Takisawa MAC-V1E Contaminated bearings, a damaged tool holder & a crash



CHALLENGE

Takisawa MAC-V1E, 6,000 RPM, permanent grease bearing lubrication, belt driven Contaminated bearings, a damaged tool holder & a crash. We usually ask our customer to send us a tool holder with their milling spindles. What we are really looking for is their retention knob (aka pull stud.) It’s just easier to ask for a tool holder because the two components are typically already assembled to one another. We ask for the customer’s retention knob because we aren’t just swapping out spindle bearings, we are performing a comprehensive analysis and rebuild of each spindle we receive at our facility. Despite having a large collection of tool holders and a variety of specialty tool gaging equipment, we can never expect to have every retention knob configuration available on the market. If we use one of our own retention knobs to check your tool retention force (incoming or outgoing), or to insure that the drawbar is actuating correctly, we will not get the same results as we would using your particular knob. When we examined this 1990’s era CNC drill/tap milling spindle on arrival, we noticed that the ID of the tooling taper was worn with some damaged areas. At our request, the customer had provided a retention knob attached to a tool holder which was scarred by a number of deep gouges. Add to that the severely damaged drive dogs, and it was easy to see that not only had the spindle been crashed, but that the customer had been beating up the spindle taper by continuing to use the damaged tool holder(s). Finally, on disassembly we found that the grease in the spindle bearings had been seriously degraded by contamination with coolant.  

SOLUTION

Our first step in this rebuild was to kiss grind the tooling taper ID (the wear & damage were not bad enough to warrant a full grind/plate/grind). We also manufactured a new set of drive dogs for installation onto the spindle shaft. We then reassembled the spindle with all new bearings, Bellevilles & assembly screws, setting the proper bearing preload & testing for proper drawbar function. Finally, we test ran the spindle for six hours to break in the new bearing grease while recording the thermal & vibration characteristics.

DETAILED CAUSE OF FAILURE

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