Shaft removal

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jcfx
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Shaft removal

Post by jcfx »

I've been slowly going over my new PM932pdf mill, vacuuming and rinsing out grinding dust,
I'm at a point where I want to rinse out the head cavity that the gears are in, apparently a shield on a
bearing "fell off" and it seemingly was run at the factory with the shield rattling around some gears.
That left quite a bit of swarf in the head.
I've taken out as many gears as I can but I'm sort of out of ideas on how to remove the three shafts that the
remaining gears are on.

The shafts have pressed on ball bearings at the bottom of the headstock case, the top ones were easy to get off
with a bearing puller, for the shaft and the bottom bearings my idea was to use a 5C collet in a collet block
gripping the shaft attached to a slide hammer to pop the shaft and bearing out.

Anyone have ideas for more elegant solution ?

pm932gear_shafts.jpg
John Hasler
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Re: Shaft removal

Post by John Hasler »

I'd rinse it out as-is. Perhaps rig a pump, hose, and nozzle and spray kerosene around inside. You could blow it out with air as well.
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SteveHGraham
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Re: Shaft removal

Post by SteveHGraham »

You could always go in there with a magnet. Microfiber is good for picking up dust and bits of junk.

I think it was a good idea to use a vacuum. It's funny; vacuuming is way smarter than blowing, but it seems like everyone is in love with the air gun.
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John Hasler
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Re: Shaft removal

Post by John Hasler »

An air blast knocks stuck-on stuff loose. Use air and vacuum together. A magnet is a good idea.

In fact, a magnet screwed down inside a gearbox is a good idea.
Milling along
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Re: Shaft removal

Post by Milling along »

I would worry about using a magnet. Normally metal chips fall to the bottom of the
gear box and hopefully get trapped in a corner. If a gear tooth gets magnetized it
may pickup some metal chips and keep recycling them in the gear teeth.

A magnetic plug is good because it catches the chips and never gets near the gears.
epanzella
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Re: Shaft removal

Post by epanzella »

There's no plate or access hole on the bottom? Usually you press bearing on or take them off by applying force to the inner race only so that there is no force on the bearing. The way this is described tapping the shaft in or using a sliding hammer to pull it out will apply the force to the inner race but it will be resisted by the outer race which is pressed into the case. The result is all the force used in removal and installation is born by the bearing itself. An unusual way for a unit to be designed.
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John Hasler
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Re: Shaft removal

Post by John Hasler »

epanzella wrote: Sun Mar 03, 2019 8:25 pm There's no plate or access hole on the bottom? Usually you press bearing on or take them off by applying force to the inner race only so that there is no force on the bearing. The way this is described tapping the shaft in or using a sliding hammer to pull it out will apply the force to the inner race but it will be resisted by the outer race which is pressed into the case. The result is all the force used in removal and installation is born by the bearing itself. An unusual way for a unit to be designed.
Good point.

Sometimes bearings are pressed into a pocket (applying force to the outer race) in such a way that they cannot be removed without destroying them, evidently on the assumption that if the bearing was still good you wouldn't want to remove it anyway.
spro
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Re: Shaft removal

Post by spro »

I think you nailed it, John. First it shouldn't have been this way. There shouldn't have been grit and chewed up shield with a new unit but there it is.
jcfx
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Re: Shaft removal

Post by jcfx »

*sigh* I agree with all the responses, without actually visiting the factory It's hard to say what conditions
the mill was assembled in, so far I've found grinding dust everywhere there is a moving part, including inside
the head, and now I'm debating whether to take the quill and spindle apart since the grease in the spindle bearings
look suspect, its a mix of amber and grayish black and I although I've never used moly grease I'm assuming it's jet black.

In regards to whether there are any access holes on the bottom, there are none, the head is oil filled so I guess the less
plugs to seal the holes the better to prevent oil leaks.

I think rather than flushing it with the shafts and lower bearings in place I'm going to proceed to try my slide hammer method
to get the shafts out.
John Hasler
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Re: Shaft removal

Post by John Hasler »

The slide hammer will probably destroy those bearings (or worse yet, not quite destroy them).
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Bill Shields
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Re: Shaft removal

Post by Bill Shields »

or they might be held in with Loctite!

bearings should be considered trash at this point and not worry about them.

If you are really progressive, you can plan on replacing bearings AND SHAFTS..
if you accept that...then getting the shafts out is quite easy.
grind flats on either side, clamp it and pull....
Too many things going on to bother listing them.
John Hasler
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Re: Shaft removal

Post by John Hasler »

Or you could just flush it out, put it back together, use it, and replace the bearings if they ever go bad.
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