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Any advice on pressurizing (grinding) spindle?

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PekkaNF:
This got me thinking...
http://madmodder.net/index.php/topic,12170.msg144823.html#msg144823

Has anybody made/mod. pressurized spindle?

Many spindles have ZZ non contact seals for low friction, not that great against abrasives. RS would seal whole lot better, but sucks on high rpm.

https://image.slidesharecdn.com/1-141227035803-conversion-gate02/95/11-bearing-types-and-appl-guidelines-17-638.jpg?cb=1419674474

Traditional way would be to use labyrinth or such and use over pressure to block contamination route into bearings. To construct that on existing spindle demands bit more head skratching.

So, what are other choices? Haven't got into microns yet, but is it a good idea to pressurize plenum between two ZZ seal ball bearings - idea being that some air is expelled from bearing seal annulus and hopefully that would expel dirt coming into that way. It would need a flinger at the front of it stop direct spray.

I see here few problems, but is that serious?
1: Small annulus on ZZ seal - translates to low flow and small cleaning -> put a simrit ring next to it?
2: Pressure pops out seals -> lower pressure.
3: Dirty air contaminates bearings -> best to avoid getting that trough bearing, but that was the whole idea here->filter the crap out of pressurized air.

Completely stupid idea or has some merit?

Thank you.

Pekka

philf:
Pekka,

What size of bearing are you thinking about?

A 10mm X 26mm OD rubber sealed bearing is good for 30,000 rpm.

I don't like the idea of pressurising between the bearings - there's a risk of forcing out the grease which you wouldn't want and, as you say, there's a risk of blowing dirt or moisture in.

Standard deep groove bearings are cheap enough to consider them as consumable.

Phil.

PekkaNF:
There are two 6002 Z bearings on front. 15x32x9 mm and one smaller bearing on rear.
http://www.skf.com/uk/products/bearings-units-housings/ball-bearings/deep-groove-ball-bearings/deep-groove-ball-bearings/index.html?designation=6002-Z

Spindle is from 900 to 6000 rpm, speed vice fine with RS, but it will rob some power, the spindle is only 250 w.

Will dump the trough purge/lube idea and change the bearings....everything seems to be glued, staring from set screw, to bell housing.

Pekka

philf:
Pekka,

I'm sure with a 250W motor you'll be fine.

My grinding spindle for the lathe has 15 X 24 X 5 2RS bearings and only has an 1/8hp (90W) motor and it still has enough power to grind.

Phil.

PekkaNF:
Thank you Phil,

What rpm is your grings spindle? Any pictures?

Some rubber selas are pretty stifs some have very little friction, some will ease pretty fast.

This is pretty slow speed drill/mill spindle and here it was used to true wobbly diamond wheel.

Got three opening sticks from loval shop to open diamond wheels, two are ment to be used wet but one is intended to be used white, it is weird, feels like heat shied foam!

There is one stubborn set screw, 2,5 mm hex key is loose, 7/64" and 3,0 mm does to fit!


Pekka

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