Bearings rumble at high RPM

[RSG]

Before I go to the place that I bought my new mill from I wanted to ask a question here pertaining to bearing noise. Once the head warms up the top bearing (at least I think it is) begins to rumble and rather loud around 3400 - 4000 RPM. I don't recall this happening to my other mills but they weren't capable of achieving those RPMs and I've never had a vari-drive before. When I dis-engage the drive and turn the machine on the noise goes away completely. Is this normal?

Thanks for the advice in advance.

RG

[RMinMN]

Two causes I can think of are lack of lubrication and a chipped roller. It might be easy to add a little grease to the bearing to see if the rumble goes away but I really think you will be replacing the bearing.

[GlennW]

I had use of a vari drie Bridgeport once and it was noisy.

Also had a friend that was one of those older guys that had been a machinist all of his life (you know the type...) and he always said that he much preferred a step pulley mill to a vari drive due to the noise.

[RSG]

Thanks for the replies. I had the vendor over the other day to look into it. Turns out it wasn't a bearing but the rack sticking. He pointed to a grease nipple hidden up under the back of the top end, that until now I didn't know existed. A squirt of grease and the noise was gone.

[Harold_V]

I had use of a vari drie Bridgeport once and it was noisy.

True.

Also had a friend that was one of those older guys that had been a machinist all of his life (you know the type...) and he always said that he much preferred a step pulley mill to a vari drive due to the noise.

I dunno! I've owned both types, and as far as function is concerned, putting up with the vari-drive noise is a small price to pay to gain variable speed, but, more importantly, higher spindle speeds. It's been too long for me to remember the top speed of the step pulley BP machine, but it's in the vicinity of only 2,800 rpm, while the vari-drive allows for 4,100. For guys who do a lot of small work, or run small fly cutters, that increased speed is very desirable. It's safe for me to say that half the time I run my BP, it's at top speed. I do a lot of fly cutting.

H