# Bridgeport knee squeal



## DMO (Jan 10, 2012)

On two separate Bridgeport series-1 mills that I have operated I have sometimes experienced a high-pitched ringing-squeal when rapidly lowering the knee. If you start fast it would sqeal, then you could keep it squealing even moving pretty slow. I was never able to figure aout the ultimate cause for this, nor could I get any help from the Bridgeport company. This happening on two separate machines for me makes me think others might know about it too. Anyone know what's causing this?
Dave


----------



## Tony Wells (Jan 10, 2012)

You're hearing a harmonic of the oscillations created by the knee dropping on it's ways and catching up to the screw suspending it. The screw turning allows space to form between it and the nut, then the knee falls to meet it, and the process repeats.


----------



## DMO (Jan 10, 2012)

That would support why it always sounded so much like a ringing. I wonder if improved lubrication somewhere would stop that, like if the lock is too dry and dragging too much? It just seemed like a bad thing whenever it happened.
Dave


----------



## 8ntsane (Jan 10, 2012)

So, does that mean his knee is sticking at bit? Maybe gib too tight, or the ways are in need of oil?

I nave heard a simular noise on a buddys mill, and it reminded me of car brakes that had a vibration/sqeele

Paul


----------



## Tony Wells (Jan 10, 2012)

I suppose one way of looking at it would be as stick/release......and a bit of oil would have an effect on it. I don't believe it is doing any damage, but it can be annoying. I have heard it many times.


----------



## pdentrem (Jan 10, 2012)

The BP at work does it mostly on lifting the knee. Oil or grease has had no effect to date.


----------



## Kennyd (Jan 10, 2012)

My BP knee squeals like a stuck pig sometimes while going down.  The previous owner said it never did it for him:thinking: Course I had the knee off to move it...


----------



## randyjaco (Jan 10, 2012)

I have mine (a BP clone) set up to run up and down via a 1/2 inch drill. If I run the drill too fast mine will squeal too. I hate the sound and have wondered if it really did any harm. But I hate the sound so much that I seldom let it squeal.

Randy


----------



## DMO (Jan 12, 2012)

Thanks everyone. I am relieved (sort of) that I'm not the only one this happens to. I distinctly remember the tech at Bridgeport implying that this never happens. And it really didn't help when I mentioned the this ALWAYS happened when operating the knee feed in rapid traverse. From then on his response to every other question I had was "The Bridgeport knee was never designed to be run with power feed", and that's when I wrote him off. But he still would not speak to the fact that I could produce it on a manual crank too.

I don't remember if it ever happened going up though. That would seem to be a little different.
Dave


----------



## Video_man (Jan 12, 2012)

I don't know if it helps, but my Grizzly knee mill started doing that. Lubing the vertical v-ways and the screw didn't help, so I took the
 crank off, pulled out a couple of parts in the crank assembly, and shot some 20-weight oil inside. So far (6 months) it seems to have fixed the problem....:thinking:


----------

