Rattley Head....

[SCzEngrgGroup]

I have a (very nice) Chi-wanese step-pulley BP clone that has a rattle in the head. I've had it apart more times than I can count, and am stumped. All bearings are tight, nothing seems at all wrong anywhere. The rattle occurs primarily when doing side-milling with 2-flute EMs, or when coasting down to rest from high speed (I run up to 8200 RPM on the spindle). I've removed the toothed belt, to ensure the noise can't be coming from the backgears. So, I'm down to only two possibilities I can see - either the dog drive, or the splines between the spindle and bull gear. It does seem to lessen if I pack grease into the spindle bore, which suggests the splines are the problem. Anyone have any ideas what I can do about this, other than getting a new bullgear and spindle, and hoping for a better fit? Any other possible noise sources I should be aware of?

BTW - Since the machine is CNC'd, the head has been pretty much stripped of all non-essentials - the quill drive and all quill pinion hardware have been removed.

Regards,
Ray L.

[Jackal66]

Ray,

I have a friend that had the same problem with a Birmingham mill.

It was about 2 years old when it got loud enough they replaced some parts in the head.

He got the supplier to warranty it after a lot of fussing & fighting.

His wasn't CNC, just a variable pulley. 4000 RPM max.

He did some of the same diagnostic work that you did.

JAckal

[SCzEngrgGroup]

Jackal,

Do you know what parts they replaced? Fortunately, parts prices seem pretty reasonable, but I still don't want to replace parts without having a high probability it will actually solve the problem. It does seem to be getting worse over time.

I've also thought about trying to put some kind of damper between the splines, since the noise seems to be triggered by vibration....

Regards,
Ray L.

[Jackal66]

Ray,

I don't know exactly. But they did replace a bearing and the vari-drive pulley and chain that adjusted it. They may have broken the pulley, while disassembling it.

A month or so later, the went in and put a new shaft somewhere?????

Sorry, wish I new more. That was in 2002 and he has moved away since then.

JAckal

PS They did do a little modifying/machining to the replacement shaft to make it fit. The repair guy said that some of the Birmingham parts don't always interchange 100%

[SCzEngrgGroup]

Ah, sounds like maybe his problem was in the Vari-Drive. Mine is a step-pulley machine, and there ain't no functional shafts left anywhere - just the spindle, quill, dog clutch and pulleys. Everything else has been either removed or disconnected.

Regards,
Ray L.

[Gundawg]

Do you have slop in a key way on the shaft holding one or 2 pulleys on?

[Idahoan]

Hi Ray

I have been down this road before with my 1887 Acra mill. There were several things wrong; first the bore in the cast aluminum belt drive cover that carries the upper pulley was too large. The tension from the drive belt would pull the dog clutch out of alignment which was the major source of the noise; the tighter the belt the worse the noise.

I re-bored the housing on my friend’s mill to clean it up and get it square with the base flange. Then more work: I bought a chunk of cast iron and machined a new upper bearing carrier that properly fit the new bore.

The next problem was the Chinese don't believe in preloaded bearings! Both the upper pulley set and the bull gear set are common off the shelf bearings and not preloaded. This causes the dog clutch to not stay in proper mesh.

I replaced the bearings with high quality standard ball bearings and then made shims to preload both sets of bearings. I understand that Bridgeport uses special bearings that are ground for proper preload when assembled.

My mill is now very quiet and the noisiest thing was the back gear drive belt; because I'm using a VFD and pretty much never use the back gear any more, I removed the belt.

It used to really get on my nerves but now it is a pleasure to use.

Also make sure your dog clutch is fully engaging; when in direct drive there should be some slop in the shifting collar. If not you may need to file the end of the ramps so the lift pins have some clearance.

Hope this helps,
Dave

[SCzEngrgGroup]

Dave,

My problem actually was the splines simply rattling due to vibrations setup by the cutting tool. The noise could be mitigated by carefully aligning everything, but it could not be eliminated. I finally came up with a simple, and very effective solution. I basically machined a spacer that goes on the head of the drawbar that consists of the Nylon sleeve with an O-ring in it. The sleeve basically keeps the drawbar, and hence the splined spindle shaft, perfectly centered in the bore. The O-ring is compressed enough to drag on the bore, acting as a damper, so when the cutting forces try to cause vibration that rattles the spines, the O-ring damps it out. The result has been a blissfully silent machine for several months now. The best part is it was a very simple solution, taking only about an hour to fab the parts.

Regards.