Cartridge Spindle Repair

Cartridge Spindle Repair – Free Inspection and Firm Quote

Cartridge spindles are very common in metalworking. They are usually mounted by bolts on the front bearing flange and are designed to drop out of the machine intact. They are commonly housed in a support with helical grooves on the outside for cooling. The may be belt driven or spider gear driven (direct drive). Some spindles are self driven and the electrical rotor is part of the assembly that drops out. Cartridge spindles usually do not exceed 12,000 rpm operating speed. These are typically CAT 30, 40 or 50 spindles for use in vertical and horizontal mills.

Inspection before Quote:

  • clamp force check and visual inspection of drawbar to check for bending and worn disc springs.
  • taper run-out, bearing journal run-out, centers run-out
  • shaft, spacers and housing for correct size and geometric tolerancing
  • shaft play in bearings

Firm Quote (doesn’t change – no surprises) to include shaft, spacer and housing regrind if necessary. Replacement bearings are made by GMN in Germany and have ABEC 7 precision. We offer different delivery dates based on our capacity and availability of parts. We offer expediting options and have worked thru the night to deliver a spindle the next day. We do everything in house. If the delivery date is not met, there is no expedite fee. All grinding work performed will yield run-outs of .0001″ or lower in the individual parts. Run-out of the assembled spindle not to exceed .00015″. If a guaranteed lower run-out is required, please let us know at the beginning of the repair and we will make sure the final assembly meets your requirement.

Warranty – Cartridge spindle comes with bearing break in procedure, temperature indicator and one year warranty. The cost of bearings is not covered. The labor for warranty work is free.

Important Information We Need from You:

  1. Are the bearings oil lubed or grease lubed?
  2. What type of pull stud you use? If possible, please send a tool with the spindle.
  3. What is the problem? How is the spindle performing compared to when it was new? Has the surface finish worsened? Is there excessive  heat or vibration?
  4. What is the most demanding job the spindle must perform: type of material cut, depth of cut. size of cutter, rpm, feed rate, etc?
  5. If you have an operators manual with a drawing and bill of material, please send a pdf file of the these to service@hsspindles.com.

This will help us select the right type of bearings and determine the rigidity required in the spindle.

All Spindles are Balanced to Grade 0.3 or Better

Balancing Machine

All spindles are balanced in two planes on our state of the art balancing stand. We can balance rotors up to 700 lbs.

Balancing is performed on all spindles regardless of operating speed. We take pride in our work and want to deliver the best product.

This step ensures the longest possible life of the bearings and will provide the smoothest surface finish possible. It can be the difference between a spindle running for one year or ten years. If you are local, we can come to your shop and measure the vibration. Ideally you want to see .1G for every 10,000 rpm of operating speed.

Our customers have often told us they can’t feel any vibration.  Probably won’t see them for a long time!





Taper Run-Out












Taper run-out is an accumulative feature affected  by other parts and how carefully the spindle was put back together. We strive to keep run-out below .0001″. This is called one ten thousandth of an inch or a “tenth”

Imagine splitting an inch into ten thousand pieces! But… to keep it under a “tenth”, everything else must be held in ten millionths of an inch or .000010″ We deal in ten millionths of an inch routinely, so it is not uncommon to see spindles completed with 50 millionths (.000050) run-out after assembly.

Run-out is important for good surface finish, high precision and low vibration. The better the run-out, the smoother the spindle will run. Run-out and vibration are the two keys for long bearing life and optimum spindle performance. Tooling will last longer also.

Here is a look into one of our previous cartridge spindle repairs

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