load run. To Warm up the spindle with a speed of 9,000 rpm for 10-15 minutes, or until the recording of the spindle bearing to reach a temperature of 36.6°C (human body temperature). During this warm-up phase, the stock footage and the spindle shaft can be reached by thermal Expansion constructive dimensions and bias voltages. A cold spindle is subjected to a load, this leads to premature failure of the bearing.

Extended Warm Up

If a spindle has been kept in stock for more than six months without rotation, it is imperative to perform an extended warm-up procedure before applying any load to the spindle. The table shows recommended warm-up times:

Cool Down

Allow cooling system (fan, compressed air or liquid) and bearing pressurization (if used) to run for 10 minutes after stopping work. This minimizes condensation and prevents contaminants from being drawn into the bearing cavities.


Keep tools sharp to reduce forces, heat and to maintain cut quality. Monitor increases in electric current to the spindle to detect loss of tool sharpness. Heat generated from tools can overheat bearing grease, evaporate its essential components and lessen bearing life. Maximum bearing temperature of bearing supports is 150º F. Excess heat will cause tool holders to jam in automatic tool change spindles. Be sure all spindle sensors operate properly to avoid damage.

CAUTIONAll electric spindles of PDS with ATC are only available for ISO or HSK tool holder is designed. BT tool holders are not interchangeable. It is only balanced tools and tool may be bracket used. All the tools must be balanced after Sharpening, re-emigrate. Non-balanced tools generated vibration, can quickly lead to the destruction of the bearings. Worn, scratched, or deformed tool holders and collets replace them with new ones to prevent a slipping of the tool and imbalance due to side impact. The normal lifespan of collets is Collet nuts to strongly attract, what leads to damage to the threads.

  1. V(1) – Spindle Voltage
  2. V(2) – Second spindle voltage (only for spindle with two voltages)
  3. Maximum voltage frequency (the beginning of the constant horsepower range)
  4. Maximum Frequency
  5. U/min (1) – the beginning of the constant power range (equivalent to #3)
  6. Maximum rpm Maximum spindle speed
  7. KW-Performance S1 ED
  8. PS of power at S1 ED
  9. Rated current at a certain voltage
  10. Serial number – usually to two Make
  11. Model number of the spindle (see Example)

The example below shows details of the spindle model number structure. In some cases, the nameplate will show only a portion of the full part number and configuration. It is important to know configuration details to help identify your spindle and tool interface when you contact PDS.

Question About Spindle Repairs?

Our trained spindle experts are available to help solve your production challenges.

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Oststrasse 68
32051 Herford
+49 (0) 5221 / 69 44 00 +49 (0) 5221 / 69 44 029

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