Refurbishing Old Tool Holders

Rusted or corroded spindles on a CNC tool holder can be chrome-plated and reground. April 29, 2006

Question
We have recently purchased a used Heian CNC router. This machine uses BT35 tool holders. I have no experience in using this type of system. Any advice on the safe operation of these tool holders would be greatly appreciated.

Forum Responses
(CNC Forum)
From contributor A:
There is nothing different about these tool holders vs other types, such BT30, 40, ISO30 etc. There are 2 types of BT35's. One is a standard from Yukiwa, which cost more. The other is a standard, which takes and ER32 system collet. COURMATT markets both these. Check to see if there is any fretting or rough spot on the taper itself, and if there is, replace them. Clean the inside of the spindle and tool holder.



From contributor B:
A small word of caution - refer to spindle maintenance guidelines. When cleaning spindles (tool holder mating surfaces) itís usually a bad idea to use compressed air.


From the original questioner:
Thanks for the replies, the tool holders are new and are in great shape. However, the spindles have a significant amount of rust in them, where the taper of the tool holder would meet the spindle. What should I use to clean the spindles so I donít damage them?


From contributor C:
If your spindle tapers have a significant amount of rust in them, your tool holders will not be in good shape for long. The rust is probably a type of corrosion that indicates movement between the holder and taper. Poor taper geometry or poor retention pressure will cause this problem initially, but even if the taper did not start out distorted, it will end up that way. The ideal fix is to have the spindle tapers hard chrome plated and reground. While the spindle is torn down, it is a good idea to replace the Belville washers that provide the drawbar retention pressure. If you are absolutely sure that your retention pressure is where it should be, you can have the tapers reground on the machine by any of several services. Bear in mind that retention pressure needs to be checked after regrinding since regrinding will shift the gage line and thus change the pressure.

A good spindle rebuilder will be able to bring most router spindles back to new specifications and give you a warranty. Heian spindles in particular are quite robust and are usually good candidates for rebuild. Check out American Precision Spindles for rebuild work. If you opt for on site taper regrinds, they can also point you in the right direction.