Taper roller bearing removal ?

[jcfx]

Hi All,

I've been chasing a bad vibration butterfly this past week on my 5 yr old PM 932 mill,
I dropped the spindle in my attempt to isolate the vibration, and so far it seems to lead to
the motor. While I had it out I figured I would repack the bearings, they're tapered roller
bearings, the top bearing grease was black where as the bottom bearing grease looked new.

I've never taken apart a spindle that has opposing taper roller bearings, what would be the best procedure
to do this, press or hammer ?

attached pictures of the victim -

PM932 quill.jpeg (117.23 KiB) Viewed 2600 times

PM932 bottom bearing.jpeg (113.55 KiB) Viewed 2600 times

PM932 top bearing.jpeg (123.81 KiB) Viewed 2600 times

[Bill Shields]

Push the shaft out with a press

Never beat on a bearing or a precision shaft with a hammer unless the intent is to scrap both

[earlgo]

If they are like automotive wheel bearings I doubt if they are secured by any more than a very light press fit. I'd try tapping the spindle on the threaded end with the black grease, toward the lower end with the new grease. But that is just me and I have no experience with this or any type of mill.
Good luck.
--earlgo

[Steggy]

Usually the cone is a light press fit. Under no circumstances would I pound on a machine spindle to extract a bearing. Use a press or a bearing puller. You will also have to extract the bearing cup out of the machine, as both cone and cup need to be replaced as a pair.

[Rich_Carlstedt]

I do not know the mill, but have worked on many spindles
First, I do not know what grade bearings they used ?
But bearing come in sets and "precision bearings " are marked ---usually with a copper dot or some other notation.
It is very important that the dots MUST be set aligned , on both the cups and the cones
You can pull the cones out without removing the cups, so your concern is with the cones
I don't see any dots, so use some nail polish and put a red dot on the lower bearing close to the setscrew on the spindle
and do the same on the other bearing ( dot on the same orientation point) so
when you reassemble the spindle the dots will control orientation location....just in case they are precision bearings.

if you are replacing bearings, then a mallet to break it loose is fine, but if you wish to reuse the bearings, then a press is the way to go.
When using a mallet, the black bearing is the one that takes the blow. the lower bearing sees no force that could damage it

You also can flush the upper bearing in lacquer thinner or some other solvent and repack it
Rich

[wildcatter]

be aware that using a hammer on the end of any shaft will "mushroom " the end. use a press only.

[jcfx]

Thanks for all the replies, a press it is to get the bearings out.
The mill is a "Precision" Matthews mill, the bearings are marked but it's hard to see
let alone photograph, they're 30207 ( lower ) and 30206 ( upper ) and are a P5/ ABEC5 class bearing.
I have a local bearing supplier looking for them.

One thing that concerns me is earlgo and Steggy's note that they're a light press fit, examining the spindle there is just
a spanner nut and a weird looking keyed lockwasher, I would have expected a double nut , one for preloading
the other to act as a jam nut. I guess you gets whats you pay for !

When I loosened the spanner nut I expected to have a bulging forehead vein experience, but it
was not very tight. Did have a false start till I saw one of the fingers of the lock nut was bent over
into one of the slots of the spanner nut.

How does one determine preload for this type of tapered bearing arrangement ?

[rmac]

The mill is a "Precision" Matthews mill

Are you less than happy with that machine? Care to elaborate?

[Bill Shields]

The keyed lock washer is very common in cases where you preload with a torque wrench, then back off a specific amount then "tab it down".

Too tight (preload) and you cook the bearings.

That being said, once you break things loose, reassembly will most likely slide together with the top bearing being a light sliding fit on the shaft.

Precision is a very loosely used term...after all, how many machines would a company expect to sell under the term " medium quality"?

Seiki (Japanese for precision) is found in many non-japanese, non-precise machines.

[jcfx]

Are you less than happy with that machine? Care to elaborate?

A lot of my disenchantment stems from poor quality control, such as a table that is not flat it
has sporadic dips, which I have to keep in mind whenever I need to clamp work directly to the table.
Lots of manufacturing grit in the gear head this was a given considering other online accounts
of similar machines. A sealed bearing that was missing a shield and that the shield was sitting
at the bottom of a captive shaft on a gear, the answer to that question was they sometimes put
in open bearings ( insert expletive ballon ! ) that answer blew my mind, still wonder about it.

[jcfx]

Thanks Bill for the info, I'll have to dig deeper on taper bearing preloading.

I wonder if it's worthwhile to put a shim washer of some sort to protect the upper bear, my assumption as to why the grease
in that bearing grease was black is that the spline was allowing stuff to fall into the bearing since it's not protected with
any sort of cap like the bottom bearing is.

[rmac]

A lot of my disenchantment stems from poor quality control ...

Thanks for the update. I had the impression that PM's products were pretty decent. Maybe not always, I guess.