Archive for December, 2010

Can I Repair My Own Spindle?

Monday, December 20th, 2010

By Claude Valenze, General Manager High Speed Technologies, Inc.

Gages are calibrated before each job
Gages are calibrated before each job.

The short response to that question is “probably not”. It is true that machine shops make precision parts: they are used to working with tight tolerances and many have skilled and capable machinist. So why do they use a qualified spindle repair shop like High Speed Technologies (HST)? There are a number of very good reasons.

First, most modern machine shops work with tolerances in the range of +/- 0.013mm (0.0005”).  To repair a modern spindle that can consistently provide parts with that accuracy our tolerances are an order of magnitude tighter. Super Precision ABEC 7 spindle bearings have tolerances called out in the +/- a few microns. So the technicians at HST must consistently work in the micron range (0.001mm).

To provide those tolerances a climate controlled assembly area is required. When setting spacers our technicians must take into account that the heat from their hands can affect the dimensions of smaller gage bocks. Grinding and finishing of journals requires additional time for parts to reach thermal equilibrium. Spindles received from air delivery services may take many hours to reach room temperature before accurate measurements can be taken.

Hand lapped spacer
Hand lapped spacer +/- 2µm

Additionally, HST technicians have “bearing know-how”. They understand spindle bearing theory; why some are mounted “back to back”, “tandem”, with spacers and without. They understand lubrication requirements, journal fits and assembly procedures. They are experts at grinding and sizing spacers to achieve the correct critical required preload.  Our technicians handle and set your bearings with extraordinary care and precision. They know that one bad move can trash an expensive pair of spindle bearings.

HST technicians have “spindle know-how”. They understand how to set draw bar tension and actuator settings. With calibrated tension gages they will set your drawbar tension back to OEM specifications.

Setting drawbar tension on an HK63
Setting drawbar tension on an HK63

HST technicians have “balance know-how”. Vibration caused by spindle imbalance cannot be tolerated when machining precision parts. It affects part finish and spindle life span. At HST no spindle is shipped until it passes stringent balance and vibration testing.

Cost is another good reason to use a qualified spindle repair house like HST. When you consider that the bearings make up between 30% – 40% of the cost and other components up to 15% you are left with about 50% for labor and margin. So how much can you save by doing the spindle yourself; probably nothing. Spindle repair is our core business. That’s what we do.

When it comes to repairing spindles we recommend you don’t try this at home. Leave it to the trained professionals.