I have a 1990's vintage Taiwanese clone of a Bridgeport varispeed milling machine (Chen Ho).
Over the past few months I have noticed a number of things:
- The spindle has been getting more and more noisy, particularly when using heavier cutters. Not so noticable on light cuts or plastics.
- There is a lot of nose when changing direction in a cut, it will seem to settle in ok over time but then as it goes round a curve, or other change of direction it suddenly goes very loud and clattery and the finish goes completely.
I checked the runout today inside the taper section of the spindle (R8) and there appears to be about 2 thou of runout but this isnt even, there is a definite sharp movement somewhere in the rotation, every turn or so.
By the time I have a tool in a toolholder in the spindle, the runout is getting nearer to 3 thou than 2 even if I fiddle with locations on the toolholder to try to cancel out some of the runout.
My assumption here is that as a minimum, the spindle bearings are shot.
Does this sound like the case to others on the forum or am I missing something here ?
To get an idea of the racket, here is a link to a short video clip I took this afternoon. As the cutter gets toward the boss sticking out on the lower left side of the part, the noise goes way up, it sounds a bit like re-cutting chips in a slot but that isnt the case, the aur keeps the work area nicely clear. Once the cutter swings past the problem direction, it can be heard to be settling back into normal cutting.
Noisy spindle cutting pocket video by koiboi_2007 - Photobucket
This is a 22mm 3 tip Alphamill cutter low carbon steel plate, 1650RPM, 250MM/Min feed and 1mm depth of cut, 4mm width (<20% cutter engagement).
I'm pretty sure, the cut is not an unreasonable ask on a machine this size in fact the feed is backed off a long way (40%) from the manufaturers anticipated minimum for the tool to keep the noise down.
Is it worth attempting to put new bearings in myself or is this strictly for the professional spindle servicing companies out there ?
Any thoughts here would be appreciated.